Calcium carbonate-based biodegradable composites as an alternative material to industrial plastics

Abstract

A biodegradable composition includes a cross-linked polyester matrix and a plurality of reinforcing particles dispersed within the matrix in a sufficient amount to enable degradation in marine environments while maintaining structural integrity during use. The reinforcing particles may include calcium-containing particles such as calcium carbonate or ground shell materials, and / or plant-derived particles such as bamboo, wood, rice, wheat, seaweed, or paper. The composition may further include a polysaccharide component such as alginate or chitosan that provides ionic crosslinking. Methods for forming the biodegradable compositions are also provided.

Description

2025-017-01CALCIUM CARBONATE-BASED BIODEGRADABLE COMPOSITES AS AN ALTERNATIVE MATERIAL TO INDUSTRIAL PLASTICSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional application Serial No.63 / 750,831 filed January 29, 2025, the disclosure of which is hereby incorporated in its entirety by reference herein.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under NA180AR4170075 awarded by the National Oceanic and Atmospheric Administration. The government has certain rights in the invention.TECHNICAL FIELD

[0003] In at least one aspect, the present invention is related to biodegradable composites incorporating natural particulates and optional polysaccharide components, and methods for their manufacture.BACKGROUND[00041 Current plastics are commonly made of polymers like polystyrene and polyethylene because of their heat resistance, robustness, and long-term stability.1,2However, due to the lack of degradation, traditional polymers contribute significantly to the global plastic pollution, which is estimated to reach over 12 billion tons by 2050. This large amount of waste leaves wildlife susceptible to entanglement and ingestion of plastics, which often induce harm and toxicity through physical impediment, starvation, and exposure to toxic substances leaching from the plastics.3-5Leachates, or supernatants, from these plastics exhibit acute toxic effects on marine life like inhibiting microalgae growth and disrupting female reproductive health in zebrafish.6,7In addition, microplastics, which are small pieces of plastic debris that are less than 5 mm in length,2025-017-01present a serious hazard to human health. Although the full effects of microplastics on human health is not fully understood, studies have shown that microplastic waste in the environment can be associated with the increasing incidence of neurodegenerative diseases, immune disorders, and cancer.8As such, there remains a need for developing safe, biodegradable, and biocompatible plastic alternatives.

[0005] Biodegradable polymers have shown promising applications in tissue engineering, drug delivery, imaging, and many other related fields. Previously, the elastomer poly (1,8-octanediol-co-citrate) (POC) was synthesized and used as the polymer phase of composites developed for orthopedic applications given citrate naturally comprises -5.5% by weight of the organic portion of bone.9POC-CC was found to incorporate high levels of hydroxyapatite (HA), the mineral phase in bone, and increasing HA content enhanced the mechanical properties of the POC composite.10-14Since bone is composed of 60-70% by weight HA, POC-HA has been adopted in both orthopedic and dental applications such as bone screws and tooth root replacement.

[0006] While HA, a form of calcium phosphate, makes up the inorganic phase of native bone, calcium carbonate (CC), makes up more than 90% of the composition in sea shells.15,16Since CC has a similar composition to HA in that they are both calcium-based compounds, CC also has the potential to act as a particulate phase of POC composites and provide similar benefits to mechanical properties for plastic application.17Moreover, the abundance of CC in organisms like marine shells, snails, and eggshells makes it a highly sustainable, inexpensive, and an ideal component in alternative plastic materials that can mimic the conditions of the marine environment.6,18,19

[0007] Accordingly, there is a need for improved biodegradable composites formed from inexpensive sources.SUMMARY

[0008] In at least one aspect, a biodegradable composition is provided. The biodegradable composition includes a cross-linked polyester matrix and a plurality of reinforcing particles dispersed within the matrix in a sufficient amount such that the biodegradable composition is2025-017-01configured to degrade in marine environments while maintaining structural integrity during use. The reinforcing particles enhance mechanical strength compared to compositions lacking these particles, and when the particles include calcium-containing materials, they provide pH stabilization during degradation. In a refinement, the biodegradable composition further includes a polysaccharide component such as alginate or chitosan.

[0009] In another aspect, persistent pollution caused by conventional plastics poses significant risks to marine ecosystems and human health. As a result, there is a need for the development of biocompatible and biodegradable materials that mimic the properties of plastics while being safe for environmental and public health. To address this issue, a plastic substitute was engineered by integrating calcium carbonate (CC), an abundant mineral naturally found in seashells, into poly(l,8-octanediol-co-citrate) (POC), a synthetic biodegradable elastomer already used as the binder in FDA-approved orthopedic fixation devices containing calcium minerals. It was hypothesized that POC-CC would function as a biocompatible plastic substitute capable of degrading in marine environments while maintaining sufficient strength for industrial applications. To test this hypothesis, POC-CC was synthesized with varying CC concentrations (0, 15, and 30 wt.%). The weight degradation rate in ocean water, the pH of ocean water after long-term incubation, the elastic modulus, and the morphology of POC-CC using SEM were evaluated over six months. The results demonstrated that the degradation rate increased with higher POC content, and the addition of CC helped maintain the pH of ocean water. Furthermore, to assess biocompatibility, Scenedesmus sp. algae were incubated with the POC-CC supernatant after its incubation in simulated ocean water for six months. High cell viability was observed, confirming the biocompatibility of POC-CC with marine microorganisms. Finally, a model can holder was fabricated using POC-CC to demonstrate its proof-of-concept as an alternative plastic material. In summary, the study highlights POC-CC as a new material and demonstrates its feasibility as a biodegradable plastic substitute.

[0010] In another aspect, a biodegradable composition includes a cross-linked polyester matrix and a plurality of natural particulates dispersed within the matrix. The natural particulates may include calcium-containing materials such as calcium carbonate, ground shells from crustaceans (e.g., shrimp shells, crab shells), ground mollusk shells, or eggshells. Alternatively or2025-017-01additionally, the natural particulates may include plant-derived materials such as ground seaweed, bamboo particles, wood particles, rice particles (e.g., rice hulls or rice straw), wheat particles (e.g., wheat straw or wheat bran), or paper particles. The composition may further include a polysaccharide component selected from alginate, chitosan, or combinations thereof, wherein the polysaccharide provides additional crosslinking and enhances biodegradability.

[0011] In another aspect, a biodegradable composition includes a cross-linked polyester matrix, a plurality of calcium carbonate particles dispersed within the matrix, and a polysaccharide component selected from alginate, chitosan, or combinations thereof. When alginate is present, it may be ionically crosslinked with calcium ions released from the calcium carbonate particles to form an egg-box structure. The combination of covalent ester crosslinking in the polyester matrix and ionic crosslinking through the polysaccharide provides enhanced mechanical properties and tunable degradation rates.

[0012] In yet another aspect, a method for forming a biodegradable composition is provided. The method includes synthesizing a polyester pre-polymer by reacting a polycarboxylic acid with a diol, combining the polyester pre-polymer with reinforcing particles, and thermally curing the mixture to form a cross-linked polyester matrix with the reinforcing particles dispersed therein. In a refinement, the method further includes adding a polysaccharide solution to the polyester pre-polymer, wherein the polysaccharide is selected from alginate, chitosan, or combinations thereof.

[0013] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] For a further understanding of the nature, objects, and advantages of the present disclosure, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein:2025-017-01

[0015] FIGURES 1A, IB, 1C, and ID. POC and POC-CC synthesis process. (A) POC-CC synthesis scheme; POC pre-polymer is formed followed by CC incorporation and further polymerization. (B) POC pre-polymer. (C) POC pre-polymer solution incorporating CC in 5 in. diameter Teflon dish. (D) POC-CC after casting onto 6 x 12 in. Teflon sheet.

[0016] FIGURES 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, 21, 2J, 2K, and 2L. The characterization of POC-CC degradation. (A) Weight degradation of POC-CC samples. (B) pH level of ocean water after incubation with POC-CC. (C) POC disk (5 mm diameter, 3 mm height) and dogbone (40 mm x 16 mm x 3 mm) used for elastic modulus and tensile strength testing. (D) Elastic modulus and tensile strength of POC-CC samples. (E) Elastic modulus of degraded POC and POC-CC samples. (F) TEM images of CC. (G-L) SEM images of nondegraded and degraded POC (G, J), POC-15CC (H, K), and POC-30CC (I, L) samples. * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001, n=6.

[0017] FIGURES 3A, 3B, 3C, 3D, and 3E. Biocompatibility of POC-CC supernatant with Scenedesmus sp. algae with brightfield images of Scenedesmus sp. (A) Treatment groups were standardized against a control group of media and simulated ocean water (dotted line). No significance was detected across any groups, n=5. (B, C) Images of Scenedesmus sp. algae in media only after 48 hours. (D, E) Images of Scenedesmus sp. algae in 90% media and 10% six-month POC-15CC supernatant mixture after 48 hours. Scale bar = 10 urn.

[0018] FIGURE 4. Application of POC-CC polymer. POC- 15CC sheet was cut out to hold three 7.5 fluid-ounce soda cans (190.5 g).

[0019] FIGURES 5A, 5B, 5C, and 5D. Synthesis and characterization of alginate-loaded POC-CC (POC-15CC-1SA). (A) Schematic showing ionic crosslinking between alginate and Ca2+ions forming egg-box structure. (B) Comparison of POC, POC-15CC, and POC-15CC-1SA samples. (C) Elastic modulus comparison. (D) Tensile strength comparison.DETAILED DESCRIPTION

[0020] Reference will now be made in detail to presently preferred compositions, embodiments, and methods of the present invention, which constitute the best modes of practicing the invention presently known to the inventors. The Figures are not necessarily to scale. However,2025-017-01it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the invention and / or as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0021] Except in the examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and / or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred. Also, unless expressly stated to the contrary: molecular weights provided for any polymers refers to weight average molecular weight unless otherwise indicated; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among the constituents of a mixture once mixed; the first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation; and, unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.

[0022] It must also be noted that, as used in the specification and the appended claims, the singular form “a,” “an,” and “the” comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components.

[0023] The term “comprising” is synonymous with “including,” “having,” “containing,” or “characterized by.” These terms are inclusive and open-ended and do not exclude additional, unrecited elements or method steps.2025-017-01

[0024] The phrase “consisting of’ excludes any element, step, or ingredient not specified in the claim. When this phrase appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

[0025] The phrase “consisting essentially of’ limits the scope of a claim to the specified materials or steps, plus those that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.

[0026] With respect to the terms “comprising,” “consisting of,” and “consisting essentially of,” where one of these three terms is used herein, the presently disclosed and claimed subject matter can include the use of either of the other two terms.

[0027] The phrase “composed of’ means “including” or “comprising.” Typically, this phrase is used to denote that an object is formed from a material.

[0028] It should also be appreciated that integer ranges explicitly include all intervening integers. For example, the integer range 1-10 explicitly includes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Similarly, the range 1 to 100 includes 1, 2, 3, 4. .. . 97, 98, 99, 100. Similarly, when any range is called for, intervening numbers that are increments of the difference between the upper limit and the lower limit divided by 10 can be taken as alternative upper or lower limits. For example, if the range is 1.1. to 2.1 the following numbers 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 can be selected as lower or upper limits.

[0029] In the examples set forth herein, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 50 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples. In a refinement, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 30 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples. In another refinement, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates,2025-017-01etc.) can be practiced with plus or minus 10 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples.

[0030] Throughout this application, where publications are referenced, the disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this invention pertains.

[0031] As used herein, “reinforcing particles” refers to discrete particles dispersed within the polyester matrix to enhance mechanical properties and / or modify degradation behavior. Such particles may include calcium-containing materials that dissolve during degradation of the composition, as well as plant-derived materials that biodegrade. The term encompasses both materials that undergo biological degradation and materials that undergo chemical dissolution in aqueous environments. In contrast to the biodegradable polyester matrix, which degrades through hydrolysis of ester bonds, calcium-containing reinforcing particles such as calcium carbonate dissolve through chemical processes and provide pH buffering that moderates acidic byproducts released during matrix degradation.

[0032] As used herein, “natural sources” refers to materials derived from biological organisms or geological processes, as distinguished from synthetic or petroleum-derived materials. Natural sources include, but are not limited to: (1) marine-derived materials such as seashells, mollusk shells, crustacean shells (e.g., shrimp, crab, lobster), and snail shells, which provide calcium carbonate and / or chitin; (2) avian-derived materials such as eggshells, which provide calcium carbonate; (3) plant-derived materials such as seaweed, bamboo, wood, rice (hulls, straw, or bran), wheat (straw, bran, or chaff), and paper or cellulose fibers; and (4) mineral sources such as naturally occurring calcium carbonate deposits (e.g., limestone, chalk, marble). Materials from natural sources may be processed by washing, drying, grinding, or other mechanical or chemical treatments to achieve desired particle sizes and properties while retaining their natural origin classification. Reinforcing particles derived from natural sources include particles obtained from marine organisms, avian sources, plants, and mineral deposits.

[0033] As used herein, “marine environments” refers to aqueous environments having characteristics similar to natural ocean or seawater conditions. Such environments are typically2025-017-01characterized by a salinity of about 32 to 37 grams per liter (e.g., about 35 g / L for average ocean water, corresponding to a specific gravity of about 1.026), a pH of about 7.5 to 8.4, and temperatures ranging from about -2°C to about 36°C. For purposes of testing degradation behavior, simulated ocean water may be prepared using commercially available sea salt formulations (e.g., Instant Ocean® Sea Salt) dissolved in deionized or purified water at concentrations approximating natural seawater salinity (e.g., about 35 g / L). The term “marine environments” encompasses natural seawater, simulated ocean water, and other aqueous environments meeting the foregoing salinity, pH, and temperature characteristics.

[0034] In at least one aspect, a biodegradable composition includes a cross-linked polyester matrix and a plurality of reinforcing particles dispersed within the matrix in a sufficient amount to enable degradation in marine environments while maintaining structural integrity during use. The reinforcing particles enhance mechanical strength compared to an analogous composition not including the plurality of reinforcing particles. As used herein, an “analogous composition” refers to a composition having the same polyester matrix but lacking the reinforcing particles. The biodegradable composition is configured to degrade in marine environments while maintaining structural integrity during use; specifically, the composition is configured such that the reinforcing particles provide mechanical reinforcement during use and the polyester matrix undergoes hydrolytic degradation upon exposure to aqueous environments. The reinforcing particles are present in a sufficient amount to provide the desired mechanical properties and degradation characteristics.

[0035] In another aspect, the reinforcing particles include calcium-containing particles. Examples of calcium-containing particles include calcium carbonate particles, calcium citrate particles, calcium chloride particles, calcium sulfate particles, hydroxyapatite particles, and combinations thereof. In a particularly useful variation, the calcium-containing particles are calcium carbonate particles. The calcium-containing particles provide pH stabilization during degradation by buffering acidic byproducts released during hydrolysis of the polyester matrix. Calcium citrate particles and calcium chloride particles may provide alternative calcium sources with different solubility characteristics compared to calcium carbonate particles.2025-017-01

[0036] In another aspect, the reinforcing particles include ground natural shell materials. Examples of ground natural shell materials include ground crustacean shells such as shrimp shells, crab shells, lobster shells, and crawfish shells; ground mollusk shells such as oyster shells, clam shells, mussel shells, and snail shells; and ground eggshells. The ground shell materials may be processed by washing, drying, and grinding to achieve a desired particle size. Ground crustacean shells advantageously contain both calcium carbonate and chitin, providing both mineral reinforcement and a natural polysaccharide component. In a refinement, the ground shell particles have an average particle size of less than 500 microns. In a further refinement, the ground shell particles have an average particle size of less than 100 microns. As used herein, “ground crustacean shell particles” refers to particles derived from grinding crustacean shells, including ground shrimp shells, ground crab shells, ground lobster shells, and ground crawfish shells. “Ground mollusk shell particles” refers to particles derived from grinding mollusk shells, including ground oyster shells, ground clam shells, ground mussel shells, and ground snail shells. “Ground eggshell particles” refers to particles derived from grinding avian eggshells, including chicken eggshells, duck eggshells, and other avian eggshells.

[0037] In another aspect, the reinforcing particles include plant-derived particles. Examples of plant-derived particles include seaweed particles, bamboo particles, wood particles, rice particles, wheat particles, and paper particles. Seaweed particles may be derived from brown algae, red algae, or green algae, and may be processed by drying and grinding. Bamboo particles may be derived from bamboo culms or bamboo leaves and processed by grinding. Wood particles may be derived from hardwoods or softwoods and may include wood flour, wood fibers, or sawdust. Rice particles may include ground rice hulls, rice straw, or rice bran. Wheat particles may include ground wheat straw, wheat bran, or wheat chaff. Paper particles may be derived from recycled paper, virgin paper pulp, or cellulose fibers. In a refinement, the plant-derived particles have an average particle size of less than 500 microns. In a further refinement, the plant-derived particles have an average particle size of from about 1 micron to about 200 microns.

[0038] In another aspect, the biodegradable composition includes a combination of two or more types of reinforcing particles. For example, the composition may include both calcium carbonate particles and ground shrimp shell particles. In another example, the composition may2025-017-01include calcium carbonate particles and bamboo particles. Such combinations can provide synergistic effects on mechanical properties, degradation rates, or both.

[0039] In another aspect, the cross-linked polyester matrix comprises poly(l ,8-octanediol-co-citrate) (POC). In a refinement, the cross-linked polyester matrix further includes another polyester that is different from POC. Examples of such additional polymers include, but are not limited to, a component selected from the group consisting of poly-L-lactic acid (PLLA), polyglycolic acid (PGA), poly(lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL), and combinations thereof. The matrix comprises a network of ester bonds formed by polycarboxylic acid and diols selected to optimize the degree of cross-linking to control elasticity and tensile strength. Higher degrees of cross-linking generally result in increased stiffness and tensile strength but reduced elasticity. The degree of cross-linking may be selected to control elasticity and achieve desired mechanical properties for the intended application.

[0040] In another aspect, the biodegradable composition further includes a polysaccharide component. The polysaccharide component may be selected from alginate, chitosan, chitin, cellulose, starch, and combinations thereof. In a refinement, the polysaccharide component is selected from alginate, chitosan, and combinations thereof. The polysaccharide component may provide ionic crosslinking, hydrogen bonding, or other non-covalent interactions that supplement the covalent ester crosslinking in the polyester matrix. Starch is a naturally occurring polysaccharide found in plants that may provide biodegradability enhancement and can be derived from com, potato, rice, or other plant sources. Cellulose is a structural polysaccharide found in plant cell walls.

[0041] In another aspect, the polysaccharide component includes alginate. In a refinement, the alginate is sodium alginate. The alginate forms an ionic crosslink network through coordination of calcium ions (Ca2+) with carboxylate and hydroxyl groups on the alginate polymer chains, creating an “egg-box” structure. This ionic crosslinking provides a secondary crosslinking mechanism that supplements the covalent ester crosslinking in the POC matrix. In a refinement, the alginate is present in an amount from 0.1 to 10 weight percent of the biodegradable composition. In a further refinement, the alginate is present in an amount from 0.5 to 5 weight2025-017-01percent. In yet a further refinement, the alginate is present in an amount of about 1 weight percent. In another aspect, the alginate has a molecular weight from about 10,000 Da to about 100,000 Da. In a refinement, the alginate has a molecular weight from about 12,000 Da to about 40,000 Da.

[0042] In another aspect, the polysaccharide component includes chitosan. Chitosan is a linear polysaccharide composed of randomly distributed -(l— »4)-linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). Chitosan may be derived from the deacetylation of chitin obtained from crustacean shells. In a refinement, the chitosan has a degree of deacetylation of at least 70%, at least 80%, or at least 85%. In a refinement, the chitosan is present in an amount from 0.1 to 10 weight percent of the biodegradable composition. Chitosan can form hydrogen bonds with the polyester matrix and may also interact with anionic species present in the composition. In some embodiments, the composition includes both alginate and chitosan, which can form polyelectrolyte complexes through ionic interactions between the anionic alginate and cationic chitosan.

[0043] In another aspect, the calcium salt (e.g., calcium carbonate) is derived from natural sources including seashells, eggshells, crustaceans, and snail shells. Seashells suitable for use as a calcium carbonate source include mollusk shells such as oyster shells, clam shells, mussel shells, scallop shells, and conch shells. Crustacean shells suitable for use include shrimp shells, crab shells, lobster shells, and crawfish shells; crustacean shells advantageously contain both calcium carbonate and chitin, providing both mineral reinforcement and a natural polysaccharide component. Eggshells from poultry such as chicken, duck, and quail provide a readily available source of calcium carbonate. Snail shells, including both terrestrial and marine gastropod shells, may also be used. The natural source materials may be processed by washing to remove residual organic matter, drying, and grinding or milling to achieve a desired particle size.

[0044] In a refinement, the plurality of reinforcing particles is present in an amount from 1 to 99 weight percent of the total weight of the biodegradable composition. In a further refinement, the plurality of reinforcing particles is present in an amount from 5 to 50 weight percent of the total weight of the biodegradable composition. In a further refinement, the plurality of reinforcing particles is present in an amount of at least 1 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 102025-017-01wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, or 15 wt.% of the biodegradable composition and in an amount of at most 99 wt.%, 90 wt.%, 80 wt.%, 70 wt.%, 60 wt.%, 50 wt.%, 40 wt.%, 35 wt.% 30 wt.% of the biodegradable composition.

[0045] In another aspect, the plurality of reinforcing particles has an average particle size of less than or equal to 500 microns to optimize dispersion and interfacial adhesion within the cross-linked polyester matrix. In a refinement, the reinforcing particles have an average diameter of from about 50 nm to about 500 microns. In some refinements, the reinforcing particles have an average diameter of at least 50 nm, 100 nm, 500 nm, 1 micron, 5 microns, 10 microns, 25 microns, 50 microns, 75 microns, or 100 microns and at most 500 microns, 470 microns, 440 microns, 410 microns, 380 microns, 350 microns, 320 microns, 290 microns, 260 microns, 230 microns, or 200 microns. The reinforcing particles preferably have an average particle size selected to optimize dispersion and interfacial adhesion within the cross-linked polyester matrix. Smaller particle sizes generally provide better dispersion and increased interfacial adhesion, leading to improved mechanical properties.

[0046] In another aspect, the composition exhibits biocompatibility with marine microorganisms and has an elastic modulus from about 0.5 to about 10 MPa prior to degradation. The composition exhibits a degradation rate of 1 to 90% weight over a six-month period in simulated ocean water. As used herein, the composition “exhibits biocompatibility with marine microorganisms” when marine organisms such as algae maintain high cell viability (e.g., greater than 70%) upon exposure to the composition or its degradation products. The six-month period provides a representative timeframe for evaluating long-term degradation behavior in marine environments.

[0047] In another aspect, the composition can be formed into a functional article such as beverage holders, packaging materials, and single-use containers. The composition may include additives selected from antioxidants, plasticizers, and stabilizers to optimize mechanical performance and degradation rates. As used herein, a “functional article” refers to an article for commercial or consumer use. Examples of functional articles include beverage holders such as can holders and cup carriers, packaging materials such as containers and wrapping films, and single-2025-017-01use containers such as food trays and disposable cups. The additives may be present in an amount from about 0.1 to about 5 weight percent of the biodegradable composition.

[0048] In another aspect, the composition further includes pores of controlled size and distribution, which are formed during a mixing process to enhance biodegradability without compromising structural integrity. In some embodiments, the biodegradable composition further includes pores of controlled size and distribution. The pores may be formed during the mixing process as air bubbles become trapped during incorporation of the reinforcing particles. The controlled porosity can enhance biodegradability by increasing surface area for hydrolytic degradation.

[0049] In another aspect, a method for forming a biodegradable composition is provided. The method includes synthesizing a polyester pre-polymer by reacting equimolar amounts of a polycarboxylic acid and a diol at an elevated temperature. In a refinement, the polycarboxylic acid is citric acid and the diol is 1,8-octanediol. In a refinement, the elevated temperature is from about 120°C to about 200°C. In a further refinement, the elevated temperature is from about 140°C to about 180°C. In a refinement, the reaction is conducted for about 1 hour per 0.1 mole of prepolymer synthesized.

[0050] In another aspect, the method further includes dissolving the polyester pre-polymer in a solvent and mixing with reinforcing particles. In a refinement, the solvent is ethanol. In a refinement, the reinforcing particles include calcium carbonate, ground shell materials, plant-derived particles, or combinations thereof. The mixture is then transferred to a mold and thermally cured at a curing temperature for a curing time to form the cross-linked polyester matrix with the reinforcing particles dispersed therein. In a refinement, the curing temperature is from about 60°C to about 100°C. In a further refinement, the curing temperature is about 80°C. In a refinement, the curing time is from about 24 hours to about 96 hours. In a further refinement, the curing time is about 48 hours. Thermally curing the composition comprises heating the mixture at the curing temperature for the curing time sufficient to form the cross-linked polyester matrix.

[0051] In another aspect, the method further includes adding a polysaccharide solution to the polyester pre-polymer prior to or simultaneously with combining with the reinforcing particles.2025-017-01In a refinement, the polysaccharide solution includes alginate, chitosan, or a combination thereof. In a refinement, the polysaccharide solution is an aqueous solution of sodium alginate. In a refinement, the polysaccharide solution has a concentration of from about 1% to about 10% by weight. In a further refinement, the polysaccharide solution has a concentration of about 4% by weight. When alginate is used and calcium-containing particles are added, calcium ions (Ca2+) released from the particles ionically crosslink with the alginate to form an egg-box structure. The combination of thermal curing and ionic crosslinking provides a dual-crosslinked network with enhanced mechanical properties. As used herein, an “aqueous solution” refers to a solution in which water is the solvent. When calcium-containing reinforcing particles such as calcium carbonate are added in the presence of alginate, calcium ions from the calcium-containing reinforcing particles ionically crosslink with the polysaccharide to form the dual-crosslinked network. This dual-crosslinked network comprises both covalent ester crosslinks in the polyester matrix and ionic crosslinks between calcium ions and the polysaccharide. In a refinement, the polysaccharide component comprises both alginate and chitosan, which may provide synergistic effects on mechanical properties and degradation behavior.

[0052] Additional details of the invention are found in Ho, N., Huang, Y. & Chung, E.J. Calcium carbonate-based biodegradable composites as an alternative material to industrial plastics. MRS Commun. 15, 219-226 (2025). https: / / doi.org / 10.1557 / s43579-025-00695-z and its supporting materials; the entire disclosure of which is hereby incorporated by reference.

[0053] The following examples illustrate the various embodiments of the present invention. Those skilled in the art will recognize many variations that are within the spirit of the present invention and scope of the claims.

[0054] To evaluate the feasibility of POC-CC as a plastic substitute, POC containing 15 wt.% and 30 wt.% CC (POC-CC) were fabricated and characterized (Fig. 1). In nature, CC makes up more than 90% of the exoskeletal chemical composition in organisms such as cockle shells and snails.20,21While this provides them with a durable shell, it is also brittle and lacks the elasticity needed to become a pliable material for molding. In addition, a previous study synthesized POC-HA with 40 wt.% HA, a similar calcium-based composition to CC, as a novel material to mimic2025-017-01bone structure, where POC was added to replicate collagen, or the elastic phase of bone.12For our application, we incorporated 15 wt.% and 30 wt.% of CC into POC-CC to ensure mechanical strength similar to POC-HA designed for bone applications, but to have a high degree of elasticity and moldability.

[0055] To further enhance the mechanical properties of the POC-CC composition, alginate was incorporated to provide ionic crosslinking (Fig. 5). POC-15CC-1SA was synthesized by first transferring POC pre-polymer into Teflon dishes, then adding 4% sodium alginate (12,000-40,000 Da molecular weight) in water dropwise to achieve 1 wt.% sodium alginate in POC (Fig. 5A). The mixture was stirred every 5 minutes for 2 hours, then 15 wt.% calcium carbonate in ethanol was added. Upon addition of the calcium carbonate, Ca2+ions began to build the egg-box structure with the carboxylate and hydroxyl groups of the sodium alginate, leading to ionic crosslinking. The mixture was stirred every 5 minutes for 2 hours and then thermally cured at 80°C for 48 hours. The resulting POC-15CC-1SA demonstrated improved mechanical properties compared to POC-15CC without alginate (Fig. 5B-D).[00561 To study the long-term degradation of POC-CC in simulated ocean water, POC-CC was incubated with simulated ocean water for up to 6 months and their weight was measured before and after incubation. The mass for each group was significantly decreased over 4 months (8.5 ± 1.5% for POC, 6.7 ± 1.8% for POC-15CC, and 8.4 ± 0.3% for POC-30CC, pO.0001, Fig.2A). This is consistent with a previous study that showed POC scaffolds degraded 8% by weight after 2 months of degradation in PBS.22,23Additionally, the pH of simulated ocean water was measured after POC-CC incubation. The pH of the supernatant at each time point increased with increasing polymer content (POC < POC-15CC < POC-30CC). As shown in Fig. 2B, simulated ocean water incubated with POC-30CC maintained a higher pH level over the period of 6 months and demonstrated the smallest change in pH (8.0 ± 0.1 to 6.9 ± 0.1) as compared to POC-15CC (7.2 ± 0.1 to 5.1 ± 0.1) and POC (5.4 ± 0.1 to 3.6 ± 0.1). This could be attributed to the higher extent of cross-linking with increased CC content in POC-30CC, which slows the degradation and reduces the concentration of acidic byproducts from POC.11In addition, similar to HA, the basic nature of CC may have buffering effect by neutralizing acidic functional groups, thereby minimizing hydrolytic degradation.242025-017-01

[0057] To compare the mechanical properties of POC-CC to current plastics, elastic modulus, and tensile strength for nondegraded samples were obtained through compression and tensile testing (ISO 7743:2017 and ISO 37 standards, respectively) (Fig. 2C-E). Disk-shaped composites were compressed at a rate of 1 mm / min to measure the elastic modulus, while POC and POC-CC dogbone-shaped composites were pulled at a rate of 13 mm / min to measure tensile strength.10Increasing calcium mineral led to higher elastic moduli, with POC, POC-15CC, and POC-30CC at 2892.2 ± 423.7 kPa, 4260.6 ± 295.3 kPa, and 4895.5 ± 681.5 kPa respectively. Regarding tensile strength, surprisingly, POC-15CC was found to have the lowest tensile strength (300.9 ± 61.7 kPa) compared to POC (549.3 ± 53.6 kPa) and POC-30CC (1191.2 ± 94.3 kPa). Incorporating higher calcium minerals by weight have typically been shown to reduce pore formation, which strengthens elastic modulus as shown in previous studies.25,26However, the lower calcium content in POC-15CC may still contribute to pore formation during CC incorporation. In contrast, the extensive cross-linking in POC-30CC results in higher interfacial adhesion and stress transfer and can thereby reduce porosity.25Future work will focus on fine tuning the polymerization process to decrease porosity and pore size without affecting the polymer’s structural integrity.

[0058] To examine the effect of degradation on the mechanical properties of POC-CC, the elastic modulus of POC-CC was measured after 6 months of degradation in simulated ocean water. Over 6 months, the elastic modulus of all the groups decreased (2892.2 ± 423.7 kPa to 683.8 ± 219.7 kPa for POC, 4260.6 ± 295.3 kPa to 2748.4 ± 1059.4 kPa for POC-15CC, 4895.5 ± 681.5 kPa to 4104.3 ± 812.9 kPa for POC-30CC) (Fig.2C-E).10This aligns with earlier reports of POC materials that show hydrolysis in aqueous conditions such as in simulated ocean water, leading to a progressive decrease in elastic modulus over time.22,27POC-CC also exhibits a similar elastic modulus as compared to silicone rubber (0.517-62.1 MPa) and natural rubber (1.5-3.00 MPa), which are often used as alternatives to plastic but are limited in recyclability and moldability. Additionally, as shown in Fig. 2C-E, POC-30CC had the highest elastic modulus after 6 months in simulated ocean water as compared to POC-15CC (3692.5 ± 321.5 kPa vs. 2635.6 ± 519.6 kPa, p<0.01), which is consistent with previous reports that higher content of calcium mineral particles in the polymer enhances the mechanical properties of the overall composite.10This higher elastic2025-017-01modulus is attributed to the enhanced interfacial adhesion and stress transfer between the CC particles and the POC matrix.28The increased CC content provides greater reinforcement within the polymer, similar to the effect seen with HA in POC-HA nanocomposites, resulting in a stronger and more durable composite.11,12After 4 months, the elastic modulus of POC-30CC was decreased by 24.6% (4895.5 ± 681.5 kPa to 3692.5 ± 321.5 kPa) while the decrease was 38.1% (4260.6 ± 295.3 kPa to 2635.6 ± 519.6 kPa) for POC-15CC and 75.3% (2892.2 ± 423.7 kPa to 713.8 ± 304.4 kPa) for POC.

[0059] Next, POC-CC samples were imaged with SEM to confirm any morphological changes after degradation (Fig. 2F-L).13We first imaged the CC particles with TEM and found the size of CC particles to be 1.6 ± 0.4 um. For POC, fine cracks were found after degradation upon SEM imaging, whereas larger structural cracks were found for POC-15CC and POC-30CC which contained CC (Fig. 4L), likely due to the increased brittleness from higher levels of the particulate phase.12Given that POC-15CC showed little cracking, a higher degradation rate, and mechanical properties within the range of current plastics, POC-15CC was used as the polymer for synthesizing a 3-pack can holder ring.

[0060] To assess the biocompatibility of POC-CC and examine any toxicity to marine microorganisms, simulated ocean water samples derived from the supernatant after incubation with POC-CC for six months was applied to Scenedesmus sp. , an algae strain that is commonly found in both freshwater and sea environments (Fig. 3).29,30Upon incubation, no statistically significant differences in cell viability were observed of POC (79.8 ± 18.3%), POC-15CC (78.8 ± 25.3%), and POC-30CC (78.8 ± 21.5 %) compared to the media-ocean water control (Fig. 3A), confirming that POC-CC has a high safety profile. In addition, Scenedesmus sp. algae were imaged via brightfield microscopy to examine if the cells displayed any morphological changes. As shown in Fig. 3B-E, healthy Scenedesmus sp. cells remain in clusters while maintaining an ovular structure and visible chloroplasts.31Thus, cells treated with POC-CC had similar features compared to healthy cells, further confirming the biocompatibility of POC-CC.

[0061] Lastly, to demonstrate and provide proof-of-concept of POC-CC as a feasible plastic substitute, a model 3-pack can holder ring was built using POC-CC. As mentioned earlier,2025-017-01although POC-30CC had higher elastic modulus and was stiffer, it showed more structural cracks under SEM after 6 months of degradation. Thus, POC-15CC was used for this application (Fig.4). Soda cans were inserted successfully into the holder without causing any mechanical defects, and POC-15CC was able to hold the weight of three soda cans, totaling 190.5 g, without compromising the structural integrity of the sheet, confirming the feasibility of POC-CC as a plastic can holder.

[0062] In recent decades, significant efforts have been made to protect marine life from the effects of plastic pollution. Conventional plastics persist in marine environments and pose severe threats to marine organisms through ingestion, entanglement, and toxic supernatants. Despite ongoing initiatives to reduce plastic, including global projects like the Ocean Cleanup project, the need for biodegradable alternatives that are both environmentally safe and suitable for industrial applications remains critical.32To our knowledge, POC-CC is the first development of a biodegradable plastic substitute that integrates CC, an abundant and naturally occurring compound, into the marine-compatible elastomer poly (1 ,8-octanediol-co-citrate). Specifically, we synthesized POC-CC with different CC levels, tested the degradation of POC-CC, and found the high degradation of POC-CC in simulated ocean water over 6 months (Fig.2). Mechanical testing showed that the elastic modulus of POC-CC samples varies from 2892.2 kPa to 4895.5 kPa (Fig.2), which is comparable to the elastic modulus of soft polymers like silicone rubber (0.517-62.1 MPa).33Although silicone rubber has been proposed as an alternative to traditional plastics, it has some disadvantages, including a complex manufacturing process and recycling challenges.34We also demonstrated that POC-CC could be cast onto a Teflon platform mold for constructing a can holder (Fig. 4). Additionally, we demonstrate biocompatibility using Scenedesmus sp. algae upon POC-CC treatment (Fig.3).

[0063] With our promising results, additional aspects of this study can still be further optimized. Specifically, during the POC-CC synthesis process, we observed that pores were nucleated by trapping air bubbles created during the mixing process.35In addition, the incorporation of high CC content increases the viscosity of the polymer mixture and accelerates the cross-linking process, which may trap air during the mixing process36. This may influence the strength of POC-CC, as evidenced by the variability in tensile strength of POC-15CC. To further2025-017-01enhance the mechanical properties of POC-CC, diols with different molecular weight and carbon chain length could be utilized in order to optimize the degree of cross-linking, leading to improved elasticity and tensile strength.25While our current study assessed the biocompatibility of POC-CC using Scenedesmus sp. algae, future research can include evaluating POC-CC biocompatibility with additional marine organisms such as zebrafish and coral.37-39Nonetheless, our development of POC-CC and these initial results show the promise of POC-CC as a new material that can be used as a biodegradable plastic substitute.

[0064] Supporting Information

[0065] Methods

[0066] Synthesis of POC-CC Polymer

[0067] POC pre-polymer synthesis was adapted from previous studies.14,26Briefly, equimolar amounts of citric acid (Category # 251275-2.5KG, Sigma Aldrich, St. Louis, Missouri) and 1,8-octanediol (Category #: Al 5402-36, Sigma Aldrich, St. Louis, Missouri) were melted and mixed in a round bottom flask with a stir bar. The reaction mixture was heated using a mineral oil bath at 140°C to 180°C for roughly 1 hour per 0.1 mole of POC that was being synthesized (e.g., 3-4 hours for 0.35 moles at 140°C, or 1 hour for 0.1 mole at 180°C). The resulting POC prepolymer was then dissolved in ethanol at 80°C. For POC samples without calcium carbonate, the POC pre-polymer was transferred into Teflon dishes (Thermo Fisher Scientific, Waltham, Massachusetts) maintained at 80°C, and the resulting POC polymers were post-polymerized at 80°C for 48 hours. For POC-CC samples, the POC pre-polymer solution was mixed with calcium carbonate (Category #: 310034-500G, <50 pm, Sigma Aldrich, St. Louis, Missouri) at concentrations of 0%, 15%, and 30% by weight. The mixtures were transferred into Teflon dishes (Thermo Fisher Scientific, Waltham, Massachusetts) maintained at 80°C. The POC-CC solutions were stirred every 5 minutes for 2 hours, then every 30 minutes for 12 hours. The resulting POC-CC polymers were post-polymerized at 80°C for 48 hours. The samples for testing were prepared using 5 mm biopsy punches.2025-017-01

[0068] For the formation of POC-CC sheets, the POC-CC polymer was thoroughly mixed at 80°C for 6 hours in a Teflon dish. The mixture was then poured onto a 6 in x 12 in x 0.375 in. Teflon sheet (BuyPlastic, Waynesboro, Pennsylvania) and polymerized at 80°C for 3 days. Molds were subsequently cut to create holding cans, demonstrating a potential application of the polymer (Fig- 1).

[0069] Synthesis of Alginate-Loaded POC-CC Polymer (POC-15CC-1SA)

[0070] For POC-15CC-1 SA, the POC pre-polymer was first transferred into Teflon dishes. Then, 4% sodium alginate (Category #: W201502-5KG, 12,000-40,000 Da, Sigma Aldrich, St. Louis, Missouri) in water was added dropwise into the POC pre-polymer to achieve 1 wt.% sodium alginate in POC. The mixture was stirred every 5 minutes for 2 hours. Then, 15 wt.% calcium carbonate in ethanol was added to the mixture. Upon addition, Ca2+ions began to build the eggbox structure with the carboxylate and hydroxyl groups of the sodium alginate, leading to ionic crosslinking. The mixture was stirred every 5 minutes for 2 hours. The resulting polymers were thermally cured at 80°C for 48 hours. For mechanical testing, the mixture was transferred from Teflon dishes into dumbbell-shaped PDMS molds and thermally cured at 80°C for 48 hours. Mechanical testing was performed in compliance with ISO 37 using Type 1 dumbbell specimens. The Instron 5942 Mechanical Testing System (Instron, Norwood, Massachusetts) was used to measure the elastic modulus and tensile strength of POC-15CC-1SA samples at a strain rate of 1.7 mm / min using Bluehill Universal software, (see Fig. 5)

[0071] Degradation

[0072] Instant Ocean® Sea Salt (Spectrum Brands, Blacksburg, Virginia) was dissolved in Milli-Q (MQ) water at 35 g / L to form simulated ocean water solution. POC-CC biopsy samples were weighed and subsequently incubated at room temperature in the ocean water at varying time points from 0-6 months. The samples were then washed twice with MQ water. Ocean water from each sample was collected before freezing and lyophilization of the samples for dehydration overnight. The samples were weighed to observe changes in mass. The pH of the simulated ocean water supernatant was measured using a S220 SevenCompact pH meter (Mettler Toledo, Columbus, Ohio).2025-017-01

[0073] Mechanical Testing

[0074] Mechanical testing was performed in compliance with ISO 7743:2017 standards for elastic modulus testing and ISO 37 standards for tensile strength testing. POC-CC samples were blotted dry after washing and measured for height and diameter. The Instron 5942 Mechanical Testing System was used to measure the elastic modulus of each POC-CC concentration at each time point (Instron, Norwood, Massachusetts). The strain was gradually applied at 1 mm / min to calculate the elastic modulus of the samples until the max load (50 N) using Bluehill Universal software. For tensile strength, dogbone-shaped POC-CC composites were formed using a laser cutter (PLS 4.5, Universal Laser Systems, Scottsdale, Arizona). Load and strain were measured using a 100 N load limit module that pulled the dogbone upwards at 13 mm / min (Mark-10 ESM303, Mark-10 Corporation, Copiague, New York). Tensile strength was obtained using MESUR®gauge Plus Software.

[0075] Biocompatibility

[0076] Scenedesmus sp. algae (UTEX Culture Collection of Algae, Austin, Texas) was cultured using Proteose Medium (UTEX Culture Collection of Algae, Austin, Texas) under a 12-hour daily light cycle with a warm white-light lamp. Algae were seeded at 25,000 cells / mL and incubated with Proteose Medium with a 9: 1 mixture of Proteose Medium and POC-CC supernatant from every degradation time point for 48 hours at room temperature. Algae concentrations and proliferation were determined by counting using a trypan blue stain and a Countess II FL Automated Cell Counter (Thermo Fisher Scientific, Waltham, Massachusetts). Cell images were taken using brightfield microscopy (EVOS XL Core, Thermo Fisher Scientific, Waltham, Massachusetts).

[0077] SEM Imaging

[0078] Cylindrical biopsy punch samples (5mm in diameter, about 3mm thick) of degraded and non-degraded POC-CC polymer samples were sputter-coated with platinum (Cressington 108, Cressington Scientific Instruments, Watford, United Kingdom). Scanning electron microscopy (SEM) was used to observe cross-section morphology after degradation of each sample (Nova2025-017-01NanoSEM 450, FEI Company, Hillsboro, Oregon). Unmagnified images were taken at 150x magnification and magnified images were taken at 8000x magnification.

[0079] TEM Imaging

[0080] Calcium carbonate was mixed with 100% ethanol before vortexing and sonication. Carbon grids were glow-discharged before 4 ul of calcium carbonate solution was applied to the grid. The solution was incubated for 2 minutes at room temperature before blotting and drying overnight and imaging (Talos F200C, FEI Company, Hillsboro, Oregon).

[0081] Statistical Analysis

[0082] All numerical data was reported as mean ± standard deviation. Analysis of variance (ANOVA) with Tukey’s HSD post hoc analysis test was used to determine significant differences within groups. A p<0.05 was considered to be significant. All statistical testing was performed using Prism (GraphPad Software, La Jolla, California).

[0083] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.

[0084] References

[0085] (1) Holden, G. Thermoplastic Elastomers. In Applied Plastics Engineering Handbook; Elsevier, 2024; pp 97-113. https: / / doi.org / 10.1016 / B978-0-323-88667-3.00020-5.

[0086] (2) Satya, S. K.; Sreekanth, P. S. R. An Experimental Study on Recycled Polypropylene and High-Density Polyethylene and Evaluation of Their Mechanical Properties. Mater. Today Proc. 2020, 27, 920-924. https: / / doi.Org / 10.1016 / j.matpr.2020.01.259.2025-017-01

[0087] (3) Diggle, A.; Walker, T. R. Environmental and Economic Impacts of Mismanaged Plastics and Measures for Mitigation. Environments 2022, 9 (2), 15. https: / / doi.org / 10.3390 / environments9020015.

[0088] (4) Ryan, P. G. Entanglement of Birds in Plastics and Other Synthetic Materials. Mar. Pollut. Bull. 2018, 135, 159-164. https: / / d0i.0rg / l 0.1016 / j .marpolbul.2018.06.057.

[0089] (5) Garcia Rellan, A.; Vazquez Ares, D.; Vazquez Brea, C.; Francisco Lopez, A.; Bello Bugallo, P. M. Sources, Sinks and Transformations of Plastics in Our Oceans: Review, Management Strategies and Modelling. Sci. Total Environ. 2023, 854, 158745. https: / / d0i.0rg / l 0.1016 / j .scitotenv.2022.158745.

[0090] (6) Schiavo, S.; Oliviero, M.; Chiavarini, S.; Dumontet, S.; Manzo, S. Polyethylene, Polystyrene, and Polypropylene Leachate Impact upon Marine Microalgae Dunaliella Tertiolecta. J. Toxicol. Environ. Health A 2021, 84 (6), 249—260. https: / / d0i.0rg / l 0.1080 / 15287394.2020.1860173.

[0091] (7) Gupta, P.; Mahapatra, A.; Suman, A.; Ray, S. S.; Malafaia, G.; Singh, R. K. Polystyrene Microplastics Disrupt Female Reproductive Health, and Fertility via Sirtl Modulation in Zebrafish (Danio Rerio). J. Hazard. Mater. 2023, 460, 132359. https: / / doi.org / 10.1016 / jjhazmat.2023.132359.

[0092] (8) Prata, J. C.; Da Costa, J. P.; Lopes, L; Duarte, A. C.; Rocha-Santos, T. Environmental Exposure to Microplastics: An Overview on Possible Human Health Effects. Sci. Total Environ. 2020, 702, 134455. https: / / doi.Org / 10.1016 / j.scitotenv.2019.134455.

[0093] (9) Dickens, F. The Citric Acid Content of Animal Tissues, with Reference to Its Occurrence in Bone and Tumour. Biochem. J. 1941, 35 (8-9), 1011-1023. https: / / doi.org / 10.1042 / bj0351011.2025-017-01

[0094] (10) Yang, J.; Webb, A. R.; Pickerill, S. J.; Hageman, G.; Ameer, G. A. Synthesis and Evaluation of Poly(Diol Citrate) Biodegradable Elastomers. Biomaterials 2006, 27 (9), 1889-1898. https: / / doi.Org / 10.1016 / j.biomaterials.2005.05.106.

[0095] (11) Chung, E. J.; Sugimoto, M. J.; Ameer, G. A. The Role of Hydroxyapatite in Citric Acid-Based Nanocomposites: Surface Characteristics, Degradation, and Osteogenicity in Vitro. Acta Biomater. 2011, 7 (11), 4057-4063. https: / / doi.Org / 10.1016 / j.actbio.2011.07.001.

[0096] (12) Qiu, H.; Yang, J.; Kodali, P.; Koh, J.; Ameer, G. A. A Citric Acid-Based Hydroxyapatite Composite for Orthopedic Implants. Biomaterials 2006, 27 (34), 5845-5854. https: / / doi.Org / 10.1016 / j.biomaterials.2006.07.042.

[0097] (13) Wan, L.; Lu, L.; Zhu, T.; Liu, Z.; Du, R.; Luo, Q.; Xu, Q.; Zhang, Q.; Jia, X. Bulk Erosion Degradation Mechanism for Poly(l,8-Octanediol- Co -Citrate) Elastomer: An In Vivo and In Vitro Investigation. Biomacromolecules 2022, 23 (10), 4268-4281. https: / / doi.org / 10.1021 / acs.biomac.2c00737.

[0098] (14) Masehi-Lano, J. J.; Chung, E. J. Engineering Citric Acid-Based Porous Scaffolds for Bone Regeneration. In Biomaterials for Tissue Engineering; Chawla, K., Ed.; Methods in Molecular Biology; Springer New York: New York, NY, 2018; Vol. 1758, pp 1-10. https: / / d0i.0rg / l 0.1007 / 978-1 -4939-7741 -3_1.

[0099] (15) Chung, E. J.; Qiu, H.; Kodali, P.; Yang, S.; Sprague, S. M.; Hwong, J.; Koh, J.; Ameer, G. A. Early Tissue Response to Citric Acid-Based Micro- and Nanocomposites. J. Biomed. Mater. Res. A 2011, 96A (1), 29-37. https: / / doi.Org / 10.1002 / jbm.a.32953.

[0100] (16) Dayashankar, C.; Deepika, P.; Siddaramaiah, B. Clinical and Radiographic Evaluation of Citric Acid-Based Nano Hydroxyapatite Composite Graft in the Regeneration of Intrabony Defects - A Randomized Controlled Trial. Contemp. Clin. Dent. 2017, 8 (3), 380. https: / / doi.org / 10.4103 / ccd.ccd_213_17.2025-017-01

[0101] (17) Kramer, R. H.; Raza, M. A.; Gedde, U. W. Degradation of Poly(Ethylene- Co-Methacrylic Acid)-Calcium Carbonate Nanocomposites. Polym. Degrad. Stab. 2007, 92 (10), 1795-1802. https: / / d0i.0rg / l 0.1016 / j .polymdegradstab.2007.07.006.

[0102] (18) Al Omari, M. M. H.; Rashid, I. S.; Qinna, N. A.; Jaber, A. M.; Badwan, A. A. Calcium Carbonate. In Profiles of Drug Substances, Excipients and Related Methodology; Elsevier, 2016; Vol. 41, pp 31-132. https: / / doi.org / 10.1016 / bs.podrm.2015.ll.003.

[0103] (19) Widyastuti, S.; Pramushinta, I. A. Mineral Contents and Their Solubility on Calcium Carbonat Calcite Nanocrystals from Cockle Shell Powder ( Anadara Granosa Linn). J. Phys. Conf. Ser. 2018, 983, 012164. https: / / doi.Org / 10.1088 / 1742-6596 / 983 / l / 012164.

[0104] (20) Zhu, Y.; Chen, D.; Yu, X.; Liu, R.; Liao, Y. Properties of Cementitious Materials Utilizing Seashells as Aggregate or Cement: Prospects and Challenges. Materials 2024, 17 (5), 1222. https: / / doi.org / 10.3390 / mal7051222.

[0105] (21) Tagliarolo, M.; Clavier, J.; Chauvaud, L.; Grail, J. Carbon Emission Associated with Respiration and Calcification of Nine Gastropod Species from the Intertidal Rocky Shore of Western Europe. Mar. Biol. 2013, 160 (11), 2891-2901. https: / / doi.org / 10.1007 / s00227-013-2279-4.

[0106] (22) Chamas, A.; Moon, H.; Zheng, J.; Qiu, Y.; Tabassum, T.; Jang, J. H.; Abu- Omar, M.; Scott, S. L.; Suh, S. Degradation Rates of Plastics in the Environment. ACS Sustain. Chem. Eng. 2020, 8 (9), 3494-3511. https: / / doi.org / 10.1021 / acssuschemeng.9b06635.

[0107] (23) Jeong, C. G.; Hollister, S. J. Mechanical, Permeability, and Degradation Properties of 3D Designed Poly(l,8 Octanediol- Co -citrate) Scaffolds for Soft Tissue Engineering. J. Biomed. Mater. Res. B Appl. Biomater. 2010, 93B (1), 141-149. https: / / d0i.0rg / l 0.1002 / jbm.b.31568.

[0108] (24) Ara, M.; Watanabe, M.; Imai, Y. Effect of Blending Calcium Compounds on Hydrolytic Degradation of Poly(Dl-Lactic Acid-Co-Gly colic Acid). Biomaterials 2002, 23 (12), 2479-2483. https: / / doi.org / ! 0.1016 / S0142-9612(01)00382-9.2025-017-01

[0109] (25) Wang, B.; Wang, X.; Xu, H.; Fu, W.; Kong, L. Effect of Bubble and Void Defects on Properties of Structural Armor Composites. J. Phys. Conf. Ser.2023, 2460 (1), 012137. https: / / doi.Org / 10.1088 / 1742-6596 / 2460 / l / 012137.

[0110] (26) Chung, E. J.; Sugimoto, M.; Koh, J. L.; Ameer, G. A. Low-Pressure Foaming: A Novel Method for the Fabrication of Porous Scaffolds for Tissue Engineering. Tissue Eng. PartC Methods 2012, 18 (2), 113-121. https: / / doi.org / 10.1089 / ten.tec.2011.0289.

[0111] (27) Gewert, B.; Plassmann, M. M.; MacLeod, M. Pathways for Degradation of Plastic Polymers Floating in the Marine Environment. Environ. Sci. Process. Impacts 2015, 17 (9), 1513-1521. https: / / d0i.0rg / l 0.1039 / C5EM00207 A.

[0112] (28) Fu, S.-Y.; Feng, X.-Q.; Lauke, B.; Mai, Y.-W. Effects of Particle Size, Particle / Matrix Interface Adhesion and Particle Loading on Mechanical Properties of Particulate-Polymer Composites. Compos. Part B Eng. 2008, 39 (6), 933-961. https: / / d0i.0rg / l 0.1016 / j .compositesb.2008.01.002.

[0113] (29) Choi, W. Y.; Kang, D. H.; Lee, S. Y.; Lee, H. Y. High Quality Biodiesel from Marine Microalga, Scenedesmus Sp. through in Situ Acid Transesterification. J. Chem. Technol. Biotechnol. 2015, 90 (7), 1245-1252. https: / / doi.org / 10.1002 / jctb.4423.

[0114] (30) Gour, R. S.; Chawla, A.; Singh, H.; Chauhan, R. S.; Kant, A. Characterization and Screening of Native Scenedesmus Sp. Isolates Suitable for Biofuel Feedstock. PLOS ONE 2016, 11 (5), e0155321. https: / / doi.org / 10.1371 / joumal.pone.0155321.

[0115] (31) Prieto-Guevara, M.; Alarcon-Fumieles, J.; Jimenez-Velasquez, C.; Hernandez- Julio, Y.; Espinosa-Araujo, J.; Atencio-Garcia, V. Cryopreservation of the Microalgae Scenedesmus Sp. Cells 2023, 12 (4), 562. https: / / doi.org / 10.3390 / cellsl2040562.

[0116] (32) Morrison, E.; Shipman, A.; Shrestha, S.; Squier, E.; Stack Whitney, K. Evaluating The Ocean Cleanup, a Marine Debris Removal Project in the North Pacific Gyre, Using SWOT Analysis. Case Stud. Environ. 2019, 3 (1), 1-6. https: / / doi.org / 10.1525 / cse.2018.001875.2025-017-01

[0117] (33) Wood, L. A,; Bullman, G. W.; Decker, G. E. Modulus of Natural Rubber Cross-Linked by Dicumyl Peroxide. I. Experimental Observations. J. Res. Natl. Bur. Stand. Sect. Phys. Chem. 1972, 76A (1), 51. https: / / doi.org / 10.6028 / jres.076A.006.

[0118] (34) Myhre, M.; Saiwari, S.; Dierkes, W.; Noordermeer, J. RUBBER RECYCLING: CHEMISTRY, PROCESSING, AND APPLICATIONS. Rubber Chem. Technol.2012, 85 (3), 408—449. https: / / doi.org / 10.5254 / rct.12.87973.

[0119] (35) Gane, P. A. C.; Ridgway, C. J. Moisture Pickup in Calcium Carbonate Coating Structures: Role of Surface and Pore Structure Geometry. Nord. Pulp Pap. Res. J. 2009, 24 (3), 298-308. https: / / doi.org / 10.3183 / nppij-2009-24-03-p298-308.

[0120] (36) Marcilia, A.; Garcia-Quesada, J. C.; Ruiz-Femenia, R.; Beltran, M. I. Crosslinking of Rotational Molding Foams of Polyethylene. Polym. Eng. Sci. 2007, 47 (11), 1804— 1812. https: / / d0i.0rg / l 0.1002 / pen.20880.

[0121] (37) Li, H.; Liu, Y.; Chen, Q.; Jin, L.; Peng, R. Research Progress of Zebrafish Model in Aquatic Ecotoxicology. Water 2023, 15 (9), 1735. https: / / doi.org / 10.3390 / wl5091735.

[0122] (38) Rothenbucher, T. S. P.; Ledin, J.; Gibbs, D.; Engqvist, H.; Persson, C.; Hulsart-Billstrom, G. Zebrafish Embryo as a Replacement Model for Initial Biocompatibility Studies of Biomaterials and Drug Delivery Systems. Acta Biomater. 2019, 100, 235-243. https: / / doi.Org / 10.1016 / j.actbio.2019.09.038.

[0123] (39) Kroeker, K. J.; Kordas, R. L.; Crim, R.; Hendriks, I. E.; Ramajo, L.; Singh, G. S.; Duarte, C. M.; Gattuso, J. Impacts of Ocean Acidification on Marine Organisms: Quantifying Sensitivities and Interaction with Warming. Glob. Change Biol. 2013, 19 (6), 1884— 1896. https: / / doi.org / 10.! 111 / gcb.12179.

Claims

2025-017-01WHAT IS CLAIMED IS:

1. A biodegradable composition comprising:a cross-linked polyester matrix; anda plurality of reinforcing particles dispersed within the cross-linked polyester matrix in a sufficient amount such that the biodegradable composition is configured to degrade in marine environments while maintaining structural integrity during use.

2. The biodegradable composition of claim 1 wherein the reinforcing particles include calcium-containing particles selected from the group consisting of calcium carbonate particles, calcium citrate particles, calcium chloride particles, calcium sulfate particles, hydroxyapatite particles, ground crustacean shell particles, ground mollusk shell particles, ground eggshell particles, and combinations thereof.

3. The biodegradable composition of claim 2, wherein the calcium-containing particles are calcium carbonate particles.

4. The biodegradable composition of claim 2, wherein the calcium-containing particles provide pH stabilization during degradation and enhance mechanical strength of the composition compared to an analogous composition not including the plurality of calcium-containing particles.

5. The biodegradable composition of claim 1, wherein the cross-linked polyester matrix comprises poly(l,8-octanediol-co-citrate) (POC) and optionally further comprises a polysaccharide component selected from the group consisting of alginate, chitosan, and combinations thereof.

6. The biodegradable composition of claim 1, wherein the reinforcing particles are derived from natural sources.

7. The biodegradable composition of claim 6, wherein the natural sources are selected from the group consisting of seashells, eggshells, crustaceans, snail shells, seaweed, bamboo, wood, rice, wheat, paper, and combinations thereof.2025-017-018. The biodegradable composition of claim 1, wherein the reinforcing particles are present in a concentration ranging from 1% to 90% by weight of the biodegradable composition.

9. The biodegradable composition of claim 1, wherein the reinforcing particles are present in a concentration ranging from 5% to 50% by weight of the biodegradable composition.

10. The biodegradable composition of claim 1, wherein the composition exhibits biocompatibility with marine microorganisms.

11. The biodegradable composition of claim 1 , wherein the composition has an elastic modulus from about 0.5 to about 10 MPa prior to degradation.

12. The biodegradable composition of claim 1, wherein the composition is formed into a functional article selected from the group consisting of beverage holders, packaging materials, and single-use containers.

13. The biodegradable composition of claim 1, further comprising additives selected from antioxidants, plasticizers, and stabilizers to optimize mechanical performance and degradation rates.

14. The biodegradable composition of claim 1, wherein the plurality of reinforcing particles has an average particle size of less than 500 microns to optimize dispersion and interfacial adhesion within the cross-linked polyester matrix.

15. The biodegradable composition of claim 1, wherein the composition exhibits a degradation rate of 1 to 90% weight over a six-month period in simulated ocean water.

16. The biodegradable composition of claim 1, wherein the cross-linked polyester matrix comprises a network of ester bonds formed by polycarboxylic acid and diols selected to optimize the degree of cross-linking to control elasticity and tensile strength.

17. The biodegradable composition of claim 1, wherein the cross-linked polyester matrix includes a component selected from the group consisting of poly-L-lactic acid (PLLA),2025-017-01polyglycolic acid (PGA), poly(lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL), and combinations thereof.

18. The biodegradable composition of claim 1, further including pores of controlled size and distribution, the pores being formed during a mixing process to enhance biodegradability without compromising structural integrity.

19. The biodegradable composition of claim 1, wherein the reinforcing particles include plant-derived particles selected from the group consisting of seaweed particles, bamboo particles, wood particles, rice particles, wheat particles, paper particles, and combinations thereof.

20. The biodegradable composition of claim 19, wherein the plant-derived particles have an average particle size of from about 1 micron to about 200 microns.

21. The biodegradable composition of claim 1, wherein the reinforcing particles include ground crustacean shell particles selected from the group consisting of ground shrimp shells, ground crab shells, ground lobster shells, and combinations thereof.

22. The biodegradable composition of claim 21, wherein the ground crustacean shell particles comprise both calcium carbonate and chitin.

23. The biodegradable composition of claim 1, further comprising a polysaccharide component.

24. The biodegradable composition of claim 23, wherein the polysaccharide component is selected from the group consisting of alginate, chitosan, chitin, cellulose, starch, and combinations thereof.

25. The biodegradable composition of claim 23, wherein the polysaccharide component comprises alginate.

26. The biodegradable composition of claim 25, wherein the alginate is sodium alginate.2025-017-0127. The biodegradable composition of claim 25, wherein the alginate is ionically crosslinked with calcium ions to form an egg-box structure.

28. The biodegradable composition of claim 25, wherein the alginate is present in an amount from about 0.1 to about 10 weight percent of the biodegradable composition.

29. The biodegradable composition of claim 25, wherein the alginate has a molecular weight from about 12,000 Da to about 40,000 Da.

30. The biodegradable composition of claim 23, wherein the polysaccharide component comprises chitosan.

31. The biodegradable composition of claim 30, wherein the chitosan has a degree of deacetylation of at least 70%.

32. The biodegradable composition of claim 30, wherein the chitosan is present in an amount from about 0.1 to about 10 weight percent of the biodegradable composition.

33. The biodegradable composition of claim 23, wherein the polysaccharide component comprises both alginate and chitosan.

34. A method for forming a biodegradable composition, the method comprising: synthesizing a polyester pre-polymer by reacting a polycarboxylic acid with a diol at an elevated temperature; combining the polyester pre-polymer with reinforcing particles; and thermally curing the combination to form a cross-linked polyester matrix with the reinforcing particles dispersed therein.

35. The method of claim 34, wherein the poly carboxylic acid is citric acid and the diol is 1,8-octanediol.

36. The method of claim 34, wherein the elevated temperature is from about 140°C to about 180°C.2025-017-0137. The method of claim 34, wherein the reinforcing particles are selected from the group consisting of calcium carbonate particles, ground shell particles, plant-derived particles, and combinations thereof.

38. The method of claim 34, further comprising dissolving the polyester pre-polymer in ethanol prior to combining with the reinforcing particles.

39. The method of claim 34, wherein thermally curing comprises heating at a temperature from about 60°C to about 100°C for about 24 to about 96 hours.

40. The method of claim 34, further comprising adding a polysaccharide solution to the polyester pre-polymer, wherein the polysaccharide is selected from the group consisting of alginate, chitosan, and combinations thereof.

41. The method of claim 40, wherein the polysaccharide solution is an aqueous solution of sodium alginate having a concentration of from about 1% to about 10% by weight.

42. The method of claim 40, wherein calcium ions from calcium-containing reinforcing particles ionically crosslink with the polysaccharide to form a dual-crosslinked network.

43. The method of claim 34, wherein the reinforcing particles are present in an amount from about 5% to about 50% by weight of the biodegradable composition.

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