Plant-based antibacterial polymer nanocomposite coated dental implant and a method for its production by electrospray deposition (ESD)

Abstract

Thanks to the dental implant subject to the invention with antibacterial surface, infections and wounds caused by dental implants in the mouth are prevented. The surface of this implant is coated with antibacterial polymer nanocomposite film material containing silver nanoparticles and plant extracts produced by green synthesis using electrospray deposition (ESD), thus providing antibacterial and anti-cancer properties to the surface of the implant. Thanks to the green nano composite used in the production of dental implants subject to the invention, the implant contains antioxidant properties, vitamins and minerals.

Description

[0001] PLANT-BASED ANTIBACTERIAL POLYMER NANOCOMPOSITE COATED DENTAL IMPLANT AND A METHOD FOR ITS PRODUCTION BY ELECTROSPRAY DEPOSITION (ESD)

[0002] Technical Field

[0003] The invention relates to a dental implant coated with antibacterial polymer nanocomposite film material containing nanoparticles and plant extracts produced by green synthesis and to the production method of this implant. The surfaces of said dental implants are coated using the electrospray deposition (ESD) method. Thanks to the herbal structures used in the production of the dental implant subject to the invention, the dental implant has both antimicrobial properties and rich content in terms of antioxidants, vitamins and minerals.

[0004] Background Art

[0005] Oral health is critical in terms of the immune system and maintaining body balance. Especially dental health is directly related to many diseases occurring in the body. Dental health contributes to proper chewing of food and appearance. For this reason, it is of great importance to treat the teeth damaged due to various reasons such as decay and fracture appropriately. The canal treatment and fillings preferred in dental treatments are applied in cases where tooth loss is preventable. In cases where tooth loss is inevitable, dental implants are applied to prevent the displacement of other teeth in the jawbone and to enable the patient to perform important activities such as eating and speaking.

[0006] Dental implants are applied where tooth loss has occurred. The implants placed at the site of tooth loss are usually screws made of titanium and act as a kind of tooth root. Artificial teeth that resemble the real tooth structure are placed on these implants implanted in the jawbone. This prevents the problems that may be caused by tooth loss faced by the patient. The number of implants applied to the patient may vary according to the patient's tooth loss and the suitability of the orthopaedic structure of the jawbone. Although dental implants allow the patient to continue their life comfortably, they also bring many problems with them. The most important problems of dental implants are infections and wounds in the gingiva. In addition, poor osseointegration properties of the implant cause the application to fail. Therefore, it is of great importance that the implant surfaces are antibacterial and biocompatible. One of the methods used to improve implant surfaces is coating. However, the content of the coating material, its mechanical strength and compatibility with living tissue are vital for the success of the implant. In the production of metallic nanoparticles added to metallic materials used in the health field to provide antibacterial properties, infection and unsuccessful osseointegration occur due to excessive toxic contents and insufficient biocompatibility of metallic parts. It is possible to increase the antibacterial properties and wear and corrosion resistance of metallic materials used in the health field, especially dental implants, and to reduce infection and wound-like irritations with green bio-nano polymer films. However, the current technique has deficiencies in green bio-nano polymer film applications.

[0007] One study in the known state of the art utilised electrospray to form photocatalytic TiO2 coatings and investigated their antibacterial and antibiofilm capacities [1]. Electrospray utilises TiO2 anatase nanoparticles prepared by a sol-gel method that forms stable suspensions of positively charged particles ( potential+22.3±3.7mV). However, the chemical content of the structures used in the surface coating may cause toxic effects for the patient.

[0008] In another state-of-the-art study, 0.2 mol% and 0.3 mol% Ag-doped hydroxyapatite (HA) powders are synthesised by precipitation method [2], HA powders combined with Ag are deposited on metallic surfaces by electrospray deposition (ESD) technique. Heat treatments are carried out at 500, 700 and 900 °C for coated 316L stainless steel (SS) and commercially pure titanium (Ti) substrates. However, the need for very high-temperature values in this study prevents the cost and widespread production of the process steps described.

[0009] The limitations and inadequacies of the solutions in the current technique, the lack of use of green bio-nano structures in current dental implant applications, the chemical content of the preferred structures in surface coatings and the need for very high temperature values have made it necessary to develop in this field. Brief Description and Objectives of the Invention

[0010] The invention discloses a dental implant coated with antibacterial polymer nanocomposite film material containing silver nanoparticles and plant extracts produced by green synthesis and the production method of this implant. The electrospray deposition (ESD) method is used for the coating of the dental implant subject to the invention.

[0011] The aim of the invention is to provide a dental implant that will not cause infection and wounds in the patient's mouth after application. By coating the surface of the dental implant mentioned in the invention with antibacterial polymer nanocomposite film material containing nanoparticles and plant extracts produced by green synthesis, any bacterial infection in the area where the implant is applied is prevented. In addition, the plant extracts ensure that the dental implant's surface has anti-cancer properties.

[0012] Another purpose of the invention is to provide a natural surface coating for dental implants. The surface of the dental implant subject to the invention is coated with silver nanoparticles prepared using hemp seed and St John's wort extracts, which have antibacterial properties. This enables the part of the dental implant in contact with the inner surface of the mouth to have antibacterial properties. Thanks to the antibacterial properties endowed to the dental implant subject to the invention, bacterial infections and wounds that occur after the implant is placed in the patient's mouth are prevented.

[0013] Another aim of the invention is to provide a dental implant with high chemical stability and mechanical strength. The stability and mechanical strength of the surface of the dental implant subject to the invention are increased by the high stability in water of the silver nanoparticles prepared by green methods.

[0014] Description of the Figures

[0015] Figure 1 : Titanium substrate images a) before and b) after coating

[0016] Figure 2: Nanosilver particles (white coloured and round particles) dispersed in the fibre in the electrospray coating structure Figure 3: Inhomogeneously distributed nano silver particles (white coloured particles) on the dip coating surface Figure 4: Coating material structure

[0017] Detailed Description of the invention

[0018] The invention relates to a dental implant with a surface coating of antibacterial polymer containing silver nanoparticles and plant extracts and to a method of manufacturing the implant. The dental implant subject to the invention is coated with antibacterial polymer nanocomposite film material containing silver nanoparticles and plant extracts produced by green synthesis using the electrospray deposition (ESD) method. Said surface coating contains 8% PVA solution and 0.05%, 0.1%, 0.3% or 0.5% silver nanoparticles. The green nanocomposite used in the invention also contains antioxidants, vitamins and minerals.

[0019] The preparation method of the dental implant subject to the invention includes the following process steps: i. synthesis of silver nanoparticles using 8 mL hemp seed and St John's wort extracts, ii. production of coating solution by adding synthesised silver nanoparticles to 8% PVA solution, iii. adding 1 mL isopropyl alcohol to the coating solution, iv. coating the surface with 5 mL of coating solution for 35 minutes at a speed of 0.020 mL / min, 15 HV power, by the electrospray deposition method

[0020] An application of the preparation method of the dental implant subject to the invention comprises the following process steps: i. synthesis of silver nanoparticles using 8 mL hemp seed and St John's wort extracts, ii. production of coating solution by adding 0.05% silver nanoparticles synthesised in 8% PVA solution, iii. adding 1 mL isopropyl alcohol to the coating solution, iv. coating the surface with 5 mL of coating solution for 35 minutes at a speed of 0.020 mL / min, 15 HV power, by the electrospray deposition method

[0021] Another application of the preparation method of the dental implant subject to the invention comprises the following process steps: i. synthesis of silver nanoparticles using 8 mL hemp seed and St John's wort extracts, ii. production of coating solution by adding 0.1% silver nanoparticles synthesised in 8% PVA solution, iii. adding 1 mL isopropyl alcohol to the coating solution, iv. coating the surface with 5 mL of coating solution for 35 minutes at a speed of 0.020 mL / min, 15 HV power, by the electrospray deposition method

[0022] Another application of the preparation method of the dental implant subject to the invention comprises the following process steps: i. synthesis of silver nanoparticles using 8 mL hemp seed and St John's wort extracts, ii. production of coating solution by adding 0.3% silver nanoparticles synthesised in 8% PVA solution, iii. adding 1 mL isopropyl alcohol to the coating solution, iv. coating the surface with 5 mL of coating solution for 35 minutes at a speed of 0.020 mL / min, 15 HV power, by the electrospray deposition method

[0023] Another application of the preparation method of the dental implant subject to the invention comprises the following process steps: i. synthesis of silver nanoparticles using 8 mL hemp seed and St John's wort extracts, ii. production of coating solution by adding 0.5% silver nanoparticles synthesised in 8% PVA solution, iii. adding 1 mL isopropyl alcohol to the coating solution, iv. coating the surface with 5 mL of coating solution for 35 minutes at a speed of 0.020 mL / min, 15 HV power, by the electrospray deposition method The polymer nanocomposite coating material mentioned in the invention is coated on TI6AI4V alloy, one of the most widely used biomaterials, by the electrospray method. Before coating, 2mm thick and 1 .5x1 ,5mm wide square substrates are cut into pieces by laser cutting. The surfaces of the cut substrates are first sanded and then roughened by etching with an etching solution. Hence, the surface is made ready for the coating process. The etching solution is prepared with 10 ml water, 5 ml nitric acid and 5 ml sulphuric acid.

[0024] The substrates with surface preparation processes completed are placed on the electrospray device panel, and the coating processes are carried out. A coating solution is prepared by mixing a mixture of hemp seed extracts, St. John's wort, rosemary, and cherry laurel leaves with nanosilver PVA produced via green synthesis. When nanosilver is added to the prepared solutions at 0.05%, 0.1%, 0.3% and 0.5%, antibacterial properties are obtained at all ratios. 8% PVA is used in coating solutions. The use of 8% PVA makes the coating smoother and more homogenous. In order for the prepared polymer solutions to be homogenously mixed and sprayed from the needle without precipitation during electrospray coating, 1 ml isopropyl alcohol is added to each solution. The coating processes are carried out with 5 mL solution for 35 minutes at a speed of 0.020 mL / min and 15 HV power. As the coating time increases, the coating solution is kept at 5 mL, and the coating time is kept at 35 minutes due to the roughening of the coating surfaces and inhomogeneous spraying of nanoparticles on the substrates. The coating process is carried out by spraying the solutions from the syringe onto the metal base. The working scheme of the electrospray deposition technique used as a coating method includes a high-voltage power supply, a syringe with metallic capillaries, a syringe pump and a grounded collector. The working process of the electrospray deposition technique involves filling a syringe with a polymeric solution followed by the application of a metallic needle (nozzle) and a high electric field, which allows a charged liquid jet to be dispersed into droplets in such a way that small particles are formed, and a narrow size distribution and particles are collected in the collector.

[0025] In the invention, a hemp seed and St John's wort extract mixture with a volume of 8 ml is obtained by using 25 g of plant. Silver nanoparticles of 34 nm in size are prepared with this plant extract mixture. The use of a higher proportion of plant extract in the invention enables the synthesised nano silver to show at least 1000 times higher antibacterial effect.

[0026] Elektrospray biriktirme ybntemi ile yapilan yuzey kaplamasi 27 m kaplama kalmligma sahiptir. This coating surface's antibacterial, thermal, mechanical and chemical stability properties are not the same as the films produced by the solventcasting method. Before coating, 1 mL of isopropyl alcohol is used in the coating solution. Hence, a more homogeneous and electrostatically stable solution is prepared, and the coating is successfully carried out.

[0027] The surface coating of the dental implant subject to the invention provides an antibacterial effect, higher biocompatibility, thermal, mechanical and chemical stability properties, anti-cancer effect and low toxic effect to this implant. The coating solution (polymer nanocomposite) consisting of silver nanoparticles produced with a mixture of hemp seed and St John's wort extracts and polyvinyl alcohol, a natural polymer, is coated on the surface of the dental implant by the electrospray deposition method. For the coating, both hemp seed and St. John's wort extracts are used as a mixture to ensure that the synthesised silver nanoparticles and the coating surface produced have higher antibacterial effects and lower toxic properties. In addition, the coating solution produced for the coating is produced with polyvinyl alcohol (PVA) polymer, which is biocompatible and does not generate waste.

[0028] The use of silver nanoparticles produced by green synthesis in the production of polymer-based materials in the invention enables the production of antibacterial and biodegradable materials with cleaner content, low energy consumption and production cost. The plant species and quantities used in green synthesis affect the quality of the synthesised nanoparticles. Plant extracts provide bio (green) synthesis of nanoparticles thanks to their biomolecules containing many different hydroxyl groups (-(OH) (carboxy, hydroxy, ortho-dihydroxy, amino-, catechol). Plant biomolecules such as terpenoids, phenolic acids, amino acids, enzymes, alkaloids, flavonoids, polyphenols, tannins, carbohydrates, phenols, saponins or proteins stabilise and reduce metal ions (M+). These biomolecules are also called secondary metabolites and generally work as both reductants and stabilisers in the green synthesis mechanism. Thus, they prevent the aggregation of synthesised metallic nanoparticles. Green synthesis of metal nanoparticles using plant extracts takes place in 3 steps. In the first step, metal ions are reduced by hydroxyl groups in biomolecules. In the second step, the reduced nanoparticles' thermodynamic stability is increased and brought together. Finally, after the growth stage, the nanoparticles form their own shape. As a result of the reduction of metal ions with active metabolites, nanoparticles are precipitated in solution by centrifugation, and the precipitate is separated from the solution by filtration and dried after washing with alcohol. Thus, the synthesised nanoparticles can be obtained as powder. Concentrations of plant extracts, pH of solutions, pressure, temperature, metallic ion concentration and amount of light are important factors determining the size, distribution and concentration of green synthesised nanoparticles. Different organic acids and phenolic groups exist in every plant variety in nature. These acids and biomolecules in the plants used in the invention are listed as follows: hemp seeds contain carboxylic acids, antioxidants, flavonoids and canniprene; St John's wort contains flavonoids, antioxidants, hypericins, hyperforins, mono- and polysaccharides, and phenolic acids. When these components in different plant extracts are used together, their pharmacokinetic and therapeutic effects increase. Although this mechanism cannot be fully explained, the increase in the formation of C-O, C-H and C-N bonds with (-OH) groups in different phenolic and carboxylic groups is shown as one of the reasons for the higher effects of the use of plant extracts in mixtures. In addition, the plant extracts used in the invention can also double the nanocomposite film's mechanical properties. In addition, since both plants are known to have antioxidant properties, using them together provides the coating to have a higher antibacterial effect. Finally, since the water absorption capacity of the nanocomposite film used in the surface coating is doubled, the surface coating film produced is more durable in aqueous environments.

[0029] In the invention, electrospray coating provides a more homogeneous distribution of nano silver in the coating material. Thus, the same technical effects are observed in all coating areas. With electrospray deposition, equal thickness and roughness are obtained on the entire surface, while the thickness of the dip coating used in the current technique varies from one area to the other. Therefore, a homogenous surface coating is obtained by the electrospray deposition method used in the invention. In addition, electrospray deposition is a much more economical method than electro spin, physical vapour deposition (PVD), chemical vapour deposition (CVD), and chemical and electrochemical deposition methods. In addition, it is impossible to ensure the homogeneous and agglomeration-free dispersion of the nanoparticle on the coating surface in other methods in the present technique. Since the electrospray deposition method uses an electric field and the nanosilvers are conductive, each particle can be dispersed in the fibres and deposited on the surface without agglomeration. Additionally, the surfaces produced by electrospray coating show 100 times more effective antibacterial properties than those produced by the dip coatings method. This is because nano silvers are distributed closer to the surface and homogenously in electrospray coating. Finally, while it is sufficient to prepare 5 mL of solution for the electrospray coating method, it is necessary to prepare at least 30 mL of solution to coat the same surface in methods such as dip coating, which causes loss of raw material.

[0030] Extracts of St. John's wort and hemp seeds are used both in the green synthesis and in the coating material in the invention. Nanosilver is used in addition to the plant extract in the coating material produced in the invention. This provides at least 10,000 times higher antibacterial effect. The invention includes the production of nanocomposite coating material as well as the coating application and method. The invention can be used not only for titanium but also for all kinds of alloys, different types of metal biomaterials and even composite materials. With the ingredients and coating method used in the invention, micron-sized coatings with very high antibacterial effects and biocompatibility can be produced. In addition, the nanocomposite coating material produced shows an anti-cancer effect. The use of the electrospray method for coating also provides a more effective coating of implant surfaces. Plant extracts and green synthesised nanosilver provide antibacterial properties. Silver nanoparticles provide an anti-cancer effect. Plant extracts and natural polymer PVA support low toxic effects. The thermal and mechanical strengths of the nanocomposite coating produced with silver nanoparticles and plant extracts are increased. The coating material produced by electrospray coating is chemically stable and reduces toxicity by preventing the release of silver ions into the living environment. The antibacterial, non-toxic, anti-cancer effective, thermally and mechanically resistant and chemically stable coating is applied to metallic implants by the electrospray deposition method. Biocompatibility is increased. The coating surface, which is softer than the metal structure, prevents the formation of wounds and infections by causing less damage to the living tissue in the mouth.

[0031] The coating method and coating material used, the content and concentrations of this material also affect the coating quality. Coating in fibres ensures that nanosilver and plant extracts are more strongly trapped in the coating material. Thus, the coating can maintain its effects without degrading in the body. PVA is a cheaper biomaterial that is easy to produce and supply. Therefore, it is more economical in terms of both cost and ease of production. Thanks to the coating, the dental implant has antibacterial effects, biocompatibility, anti-cancer and low toxic effects. Hence, the metal materials used in the mouth or in the body bond more strongly with living tissue and the formation of infections and wounds that may occur in the surrounding tissue is prevented.

[0032] REFERENCES

[0033] [1] Jalvo B, Faraldos M, Bahamonde A, Rosal R. "Antibacterial surfaces prepared by electrospray coating of photocatalytic nanoparticles". Chemical Engineering Journal, Volume 334, 15 February 2018, Pages 1108-1118.

[0034] [2] Gokcekaya O, Webster TJ, Ueda K, Narushima T, Ergun C. "In vitro performance of Ag-incorporated hydroxyapatite and its adhesive porous coatings deposited by electrostatic spraying". Materials Science and Engineering: C, Volume 77, 1 August 2017, Pages 556-564

Claims

CLAIMS1. It is a dental implant with antibacterial properties characterised by its surface coating containing antibacterial polymer nanocomposite containing silver nanoparticles and plant extracts.

2. A dental implant according to claim 1 , characterised in that the implant is an alloy or metal biomaterial or composite.

3. A dental implant according to claim 1 or 2, characterised in that said surface coating comprises 8% PVA solution and 0.05%, 0.1%, 0.3% or 0.5% silver nanoparticles.

4. A method of preparing the dental implant with antibacterial properties, which is characterised by the following process steps: i. synthesis of silver nanoparticles using 8 mL hemp seed and St John's wort extracts, ii. production of coating solution by adding synthesised silver nanoparticles to 8% PVA solution, iii. adding 1 mL isopropyl alcohol to the coating solution, iv. coating the surface with 5 mL of coating solution for 35 minutes at a speed of 0.020 mL / min, 15 HV power, by the electrospray deposition method5. A method of preparing the dental implant with antibacterial properties according to claim 3, which is characterised by the following process steps: i. synthesis of silver nanoparticles using 8 mL hemp seed and St John's wort extracts, ii. production of coating solution by adding 0.05% silver nanoparticles synthesised in 8% PVA solution, iii. adding 1 mL isopropyl alcohol to the coating solution, iv. coating the surface with 5 mL of coating solution for 35 minutes at a speed of 0.020 mL / min, 15 HV power, by the electrospray deposition method6. A method of preparing the dental implant with antibacterial properties according to claim 3, which is characterised by the following process steps: i. synthesis of silver nanoparticles using 8 mL hemp seed and St John's wort extracts, ii. production of coating solution by adding 0.1% silver nanoparticles synthesised in 8% PVA solution, iii. adding 1 mL isopropyl alcohol to the coating solution, iv. coating the surface with 5 mL of coating solution for 35 minutes at a speed of 0.020 mL / min, 15 HV power, by the electrospray deposition method7. A method of preparing the dental implant with antibacterial properties according to claim 3, which is characterised by the following process steps: i. synthesis of silver nanoparticles using 8 mL hemp seed and St John's wort extracts, ii. production of coating solution by adding 0.3% silver nanoparticles synthesised in 8% PVA solution, iii. adding 1 mL isopropyl alcohol to the coating solution, iv. coating the surface with 5 mL of coating solution for 35 minutes at a speed of 0.020 mL / min, 15 HV power, by the electrospray deposition method8. A method of preparing the dental implant with antibacterial properties according to claim 3, which is characterised by the following process steps: i. synthesis of silver nanoparticles using 8 mL hemp seed and St John's wort extracts, ii. production of coating solution by adding 0.5% silver nanoparticles synthesised in 8% PVA solution, iii. adding 1 mL isopropyl alcohol to the coating solution, iv. coating the surface with 5 mL of coating solution for 35 minutes at a speed of 0.020 mL / min, 15 HV power, by the electrospray deposition method9. An antibacterial dental implant produced by a method according to any one of claims 3-7.

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