Biodegradable NIR Capsules With Size-Controlled Poly(Amino Acid) Shells
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Solution Overview
Problem
Existing encapsulation methods for NIR absorbers, such as cyanine dyes, face challenges in achieving biodegradability, size control, mechanical strength, and stealth properties, limiting their application in biomedicine, particularly for photothermal therapy, photodynamic therapy, and fluorescence imaging.
Innovation Solution
A scalable interfacial polymerization method using poly(amino acids) to encapsulate NIR absorbers, forming capsules with controlled particle sizes below 1 μm, biodegradable shells, and stealth properties, suitable for aqueous dispersions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If inorganic nanoparticles (gold nanomaterials, carbon nanomaterials, metal sulfides, metal oxides) are used as NIR absorbers, then excellent NIR response is achieved, but biodegradability is lost and bioaccumulation risk increases
Solution Approach 1:
The patent changes the material composition parameter from inorganic nanoparticles to organic dyes (cyanine dyes, indocyanine green) encapsulated in poly(amino acid) capsules. This parameter change maintains the NIR absorption functionality while eliminating the bioaccumulation risk associated with inorganic materials, as the organic capsules are biodegradable and excretable.
Solution Approach 2:
The patent creates a composite system combining organic NIR absorbers (cyanine dyes, indocyanine green) with biodegradable poly(amino acid) capsules. This composite structure provides both the excellent NIR response of the dye and the biocompatibility/biodegradability of the polymer shell, resolving the contradiction between optical performance and biological safety.
2Object-affected harmful factors
If poly(amino acids) are used to encapsulate NIR absorbers, then biocompatibility and biodegradability are improved, but mechanical strength of the shell is reduced
Solution Approach 1:
The patent applies local quality by creating a crosslinked shell structure where the poly(amino acid) matrix provides biocompatibility and biodegradability, while the crosslinked network provides mechanical strength. The crosslinking density can be locally adjusted to optimize both biocompatibility and mechanical properties in different regions of the capsule shell.
Solution Approach 2:
The patent uses composite materials by incorporating crosslinking agents into the poly(amino acid) matrix, creating a dual-function shell that is both biocompatible and mechanically strong. The crosslinked polymer network acts as a reinforcement within the biodegradable matrix, resolving the contradiction between biological safety and structural integrity.
3Ease of manufacture
If coacervation method is used to encapsulate NIR absorbers, then encapsulation is achieved, but shell strength is reduced and water permeability increases
Solution Approach 1:
The patent changes the encapsulation method from coacervation to interfacial polymerization, fundamentally altering the shell formation mechanism. This parameter change results in a denser, stronger shell with lower water permeability, as interfacial polymerization creates a more compact polymer structure compared to the looser coacervate structure.
Solution Approach 2:
The patent replaces the physical coacervation mechanism with a chemical interfacial polymerization mechanism. This substitution allows for controlled shell formation with superior mechanical properties, as the chemical polymerization process creates strong crosslinked bonds within the shell structure, eliminating the weakness of physically aggregated coacervates.
4Adaptability or versatility
If amphiphilic block copolymers are used to form micelles, then NIR absorbers can be encapsulated, but shell strength is reduced and crosslinking is required for bio-stability
Solution Approach 1:
The patent extracts the need for crosslinking by using a different polymerization approach. Instead of forming micelles that require crosslinking for stability, the interfacial polymerization method directly produces stable capsules without additional crosslinking steps, eliminating the source of mechanical weakness while maintaining encapsulation capability.
Solution Approach 2:
The patent substitutes the micelle-based encapsulation system with an interfacial polymerization system. This replacement eliminates the need for crosslinking to achieve bio-stability, as the polymerization process itself creates a stable, strong shell structure that provides both encapsulation capability and mechanical integrity without additional chemical modifications.
5Use of energy by moving object
If classical organic NIR absorbers (cyanine dyes) are used, then high molar extinction coefficient is achieved, but encapsulation is required to prevent photo-bleaching and increase lifetime
Solution Approach 1:
The patent applies the nested doll principle by placing the cyanine dye molecule inside the poly(amino acid) capsule shell. This nested structure protects the sensitive dye from photo-bleaching and enzymatic degradation while maintaining its high molar extinction coefficient, thereby extending its lifetime in the body without sacrificing its optical properties.
Solution Approach 2:
The patent creates a composite system where the cyanine dye is encapsulated within the poly(amino acid) matrix. This composite structure protects the dye from environmental factors that cause photo-bleaching, while the dye maintains its high molar extinction coefficient, thus extending operational lifetime without compromising optical performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables efficient encapsulation of NIR absorbers in biocompatible capsules with controlled release and reduced bioaccumulation, enhancing therapeutic efficacy and diagnostic accuracy in medical applications.
Implementation Method 1
The shell comprises an oligo- or poly(amino acid), obtained by oligomerization or polymerization of at least one N-carboxy-anhydride monomer
Implementation Method 2
Near infrared (NIR) laser technology is gaining importance in non-invasive treatment of different diseases and in medical diagnostics, including photothermal therapy
Data Source
AI summary
A capsule comprising a polymeric shell surrounding a NIR absorber, the polymeric shell comprises a poly(amino acid) and is obtainable by interfacial polymerization of a N-carboxy-anhydride monomer according to general structure (I). The capsule is suitable for opto-medical applications such as phototherapies including photothermal therapy (PTT), photodynamic therapy (PDT), photo stimulated drug release and fluorescence medical imaging.