Modified Polyesters for Injectable Drug Delivery
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Solution Overview
Problem
Current biodegradable polymer-based carrier systems for controlled release of active ingredients face challenges such as complex degradation kinetics, acidic pH environments that can inactivate drugs, and difficulties in controlling release profiles, leading to inconsistent and unpredictable therapeutic outcomes.
Innovation Solution
The development of linear polyesters formed by esterification of dicarboxylic acids and polyhydric alcohols, which allow for the formation of polymers with free hydroxyl groups that can be covalently linked with active ingredients or fatty acids, enabling controlled release through enzymatic reactions and tailored lipophilicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If biodegradable polymer-based carrier systems are used for controlled release, then drug delivery is achieved, but complex degradation kinetics and acidic pH environments occur leading to difficult-to-control release profiles
Solution Approach 1:
The patent changes the chemical parameters of the polymer system by using polyesters formed from dicarboxylic acids and polyhydric alcohols with free hydroxyl groups, which can be covalently linked with active ingredients. This fundamental parameter change in polymer chemistry enables controlled enzymatic degradation and eliminates the autocatalytic hydrolysis problem that causes complex degradation kinetics and acidic microenvironments in conventional systems.
Solution Approach 2:
The invention creates a composite system where the polymer matrix combines hydrophilic and lipophilic characteristics through the presence of free hydroxyl groups that can be covalently linked with active ingredients or fatty acids. This composite structure at the molecular level provides both controlled enzymatic degradation and tailored lipophilicity, enabling reproducible release profiles without the harmful acidic microenvironment.
2Reliability
If conventional biodegradable polymers are used, then drug carrier function is provided, but acidic pH values inactivate active ingredients before release
Solution Approach 1:
The patent converts the potential harm of polymer degradation into a benefit by designing a system where enzymatic degradation produces neutral byproducts rather than acidic ones. The free hydroxyl groups in the polymer structure enable this beneficial transformation, allowing the degradation process to maintain physiological pH and protect active ingredients from inactivation.
Solution Approach 2:
The invention fundamentally changes the degradation chemistry parameter from autocatalytic hydrolysis (acidic) to enzymatic degradation (neutral). This parameter change in the degradation mechanism eliminates the generation of acidic microenvironments while maintaining the controlled release function.
3Reliability
If microparticles are used for drug delivery, then controlled release is achieved, but production complexity and incomplete syringe emptying occur
Solution Approach 1:
The patent changes the physical state parameter of the drug delivery system from solid microparticles to liquid or semi-solid injectable formulations. This parameter change enables direct injection without complex manufacturing processes while maintaining controlled release through the polymer's enzymatic degradation and the covalent linking of active ingredients.
Solution Approach 2:
The invention extracts the controlled release function from the complex microparticle structure and implements it through the chemical properties of the polymer system itself. The free hydroxyl groups and covalent linking provide intrinsic controlled release without requiring complex particle manufacturing processes.
4Reliability
If preformed solid implants are used, then drug delivery is achieved, but large cannula insertion and foreign body perception cause pain
Solution Approach 1:
The patent utilizes phase transition by providing the polymer system in a liquid or semi-solid state for injection, which then transitions to a solid depot in situ after injection. This phase transition enables delivery through small-gauge needles, eliminating the need for large cannulas and reducing patient discomfort while maintaining the drug delivery function.
Solution Approach 2:
The invention inverts the conventional approach by injecting a liquid/semi-solid formulation that forms a solid implant in situ, rather than inserting a preformed solid implant. This inversion of the physical state sequence improves ease of administration while achieving the same therapeutic outcome.
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
This approach allows for the creation of injectable implants with controlled and reproducible release profiles, avoiding the limitations of acidic degradation and improving the bioavailability of active ingredients by using modified poly(dicarboxylic acid multiol esters that can be directly injected and form stable depots in the body.
Implementation Method 1
linear polyesters formed by esterification of dicarboxylic acids and polyhydric alcohols
Implementation Method 2
free hydroxyl groups that can be covalently linked with active ingredients or fatty acids
Implementation Method 3
enabling controlled release through enzymatic reactions
Data Source
Figure 1
Figure 2
Figure 3a~3c
AI summary
The problem addressed by the invention was to show an alternative to the previously clinically used biodegradable polymers based on monomers having a hydroxycarboxylic acid structure. This problem was solved according to the invention by means of linear polyesters that are produced by esterifying dicarboxylic acids and multivalent alcohols (diols, trioles, or higher-valency alcohols) (figure 1). It was found that modified poly(dicarboxylic acid multiol esters) without further additives are suitable as injectable implants. The polymers can be directly injected without using an organic solvent. Furthermore, it was found that modified poly(dicarboxylic acid multiol esters) can be mixed with and injected with suitable biocompatible organic solvents or preformed as an implant. The carrier systems are used for the controlled release of active ingredient in human and veterinary medicine.