Core-Shell Microspheres for High-Loading Controlled Drug Release
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Solution Overview
Problem
Existing methods for encapsulating drugs in biodegradable polymers destabilize macromolecules due to harsh processing conditions, and there is a need to increase drug loading while maintaining a steady release profile, particularly for long-acting contraceptives like transdermal microneedle patches.
Innovation Solution
Microspheres with a core-shell design are developed, comprising a core with a first polymer and a therapeutic agent, surrounded by a substantially impermeable shell, allowing for high drug loading and a controlled, zero-order release profile over several months.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If harsh processing conditions (organic solvents, excess heat, homogenization) are used for encapsulating drugs in biodegradable polymers, then encapsulation efficiency is improved, but drug stability deteriorates
Solution Approach 1:
The patent replaces harsh mechanical processing methods (homogenization, sonication, high-speed agitation) with a gentle emulsion-based encapsulation process. The core-shell microsphere structure is formed through controlled emulsion formation and solvent evaporation, avoiding mechanical forces that destabilize macromolecules while maintaining high encapsulation efficiency.
Solution Approach 2:
The patent changes the processing parameters from harsh conditions (high heat, strong solvents, mechanical agitation) to mild conditions (ambient or controlled temperature, aqueous or biocompatible solvents, minimal agitation). The emulsion process allows encapsulation at controlled temperatures and with gentle mixing, preserving drug stability.
2Quantity of substance
If drug loading is increased in the polymer material, then therapeutic efficacy is improved, but release control becomes difficult
Solution Approach 1:
The patent divides the microsphere into distinct core and shell regions with different functions. The core contains the therapeutic agent at high concentration, while the shell provides controlled release functionality. This segmentation allows high drug loading in the core without compromising release control, as the shell acts as a rate-limiting barrier.
Solution Approach 2:
The patent applies different properties to different parts of the microsphere: the core has high drug concentration and permeability, while the shell has controlled permeability and degradation rate. This local differentiation of properties enables both high drug loading and controlled release, as each region performs its specific function optimally.
3Stability of the object's composition
If a substantially impermeable shell is added to achieve controlled release, then release control is improved, but device complexity increases
Solution Approach 1:
The patent uses a nested core-shell structure where the core (containing drug and first polymer) is embedded within the shell (second polymer). This nested architecture provides controlled release functionality while maintaining a relatively simple overall structure that can be manufactured in a single process step.
Solution Approach 2:
The patent employs composite polymer materials in the core and shell regions. The first polymer in the core and second polymer in the shell work together to provide both high drug loading capacity and controlled release. The composite structure leverages the complementary properties of different polymers to achieve dual functionality without excessive complexity.
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 microspheres achieve elevated drug loading and a consistent release rate, reducing initial burst release and providing a controlled drug delivery system with a steady release profile for up to 7 months.
Implementation Method 1
electrohydrodynamic (EHD) jetting process
Implementation Method 2
The core and shell solutions are sprayed through a coaxial needle and the solvent evaporates to form microspheres
Data Source
AI summary
The disclosure relates to microspheres comprising a core and a shell. More particularly the disclosure relates to microspheres for extended, controlled release of a poorly water-soluble therapeutic agent having a solubility in water of 50 μg/mL or less, the microsphere having a core comprising the therapeutic agent, and a substantially impermeable shell surrounding the core. Methods of making and using the microspheres are also provided.