Thiolated Polymer Hydrogel for Reversible Vas Deferens Occlusion

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Solution Overview

Problem

Current male contraceptive methods, such as RISUG and Vasalgel, face challenges with irreversible occlusion and difficulty in infusion and redissolution, leading to complications and poor reversibility.

Innovation Solution

A polymer system comprising a water-soluble, partially thiolated poly(styrene-co-maleic acid) polymer and a cross-linking agent forms a hydrogel in situ within the vas deferens, using reversible thioester bonds that can be dissolved on demand with a cysteamine methyl ester solution, ensuring safe and reversible contraception.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If higher molecular weight poly(styrene-co-maleic acid) polymers are used to form Vasalgel, then contraceptive reliability is improved, but ease of operation deteriorates due to difficulty in infusion and redissolution

Engineering Contradiction:

Improvecontraceptive reliabilityVSAvoidease of infusion and redissolution

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The polymer system is divided into two separate components: a thiolated poly(styrene-co-maleic acid) polymer and a crosslinking agent. These components are administered separately and only form the contraceptive gel at the target site, combining the benefits of low molecular weight (ease of infusion) with crosslinked structure (contraceptive reliability).

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the molecular weight parameter from high (Vasalgel) to low (10,000-85,000 g/mol), making the polymer easier to infuse. Contraceptive reliability is then achieved through chemical crosslinking rather than relying on high molecular weight alone.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If RISUG or Vasalgel is used for vas occlusion, then contraceptive efficacy is improved, but reversibility deteriorates due to irreversible occlusion and tissue damage

Engineering Contradiction:

Improvecontraceptive efficacyVSAvoidreversibility

Core Design Contradiction:

ReliabilityVSEase of repair

Solution Approach 1:

The contraceptive gel is designed to be dynamic rather than static. The crosslinked network can be reversibly broken down by treating with a reducing agent (such as dithiothreitol or beta-mercaptoethanol) that cleaves the disulfide bonds, allowing the gel to dissolve and be flushed from the vas deferens, restoring fertility.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The polymer gel can be discarded (dissolved and removed) when no longer needed for contraception. The disulfide crosslinks can be broken and the polymer chains recovered in a dissolved state, enabling reversal of the contraceptive effect without permanent tissue damage.

Inventive Principle:

Principle #34Discarding and recovering

3Reliability

If viscous polymer material is infused into the narrow lumen of the vas deferens, then occlusion effectiveness is improved, but ease of operation worsens due to significant pressure requirements and post-operative complications

Engineering Contradiction:

Improveocclusion effectivenessVSAvoidease of infusion

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system separates the polymer and crosslinking agent into two components. Each component can be infused as a low-viscosity solution separately, avoiding the need to force viscous material through the narrow lumen. The gel forms only after both components are in place and begin to crosslink.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The polymer and crosslinking agent are infused in a preliminary state as soluble, low-viscosity solutions. The gelation occurs after infusion is complete, eliminating the need to infuse pre-formed viscous gel and reducing infusion pressure requirements.

Inventive Principle:

Principle #10Preliminary action

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 hydrogel effectively occludes the vas deferens to prevent sperm transport, is biocompatible, and can be readily dissolved to restore fertility, minimizing tissue damage and complications.

Implementation Method 1

using reversible thioester bonds that can be dissolved on demand with a cysteamine methyl ester solution

Methodology Applied

Scientific EffectThioester bond formation: Chemical Bonding

Implementation Method 2

The hydrogel effectively occludes the vas deferens to prevent sperm transport

Methodology Applied

Scientific EffectPhysical occlusion: Physical Containment

Implementation Method 3

can be readily dissolved to restore fertility, minimizing tissue damage and complications

Methodology Applied

Scientific EffectThioester bond cleavage: Chemical Bonding

Data Source

PatentUS20250332319A1Polymer system for forming a hydrogel

Publication Date: 2025.10.30 STELLENBOSCH UNIVERSITY

AI summary

A polymer system for forming a hydrogel and a male contraceptive method of reversibly occluding a vas deferens with the hydrogel are provided. The polymer system comprises a water-soluble and at least partially thiolated poly(styrene-co-maleic acid) polymer and a water-soluble cross-linking agent with suitable reactive functional groups at its ends which are configured to crosslink to the thiol groups of the thiolated poly(styrene-co-maleic acid) polymer, when aqueous solutions of the at least partially thiolated poly(styrene-co-maleic acid) polymer and cross-linking agent are combined to form the hydrogel in use. The hydrogel includes dynamic covalent bonds which can be broken with an appropriate solution to dissolve the hydrogel in situ.