Question

A water insoluble polymeric biomaterial can become water soluble \(\textit{in vivo}\) by which of the following mechanisms?

• A. Cleavage of crosslinks between water soluble polymer chains
• B. Cleavage of side chains leading to formation of non-polar groups
• C. Cleavage of backbone linkages between polymer repeat units leading to the formation of polar groups
• D. Enzymatic degradation of crosslinks between water soluble polymer chains

Hint:

- Solubility of polymers increases with \textbf{lower crosslink density}, \textbf{lower molecular weight}, and \textbf{higher polarity}.
- Enzymatically cleavable crosslinks are common triggers for \textit{in vivo} solubilization/degradation.

Answer 1

The Correct Option is A, C, D

Step 1: A crosslinked network can be water-insoluble even if the individual chains are hydrophilic. Breaking the crosslinks (chemically or enzymatically) converts the network to discrete, water-soluble chains. Hence (A) and (D) are valid. 

Step 2: Hydrolytic/oxidative cleavage of the \emph{backbone} can both reduce the molecular weight and generate polar end groups (e.g., \(-\mathrm{COOH}\), \(-\mathrm{OH}\)), increasing hydrophilicity and solubility. Hence (C) is also valid. 

Step 3: In contrast, cleaving side chains to form \emph{non-polar} groups would decrease hydrophilicity and does not promote solubility; therefore (B) is incorrect.