# The Effect of pH during Fabrication of Platinum-Containing Polymeric Arsenical Hydrogels

## TL;DR

This paper explores how pH affects the properties of hydrogels containing platinum and arsenic, which could be useful for drug delivery and fighting infections.

## Contribution

The study introduces pH-responsive platinum-arsenical hydrogels with tunable mechanical and antimicrobial properties.

## Key findings

- Hydrogel stiffness increases with pH due to stronger metal-ligand interactions.
- Antimicrobial activity of the hydrogels is effective against both Gram-positive and Gram-negative bacteria.
- Swelling and structural stability are influenced by pH and ionic strength.

## Abstract

Intrinsic and acquired resistance, along with the systemic
toxicity
of platinum and arsenic therapeutics, necessitate the development
of alternative chemistries and delivery strategies for Pt- and As-containing
drugs. Stimuli-responsive hydrogels offer dynamic physicochemical
adaptability, making them highly suitable for biomedical applications.
Herein, we investigate the pH-responsive mechanical and antimicrobial
properties of platinum-containing arsenical hydrogels. Poly­(N,N-dimethylacrylamide-co-4-(N-acrylamido)­phenylarsonic acid), P­(DMAm0.92-co-AsAm0.08), P

As
was
cross-linked with PtII (from K2PtCl4) under varying pH conditions to form hydrogels. Spectroscopic techniques
(UV–vis, FT-IR, 1H, and 195Pt NMR) revealed
that arsenic acid protonation influences PtII–O–AsV interactions, impacting hydrogel integrity and dynamic behavior.
Rheological analysis confirmed the pH-dependent mechanical properties,
where increased pH strengthened metal–ligand interactions,
enhancing material’s stiffness. Self-healing properties were
demonstrated via strain recovery upon cutting for all materials, while
resilience upon stretching was enhanced for the looser network environment
under acidic conditions. Swelling studies indicated better stability
in neutral environments, whereas increased ionic strength contributed
to additional structural integrity. SEM-EDX confirmed morphological
changes as a function of pH, corroborating the presence of both As
and Pt under all pH conditions. The antimicrobial potential of these
hydrogels was evaluated against Gram-positive (, ) and Gram-negative (uropathogenic , K12 MG1655) bacteria, demonstrating a similarif
not improvedantimicrobial profile in all cases compared to
the individual components. This study advances the understanding of
pH-modulated mechanical properties and antimicrobial activity of arsenic–platinum
hydrogels, which are promising candidates for infection treatment
or targeted drug delivery applications.