Reversible adsorption by a pH- and temperature-sensitive acrylic hydrogel.

Area of Science:

• Polymer Science
• Materials Science
• Biomedical Engineering

Background:

• Thermo- and pH-sensitive hydrogels are advanced materials with tunable properties.
• Controlled release systems are crucial for targeted drug delivery and therapeutic applications.
• N-isopropylacrylamide (NIPA) and N-aminopropylmethacrylamide based hydrogels offer unique responsive characteristics.

Purpose of the Study:

• To synthesize and characterize thermo- and pH-sensitive hydrogels.
• To investigate the loading and release kinetics of a divalent molecule (naphthalenedisulfonic acid, NS-2).
• To optimize hydrogel performance for controlled release applications by studying environmental factors.

Main Methods:

• Synthesis of hydrogels via cross-linking NIPA and N-aminopropylmethacrylamide.
• Analysis of swelling behavior using Flory-Huggins theory.
• Study of NS-2 loading and release under varying pH, ionic strength, and temperature.
• Langmuir adsorption isotherm model applied to uptake process.

Main Results:

• Hydrogel swelling is dependent on cross-linking density.
• Optimal NS-2 loading achieved at acidic pH with low cross-linking and collapsed state.
• Release is temperature-dependent: rapid release below 33°C, inhibited release/re-uptake above 33°C.
• Release rate at 37°C is pH- and salt-dependent, enabling tunable delivery.

Conclusions:

• The synthesized hydrogels exhibit reversible and reproducible loading/release of NS-2.
• The hydrogels function as pH- and salt-sensitive delivery systems.
• Controlled release can be prolonged due to hydrogel collapse at higher temperatures.