# Self-Assembled (Nano)Structures of Human Serum Albumin with Thermoresponsive Chitosan-g-PNIPAM Graft Copolymer

## TL;DR

This paper explores how human serum albumin interacts with a thermoresponsive polymer to form nanostructures or macrostructures depending on mixing conditions.

## Contribution

The study introduces a new thermoresponsive graft copolymer and investigates its interaction with HSA under varying molar ratios and addition orders.

## Key findings

- Nanostructures or macrostructures form depending on the molar ratio and order of addition of HSA and Chit-g-PNIPAM.
- Thermoresponsiveness and stability of the formed structures were analyzed using turbidimetry and DLS.
- Dynamic light scattering shows structure formation depends on the mixing sequence and component ratios.

## Abstract

Protein–polyelectrolyte entities (complex, coacervates, flocs, gels, etc.) are of great interest due to their potential applications in biological and medical fields. This study focuses on investigating the interactions between a model protein, human serum albumin (HSA) and a newly synthesized hybrid thermoresponsive copolymer based on chitosan polysaccharide grafted with poly(N-isopropylacrylamide) synthetic polymer chains (Chit-g-PNIPAM), in aqueous media, by mixing the individual component aqueous solutions. Depending on the mixing molar ratio and the order of addition of the two components (protein and copolymer), either stable nanostructured suspension or macrostructures’ phase separation have been observed. Dynamic light scattering (DLS) results reveal that the Chit-g-PNIPAM/HSAx (molar ratio 5:x, where x = 1, 2, 3, 5, 10 and 15) nanostructures’ and HSA/Chit-g-PNIPAMx (molar ratio 100:x, where x = 1, 2, 3, 10, 20, 30, 40 and 50) structures’ formation depend on the molar ratio of the two components as well as on the order of addition, with first component amount being kept constant in aqueous solution and second component solution added drop-by-drop in the solution of the first component. Additional information regarding the thermoresponsiveness and stability vs time of the formed (nano)structures were acquired using turbidimetry and DLS measurements.