Preparation and Quantitative AFM Analysis of Soft, Swollen, Hydrated, Non-Cytotoxic Biopolymer Microgels: Linking Morphology, Crosslink Density, and Nanomechanics

Oleksii Kotko
Lecture of the lecture cycle
30.4.2026 10:00, Lecture room A

Microgels are hydrophilic, crosslinked colloidal hydrogel particles with sizes ranging from 100 nm to hundreds of micrometers, widely explored in biomaterials due to their swelling behaviour, tunable structure, and controlled payload release. In this work, we report the preparation of soft, micron-sized polypeptide microgels via enzymatic horseradish peroxidase (HRP)/hydrogen peroxide (H₂O₂)-mediated crosslinking in inverse suspension. The microgels were synthesized from a poly(amino acid)-based polymer precursor (P2HPG-Tyr) containing crosslinkable tyramine units. By varying the H₂O₂-to-tyramine ratio and employing SPAN 80 as a stabilizer with a pre-emulsification step, spherical and colloidally stable microgels were obtained. Morphology and size distribution were characterized by light microscopy. The resulting microgels were non-cytotoxic and bacterially viable, and enabled successful encapsulation of magnetic γ-Fe₂O₃ nanoparticles within a soft, hydrated microgel shell. A versatile APTES-based immobilization strategy was developed to enable atomic force microscopy (AFM) characterization in liquid environments. AFM analysis of the swollen hydrated microgels was performed using PeakForce Quantitative Nanomechanical Mapping (PF-QNM) in ultrapure water and PBS (pH 7.4), revealing surface topography and viscoelastic behavior, with Young’s moduli in the range of tens to hundreds of kPa. The crosslink density of the microgels was further evaluated, confirming structure–property relationships. The developed methodology was successfully extended to the preparation of hyaluronic acid-based microgels, demonstrating the versatility of the approach.

The lecture is presented in English