Swelling-induced structural changes and microparticle uptake of gelatin gels probed by NMR and CLSM

Abstract

Gelatin gels are increasingly involved in many industrial applications due to several advantages including cost efficiency and biocompatibility. Generally, their production requires the use of aqueous solvents, which cause significant swelling, due to the ability of solvent molecules to penetrate through the gel microstructure and increase its volume. Since swelling mechanisms and their effect on the gel structure are not fully understood, further investigations are required. In this work, we combine macroscopic measurements of the swelling ratio (SR) with Nuclear Magnetic Resonance (NMR) and Confocal Laser Scanning Microscopy (CLSM) to investigate changes in the gelatin structure as a function of both polymer concentration and swelling time. SR values increase as a function of time until a maximum is reached and then show a slight drop for all the gelatin concentrations after 24 h swelling time, probably due to a network relaxation process. NMR allows determination of mass transport and molecular dynamics of water inside the gelatin pores, while CLSM is used to visualize the penetration of tracers (polystyrene microbeads) with a diameter much larger than the gel pores. Structural parameters, such as average pore size and tortuosity, are estimated. In particular, the pore size decreases for higher polymer concentration and increases during swelling, until reaching a maximum, and then dropping at longer times. The penetration of tracers provides evidence of the heterogeneity of the gel structure and shows that single microcarriers can be loaded in gelatin gels upon swelling.

Transient bio-inspired gliders with embodied humidity responsive actuators for environmental sensing

“…A video of the CNF:G—0.25:0.75 film taken inside the climatic chamber at a run from 55% relative humidity to 90% is shown in Supplementary Movie S2 . The behavior is caused by water molecules intercalating between gelatin chains and disrupting inter-chain hydrogen bonds formed by amide groups at high relative humidity D’Agostino et al (2017) ; Liu et al (2021) . The intercalation allows the active layer of CNF:G to absorb more water and therefore swell more than the water-resistant Zhang et al (2020) side, leading to the film bending towards the shellac-coated side.…”

Investigating the behaviour of NaCl brines and hydrocarbons in porous alumina using low-field NMR relaxation and diffusion methods

“…This parameter can be used to characterise the reduction of diffusivity within a porous medium, which effectively includes contributions of both tortuosity and surface interactions, and thus it can also be referred to as “apparent tortuosity”. 49,50…”

“…This parameter can be used to characterise the reduction of diffusivity within a porous medium, which effectively includes contributions of both tortuosity and surface interactions, and thus it can also be referred to as ''apparent tortuosity''. 49,50 The x value for the alumina samples is slightly lower for the low salinity brines, indicating that the decrease in the movement of water molecules within the alumina samples is slightly greater for lower salinities. This could be partly due to stronger interaction of water molecules with the pore walls for the lowsalinity brines, which is supported by the relaxation measurements presented in the next section.…”

Magnetic Particle Imaging: From Tracer Design to Biomedical Applications in Vasculature Abnormality

“…Biomacromolecules that act as coating layers, like dextran, [89,164,165] chitosan, [166,167] gelatin, [168,169] and bovine serum albumin (BSA), [157,170,171] play a prominent role in improving the biocompatibility of tracers.…”