Contact time- and pH-dependent adhesion and cohesion of low molecular weight chitosan coated surfaces

Abstract

a b s t r a c tLow molecular weight chitosan (LMW chitosan, ∼5 kDa) potentially has many desirable biomedical applications such as anti-microbial, anti-tumor, and anti-diabetes. Unlike high molecular weight chitosan, LMW chitosan is easily dissolvable in aqueous solutions even at neutral and basic pH, but its dissolution mechanism is not well understood. Here, we measured adhesion and cohesion of molecularly thin LMW chitosan films in aqueous solutions in different buffer pHs (from 3.0 to 8.5) using a surface forces apparatus (SFA). Interestingly, significantly lower adhesion force was measured for LMW chitosan films compared to the high molecular weight chitosan (∼150 kDa) films. Not only the strength of adhesion is lower, but also the critical contact time where adhesion starts to increase with contact time is longer. The results from both the SFA and atomic force microscopy (AFM) indicate that, in physiological and basic conditions, the low cohesion of LMW chitosan due to the stiffness of the chain which cause strong electrostatic correlation energy penalty when they are aggregated. Here, we propose the reduction in cohesion for shorter chitosan (LMW chitosan) as an explanation of its high solubility of LMW chitosan in physiological pHs.

Supramolecular β‐Sheet Suckerin–Based Underwater Adhesives

“…[ 23,33 ] We also measured higher maximum adhesive forces as the contact time increased from 2 min to 1 h in all cases (Figure 5), indicating that both suckerin‐12 and suckerin‐12‐Dopa favorably developed molecular reorientation or rearrangement, which are typical signatures of pressure‐sensitive adhesives. [ 11h,31 ] Furthermore, the higher adhesive forces of suckerin‐12 at longer contact times correlated with decreased steric wall thickness D sw, from 13.7 nm at t c = 2 min to 6.9 nm at t c = 1 h, which corroborates the molecular rearrangement of pressure‐sensitive adhesives. [ 32 ]…”

Extending Viability of Bifidobacterium longum in Chitosan-Coated Alginate Microcapsules Using Emulsification and Internal Gelation Encapsulation Technology

“…It is a non-toxic, biodegradable material with desirable biocompatibility and biological adhesion properties, and has been widely used in the food and pharmaceutical industries (Lee et al, 2013; Huang et al, 2015). Chitosan molecules contain a large amount of primary amino groups; hence, ionization results in positive charges when the solution pH is lower than pKa 6.5 (Lim et al, 2015). Therefore, chitosan can be electrostatically combined with a negatively charged polymer, such as sodium alginate.…”

Probing molecular mechanisms of M13 bacteriophage adhesion

“…All the adhesion energies measured at pH 3.0 were higher at t c = 1 h compared with those at t c = 5 s. The increase in adhesion with t c is a typical sign of structural rearrangements or reorientation of biological macromolecules 39,40 , indicating that the adhesive bonds (physical interactions, including van der Waals, H-bonding, and hydrophobic attraction in this study) developed favorably while the functional groups and DSPH were in contact. The decrease in D sw during contact also suggests that molecular rearrangement occurred ( Supplementary Fig.…”