Water-Dependent Blending of Pectin Films: The Mechanics of Conjoined Biopolymers.

Yifan Zheng,Willi L Wagner,Aidan Pierce,Steven J Mentzer,Maximilian Ackermann,Henrik V Scheller,Debra Mohnen

doi:10.3390/molecules25092108

Abstract

Biodegradable pectin polymers have been recommended for a variety of biomedical applications, ranging from the delivery of oral drugs to the repair of injured visceral organs. A promising approach to regulate pectin biostability is the blending of pectin films. To investigate the development of conjoined films, we examined the physical properties of high-methoxyl pectin polymer-polymer (homopolymer) interactions at the adhesive interface. Pectin polymers were tested in glass phase (10–13% w/w water content) and gel phase (38–41% w/w water content). The tensile strength of polymer-polymer adhesion was measured after variable development time and compressive force. Regardless of pretest parameters, the adhesive strength of two glass phase films was negligible. In contrast, adhesion testing of two gel phase films resulted in significant tensile adhesion strength (p < 0.01). Adhesion was also observed between glass phase and gel phase films—likely reflecting the diffusion of water from the gel phase to the glass phase films. In studies of the interaction between two gel phase films, the polymer-polymer adhesive strength increased linearly with increasing compressive force (range 10–80 N) (R2 = 0.956). In contrast, adhesive strength increased logarithmically with time (range 10–10,000 s) (R2 = 0.913); most of the adhesive strength was observed within minutes of contact. Fracture mechanics demonstrated that the adhesion of two gel phase films resulted in a conjoined film with distinctive physical properties including increased extensibility, decreased stiffness and a 30% increase in the work of cohesion relative to native polymers (p < 0.01). Scanning electron microscopy of the conjoined films demonstrated cross-grain adhesion at the interface between the adhesive homopolymers. These structural and functional data suggest that blended pectin films have emergent physical properties resulting from the cross-grain intermingling of interfacial pectin chains.

Highlights

A variety of polysaccharide polymers have been recommended for biomedical applications including cellulose [1], alginate [2], chitin [3], agarose [4], and pectin [5]
The progressive loss of water content (Wc ) of the pectin resulted in the transition of the liquid pectin into gel phase and subsequently glass phase films (Figure 1)
Biodegradable pectin polymers have been implicated in a variety of biomedical applications ranging from the delivery of oral drugs to the repair of injured visceral organs

Summary

Introduction

A variety of polysaccharide polymers have been recommended for biomedical applications including cellulose [1], alginate [2], chitin [3], agarose [4], and pectin [5]. Pectin is a potentially useful polysaccharide because of its chemical and functional properties. Commercial pectins contain primarily linear chains of homogalacturonan, a partially methyl esterified polymer of (14–)-α-d-galacturonic acid (GalA) [6], along with lesser amounts of rhamnogalacturonan [7]. Pectin demonstrates remarkable adhesivity to gut mucins, providing a useful mechanism for controlled oral drug delivery [10]. Pectin binds the mesothelial glycocalyx of visceral organs [5] suggesting a potential role as a mesothelial sealant [11]

Methods

Results

Conclusion