Yifan Zheng

Hydrogels are hydrophilic 3-dimensional networks characterized by the retention of a large amount of water. Because of their water component, hydrogels are a promising method for targeted drug delivery. The water component, or “free volume”, is a potential vehicle for protein drugs. A particularly intriguing hydrogel is pectin. In addition to a generous free volume, pectin has structural characteristics that facilitate hydrogel binding to the glycocalyceal surface of visceral organs. To test drug function and pectin integrity after loading, we compared pectin films from four distinct plant sources: lemon, potato, soybean, and sugar beet. The pectin films were tested for their micromechanical properties and intrinsic antibacterial activity. Lemon pectin films demonstrated the greatest cohesion at 30% water content. Moreover, modest growth inhibition was observed with lemon pectin (p < 0.05). No effective inhibition was observed with soybean, potato, or sugar beet films (p > 0.05). In contrast, lemon pectin films embedded with carbenicillin, chloramphenicol, or kanamycin demonstrated significant bacterial growth inhibition (p < 0.05). The antibacterial activity was similar when the antibiotics were embedded in inert filter disks or pectin disks (p > 0.05). We conclude that lemon pectin films represent a promising structural platform for antibacterial drug delivery.

Background Persistent air leaks after thoracic trauma are associated with significant morbidity. To evaluate a novel pectin sealant in a swine model of traumatic air leaks, we compared a pectin biopolymer to standard surgical and fibrin-based interventions. Methods A standardized lung injury was created in male Yorkshire swine. Interventions were randomized to stapled wedge resection (N=5), topical fibrin glue (N=5), fibrin patch (N=5) and a pectin sealant (N=6, Figure). Baseline, pre- and post-intervention tidal volumes (TV) were recorded. Early success was defined as the return to near-normal TV (> 95% of baseline). Late success was defined as no detectable air leak in the chest tube after chest closure. Results There were no differences in injury severity between groups (mean TV loss = 62ml±17, p =0.2). Early success was appreciated in 100% (N=6) of the pectin interventions which was significantly better than the fibrin sealant (20%, N=1), fibrin patch (20%, N=1) and stapled groups (80%, N=4, p=0.01). The percent of return to baseline TV after sealant intervention was significantly increased in the pectin (98%) and staple arms (97%) compared to the fibrin sealant (91%) and fibrin patch arms (90%) (p = 0.02; p = 0.03). Late success was also improved with the pectin sealant: no air leak was detected in 83% of the pectin group compared to 40% in the stapled group (p=0.008)—90% of the fibrin-based interventions resulted in continuous air leaks (p=0.001). Conclusion Pectin-based bioadhesives effectively seal traumatic air leaks upon application in a porcine model. Further testing is warranted as they may provide a superior parenchymal-sparing treatment option for traumatic air leaks. Level of Evidence Not applicable as an animal study Study Type Orginal Article

Pectin binds the mesothelial glycocalyx of visceral organs, suggesting its potential role as a mesothelial sealant. To assess the mechanical properties of pectin films, we compared pectin films with a less than 50% degree of methyl esterification (low-methoxyl pectin, LMP) to films with greater than 50% methyl esterification (high-methoxyl pectin, HMP). LMP and HMP polymers were prepared by step-wise dissolution and high-shear mixing. Both LMP and HMP films demonstrated a comparable clear appearance. Fracture mechanics demonstrated that the LMP films had a lower burst strength than HMP films at a variety of calcium concentrations and hydration states. The water content also influenced the extensibility of the LMP films with increased extensibility (probe distance) with an increasing water content. Similar to the burst strength, the extensibility of the LMP films was less than that of HMP films. Flexural properties, demonstrated with the 3-point bend test, showed that the force required to displace the LMP films increased with an increased calcium concentration (p < 0.01). Toughness, here reflecting deformability (ductility), was variable, but increased with an increased calcium concentration. Similarly, titrations of calcium concentrations demonstrated LMP films with a decreased cohesive strength and increased stiffness. We conclude that LMP films, particularly with the addition of calcium up to 10 mM concentrations, demonstrate lower strength and toughness than comparable HMP films. These physical properties suggest that HMP has superior physical properties to LMP for selected biomedical applications.