(771e) Understanding the Interaction of the Polysaccharide, Chitosan, with a Novel Cuticular Protein, CPR 27, Using Quartz Crystal Microbalance with Dissipation

The exoskeleton of the insects is made up of cuticle, which contains the polysaccharide, chitin, and several cuticular proteins [CPs]. Chitin is the second-most abundant biopolymer, and its N-deacetylated derivative, chitosan, is a potential source of polysaccharide. Chitosan is biocompatible, biodegradable, and non-toxic; naturally, it finds a number of applications that includes the development of biomimetic materials. It has been used in cosmetics, in making artificial skin, in formulating wound-healing products and as drug-delivery systems for controlled release. In this report, we attempt to understand the interaction of chitosan with a novel cuticular protein, named CPR 27, using Quartz Crystal Microbalance with Dissipation [QCM-D]. Abundant quantities of CPR 27 are found in the elytra of the beetle, Tribolium castenium. It has been hypothesized that a conserved sequence of amino acids in CPR 27, the Rebers and Riddiford [RR] sequence, helps CPR 27 to bind with chitin. Therefore, we speculate that chitosan binds similarly to CPR 27. This hypothesis was tested using QCM-D, where a change in frequency of the resonating quartz crystal is noted with the adsorption of the material of interest. Chitosan was first adsorbed onto a silica surface, and CPR 27 was subsequently adsorbed to chitosan. Increase in mass of CPR 27 was observed with an increase in concentration. However, the opposite trend was observed in the case of rising temperature, where less amount of CPR 27 adsorbed with an increase in temperature. A possible explanation is the influence of temperature on the RR sequence with the gradual unfolding of the protein. However, further studies along with kinetic evaluation of the binding are necessary to have a better understanding of the interaction. The ultimate goal here is to come up with a novel chitosan-CP composite that will be suitable for biomedical applications.