Intelligent copolymers based on poly (N-isopropilacrylamide). Part ii: Grafts polysaccharide to obtain new biomaterials for biomedical and pharmacological applications

Biopolymers such as polysaccharides are compounds that have functional groups and they are very susceptible to be used in chemical modifications and also allows them to synthesizer of new copolymers (used as graft-like chains). Poly (N-Isopropylacrylamide) PNIPAm, is a thermosensitive synthetic polymer widely used in the preparation of intelligent gels for the biomedical field, but have some limitations in use as biodegradable matrix or scaffolds. In this research wered the synthesis and characterization of copolymers their PNIPAm grafted with the polysaccharides: chitosan (CS) or hyaluronic acid (HA), were performed to obtain new biodegradable and biocompatible biomaterials that conserve the intelligent character (thermosensitivity).The PNIPAm was in first chemically modified with 3-butenoic acid in order to generate carboxyl end groups on the graft-polymer chain (PNIPAm-co-COOH) which serve as anchor points and then covalently graft the polysaccharides. For the specific case of grafting with hyaluronic acid, it was necessary to perform a second modification using piperazine (PIP) and obtain the graft-polymers PNIPAm-co-COO-g-PIP. All this modification process was previously reported (Carrero et al, 2018). In this case, the polysaccharides used as grafts-like chains were: (1) chitosan oligomers obtained by acid degradation and (2) hyaluronic acid. The characterization of all copolymers obtained was follow by infrared spectroscopic (FT-IR); the differential scanning calorimetric (DSC) technique was used to determine the lower critical solution transition temperature (LCST), resulting in the range of 29-34 °C. Its morphology was studied using scanning electron microscopy (SEM), but previously was simulate an inject process, for the reversible gel character presented by these novel copolymers; resulting a high porosity and interconnection between pores (scaffold-like micrometric structures). Hemocompatibility assays were performed on agar/blood systems, showing non cytotoxicity. All these results give these graftcopolymers a high potentiality of use as scaffolds in tissue engineering and also for pharmacological applications.