Nanopartículas termossensíveis de sulfato de celulose bacteriana enxertado com N-isopropilacrilamida

Abstract

Amphiphilic copolymer nanoparticles based on polysaccharides and its derivatives have been widely studied due to its features like biocompatibility and biodegradability, which make them promising for biomedical application. In this line, this work intends to synthesize and characterize thermoresponsible nanoparticles based on bacterial cellulose sulfate grafted with poly (N-isopropylacrylamide) (PNIPAM). Bacterial cellulose (BC) was chemically modified through sulfatation reaction by using the complex made of chlorosulfonic acid and N,N – dimethylformamide (HSO3Cl/DMF) in DMF. Two derivatives were synthesized with different degrees of sulfatation. They were characterized by fourier transform infrared spectroscopy (FTIR), 13C magnetic nuclear resonance (13C NMR), X-ray diffraction (XRD) and gel permeation chromatography (GPC). Sulfation degree (GS) was determined by elementary analysis. The SCB 1,2 and SCB 2 derivatives presented GS of 0.8 and 1.56, respectively. FTIR and RMN confirmed the sulfation reaction on cellulose and DRX analysis shows that sulfate cellulose derivatives are amorphous The copolymers were synthesized by radical polymerization. The influences of the type of chemical initiator, temperature, initiator quantity, and NIPAM quantity were studied. The employed chemical initiators were potassium persulfate (KPS) and cerium (IV) ammonium nitrate (CAN) and the products obtained were characterized by FTIR, NMR, critical association concentration (CAC) and dynamic light scattering (DLS). The insertion of PNIPAM chain sulfate cellulose using KPS as initiator was lower them when CAN was used. The change in temperature of synthesis (room temperature and 60 ºC) influenced the grafting effectiveness because only the reactions that took place at 60 ºC presented bands on infrared characteristics of functional groups PNIPAM. The copolymers synthesized with the initiator KPS presented an increase of particle size as temperature increases and a high lower critical solution temperature (LCST) (46 °C), while copolymers obtained with CAN showed a decrease of size upon heating and lower LCST (33-34 ºC), which is characteristic of copolymers containing higher grafting content. In addition, the CAC above the LCST was shown to be dependent on the percentage of PNIPAM in the copolymers. Therefore, it was possible to synthesize copolymers of bacterial cellulose sulfate grafted with PNIPAM with thermoresponsible properties, which led to formation of self-assembled nanoparticles.