Preparation And Characterization Of PNIPAM And Its Copolymers Nanogels

The design and preparation of nanogels have attracted a great deal of interest in biomedical engineering, pharmaceutical applications, and biomaterials science because of their tunable advantage. Nanogels have tunable size from nanometers to several micrometers and a large surface area for multivalent bioconjugation. They also have an interior network for the incorporation of biorelated molecules. Physical entrapment of bioactive molecules such as drugs, proteins, carbohydrates, and DNA in the polymeric network, as well as their in vitro release behavior, have been extensively investigated as targeted drug delivery carriers for biomedical applications.N-isopropylacrylamide (NIPAM) was choosed as a temperature-sensitive monomer, acrylic acid (AA) and chitosan (CS) of biocompatibility as pH-sensitive monomers, a series of temperature-and pH-sensitive nanogels were prepared by surfactant-free emulsion polymerization (SFEP). The paricle size and distribution, swelling properties and drug release of nanogels were studied. The main contents and conclusions are as follows:(1) The nanogels of PNIPAM, P(NIPAM-co-AA), P(NIPAM-co-AA)/CS obtained by SFEP have perfect spherical structure and uniform distribution of particle size. The particle size of nanogels prepared by continuous SFEP is smaller and more homogeneous than intermittent SFEP, and it be controlled smaller than 200nm.(2) With a designed concentration of monomer, when the size and the swelling ratio of nanogels PNIPAM decrease with the content of crosslinking agent (MBA) increasing. Under the same polymerization conditions, the size of nanogels becomes significantly smaller with the content of sodium dodecyl sulfate (SDS) increase, but the swelling ratio changed little. The appropriate amount of crosslinking agent and emulsifier monomer amount of substance are 8% and 0.4% by SFEP.(3) The particle size of P(NIPAM-co-AA) nanogels became bigger with the increasing of the AA comonomer content. The swelling rate in acidic medium was slow, and increased with the increase of pH, went to maximum in alkaline medium. pH sensitivity of P(NIPAM-co-AA) hydrogels was more and more obvious with the increase of the AA monomer proportion. Nanogels have obvious temperature sensitivity in acidic media, the phase transition temperature becoming less distinct with the medium pH value increases. P(NIPAM-co-AA) nanogels NL-a (7%) and NZ-a (7%) which containing aspirin have temperature and pH sensitivity, Their maximum release were greater at 37℃than at 25℃. The release rate was significantly lower in simulated gastric juice than in the simulated intestinal fluid at 37℃.(4) The surface of P(NIPAM-co-AA)/CS gels was not smooth any more, nano-particle size became bigger with the comonomer AA/CS content increases. The swelling rate of P(NIPAM-co-AA)/CS gels was fast in acidic medium, slower in the neutral medium, fastest in the alkaline medium. At body temperature and intestinal fluid in the simulation environment, the drug release of N-as (20%) nanogel was less, and maintained with a stable release rate. This Double-Sensitive Nanogel is expected to play an important role in biomedical application.