Synthesis And Stimuli Responsive Behaviors Of Temperature-responsive Polymer Conjugates

Proteins are biological macromolecules having a unique role in biomedicine,nanotechnology, materials science and other fields. Because the solubility, the retention time,the stability and and other properties are different in different environments, the function ofprotein is limited. The bioconjugates based on protein grafted covalently into polymers havebeen shown a significantly effect to broaden and improve the scope and efficiency of protein.It is well known that Poly(dimethylaminoethylmethaerylate)(PDMAEMA) synthesizedby using atom transfer radical polymerization (ATRP) is a pH/thermo-responsive polymers,which is widely used in environmental protection, drug release, gene therapy, biomedicalmaterials and other fields because of its good hydrophilicity, biocompatibility, ease offunction and other characteristics. The BSA-PDMAEMA is designed to retains the uniquestructure of protein and the environment-responsive basic structural units of polymers. So itcan be expected to obtain better achievement from the self-assembly of theBSA-PDMAEMA.Based on the above, modification of proteins, environment-responsive polymer and itsactive controlled radical polymerization were introduced importantly. Considering of thespecial properties of PDMAEMA. The synthesis of PDMAEMA were achieved by ATRP,and the BSA-PDMAEMA were prepared by using “grafting to” technology. The changeregulation of LCST of PDMAEMA and BSA-PDMAEMA and the self-assembly behavior ofBSA-PDMAEMA were studied. The main results obtained in this thesis are as follows.The N-succinimidyl-2-bromoisobutyrate (NHS-BIBA ester) have been synthesized byesterification of N-hydroxysuccinimide and2-Bromoisobutyrate under the EDAC.Poly[N,N-(dimethylamino) ethyl methacrylate](PDMAEMA) was polymerized usingN-Succinimidyl-2-Bromoisobutyrate(NHS-BIBA ester) as initiator and CuBr/bpy as catalystby atom transfer radical polymerization (ATRP) in distilled water. Effect of the temperature,reaction time, pH value and concentration on the polymerization yield was studied in detail.FT-IR,1H-NMR and GPC analyses indicate that the polymerization is well controlled withlow polydispersities in the optimum technological condition. It is consistent with the expectedmolecular weight and structure.BSA directly conjugating with PDMAEMA was achieved by covalent bonds in PBSbuffer.The molecular weight of the bioconjugates was characterized approximately bySDS-PAGE and Native-PAGE, and then it was mensurated accurately by MALDI-TOF MS.The amide bond of the modification sites was characterized by FT-IR.UV-Vis was used to characterized the pH/thermo-responsive properties of thePDMAEMA and BSA-PDMAEMA. The result show that changes in the environment such as pH and ionic strength have an important influence on the PDMAEMA’s lower criticalsolution temperature (LCST). The LCST of the BSA-PDMAEMA is lower than thePDMAEMA.The self-assembly behavior of BSA-PDMAEMA were studied by TEM, SEM andUV-Vis. The result show that heating temperature and changing pH value effected on theself-assembly behavior of the PDMAEMA and BSA-PDMAEMA. The TEM results showedthat the average particle size of the non-spherical aggregates increase from about400nm toabout700nm by heating temperature. As the solution pH increase from7.4to14, the averageparticle size have little change and irregular clusters and vesicles were obvious. The SEMresults showed that the agglomeration was induced by heating temperature and thebioconjugates formed uneven and inerratic aggregates with increasing the pH value. Theabsorbency of BSA-PDMAEMA was inspected using UV-Vis in different temperature andpH value, which revealed that hydrophobic interactions is significant at the self-assembly ofthe BSA-PDMAEMA.