The Study Of Constructing Bioactive Surfaces Via Host-guest Interactions

Bioactive surfaces refer to material surfaces with immobilized bioactive molecules(peptides, carbohydrates, nucleic acid, antibody, enzyme, etc.) aimed specifically at achieving or promoting particular biological functions, which have significant applicatio ns in biomedical devices and biomaterials. Currently, the construction of bioactive surfaces is mainly by attaching bioactive molecules to antifouling polymer layers. Traditional covalent modification methods have limitations when they were used in microfluidic devices with complex manufacturing, sophisticated biomedical devices, biosensors, and so on. So, it is important both theoretically and practically to develop effective, mild, facile and controllab le methods for preparing antifouling bioactive surfaces. As a new surface modification method, host-guest modification has some advantages, such as adaptability, reversibility, facile process, and good biocompatibility. This paper is focused on constructing antifoul ing bioactive surfaces based on bio-functionalized β-CD derivatives, and the versatilit y, regenerability and adjustability of the surfaces have been studied in detail.Detailed research contents are as follows:Firstly, ligand- monosubstituted and-heptasubstituted β-CD derivatives were successfully prepared via copper-catalyzed azide–alkyne cycloaddition reaction. The measurements of 1H NMR, 13 C NMR, FTIR and mass spectrometry proved the successful synthesis of mannose-heptasubstituted β-CD, biotin-heptasubstituted β-CD, lysine-heptasubstituted β-CD and lysine-monosubstituted β-CD.Secondly, the influences of the host–guest interactions between mannose-heptasubstituted β-CD [CD(mannose)] and surfaces and the influences of adamantane(Ada) content on the surface thermoresponsivity and surface wettability were studied. Silicon surfaces were modified by poly(NIPAAm-co-Ada) statistical copolymer brushes via surface-initiated single electron transfer living radical polymerization(SI-SET-LRP). 1H NMR and FTIR spectra demonstrated that the composition ratio of Ada and NIPAAm on the surface was very close to the feed ratio. Surfaces with different thermorespons ive copolymers and different surface wettability were acquired by modulating Ada feed ratios. The effects of CD(mannose) on the thermoresponsivity of poly(NIPAAm-co- Ada) copolymer and the surface wettability were constrained by Ada content. Experimental results of surface wettability and surface topography measured by AFM were consistent with theoretical simulation, which indicates that the spacing between adjacent Ada units is too smal, producing steric hindrance to impede the conjugation of CD(mannose) onto polymer brushes.Thirdly, mannose-heptasubstituted β-CD [CD(mannose)] and biotin-heptasubstit uted β-CD [CD(biotin)] were integrated onto Si-poly(NIPAAm-co-Ada) surfaces to study the versatility and the regenerability of copolymer surfaces used as a thermoreponsive platform for molecular recognition. Results of 125I-labeled ConA and HSA adsorption showed that poly(NIPAAm-co-Ada)/CD(mannose) glycopolymer surfaces exhibited a low nonspecific protein adsorption even less than that on PNIPAAm surfaces. And surfaces containing more mannoses had higher ConA adsorption. As the thermoresponsive glycopolymer surfaces have different LCST, they can adjust ConA adsorption in different temperature range. Moreover, poly(NIPAAm-co-Ada)/CD(biotin) surfaces also can specifically and thermoresponsively regulate FITC-labeled avidin adsorption, while keeping resistant to nonspecific BSA adsorption. In addition, the multiple recycles of regeneration/reuse of copolymer surfaces were achieved by SDS washing.Fourthly, the regulation of surface ligand density and protein binding capability of bioactive surfaces by using the host–guest post-modification method based on β-CD derivatives were achieved. Silicon wafers were modified by the statistical copolymer brushes of HEMA and AdMA(PHAda) via surface-initiated atom transfer living radical polymerization(SI-ATRP), to which lysine-decorated β-CD derivatives were integrated. Measurement of surface lysine density showed that surface lysine density has been successfully tuned by changing lysine valency on β-CD scaffold and by diluting lysine-heptasubstituted β-CD [CD(Lys)7] with pure β-CD. 125I-labeled plasminogen(Plg) adsorption showed that compared with monovalent lysine surfaces, copolymer surfaces integrated by heptavalent lysines revealed higher Plg adsorption and higher Plg binding affinity. When CD(Lys)7 was diluted with pure β-CD, Plg adsorption on surfaces could be linearly regulated by varying the ratio of CD(Lys)7/CD. Moreover, the Hill coefficie nts calculated from the equilibrium isotherms of Plg adsorption indicated that the Plg binding on monovalent lysine surfaces occurred in a monovalent way, while the heptavalent lysine surfaces enhanced Plg binding affinity through multivalent binding. Thus, the host–guest post-modification method to construct bioactive polymer brushes is facile and adjustable.Fifthly, gold nanoparticle layer with micro/nano structures(GNPL) was deposited onto gold surfaces via chemical plating method. The synergistic effects of GNPL and bioactive polymer brushes prepared by host–guest post-modification method on surface wettabilit y and specific protein adsorption were investigated. SEM, AFM and cyclic voltammetry were used to characterize the surface morphology, surface roughness and surface area of GNPL, respectively. GNPL was further modified by the statistical copolymer brushes of OEGMA and AdMA(POEGAda) via the SI-ATRP method. The dry and wet polymer thickness on GNPL were measured by AFM. After the integration of CD(mannose) onto copolymer surfaces, results of surface wettability showed that GNPL significantly enhanced the influences of CD(mannose) on surface wettability. The specific ConA adsorption on surfaces with GNPL was increased mainly through the increased surface area.As a conclusion, different bioactive surfaces with versatility, regenerability or controllability were constructed by using the host–guest interactions between the biofunctionalized β-CD and antifouling polymer brushes containing Ada. Researches in the paper provide fundamental results of the construction of bioactive surfaces potentially used in sophisticated biomedical devices, biosensors, microfluidic channels, biomaterials, and so on.