| With the development of modern medicine and biological technology,an increasing number of artificial materials and devices have been broadly applied in biological,medical and their related fields.Therefore,a crucial factor that directly dominate the biocompatibility and function of artificial materials is the interfacial interactions between living system and materials,which depends to a great extent on interfacial properties of materials.Here,an appealing strategy for resolving problems stemming from interfacial interactions,for example nonspecific adhesion and biofouling,is to modulate surface physical and chemical properties of materials.However,although great developments have been achieved for traditional stimuli-responsive biointerface materials,the introduction of external physical or chemical stimuli makes such responsive system fail to satisfy the requirement of applications in bio-related fields.Therefore,it is quite urgent to develop a new generation of smart biointerface materials or smart devices based on stimuli or triggered factors or inspirations from living system themselves.In living system,biomolecular recognition events involving carbohydrate-protein interactions have widely participated in numerous biological processes,and performed various biofunctions,the intrinsic nature of which is multiple synergetic non-covalent weak interactions.Therefore,these bring much inspirations for us to utilize biomolecular recognition based on non-covalent weak interactions to regulate macroscopic properties of artificial materials,and thus further realize unique biofunctions or innovative bio-device applications,which provides a novol strategy for the design and development of emerging smart biomaterials.In this research work,we designed and developed several saccharide-bearing multi-component smart polymer film materials,and systematically studied saccharide-peptide interactions-driven macroscopic properties transformation of materials surface.Furthermore,the underlying molecular mechanism of such transformation,and application potential of this smart polymer film materials in the aspect of glycopeptide enrichment were investigated in detail.The main research work and results are described as follows.1.Combining with main research characteristic on interface materials of our research groups,based on“Recognition-Mediating-Function”?R-M-F?design concept,we introduced monosaccharide?Glc?as a recognition unit,chose trifluoromethyl phenylthiourea?PT?as a mediating unit,chose PNIPAAm as functional framework,thus designed a saccharide-bearing three-component smart polymer PNI-co-PT-co-Glc.Then the polymer was grafted onto flat silicon substrate,textured silicon substrate and QCM resonator substrate by surface-initiated atom transfer radical polymerization?SI-ATRP?to obtain smart polymer film materials for following work.Furthermore,according to the similar design concept,several reference polymer film mateirals,such as the tetra-acetylated monosaccharide-bearing PNI-co-PT-co-Ac4Glc,PNI-co-PT containing PT units,PNI-co-Glc containing monosaccharide units,were also developed.These polymer films with flat morphology and thickness in a range of 30-40 nm laid the solid foundation for the following investigations.2.In order to assess the impact on surface property of the polymer film upon interaction with peptides,a set of peptides was synthesized as model peptides.Then responsive changes on various surface properties of polymer film after being treated with various peptide solutions were investigated by using a variety of test methods.The results of surface contact angle?CA?measurements indicated,after being treated by aromatic peptide FFF,the PNI-co-PT-co-Glc polymer film became hydrophilic and obvious CA decrease from 92±2°to 47.4±2°was observed.In contrast,other non-aromatic peptides only caused smaller changes in CA.In addition,combining with magnification effect of surface micro-and nano-composite structures on wettability,the polymer film on a textured silicon substrate exhibited wettability switching from superhydrophobicity?CA.154.5±2.2°?to superhydrophilicity?CA.11.3±3.6°?,upon treatment with aromatic peptide FFF.And the decreased CA of the film could revert to the original value upon further treatment by pure water,thus the wettability switching exhibited excellent reversibility.Furthermore,the results from investigation on wettability change of reference polymer film showed that the monosaccharide Glc units indeed serve as recognition units capable of discriminating the aromatic peptides from other peptides,and interaction between Glc and aromatic peptides is the main driving force for wettability switching.Moreover,the participation of PT units obviously enhanced the initial surface hydrophobicity,and enlarged the extent of surface wettability switching.3.Water adhesion measurements of the PNI-co-PT-co-Glc polymer film in response to different peptides were further performed.The results were highly consistent with those in CA measurements,indicated surface water adhesion dramatically increased when the film was treated with aromatic peptide FFF.In addition,results of QCM indicated the PNI-co-PT-co-Glc polymer film exhibited a strong adsorption toward FFF,inducing a frequency decrease??f?of the resonator of about 39 Hz and a dissipation increase??D?of about 7.2×10-6.Meanwhile,such adsorption further induced a much softer conformation for the PNI-co-PT-co-Glc polymer film,and surface Young's modulus changed from 97.7±5.6 MPa to 17.5±1.5 MPa after being treated with FFF according to results of AFM in QNM mode.4.On the basis of the above work,we further investigated molecular mechanism from the single-molecular level by means of fluorescent titration experiments,NMR titration experiments,IR experiments,and quantum chemistry calculations.And,we also explored the conformational transformation of PNI-co-PT-co-Glc polymer by studying the temperature-responsive behaviors of the polymer before and after being treated with aromatic peptide FFF.Detailed studies indicate that,the monosaccharide Glc unit and aromatic peptide FFF formed complex via CH-?interaction,which broke the initial the hydrogen-bond network of polymer,resulting in contraction-swelling conformational transition for polymer chains and subsequent dramatic switching in surface properties.5.Based on above work,application potential of PNI-co-PT-co-Glc polymer material in the field of glycopeptide enrichment was further explored.Firstly,we chose several frequently occurring monosaccharides in natural glycopeptides to treat the PNI-co-PT-co-Glc polymer film,and further investigated the responsive changes in surface properties of the film.The results showed that the PNI-co-PT-co-Glc polymer selectively interacted with sialic acid Neu5Ac,this interaction led to the conformational transformation form initial contracted form to a swollen and loose form for the polymer.Consequently,the polymer film became much softer and more hydrophilic,and this switching could also exhibited reversibility upon further water treatment.Therefore,these features of reversible polymer conformation transformation and concomitant surface macroscopic properties switching resulting from interaction of polymer with sialic acid,make the smart polymer material a promising candidate for glycopeptide enrichment,silalylated glycopeptide in particular.Furthermore,the results of glycopeptides enrichment experiment demonstrated that 26 glycopeptides were detected in MS spectra from the tryptic digests of Fetuin after enrichment with PNI-co-PT-co-Glc@SiO2 when eluted with50%ACN/50%H2O/5 mol·L-1 NH4HCO3.Moreover,24 glycopeptides were detected in the presence of interference BSA?molar ratio of Fetuin and BSA is 1:100?,and most of these glycopeptides were sialylated glycopeptides according to the results of Tandem MS analysis.In summary,smart polymer PNI-co-PT-co-Glc exhibited good selectivity and anti-interference performance for sialylated glycopeptides enrichment,which provides guidance for the development of highly efficient enrichment materials. |
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