Molecularly Imprinted Polymer Sensing Coating Based On Macromolecular Self-Assembly

In view of some challenges and difficulties in the development of molecular imprinting technology,this work proposed a universal strategy for constructing water-dispersed molecularly imprinted polymer nanoparticles based on the weak intermolecular interaction.Employing photosensitive or electroactive amphiphilic polymers as basic building blocks,and bioactive molecules with different sizes as template molecules,a series of nanoscale molecularly imprinted polymer(MIP)aggregates were constructed through multi-component co-assembly and organic/inorganic hybrid assembly in the aqueous phase.These MIP aggregates were further used to modify the electrode surface,forming electrochemical sensing coatings with specific recognition function after fixing the recognition sites by photo-crosslinking or electro-polymerization.Subsequently,the template molecules were eluted.Meanwhile,either organic or inorganic electroactive elements were introduced to improve the comprehensive material and sensing performance.Through systematic research on the influence of polymer structural components,different assembly conditions,and assembly methods on the formation and performance of MIP nanoparticles,this work revealed the interaction between different functional polymers and multi-scale template molecules,and the formation process of MIP aggregates.Moreover,this work clarified the formation mechanism of multi-component and hierarchically-assembled MIP nanoaggregates based on weak intermolecular interaction,as well as the structure-property relationship between different structures and the sensing properties of materials.The detailed researches are as follows: 1.Construction of water-dispersed and self-assembled molecularly imprinted polymer nanoparticles(MIPNs)based on weak interactionThrough the simulation calculation of the interaction between functional monomers and different template molecules,and combining with the experimental design,the general rules of constructing water-dispersed MIPNs and their electrochemical sensing coatings based on weak interactions are summarized.A kind of photosensitive amphiphilic random copolymer UPoly(DMA-co-EHA-HEA-co-St)(UPDEHS)was synthesize employing DMA,EHA,HEA,and St as monomers,after modification with double bond.UPDEHS was used as the building block to form a polymer/template complex by the weak interactions with different template molecules in aqueous solution,resulting in a series of water-dispersed MIPNs by self-assembly process.The polymer chains constructed a three-dimensional network structure around the template molecules,which formed molecularly imprinted cavities that match the template molecule in the shape and size as well as the site of action.These MIPNs had good water dispersibility and soft particle characteristics.The MIPNs were induced to perform a cathode electrophoretic coating by an external electric field,forming a molecularly imprinted polymer coating on the electrode surface.The imprinted sites were fixed by UV light to improve the stability of the coating,and an electrochemical MIP sensor was generated after eluting the template molecules.A series of results showed that the construction of water-dispersed MIPNs based on weak interactions is effective,which could be extended to other polymer and template molecules.2.Construction of sensing coating based on Au NPs-enhanced self-assembled MIPNsConsidering the electrochemical inertness of UPDEHS,a high-performance molecularly imprinted polymer nanoparticle(Au@MIPNs)enhanced with Au NPs was prepared,and the application of Au NPs in the performance enhancement of the sensing coating was explored.Using glucose as template molecule and chloroauric acid as precursor,Au@MIPNs wre formed by multi-component co-assembly in aqueous solution.In this process,chloroauric acid ions were converted into Au NPs due to the reducibility of the imine groups in the UPDEHS molecules under acidic conditions.UPDEHS can simultaneously act as a reducing agent and stabilizer for Au NPs.The pH,concentration of template molecule,and salt concentration had influence on the formation of Au NPs and Au@MIPNs.Owing to the positively charged characteristics of Au@ MIPNs,they were subjected to cathodic electrophoretic deposition under the induction of an external electric field,and the imprinted sites were fixed by UV crosslinking while improving the solvent resistance of the coating.After eluting the template molecules,a molecularly imprinted sensing coating for glucose recognition was obtained,which can be applied to detect glucose in human urine.Compared with the MIP coating without Au NPs modification,the Au@ MIPNs sensor coating has higher sensitivity,wider detection range,and lower detection limit.This is mainly due to that the Au NPs built a conductive path inside the coating,which accelerated the electron transmission rate between the imprinting holes and the sensor electrode.And also,electrochemical activity of the sensing coating was enhanced.The resultant sensor has great potential application prospects in biomedical detection and other fields.3.Construction of sensing coating based on photo-crosslinked protein-imprinted MIPNsIn order to extend the method of constructing water-dispersed MIPNs based on weak intermolecular interactions from small molecule templates to biological macromolecular templates,this work proposed a simple strategy for specific recognition and detection of proteins based on a UV-crosslinkable molecularly imprinted polymer as a “macromonomer”.A linear photo-crosslinkable amphiphilic random copolymer UPoly(DMA-co-HEA-co-St)(UPDHS)was designed and synthesize employing DMA,HEA,and St as monomers.Then UPDHS was co-assembled with the template protein namely BSA through weak interaction in aqueous solution,obtaining water-dispersed protein-imprinted polymeric nanoparticles(BSA@UPDHS NPs).The linear macromolecular chains could form a three-dimensional structure around the protein molecule,which could form imprinted cavities while protecting the structural integrity of the protein molecules.The effects of assembly environment and polymer structure on the formation of BSA@UPDHS NPs were studied.BSA@UPDHS NPs were fixed on the electrode surface,and the imprinted cavities were fixed by UV-crosslinking.Also,the stability of the coating was improved.After eluting the template molecules,the BSA@UPDHS sensor coating was prepared.The results showed that the sensor coating has high selectivity,anti-interference ability and stability,and it can achieve wide linear range for BSA detection.The versatility of the method was also confirmed by using other proteins(such as OVA)as template molecules.The results indicated that it is an effective method to construct water-dispersible protein-imprinted polymer nanoparticles by using the UV-crosslinkable amphiphilic macromolecule UPDHS as a “macromonomer”.This work provided a new concept for preparing high-performance protein imprinted materials based on fully-synthetic polymers.Also,this work showed great enlightening significance for the preparation of bio-composites.4.Construction of sensor coating based on electropolymerized protein-imprinted MIPNsConsidering the electrochemical inertness of traditional molecularly imprinted polymers,this work proposed a simple strategy for constructing protein-imprinted polymer nanoparticles using electrically-polymerizable amphiphilic macromolecules as “macromonomers”.A linear electro-polymerizable amphiphilic random copolymer Poly(AM-co-HEA-co-Nvc)(PAHN)was designed and synthesized employing AM,HEA,and Nvc as monomers.Then PAHN was combined with the template molecule namely BSA in aqueous solution through weak interaction,and they co-assembled to form water-dispersed protein-imprinted polymer nanoparticles(BSA@PAHN NPs).The linear macromolecular chains not only protected the structural integrity of proteins,but also improved the protein affinity.The nanoparticles were fixed on the electrode surface,and the imprinted cavities were fixed by the electrochemical oxidation polymerization of the carbazole elements in PAHN polymers.Meanwhile,the formation of a polycarbazole conductive network provided the coating with electrochemical activity.After eluting the template molecules,the BSA@PAHN sensing coating was obtained.Compared with the BSA@UPDHS coating,BSA@PAHN has better recognition and detection performance,which was mainly due to the stronger affinity of the PAHN polymers and the formation of electro-polymerized polycarbazole network inside the coating.The conductive paths accelerated the electron transmission rate between the imprinted cavities and the sensing electrode,and thus improved the overall sensing performance of the coating.Using trypsin as a template molecule,the versality was studied.The results showed that this work provided a way to solve the electrochemical inertness of imprinted polymers based on the molecular structure design and the selection of suitable electroactive monomers to prepare “macromonomers”.Using electro-polymerization instead of photo-crosslinking to construct protein-imprinted sensing coating,the comprehensive sensing performance was further improved while ensuring the stability of the coating structure and the effectiveness of the imprinting effect.5.Construction of sensor coating based on polymer nanoparticles decorating MWCNTsTaking advantage of the large number of carbazole moieties in the PAHN polymers,an “olive-like” nanocomposites(PAHN/MWCNTs NC)with MWCNTs as the axis and PAHN as beads were prepared in aqueous solution through the non-covalent functional modification of MWCNTs due to the ?-? interaction between carbon nanotubes and polymers.The carbazole content and compound ratio had a great influence on the formation and interface performance of the PAHN/MWCNTs NC.On the one hand,the PAHN/MWCNTs NC was explored for constructing an enzyme-free sensing coating for nitrite detection.It showed excellent sensing performance for nitrite determination in complex aqueous solutions.On the other hand,a protein-imprinted polymer/carbon nanotube composite(BSA@PAHN/MWCNTs NC)was formed using BSA as the template molecule based on the “macromonomer” property of PAHN.The BSA detection results showed that the material has excellent recognition ability for BSA,and can achieve quantitative detection of BSA in a wide linear range.The excellent sensing performance was mainly attributed to the polycarbazole network formed after electro-polymerization and the interpenetrating conductive network built combining with MWCNTs.As a result,the electrochemical response of the coating was improved,and so was the signal-to-noise ratio.At the same time,the “olive-like” structure provided the coating with a certain surface microstructure,which offered abundant electroactive sites for analyte detection.The above results indicated that the use of weak intermolecular interactions can prepare nanocomposites with special morphology,which provides strong evidence and theoretical reference for the construction of high-performance composites based on weak interactions.In summary,this thesis validated the effectiveness of building high-performance molecularly imprinted polymer coatings based on weak intermolecular interactions by combining the theory and experiment.It not only enriches the preparation method of water-dispersed MIP NPs,but also provides new ideas for the construction of functional polymer-based recognition materials with complex structures and functions.At the same time,this strategy has certain versality and can be extended to other functional polymers and active molecules,thus providing valuable theoretical guidance and reference significance for the construction of hierarchically-assembled structures and their applications based on functional macromolecular colloids.