Preparation And Application Of Non-Covalent Polymeric Antifouling Coatings

It will affect the performance of the biomaterials if there is non-specific protein adsorption on the surface of the materials, thus low/non-specific adsorption by proteins or cells is a key factor for developing biomedical devices, and the polymer coatings were always used to achieve this goal. Now the methods to prepare polymer coating were shown below:1. Covalent bonded coatings:the coatings formed by this way were stable enough, but the procedure was complicated, time-consuming and poor controllability;2. Non-covalent banded coatings:the coating process was simple and fast, but the coatings were easily washed off due tothe poor stability. In order to enhance the stability of the non-covalent banded coatings, we developed some method as follows:1. In order to enhance the hydrophobic interaction bween the polymers and substrates, a series of double-hydrophilic double-grafted PMA-g-PEG/PDMA copolymers (containing poly(methacrylate)(PMA) as backbone, poly(ethylene glycol)(PEG) and poly(N,N-dimethylacrylamide)(PDMA) as side chains) were synthesized successfully by using reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP). Then, they were used as physical coatingstoevaluatethe protein-resistant properties by using capillary electrophoresis (CE). In the wide pH range (pH=2.8-9.8), the mobility of electroosmotic flow (EOF) could be suppressed by the PMA-g-PEG/PDMA copolymer coatings, and the EOF mobility decreased when themolecular massof copolymer or PDMA content wasincrease. In the meantime, theoretical plate number of separation, the repeatability of migration time and protein recovery demonstrated that antifouling efficiency was enhanced with the increament of molecular mass or PEG content.2. In order to increase the coatings’stability, andtest the quality level of medicinal human albumin (HA) by using capillary electrophoresis, we prepared thermal-crosslinked poly(vinyl pyrrolidone)(PVP) coated fused silica capillary to resist HA adsorption. This type of capillary was easily obtained by injecting the aqueous PVP solution into the ordinary fused silica capillary, sealed with silicone rubber and then thermally annealing it at200℃. In the PVP coated capillary, notably low and stable EOF was obtained at the wide pH range from2.20to9.00; excellent repeatability and separation efficiencywere exhibited when separating a mixture of four basic proteins, and baseline separation of these four basic proteins could even be achieved at pH7.00. The protein recovery percentage of human serum albumin (HSA) in single-protein solution and mixed-blood-proteins solution was determined to be97.03%and95.40%in the PVP50-3capillary (representing the concentration of the capillary-injected PVP aqueous solution,50mg/mL, and thermal annealing time,3h), respectively. Based on the results above, we used the PVP50-3-coated capillary to quantify the content of HA, and the results (obtained from run to run, capillary to capillary and day to day) verified that the coated capillary could be used to test the quality of commercially available HA.3. In order to enhance the coating ability of poly(2-methyl-2-oxazoline), we synthesized a series of novel well-defined poly(2-methyl-2-oxazoline)-block-poly(4-vinyl pyridine)(PMOXA-b-P4VP) diblock copolymers by using copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction of α-alkynyl-PMOXA and ε-N3-P4VP, in which a-alkynyl-PMOXA and ε-N3-P4VP were prepared by cationic ring opening polymerization (CROP), and atom transfer radical polymerization (ATRP), respectively. Afterwards, with the hydrogen-bonding interaction between P4VP and poly(acrylic acid)(PAA), micellization happened with crosslinking when dropping PAA solution on the top of PMOXA-b-P4VP coating, and the size of the micelles decreased with the increment of the chain length of PMOXA block. The long-term stability of these PMOXA-b-P4VP/PAA coatings showed that increasing PMOXA chain length can improve not only the hydrophilicity but also the stability of the coatings. Due to the pH sensitivity of hydrogen bond interaction between P4VP and PAA, the PMOXA-b-P4VP/PAA coatings could be removed at low or high pH value, and these coatings were stable at pH=3-7. This simple method can form stable coatings on either inoganic (such as, silicon wafer) or organic material (such as, poly(methyl methacrylate)(PMMA) sheet) surface, and it could greatly enhance the antibiofouling properties of the surfaces.4. Considering the study of Yan et al., there would be free radical formation on the backbone of P4VP under UV irradiation, and the coupling of radical can lead to the crosslinking of P4VP. Based on this, we proposed a simple procedure to obtain a stable PMOXA coating. First, we prepared the spin-coated PMOXA-b-P4VP coatings, and then UV irradiated. The hydrophilicity of the coatings was obviously decreased after UV curing, and the water contact angle was similar to the crosslinked P4VP homopolymer coating. In order to increase the content of the PMOXA chain exposed to the surface, we synthesized a series of brush copolymer P(4VP-co-PMOXA), and then prepared the UV-crosslinked coatings under the same condition. The hydropholicity was still decreased, but more excellent than block copolymer coatings. The content of P4VP in brush copolymer would affect the stability of coating. The crosslinking rate was low while the P4VP content was low, which led to the thinner coating and poorer stability; with the increasing of P4VP content, the crosslinking rate reaching a certain degree, the thickness of the coating was increasing, and the stability was enhanced. Then, the protein-resistant property of these P(4VP-co-PMOXA) coatings was studied, the results showed all the coatings have well antifouling capacity, and the adsorbed BSA on the stable coatings was less than1%compared to the unmodified surface.