Polymer Science and Engineering Division, National Chemical Laboratory, Pune 411008, India.
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
Langmuir. 2021 Mar 9;37(9):2974-2984. doi: 10.1021/acs.langmuir.1c00047. Epub 2021 Mar 1.
Surface coatings play an important role in improving the performance of biomedical implants. Polydimethylsiloxane (PDMS) is a commonly used material for biomedical implants, and surface-coated PDMS implants frequently face problems such as delamination or cracking of the coating. In this work, we have measured the performance of nano-coatings of the biocompatible protein polymer silk fibroin (SF) on pristine as well as modified PDMS surfaces. The PDMS surfaces have been modified using oxygen plasma treatment and 3-amino-propyl-triethoxy-silane (APTES) treatment. Although these techniques of PDMS modification have been known, their effects on adhesion of SF nano-coatings have not been studied. Interestingly, testing of the coated samples using a bulk technique such as tensile and bending deformation showed that the SF nano-coating exhibits improved crack resistance when the PDMS surface has been modified using APTES treatment as compared to an oxygen plasma treatment. These results were validated at the microscopic and mesoscopic length scales through nano-scratch and nano-indentation measurements. Further, we developed a unique method using modified atomic force microscopy to measure the adhesive energy between treated PDMS surfaces and SF molecules. These measurements indicated that the adhesive strength of PDMS-APTES-SF is 10 times more compared to PDMS-O-SF due to the higher number of molecular linkages formed in this nanoscale contact. This lower number of molecular linkages in the PDMS-O indicates that only fewer numbers of surface hydroxyl groups interact with the SF protein through secondary interactions such as hydrogen bonding. On the other hand, a larger number of amine groups present on PDMS-APTES surface hydrogen bond with the polar amino acids present on the silk fibroin protein chain, resulting in better adhesion. Thus, APTES modification to the PDMS substrate results in improved adhesion of nano-coating to the substrate and enhances the delamination and crack resistance of the nano-coatings.
表面涂层在改善生物医学植入物的性能方面发挥着重要作用。聚二甲基硅氧烷（PDMS）是生物医学植入物常用的材料，表面涂覆 PDMS 植入物经常面临涂层分层或开裂等问题。在这项工作中，我们已经测量了生物相容性蛋白聚合物丝素（SF）纳米涂层在原始和改性 PDMS 表面上的性能。PDMS 表面已通过氧等离子体处理和 3-氨丙基三乙氧基硅烷（APTES）处理进行改性。尽管这些 PDMS 改性技术已经为人所知，但它们对 SF 纳米涂层附着力的影响尚未得到研究。有趣的是，使用拉伸和弯曲变形等整体技术对涂层样品进行测试表明，与氧等离子体处理相比，当 PDMS 表面经过 APTES 处理改性时，SF 纳米涂层表现出更好的抗裂性。通过纳米划痕和纳米压痕测量，在微观和介观长度尺度上验证了这些结果。此外，我们开发了一种使用改性原子力显微镜测量处理过的 PDMS 表面和 SF 分子之间粘附能的独特方法。这些测量表明，由于在纳米级接触中形成的分子键数量更多，PDMS-APTES-SF 的粘附强度是 PDMS-O-SF 的 10 倍。这表明在 PDMS-O 中形成的分子键数量较少，这意味着只有较少数量的表面羟基基团通过氢键等次级相互作用与 SF 蛋白相互作用。另一方面，PDMS-APTES 表面上存在大量的胺基团与丝素蛋白链上的极性氨基酸形成氢键，从而导致更好的粘附性。因此，对 PDMS 基底进行 APTES 改性可改善纳米涂层对基底的附着力，并增强纳米涂层的分层和抗裂性。
