Self-adhesive lubricated coating for enhanced bacterial resistance

Abstract

Limited surface lubrication and bacterial biofilm formation pose great challenges to biomedical implants. Although hydrophilic lubricated coatings and bacterial resistance coatings have been reported, the harsh and tedious synthesis greatly compromises their application, and more importantly, the bacterial resistance property has seldom been investigated in combination with the lubrication property. In this study, bioinspired by the performances of mussel and articular cartilage, we successfully synthesized self-adhesive lubricated coating and simultaneously achieved optimal lubrication and bacterial resistance properties. Additionally, we reported the mechanism of bacterial resistance on the nanoscale by studying the adhesion interactions between biomimetic coating and hydrophilic/hydrophobic tip or living bacteria via atomic force microscopy. In summary, the self-adhesive lubricated coating can effectively enhance lubrication and bacterial resistance performances based on hydration lubrication and hydration repulsion, and represent a universal and facial strategy for surface functionalization of biomedical implants.

Keywords: Bacterial resistance; Biomimetic coating; Dopamine; Lubrication; Self-adhesive.

Graphical abstract

Fig. 1

Illustration showing the facile fabrication of PDA/DMA-MPC biomimetic coating for (A) excellent lubrication property based on hydration lubrication mechanism and (B1–C2) enhanced bacterial resistance property based on hydration repulsion: (B1) quantitative evaluation of dynamic adsorption of proteins on copolymer-coated Au–Ti sensors using QCM, (B2) qualitative/quantitative evaluation of bacterial resistance of copolymer-coated Ti6Al4V substrates, and force measurements probing the interactions between biomimetic coating and (C1) hydrophobic tips or (C2) living bacteria on the nanoscale using AFM.

Fig. 2

Material characterizations and tribological measurements. (A) ¹H NMR spectra of three different proportions of copolymers DMA-MPC. (B) XPS and (C1–C4) WCA of bare Ti6Al4V and three kinds of Ti6Al4V@DMA-MPC. (D) Schematic illustration showing the setup of tribological measurements, with a typical contact pair between PS microsphere and Ti6Al4V substrate. (E) The COF values under four normal force conditions in the tribological measurements.

Fig. 3

(A) XPS of four different Ti6Al4V substrates. (B) High-resolution narrow spectrum of N 1s for (B1) Ti6Al4V@PDA, (B2) Ti6Al4V@DMA-MPC and (B3) Ti6Al4V@PDA/DMA-MPC. (C) WCA and (D) surface morphologies of (C1, D1) Ti6Al4V, (C2, D2) Ti6Al4V@PDA, (C3, D3) Ti6Al4V@DMA-MPC (1:4) and (C4, D4) Ti6Al4V@PDA/DMA-MPC (1:4). The Ti6Al4V substrates were treated with plasma to obtain hydroxylated surfaces. (E) Frequency and dissipation changes associated with the self-adhesive biomimetic coating for (E1) DMA-MPC and (E2) PDA/DMA-MPC. (F) Quantitative characterization of the durability of the copolymer coating by monitoring the change of fluorescence intensity in the microfluidic channel under flow scouring test. The fluorescence images of various scouring times: (F1) 0 h, (F2) 7 h, (F3) 1 d, and (F4) 3 d (F5) The change of fluorescence intensity at different scouring times.

Fig. 4

(A) Frequency and dissipation changes associated with dynamic adsorption of BSA on bare and copolymer-coated Au–Ti sensors. (B) The bacterial resistance property tested by spread plate assay. (B1) The bacterial resistance ratio of different substrates. The colony images of (B2) bare Ti6Al4V, (B3) Ti6Al4V@DMA-MPC, and (B4) Ti6Al4V@PDA/DMA-MPC with the bacterial count as 100%, 17.5%, and 1.9%, respectively. (C) Representative SEM images showing E. coli adhesion on the Ti6Al4V substrates after culturing for 24 h: (C1) bare Ti6Al4V, (C2) Ti6Al4V@DMA-MPC, and (C3) Ti6Al4V@PDA/DMA-MPC.

Fig. 5

Representative force-distance curves during approach and separation process in the force measurements using AFM for (A1-A3) hydrophilic tip and (B1–B3) hydrophobic tip against the bare Ti6Al4V, Ti6Al4V@DMA-MPC and Ti6Al4V@PDA/DMA-MPC substrates. The inset figures are the SEM images of the tips. (A4, B4) Statistical analysis of adhesion force and adhesion energy obtained from the separation process. (C1) Schematic illustration showing the force measurements between copolymer-coated AFM tip against bacteria-coated substrate, with different dwell times of 0 s, 10 s and 30 s (C2) Microscopy images of the bacteria-coated substrate. (C3) Microscopy images in the force measurements between AFM tip and bacteria-coated substrate. The green fluorescence indicates that the immobilized bacteria are alive (C4) before and (C5) after the force measurements. (D) Representative force-distance curves during approach and separation process in the force measurements for (D1) Ti tip, (D2) Ti@D-M tip and (D3) Ti@P/D-M tip against bacteria-coated substrates. (E) The adhesion force and adhesion energy between three different AFM tips and bacteria-coated substrates obtained from the separation process under the dwell time of (E1) 0 s, (E2) 10 s and (E3) 30 s. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)