Significantly improved cell affinity of polydimethylsiloxane enabled by a surface-modified strategy with chemical coupling

Abstract

Polydimethylsiloxane (PDMS) is a commonly used insulation/packaging material for implantable neural electrodes. Nevertheless, the PDMS-initiated tissue response would lead to the deterioration of the electrode performances post-implantation, owing to its intrinsic hydrophobic and cell-repellent surface. The conventional physical coatings by hydrophilic hydrogels or bioactive molecules are unable to maintain during the long-term implantation due to their low stability by physical adhesion. In this work, we first anchor both hydrophilic polyethylene glycol (PEG) and bioactive molecule poly-L-lysine (PLL) on the PDMS surface by chemical coupling to change the PDMS surface from hydrophobic and cell-repellent to hydrophilic and cell-adhesive. XPS tests indicate the chemically coupled modification layers are stable on the PDMS surface after experiencing a harsh rinse process. Contact angle measurements show that the use of PEG 600 with the moderate molecular weight results in the highest hydrophilicity for the resulting PDMS-PEG-PLL. PC12 cell evaluation results exhibit that the PDMS-PEG-PLL with PEG 600 leads to significantly larger cell adhesion area, more neurite number, and longer neurite length than the PDMS. The PDMS-PEG-PLL with PEG 600 featuring stable modification layers, high hydrophilicity, and superior cell affinity has great potential in stabilizing the neural electrode-tissue interface for the long-term implantation.

Effects of methoxy polyethylene glycol‐polycaprolactone block copolymers and silica nanoparticles on the mechanical, tissue affinity and antibacterial properties of n‐butyl cyanoacrylate adhesive

“…Figure 9 shows the contact angles between sample droplets and pigskin surfaces at the moment of contact, and Table 2 gives the contact angle ( θ 1 ), γ l , and W a . The hydrophilicity of BCA increases with the addition of MP‐3, which contributes to improving the tissue affinity of the adhesive droplets 16 . Thus, 0.5MP‐3 exhibits the smallest contact angle and the largest W a .…”

“…The hydrophilicity of BCA increases with the addition of MP-3, which contributes to improving the tissue affinity of the adhesive droplets. 16 Thus, 0.5MP-3 exhibits the smallest contact angle and the largest W a . The incorporation of SNPs with hydrophobic surfaces into 0.5SNPs/0.5MP-3 leads to a slight decrease in W a compared to 0.5MP-3 because the increased hydrophobicity is unfavorable for adhesion.…”

“…Methoxy polyethylene glycol (MPEG) is a hydrophilic polymer with excellent compatibility with BCA. The addition of MPEG can improve the tissue affinity of BCA by increasing the hydrophilicity 16 . However, its hydroxyl end group may initiate polymerization of BCA, which is unfavorable to long‐term storage.…”

“…The addition of MPEG can improve the tissue affinity of BCA by increasing the hydrophilicity. 16 However, its hydroxyl end group may initiate polymerization of BCA, which is unfavorable to long-term storage. Polycaprolactone (PCL) is often used as a macromolecular plasticizer to improve the flexibility of rigid polymers, and the long-chain PCL can also be physically entangled with poly(n-butyl cyanoacrylate) (PBCA) molecular chains to enhance the cohesion and adhesion strength of the adhesive.…”

Challenges and Opportunities of Implantable Neural Interfaces: From Material, Electrochemical and Biological Perspectives

“…To realize a long-lasting and stable neural interface, the adhesion between electrode and modified layers cannot solely depend on the mechanical interaction with the rough nanostructure, but must be supported by chemical bonding significantly. [220,222] Wei et al [223] prepared 2,3-dihydrothieno(3,4-b)(1,4)dioxine-2carboxylic acid (EDOT-acid), chemically bonded on the activated substrates through the chemisorption of carboxylic group, followed by polymerizing PEDOT. The adhesion between PE-DOT coating and the substrate was significantly enhanced by covalent bonding since the EDOT moiety in EDOT acid facilitated the convenient copolymerization with PEDOT.…”