The development of innovative, biocompatible, and ecologically acceptable materials is being driven by the requirement for long-lasting, antifouling surfaces. Antifouling coatings are required for many medical devices that are made of or covered in silica. To resist the adsorption of proteins and bacteria, various biomedical surfaces, such as endoscopic lenses, joint joints, and implants, should have excellent anti-adhesive qualities.
Inspired by lubricin (LUB), which has excellent anti-fouling properties, Alfa Chemistry designs a bottle brush structured polymer coating on silica surfaces with stability and ease of use. The coating has a very low fouling rate and effectively prevents the adsorption of serum albumin and lysozyme.
Lubricin (LUB), a form of mucin that is found as a glycoprotein-like protein in mammalian synovial fluid, is also an effective anti-adhesive agent. LUB has a great anti-adhesive capacity and a very low friction coefficient. The unusual molecular structure, often known as the "bottle brush" structure, is largely responsible for its exceptional qualities.
An extended bottle brush mucilage domain is sandwiched between two spherical sticky end domains of the LUB molecule. Due to the strong attachment of LUB to the surface through these two end regions, this unique tri-block polymer has outstanding antifouling capabilities. Furthermore, the presence of a firmly bonded hydration layer in the vicinity of the polymer is facilitated by the huge amount of negative charge on the mucus domain, giving LUB outstanding anti-adhesive capabilities.
Fig 1. (a) Schematic structure of lubricin. (b) Complex and detailed block-copolymer type structure of lubricin with functional end groups. (Materials S, et al. 2018)
The substantial negative charge of LUB, on the other hand, may prevent positively charged proteins from adsorbing non-specifically. The capacity of LUB to adopt the conformation required for efficient antifouling is hampered by its adsorption on positively charged surfaces. However, Alfa Chemistry overcame these challenges by designing and synthesizing LUB-inspired block polymers that provide superb antifouling properties.
For our customers, Alfa Chemistry has designed and synthesized a library of LUB-inspired block polymers. Poly (2-methacryloyloxyethyl phosphorylcholine) polyampholytic branches are grafted onto the flexible hydrophobic copolymer backbone in these polymers, replacing the mucoadhesive structural domain of LUB (Polymer B). Polymers are given a neutral charge by the polyampholytic branching chains, which improves their anti-adhesive characteristics and biocompatibility.
Binder blocks (Block A containing positively charged quaternized 2-(dimethylaminoethyl) methacrylate, monomer and hydrophobic methyl methacrylate monomer) are incorporated into the structure to enhance adsorption and stability through electrostatic interactions. The ABA triblock polymer has a bottle brush structure in the center and two lateral linear blocks that are designed to be firmly adhered to the surface. Only one binder block is used in the two-block structure AB.
Fig 2. The molecular structures of ABA, AB, and B polymers. The anchoring side groups are depicted in orange and the pendant zwitterionic chains of the bottlebrush polymers are in blue. (Xia Y. Q, et al. 2019)
By using simple drop-casting or in-line exposure procedures, these bottle-brush shaped polymers strongly adsorb onto the silica surface to produce a homogenous film coating in less than 10 minutes, and they are particularly stable in high salinity solutions and throughout a wide pH range. Using various methodologies, we examined the coatings' antifouling capabilities against proteins and bacteria, demonstrating ultra-low fouling performance. When serum albumin and lysozyme adsorb less than 0.2 ng cm-2, such polymer coatings are 50 to 25 times more effective than LUB and other known ultra-low fouling coatings.
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