Chemisorbed poly(propylene sulphide)-based copolymers resist biomolecular interactions

Abstract

Alkanethiolates have been widely used as chemisorbates to modify gold surfaces, in spite of their relatively poor oxidative stability. We introduce gold-chemisorbing block copolymers bearing an anchoring block of poly(propylene sulphide) (PPS), selected in the expectation of greater stability. These materials offer a more robust approach to surface modification of gold. As an example, a triblock copolymer with poly(ethylene glycol) (PEG) was selected, with the goal of minimizing biological adsorption and adhesion. The copolymer PEG17-bl-PPS25-bl-PEG9 chemisorbed to form a dense monolayer of 226 +/- 26 ng cm(-2), approximately 2.2 nm thick. The copolymeric adlayer was much more stable to oxidation than commonly used alkanethiolates. Its presence greatly reduced protein adsorption (>95%), even after exposure to whole blood serum (>55 mg x ml(-1)), as well as cell adhesion over long culture durations (>97%). PPS-containing copolymers are an attractive alternative to alkanethiolates, and PEG-bl-PPS-bl-PEG presents a powerful example for use in biodiagnostic and bioanalytical devices.

Construction of a densely poly(ethylene glycol)-chain-tethered surface and its performance

“…We have already confirmed the usefulness of the oligoamine anchor 15,16,26,27,56,[72][73][74][75][76] instead of the sulfanyl group anchor [77][78][79] for molecular immobilization on gold surfaces and developed polyamineended PEG-modified gold surfaces using PEG-block-poly [2- Densely PEG-chain-tethered biointerface Y Nagasaki platform for ssDNA immobilization and detection; 73 in our scheme, PEG-b-PAMA was immobilized onto the gold surface followed by treatment with a ssDNA-SH, resulting in the formation of ssDNA-SH/ PEG-b-PAMA co-immobilized gold surface.…”

“…46,47 However, the Au-S linkage is not strong enough under physiological conditions because of the limited oxidative stability of thiolate species, [48][49][50] as well as the exchange reactions with thiolated compounds that occur inside the body. Thiolatemodified surfaces are also damaged by exposure to light, high temperature and oxygen.…”

“…Thiolatemodified surfaces are also damaged by exposure to light, high temperature and oxygen. [48][49][50] To improve the long-term stability of Scheme 1 Mixed-poly(ethylene glycol) (PEG) tethered-chain surface (long PEG chain improves non-fouling character, and short PEG chain increases PEG chain density). solutions of the proteins and several peptides possessing different molecular weights were analyzed using a conventional PEG (5k) chain surface (squares), a mixed-PEG (5k/2k) chain surface (circles), and a commercial CM5 chip (triangles) blocked by ethanol amine via the active-ester method, n¼4.…”

Nano-scale superhydrophobicity: suppression of protein adsorption and promotion of flow-induced detachment

“…Reducing protein adhesion has been approached in several ways in the past, including chemically coating the surfaces with hydrophilic groups such as poly(ethylene glycol) 7,8 , filling the surface sites with other molecules 9 and attaching proteolytic enzymes to surfaces 10 . Surfaces that employ flow shear removal are used in a small number of applications, typically fast boats as the shear rate required is high and the material used can easily become damaged.…”

“…Highly hydrophilic surfaces are usually used to reduce protein fouling. 7,8 It has, however, been suggested that superhydrophobic surfaces could reduce the extent of protein adsorption due to the reduction in solid surface area at the liquid interface (Cassie-Baxter bridging case only) 13,14,15 . A recent publication highlights the possibilities of superhydrophobic coatings but also shows how little work has been undertaken in this area.…”