Abstract
The synthesis of polymer brush decorated silica nano-particles is demonstrated by activator regeneration by electron transfer atom transfer radical polymerization (ARGET ATRP) grafting of poly(tert-butyl methacrylate). ATRP initiator decorated silica nano-particles were obtained using a novel trimethylsiloxane derivatised ATRP initiator obtained by click chemistry. Comparison of de-grafted polymers with polymer obtained from a sacrificial initiator demonstrated good agreement up to 55% monomer conversion. Subsequent mild deprotection of the tert-butyl ester groups using phosphoric acid yielded highly colloidal and pH stable hydrophilic nano-particles comprising approximately 50% methacrylic acid groups. The successful bio-conjugation was achieved by immobilization of Horseradish Peroxidase to the polymer brush decorated nano-particles and the enzyme activity demonstrated in a conversion of o-phenylene diamine dihydrochloride assay.
Highlights
The advent of nano-technology and more recently nano-medicine has increased the demand for well-defined nano-particles (NPs) for example in areas such as diagnostics, drug delivery, bio-separation among others [1,2,3,4,5,6]
We are interested in the decoration of Silica nano-particles (Si-NPs) with poly(methacrylic acid) (PMAA) or poly(acrylic acid) (PAA) as they can be conjugated with biomolecules by conventional coupling chemistry [12]
After cooling to room temperature, the mixture was filtered and the filtrate concentrated under reduced pressure by rotary evaporation at 35 °C, 0.1 mbar for 2 h to yield a yellow liquid as product. 1H nuclear magnetic resonance (NMR) (600 MHz, CDCl3, δ): 3.57 (s, 9H, O–CH3), 3.27, 1.71 (m, 2H, CH2), 0.71 (m, 2H, Si-CH2)
Summary
The advent of nano-technology and more recently nano-medicine has increased the demand for well-defined nano-particles (NPs) for example in areas such as diagnostics, drug delivery, bio-separation among others [1,2,3,4,5,6]. Silica nano-particles (Si-NPs) is among the most widely applied class of nano-particles owing to their well-documented synthetic accessibility by the base or acid catalyzed condensation of low molecular weight silicates This process is known as the Stöber synthesis (and variations thereof) allows the synthesis of Si-NPs ranging from 15 to 800 nm [7,8] with good size control and, if desired, the incorporation of dyes or active molecules [9]. While the catalyst can be removed when micro or macroscopic substrates are used (e.g., silicon wafers), removal of the catalyst from NP is challenging This drawback can be overcome by activator regeneration by electron transfer (ARGET) ATRP [21,22,23]. (PBMA) yielded hydrophilic PAA decorated Si-NP with high colloidal stability
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