International audienceThe efficacy of biomaterials is frequently dependent upon the interface between a synthetic material and the surrounding biology. While silicones offer many benefits in biomaterials applications, they can suffer from insufficient hydrophilicity. We present a controlled and generic route to the surface modification of silicones that permits the introduction of a passivating poly(ethylene glycol) (PEG) layer capped with biologically relevant molecules. High-density, tosylate-modified, PEG-tethered silicone surfaces are readily prepared. These surfaces provide a generic platform for further surface modification by nucleophilic substitution (SN2). The efficiency of substitution at the surfaces was established using a broad variety of nucleophiles: although triphenylphosphine did not modify the tosylated surface, the surface reaction of primary amines, azide, and a thiol was demonstrated to be highly efficient in organic solvents at several temperatures. Changes in surface chemistry and properties were demonstrated by water contact angle, ATR-FTIR, XPS and 13C solid-state NMR spectroscopy

Fabrication of monolithic protein-doped capillary columns was reported almost 10 years ago. These columns were derived from a diglycerylsilane precursor, however this material is not commercially available, is difficult to produce in large quantities and has very short phase separation and gelation times, which leads to issues with column reproducibility. Herein, we investigate the use of sodium silicate (SS), a commercially available biofriendly sol-gel precursor, for the fabrication of bimodal meso/ macroporous protein-doped monolithic silica columns that are suitable for immobilized enzyme reactor (IMER) assays. Using an automated liquid handler and platereader, a hierarchical materials screening approach was applied to $1400 formulations, from which we have identified materials with long gelation times that can form robust bimodal meso/macroporous materials suitable for fabrication of monolithic silica columns. A subset of these materials was observed to have good chromatographic behavior (appropriate backpressure and good stability). A secondary screen around lead materials was performed to identify optimal materials for fabrication of IMER columns. These materials were tested for leaching and activity of immobilized acetylcholine esterase to identify an optimal material for IMER column fabrication. The optimal material was formed from 2% (w/v) silica which was combined with 1.25% PEG 600 at pH 6.4 in 100 mM TRIS buffer. Such columns showed reproducible IMER performance and were able to quantitatively measure the inhibition of immobilized AChE by galanthamine with an inhibition constant of 175 AE 5 nM, which is in excellent agreement with the literature value.

Analytical derivatizations (AD) can increase the sensitivity of analyses-including those with mass spectrometric detection-by as much as three orders of magnitude. The extra steps required, however, are a possible impediment to their use. To simplify AD we investigated solid-phase analytical derivatization (SPAD) of compounds with diverse structures by using pentafluorobenzyl bromide (PFBBr) as the reagent. Model compounds were organic acids (e.g. phenols, chlorophenols and carboxylic acids) which were simultaneously extracted and derivatized from 0.1 M NaOH onto a polystyrene-divinylbenzene resin (XAD-4) as their pentafluorobenzyl (PFB) derivatives. Test analytes ranged in molecular weight from 94 for phenol to 266 for pentachlorophenol and octanol-water partition coefficients (log P) values ranged from 1.48 for phenol to 7.15 for hexadecanoic acid. Under SPAD conditions, reaction rates rapidly increased with log P, but yields for less lipophilic compounds, although precise, were unacceptably low. Use of the tetrabutylammonium (TBA) cation as a phase transfer catalyst increased the yield of compounds with low log P; but, unexpectedly, as the log P of the analyte increased, the phase transfer catalyst caused a decrease in yield. The data from this study define the log P range of compounds that require TBA for optimal yield and the log P range of compounds for which TBA compromises yield. This insight led to a simple, two-step, one-pot technique that gave high yields of the PFB derivatives for the entire range of analytes studied. SPAD first extracted/derivatized the lipophilic analytes from aqueous solution onto the solid phase. Extraction/derivatization of the polar analytes followed upon addition of TBA to the reaction mixture. The PFB ethers and esters of the entire range of analytes were then eluted from the XAD-4. The two-step procedure was faster, used less reagent and required lower temperature than comparable methods in the literature. With the twostep procedure, pentafluorobenzylation of phenols and carboxylic acids from water gave yields in excess of 88% with the exception of phenol and pentachlorophenol which were recovered in 57 and 44%, respectively. For all analytes, relative standard deviations were below 15%. The effect of matrix on yield varied between zero and a decline in recoveries of approximately 20-30% depending on the analyte and concentrations of NaCl or humic acid. In the presence of matrix components relative standard deviations remained below 20%.