Materials Silica nanoparticles (diameter 10 nm), acrylamide (AAm, ≥98%), N-hydroxymethyl acrylamide solution (HMAAm, 48%), N,N,N', 99%) and ammonium persulfate (APS, 98%) were purchased from Sigma-Aldrich (Gillingham, UK). N,N-methylenebisacrylamide (BIS) was obtained from ICN Biomedicals Inc. Fluorescein isothiocyanate (FITC, ≥ 90%) was supplied by Fluka (Dorset, UK). Bovine serum albumin (BSA; MW 69 kDa, pI 4.9), hemoglobin (Hb; MW 65 kDa, pI 6.8-7.0), myoglobin (Mb; MW 17.5 kDa, pI 6.8-7.2)

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... nd ovalbumin (OVA, albumin from egg; MW 43.0 kDa, pI 4.5) were obtained from Sigma-Aldrich. Sodium dodecyl sulphate (SDS, 98%) and dichlorodimethylsilane (DCDMS, 98%) were obtained from Merck (Darmstadt, Germany). Other solvents and inorganic salts were of analytical reagent grade and were used without further purification. Fluorescent labeling with FITC To analyze the concentration of OVA and BSA easily, OVA and BSA were labeled with FITC. OVA and BSA (50 mg) were added to 30 mL aqueous solution of FITC (20 mg mL -1 ), and the mixture was incubated at room temperature in dark for 12 h. The proteins were separated by centrifugation with a Vivaspin 20 centrifugal concentrator (Membrane: 30,000 WMCO PES). To remove the excessive FITC, the proteins were washed with water until no fluorescence could be observed in the flow through. The FITC-labeled proteins were then lyophilized in a freeze dryer. Synthesis of DCDMS modified silica nanoparticles Silica nanoparticles with a diameter of 220 nm were prepared using a procedure described in our previous work. 1 In brief, 3.6 g of silica particles (10 nm in diameter, used as seeds) were dispersed into a mixture of methanol (160 mL), water (32 mL) and ammonia (25%, 8 mL) at room temperature. After a sonication of 3 min, 10 mL of TEOS was added to the mixture under stirring, and the mixture was again stirred at room temperature for 12 h. The silica nanoparticles were separated by centrifugation, washed with methanol and water, and dried in a vacuum chamber. Hydrophobic modification of SiO 2 particles was achieved by silanization of the particles with dichlorodimethylsilane (DCDMS) using a procedure similar to that described by Horozov et al. 2 Typically, the silica particles (4 g) were dried at 150 °C for 60 min. After cooling, the silica particles were dispersed in 100 mL of n-hexanen containing 8 mL of DCDMS. The mixture was agitated for 12 h using a magnetic stirrer. The DCDMS modified silica nanoparticles were settled by centrifugation, washed with n-hexanen and methanol, and then dried at 150 °C. Preparation of MIP hydrogels by Pickering emulsion polymerization A water phase was first prepared as the following: 80 mg of Hb was dissolved in 8 mL of PBS buffer (150 mM, pH=7.4). After addition of AAm (250 mg), NHMAAm solution (2000 μL) and BIS (100 mg), the mixture was shaken by hand for 5 min. To break the foams, the mixture was centrifuged at a low speed (4000 rpm) for 5 min. An oil phase was prepared as the following: 300 mg of DCDMS-SiO 2 particles, 15 Electronic Supplementary Material (ESI) for Chemical Communications This journal is