Surface-initiated Reversible Addition-fragmentation Chain Transfer Research Articles

Copolymers with fluorescence properties in mesoporous silica SBA-15: Synthesis and characterization

Abstract A novel copolymer with fluorescence properties in mesoporous silica SBA-15 was prepared via a combination of surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization and “click” chemistry. A sufficient amount of peroxide groups were introduced into mesoporous silica SBA-15 channel pores and were further used to initiate the RAFT polymerization of styrene and 4-vinylbenzyl azide, resulting in SBA-15 supported polystyrene-co-poly(4-vinylbenzyl azide) copolymer (PS-co-PVBA/SBA-15) hybrid material. The samples were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), thermogravimetry analysis (TGA), N 2 adsorption–desorption isotherms and X-ray diffraction (XRD), respectively. The results show that the styrene and 4-vinylbenzyl azide had copolymerized inside mesoporous silica SBA-15. Subsequently, N -propargyl-carbazole (PC) was connected to PS-co-PVBA/SBA-15 hybrid material via “click” reaction, resulting in PS-co-PVBC/SBA-15 with carbazole side groups hybrid material. The fluorescence spectrum is dominated by a broad band from 350 nm to 400 nm in narrow region and the maximum peak is 362 nm, indicating the characteristic absorption of the carbazole group of PS-co-PVBC/SBA-15 hybrid material.

Well-defined nanostructured surface-imprinted polymers for highly selective magnetic separation of fluoroquinolones in human urine.

The construction of molecularly imprinted polymers on magnetic nanoparticles gives access to smart materials with dual functions of target recognition and magnetic separation. In this study, the superparamagnetic surface-molecularly imprinted nanoparticles were prepared via surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization using ofloxacin (OFX) as template for the separation of fluoroquinolones (FQs). Benefiting from the living/controlled nature of RAFT reaction, distinct core-shell structure was successfully constructed. The highly uniform nanoscale MIP layer was homogeneously grafted on the surface of RAFT agent TTCA modified Fe3O4@SiO2 nanoparticles, which favors the fast mass transfer and rapid binding kinetics. The target binding assays demonstrate the desirable adsorption capacity and imprinting efficiency of Fe3O4@MIP. High selectivity of Fe3O4@MIP toward FQs (ofloxacin, pefloxacin, enrofloxacin, norfloxacin, and gatifloxacin) was exhibited by competitive binding assay. The Fe3O4@MIP nanoparticles were successfully applied for the direct enrichment of five FQs from human urine. The spiked human urine samples were determined and the recoveries ranging from 83.1 to 103.1% were obtained with RSD of 0.8-8.2% (n = 3). This work provides a versatile approach for the fabrication of well-defined MIP on nanomaterials for the analysis of complicated biosystems.

Synthesis of Poly(4-vinylpyridine)-Grafted Ordered Mesoporous Silica via Surface-Initiated Reversible Addition-Fragmentation Chain Transfer Polymerization

Synthesis of Poly(4-vinylpyridine)-Grafted Ordered Mesoporous Silica via Surface-Initiated Reversible Addition-Fragmentation Chain Transfer Polymerization

“Grafting-from” Polymerization of PMMA from Stainless Steel Surfaces by a RAFT-Mediated Polymerization Process

The synthesis of grafted PMMA homopolymer films is reported using a surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization from a RAFT-agent immobilized on a silanized stainless steel surface. Therefore, stainless steel surfaces were hydroxylated with piranha solution followed by silanization with 3-aminopropylsilane (APS). The pendant primary amino groups of the cross-linked polysiloxane layer were reacted with 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid N-hydroxysuccinimide ester to produce a surface with covalently immobilized RAFT agents. PMMA homopolymers of different molecular weights between 13 060 and 45 000 g/mol were then prepared by a surface-initiated RAFT polymerization. Molecular weight (MW) and polydispersity index (PDI) were determined from sacrificial polymerization in solution. The different steps of stainless steel surface modification and the ultrathin films were investigated using atomic force microscopy (AFM), static, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance infrared spectroscopy (ATR-IR), and ellipsometry.

COVALENT IMMOBILIZATION OF GLUCOSE OXIDASE ON WELL-DEFINED POLYMER-SILICON WAFER HYBRIDS VIA SURFACE-INITIATED RAFT-MEDIATED PROCESS

A surface modification technique was developed for the functionalization of silicon surface with glucose oxidase (GOD). The silicon surface was first graft copolymerized with glycidyl methacrylate (GMA) via surface-initiated reversible addition-fragmentation chain-transfer (RAFT)-mediated process. GOD was then covalently immobilized through the ring-opening reaction between the amine groups of the GOD and the epoxide groups of the grafted GMA polymer chains. X-ray photoelectron spectroscopy (XPS) was used to characterize the surface-modified surface after each modification stage. Increasing the thickness of the polymer layer and the immobilization time could allow a great amount of GOD to be immobilized on the silicon surface. The GOD-functionalized silicon hybrids are promising candidates for the silicon-based glucose biosensors. 1-4 It is of great importance to improve the biocompatibility of the silicon microdevices and to develop silicon surfaces with controllable cell adhesion. Immobilization of biomolecules on silicon substrates can be achieved via many methods such as adsorption, entrapment, covalent binding, etc. Functionalization of silicon surface with organics is a key in the development of new silicon-based biomedical devices. Tethering of polymer brushes on the solid substrate is an effective method of modifying the surface of the various substrates. 5-6 The dense polymer brushes can alter the properties of the surface, supply excellent mechanical and chemical protection to the substrate, and indicate new pathways to the functionalization of silicon surfaces for molecular recognition and sensing. 7-10 USA). The silicon wafers were cut into square chips of about 1.2 cm × 1.2 cm in size. The monomer, GMA, was passed through inhibitor-removing columns and then stored under an argon atmosphere at -10 °C. The initiator a,a'-azobis(isobutyronitrile) (AIBN, 97%) was obtained from Kanto Chemical Co. (Tokyo, Japan) and was recrystallized in anhydrous ethanol. The silane coupling agent (3-(trimethoxysilyl) propyl methacrylate (TMSPM, 98%)) was obtained from Aldrich Chemical Co. (St. Louis, MO, USA). The chain transfer agent (CAT), 1-phenylethyl dithiobenzoate (PDB), was synthesized according to the published procedures.19 GOD (Type II, 15500 units g-1 from Aspergillus niger) was purchased from Sigma Chemical Co. (St. Louis, MO, USA). Dulbecco's phosphate buffer solution (PBS, pH=7.4) was freshly prepared. Bio-Rad dye reagent for protein assay (Catalog No. 500-0006) was obtained from BioRad (Hercules, CA, USA). The other reagents were of analytical grade and were used without further purification unless otherwise mentioned. Immobilization process The process of surface functionalization of silicon was shown in Fig. 1. Coupling of the RAFT initiator to the silicon wafer was first achieved by adding TMSPM (0.41 mmol), AIBN (0.23 mmol), and PDB (0.46 mmol) at a molar ratio of 1.8:1:2 into 5 mL of dry DMF in a Pyrex tube containing the silicon chip. After purging the mixture with argon for 30 min, the surface coupling reaction continued at 60 °C for 24 h under an argon atmosphere. After the reaction, the modified substrate was washed with CH 2 Cl 2 and then with an ethanol/water mixture.

Terminal-Functionality Effect of Poly(N-isopropylacrylamide) Brush Surfaces on Temperature-Controlled Cell Adhesion/Detachment

Terminally functionalized poly(N-isopropylacrylamide) (PIPAAm) brush grafted glass surfaces were prepared by a surface-initiated reversible addition-fragmentation chain transfer radical (SI-RAFT) polymerization. SI-RAFT mediated PIPAAm chains possessed terminal dodecyl trithiocarbonate groups which can be substituted with various functional groups. In this study, dodecyl groups were substituted with hydrophilic maleimide groups for controlling the thermoresponsive character of PIPAAm brushes. PIPAAm brushes exhibited reversible temperature-dependent surface wettability changes around PIPAAm's lower critical solution temperature. Phase transition of dodecyl-terminated PIPAAm brushes clearly shifted to lower temperature than that of maleimide-terminated PIPAAm brushes, and this shift was attributed to promoted PIPAAm dehydration via terminal hydrophobes. By using this feature, the specific adhesion temperatures of bovine carotid artery endothelial cells (BAECs) on the PIPAAm brush surfaces were successfully controlled. BAECs were initiated to adhere on dodecyl-PIPAAm surfaces at 31 °C, while their adhesion was significantly suppressed on maleimide-PIPAAm surfaces under 33 °C. In contrast, terminal functionality scarcely affected the thermoresponsive behavior of PIPAAm brushes in the polymer rehydration process by reducing temperatures, and thus, the difference in spontaneous cell detachment from different PIPAAm-brush surface was negligible. Consequently, confluently cultured cells were able to be harvested as contiguous cell sheets from individual surfaces with comparable periods at 20 °C.

Monodisperse, Charge-Stabilized, Core–Shell Particles via Silica-Supported Reversible Addition–Fragmentation Chain Transfer Polymerization for Cell Imaging

We describe the formation of monodisperse silica–polymer core–shell particles of tunable particle sizes. Incorporation of a comonomer in the surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization resulted in fluorescent particles, which were further functionalized to yield hydrophilic, highly uniform particles that are sterically stable in biologically relevant conditions. The particles were further shown to adhere to the walls and be endocytosed into the human colon cancer cells, allowing the cells to be imaged using confocal microscopy.

Fabrication of magnetic nanofibers via surface-initiated RAFT polymerization and coaxial electrospinning

A simple and continuous approach for fabricating magnetic polyacrylonitrile nanofibers (MNFs) with the diameter of about 200nm has been developed by combining surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization and coaxial electrospinning. The RAFT polymerization of acrylonitrile was carried out on the surface of RAFT agent immobilized Fe3O4 nanoparticles. The room-temperature saturation magnetizations of the prepared MNFs can be easily adjusted. In addition, the aligned fibers can be conveniently obtained via magnetic electrospinning using a specially designed fiber collector.

A new selenium-based RAFT agent for surface-initiated RAFT polymerization of 4-vinylpyridine

A new selenium-based reversible addition-fragmentation chain transfer (RAFT) agent, 4-cyanopentanoic acid diselenobenzoate (RAFT-Se), was synthesized and utilized in the surface-initiated RAFT polymerization of 4-vinylpyridine (4VP) on silicon substrate. The results indicate that the RAFT-Se can control the surface-initiated RAFT polymerization, as evidenced by the number-average molecular weight that increase linearly with monomer conversion, molecular weights that agreed well with the predicted values, and the relatively low polydispersity indexes. The surface-initiated RAFT polymerization with the RAFT-Se was the same polymerization mechanism as its analog, 4-cyanopentanoic acid dithiobenzoate (RAFT-S). The grafting density of the poly(4-vinylpyridine) brushes prepared in the presence of RAFT-Se (σRAFT-Se) and RAFT-S (σRAFT-S) was estimated to be about 0.51 and 0.66 chains/nm2, respectively. In addition, the end of polymer chains on silicon substrate contains selenium element which may be useful in biosensor applications.

Fluoro-Polymer@BaTiO3 Hybrid Nanoparticles Prepared via RAFT Polymerization: Toward Ferroelectric Polymer Nanocomposites with High Dielectric Constant and Low Dielectric Loss for Energy Storage Application

Polymer nanocomposites with high energy density and low dielectric loss are highly desirable in electronic and electric industry. Achieving the ability to tailor the interface between polymer and nanoparticle is the key issue to realize desirable dielectric properties and high energy density in the nanocomposites. However, the understanding of the role of interface on the dielectric properties and energy density of polymer nanocomposites is still very poor. In this work, we report a novel strategy to improve the interface between the high dielectric constant nanoparticles (i.e., BaTiO3) and ferroelectric polymer [i.e., poly(vinylidene fluoride-co-hexafluoro propylene)]. Core–shell structured BaTiO3 nanoparticles either with different shell thickness or with different molecular structure of the shell were prepared by grafting two types of fluoroalkyl acrylate monomers via surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization. The dielectric properties and energy storage c...

Poly(2-hydroxyethyl methacrylate) grafted halloysite nanotubes as a molecular host matrix for luminescent ions prepared by surface-initiated RAFT polymerization and coordination chemistry

A fluorescent nanohybrid complex comprising of halloysite nanotubes (HNTs), poly(2-hydroxyethyl methacrylate) (PHEMA), and europium ions (Eu3+) was synthesized by the combination of surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization and coordination chemistry. Initially, PHEMA was grafted from the HNTs by SI-RAFT and then reacted with succinic anhydride to provide carboxyl acid groups on the external layers of HNTs-g-PHEMA nanohybrids. The subsequent coordination of the nanohybrids with Eu3+ ions afforded photoluminescent Eu3+ tagged HNTs-g-PHEMA nanohybrid complexes (HNTs-g-PHEMA-Eu3+). The structure, morphology, and fluorescence properties of the Eu3+ coordinated nanohybrid complexes were investigated by respective physical and spectral studies. FT-IR, XPS, and EDS analyses suggested the formation of the HNTs-g-PHEMA-Eu3+ nanohybrids. FE-SEM images indicated the immobilization of polymer layers on HNTs. TGA scans further demonstrated the grafting of PHEMA onto HNTs surface. The optical properties of HNTs-g-PHEMA-Eu3+ nanohybrid complexes were investigated by photoluminescence spectroscopy.

Synthesis and Characterization of Dye-Labeled Poly(methacrylic acid) Grafted Silica Nanoparticles

The synthesis of dye-labeled poly(methacrylic acid) (PMAA) grafted silica nanoparticles was studied. Surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization of tert-butylmethacrylate (tBuMA) was conducted on dye-labeled CPDB coated silica nanoparticles followed by sequential removal of the thiocarbonylthio end groups and the tert-butyl moieties. Additionally, as a more straightforward strategy, direct polymerization of methacrylic acid on silica nanoparticles with a diameter size as small as 15 nm was conducted via the RAFT polymerization technique. A variety of PMAA brushes with different lengths and densities were prepared on nanoparticle surfaces via surface-initiated RAFT polymerization with excellent control and surface grafting densities as high as 0.65 chains/nm2. The grafted PMAA was methylated by trimethylsilyldiazomethane to conduct organic phase GPC characterization. The dye-labeled PMAA grafted nanoparticles provide a platform to bind biomolecules and to track the movement of the nanoparticles in biological systems.

Surface-initiated RAFT polymerization of NIPAM from monolithic macroporous polyHIPE

Amino-functional macroporous monoliths from polymerized high internal phase emulsion (polyHIPE) were surface decorated with chain transfer agents (CTAs) for Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization. Surface initiated RAFT polymerization of N-isopropylacrylamide resulted in a dense coating of PNIPAM on the polyHIPE surface. Through addition of free CTA the amount of the PNIPAM grafted to the monolith could be modulated corresponding linearly to the molecular weight of the free polymer chains. Scanning Electron Microscopy (SEM) analysis suggests a homogeneous polymer coating throughout the interior pores of the monoliths. The PNIPAM coated polyHIPEs were rendered hydrophilic displaying faster water uptake with increasing amount of grafted PNIPAM. Considering the high flexibility RAFT polymerization offers in the choice of monomers, simplicity of reaction and absence of any catalyst this approach opens a convenient route to highly functional polymeric monoliths.

Poly(allyl methacrylate) functionalized hydroxyapatite nanocrystals via the combination of surface-initiated RAFT polymerization and thiol–ene protocol: A potential anticancer drug nanocarrier

Hydroxyapatite nanocrystals (HAP NCs) were encapsulated by poly(allyl methacrylate) (PolyAMA) employing controlled surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization of allyl methacrylate to afford HAP-PolyAMA nanohybrids. The subsequent thiol–ene coupling of nanohybrids with 2-mercaptosuccinic acid resulted HAP-Poly(AMA-COOH) possessing multicarboxyl group. The formation of the nanohybrids was confirmed by FT-IR and EDS analyses. The TGA and FE-SEM investigation were further suggested the grafting of PolyAMA onto HAP NCs. The utility of the HAP-PolyAMA nanohybrid as drug carrier was also explored. The pendant carboxyl groups on the external layers of nanohybrids were conjugated with anticancer drug cisplatin to afford HAP-Poly(AMA-COOH)/Pt complex. The formation of the complex was confirmed by FT-IR, XPS, and FE-SEM. In vitro evaluation of the synthesized complex as nanomedicine revealed its potential chemotherapeutic efficacy against cancer cell lines.

Tunable pH and temperature response of weak polyelectrolyte brushes: role of hydrogen bonding and monomer hydrophobicity

We report on weak polyacid brushes with highly tunable pH and temperature response characteristics. This was achieved by synthesizing a series of homo- and copolymers which contain 2-alkylacrylic acids (aAAs) of increased hydrophobicity, i.e. acrylic acid (AA), methacrylic acid (MAA), or 2-ethylacrylic acid (EAA), using surface-initiated reversible addition–fragmentation chain transfer (SI-RAFT) polymerization. As revealed by contact angle measurements, in situ ellipsometry and AFM studies of brush swelling, the pH-response of PAA and PMAA brushes was similar, with brushes remaining highly swollen (swelling ratio 2.5–3.0) at low pH values. The PEAA brush, however, was unique as it showed low degrees of water uptake ( 70°) contact angles in the entire pH region from 2 to 8. Copolymer brushes of aAAs with N-isopropylacrylamide (NIPAM), denoted as P(AA-co-NIPAM), P(MAA-co-NIPAM) and P(EAA-co-NIPAM), demonstrated dual pH and temperature response, which was strongly dependent on the type of aAA co-monomer. P(AA-co-NIPAM) and P(MAA-co-NIPAM) brushes underwent large-amplitude pH-induced changes in brush swelling and water contact angle in the range of pH from 3 to 6, and were only weakly responsive to temperature in the transition region. In contrast, more hydrophobic P(EAA-co-NIPAM) brushes demonstrated both pH and temperature responses at physiologically relevant neutral/basic pH values even when the content of EAA units in the copolymer was as high as ∼50%. We discuss the role of inter- and intra-molecular hydrogen bonding and monomer hydrophobicity and ionization (quantified by FTIR) in determining pH ranges for brush response. These findings might enable control of molecular/cellular adhesion and flow at interfaces potentially useful in microfluidic and biomedical applications.

Surface-initiated RAFT polymerization of sulfobetaine from cellulose membranes to improve hemocompatibility and antibiofouling property

Two major complications generally occur in blood-contacting devices, namely thrombus formation and microbial invasion and infection. Therefore, hemocompatible and antibiofouling surfaces, which function as barriers to bacterial and cell adhesion, are essential. Herein, we report the successful grafting of zwitterionic polysulfobetaine brushes onto a cellulose membrane (CM) via surface-initiated reversible addition–fragmentation chain-transfer (SI-RAFT) polymerization for improving hemocompatibility and antibiofouling property. Both pristine and polysulfobetaine brush-modified CM substrates were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements (WCA), X-ray photoelectron spectroscopy analysis (XPS), and atomic force microscopy (AFM). Experimental observations demonstrated the successful grafting of polysulfobetaine brushes, where brush thicknesses were found to increase gradually with polymerization time and monomer concentrations. Tests conducted by investigating platelet adhesion, hemolytic rates and protein adsorption indicated that polysulfobetaine brush-grafted CMs had excellent hemocompatibility featuring lower platelet adhesion and protein adsorption properties without causing hemolysis. E. coli adhesion and HeLa cell adhesion tests showed that grafted CMs had superior antibacterial adhesion properties and long-term cell adhesion resistance for up to four days. The functionalized cellulose substrate described holds great potential for use in biomedical applications.

Grafting Bimodal Polymer Brushes on Nanoparticles Using Controlled Radical Polymerization

RAFT (reversible addition–fragmentation chain transfer) polymerization has been widely used to synthesize different polymer architectures such as polymer brushes on nanoparticles for incorporation into polymer nanocomposites. It is believed that these polymer brushes, with the same chemistry as the matrix polymer, can be employed to improve filler dispersion by compatibilizing unfavorable enthalpic interactions between the inorganic nanoparticles and their organic host matrices. However, monomodal brush graft nanoparticles are found to aggregate into a range of isotropic and anisotropic morphologies, formed due to a delicate balance between enthalpic and entropic interfacial interactions. This coupling of enthalpy and entropy leaves only a small window of graft densities and molecular weights to obtain randomly dispersed filler morphologies. These issues can be countered by using a bimodal polymer brush that contains a small number of long homopolymer chains that can entangle, and a high density of short brushes that screens the particle/particle attraction, thereby aiding in decoupling the interfacial enthalpic and entropic interactions. In the present work, we demonstrate a robust step-by-step technique using RAFT polymerization to synthesize these bidisperse/bimodal polymer brush-anchored nanoparticles. A layer of dense brush of the first population was initially prepared using surface-initiated RAFT polymerization from colloidal silica nanoparticles. After cleavage of the chain transfer agent from the first population of chain ends, a second RAFT agent was attached onto the silica nanoparticles and then a monomer, which may be the same or different from the first brush, was polymerized. This versatile and widely applicable route enables us to independently control the molecular variables of the attached chains, such as composition, molecular weights and graft densities of the individual populations. The bimodal brush-grafted colloidal silica nanoparticles show superior dispersion and interaction with a homopolymer matrix when compared to monomodal brush-grafted particles.

Composites of Silica and Molecularly Imprinted Polymers for Degradation of Sulfadiazine

We report on the fabrication of silica/zinc oxide/zinc sulfide nanoparticles (SiO2/ZnO/ZnS NPs) wrapped with thermoresponsive molecularly imprinted polymers (TMIPs) for photocatalysis (PC) applications. TMIPs were prepared via surface-initiated reversible addition–fragmentation chain transfer (SI-RAFT) polymerization of N-isopropylacrylamide (NIPAm) and ethylene glycol dimethacrylate (EGDMA), rendering the material solution accessible and temperature sensitive. Photodegradation of sulfadiazine (SD) was used as a probe to evaluate the effect of coated TMIPs on the PC performance of SiO2/ZnO/ZnS NPs. The results showed that TMIPs made SiO2/ZnO/ZnS NPs have an outstanding specific affinity PC activity toward template SD. Modification of SiO2/ZnO/ZnS NPs with Ag2S resulted in a tunable PC ability of the prepared material. For SI-RAFT conducted in a controlled manner, a thin layer of polymers (∼100 nm) formed around NPs was measured by a transmission electron microscopy (TEM). Also the polymers were characteri...

Polymer brush with pendent glucosylurea groups constructed on a glass substrate by RAFT polymerization

A polymer brush with pendent d-glucosylurea groups (Poly(glucosylureaethyl methacrylate), PolyGUMA) was obtained by surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization of GUMA on a glass substrate. The linear relationship between the loge ([M]o/[M]) value and the reaction conversion, and the small polydispersity in Mw/Mn value of PolyGUMA produced in liquid phase at the same time suggested that the polymerization proceeded in a living manner. The bicinchoninic acid method indicated that the PolyGUMA brush was significantly resistant against non-specific adsorption of albumin (bovine serum) and lysozyme (egg white). Furthermore, the adhesion of cells such as HepG2, and HEK293 cells was strongly suppressed by the presence of PolyGUMA brush. The glucosylurea group-carrying polymer brush prepared here might be quite useful to provide a “bio-inert (anti-biofouling)” surface in bio-medical fields.

Poly(acrylic acid)-silicon Hybrids Prepared via a RAFT-mediated Process and Covalent Immobilization of Glucose Oxidase

A surface modification technique was proposed for the modification of silicon surface with glucose oxidase (GOD). The silicon surface was first graft copolymerized with acrylic acid (AAc) via surface-initiated reversible addition-fragmentation chain-transfer (RAFT)-mediated process. With the aid of a water-soluble carbodiimide, GOD was then covalently immobilized on the silicon surface through the amide linkage between the amino group of GOD and the carboxyl group of the grafted AAc polymer. The changes in the surface composition after polymer grafting and enzyme immobilization on the silicon surface were investigated using X-ray photoelectron spectroscopy (XPS). The amount of GOD immobilized could be varied by changing the thickness of the polymer layer and the immobilization time. The GOD-functionalized silicon hybrids are potential useful in the application of the silicon-based biosensors.