Dendritic poly(ether imine) based gene delivery vector

The nonviral vector based gene delivery approach is attractive due to advantages associated with molecular-level modifications suitable for optimization of vector properties. In a new class of nonviral gene delivery systems, we herein report the potential of poly(ether imine) (PETIM) dendrimers to mediate an effective gene delivery function. PETIM dendrimer, constituted with tertiary amine branch points, n-propyl ether linkers and primary amines at their peripheries, exhibits significantly reduced toxicities, over a broad concentration range. The dendrimer complexes pDNA effectively, protects DNA from endosomal damages, and delivers to the cell nucleus. Gene transfection studies, utilizing a reporter plasmid pEGFP-C1 and upon complexation with dendrimer, showed a robust expression of the encoded protein. The study shows that PETIM dendrimers are hitherto unknown novel gene delivery vectors, combining features of poly(ethylene imine)-based polymers and dendrimers, yet are relatively nontoxic and structurally precise.     

Adsorption of lipoproteins with the aid of carboxymethylchitosan mircrospheres crosslinked with poly(ethylene glycol) bisglycidyl ether

Carboxymethylchitosan microspheres crosslinked with poly(ethylene glycol) bisglycidyl ether were prepared and then tested as an adsorbent for selective removal of low-density lipoprotein (LDL) in human plasma. The microspheres were formed by a method of electrostatic instillation and crosslinked with poly(ethylene glycol) bisglycidyl ether. FTIR spectral analyses and X-ray photoelectron spectroscopy revealed that carboxymethylchitosan was crosslinked through amino groups to poly(ethylene glycol) bisglycidyl ether. The plasma lipoprotein sorption tests showed that the adsorption properties of the crosslinked microspheres for LDL were dependent on the concentrations of carboxymethylchitosan and poly(ethylene glycol) bisglycidyl ether. When the concentrations of carboxymethylchitosan and poly(ethylene glycol) bisglycidyl ether were 3.5% and 6%, respectively, 40% LDL and lower than 10% high density lipoprotein in plasma could be removed and the adsorption could be reach an equilibrium in 30 min.     

Interaction forces and morphology of a protein-resistant poly(ethylene glycol) layer

The molecular interactions on a protein-resistant surface coated with low-molecular-weight poly(ethylene glycol) (PEG) copolymer brushes are investigated using the extended surface forces apparatus. The observed interaction force is predominantly repulsive and nearly elastic. The chains are extended with respect to the Flory radius, which is in agreement with qualitative predictions of scaling theory. Comparison with theory allows the determination of relevant quantities such as brush length and adsorbed mass. Based on these results, we propose a molecular model for the adsorbed copolymer morphology. Surface-force isotherms measured at high resolution allow distinctive structural forces to be detected, suggesting the existence of a weak equilibrium network between poly(ethylene glycol) and water--a finding in accordance with the remarkable solution properties of PEG. The occurrence of a fine structure is interpreted as a water-induced restriction of the polymer's conformational space. This restriction is highly relevant for the phenomenon of PEG protein resistance. Protein adsorption requires conformational transitions, both in the protein as well as in the PEG layer, which are energetically and kinetically unfavorable.     

Coupling of biotin-(poly(ethylene glycol))amine to poly(D,L-lactide-co-glycolide) nanoparticles for versatile surface modification

Generally, polymeric nanoparticles (NP) for drug targeting are designed to entrap the drug moiety in the core and to present the targeting moiety on the surface. However, in most cases, common preparation techniques of polymeric NP need to be specifically arranged for each compound to be entrapped or attached. In the present work, we introduce a method for versatile conjugation of targeting moieties to the surface of preformed, polymeric NP. Moreover, due to taking advantage of biotin-avidin interactions, our regime opens the additional possibility of a rapid fluorescence labeling of NP. Poly(D,L-lactide-co-glycolide) (PLGA) NP in the size of 210 nm were prepared by the classic oil-in-water method. Such NP were functionalized with biotin-(poly(ethylene glycol))amine (BPEG) by means of cyanuric chloride chemistry. The amount of surface-associated biotin was 850 pmol per milligram of polymer, corresponding to roughly 2650 molecules of biotin per NP. When drawn to scale, such surface coating appeared to be well-suited for subsequent binding of avidin or avidin-linked ligands. By resonant mirror measurements, we could prove specific binding of biotinylated NP to a NeutrAvidin (NAv)-coated surface. Furthermore, after coupling of NAv-linked fluorescence dyes to BPEG-functionalized NP, differences in binding and uptake could be demonstrated using two epithelial cell lines (Caco-2, A549).     

Transgene delivery using poly(amino ether)-gold nanorod assemblies

Gold nanorods (GNRs) have emerged as promising nanomaterials for biosensing, imaging, photothermal treatment, and therapeutic delivery for several diseases, including cancer. We have generated poly(amino ether)-functionalized gold nanorods (PAE-GNRs) using a layer-by-layer deposition approach; polymers from a poly(amino ether) library recently synthesized in our laboratory were employed to generate the PAE-GNR assemblies. PAE-GNR assemblies demonstrate long-term colloidal stability as well as the capacity to bind plasmid DNA by means of electrostatic interactions. Sub-toxic concentrations of PAE-GNRs were employed to deliver plasmid DNA to prostate cancer cells in vitro. PAE-GNRs generated using 1,4C-1,4Bis, a cationic polymer from our laboratory demonstrated significantly higher transgene expression and exhibited lower cytotoxicities when compared to similar assemblies generated using 25 kDa poly(ethylene imine) (PEI25k-GNRs), a current standard for polymer-mediated gene delivery. The roles of polyelectrolyte chemistry and zeta-potential in determining transgene expression efficacies of PAE-GNR assemblies were investigated. Our results indicate that stable and effective PAE-GNR assemblies are a promising engineered platform for transgene delivery. PAE-GNRs also have the potential to be used simultaneously for photothermal ablation, photothermally enhanced drug and gene delivery, and biological imaging, thus making them a powerful theranostic platform.     

Selective adsorption of serum albumin on biomedical polyurethanes modified by a poly(ethylene oxide) coupling-polymer with cibacron blue (F3G-A) endgroups

A tri-block-coupling polymer, "PEO-MDI-PEO" ["poly(ethylene oxide)-4,4'-methylene diphenyl diisocyanate-poly(ethylene oxide)", abbreviated "MPEO"], was used to react with a triazine dye, Cibacron Blue F3G-A (ciba), in an alkaline environment. The product of this nucleophilic reaction was a penta-block-coupling polymer, "ciba-PEO-MDI-PEO-ciba" (abbreviated "cibaMPEO"). The cibaMPEO-modified poly(ether urethane) (PEU) surfaces were prepared by dip-coating and detected by XPS. The surface enrichment of both ciba endgroups and poly(ethylene oxide) spacer-arms was revealed. On the modified surfaces, bovine serum albumin (BSA)-adsorbing experiments were carried out, respectively, in the low and high BSA bulk-concentration solutions, and accordingly, the methods of radioactive (125)I-probe and ATR-FTIR were, respectively, employed for the characterization. The competitive adsorption of BSA and bovine serum fibrinogen (Fg) in the BSA-Fg binary solutions was also studied using a (125)I-probe, and through which the reversibly BSA-selective adsorption on cibaMPEO-modified PEU surfaces was confirmed. Finally, the improvement of blood-compatibility on the modified surfaces was verified by the plasma recalcification time (PRT) test.     

Spatially well-defined binary brushes of poly(ethylene glycol)s for micropatterning of active proteins on anti-fouling surfaces

We report a novel method for micropatterning of active proteins on anti-fouling surfaces via spatially well-defined and dense binary poly(ethylene glycol)s (PEGs) brushes with controllable protein-docking sites. Binary brushes of poly(poly(ethylene glycol) methacrylate-co-poly(ethylene glycol)methyl ether methacrylate), or P(PEGMA-co-PEGMEMA), and poly(poly(ethylene glycol)methyl ether methacrylate), or P(PEGMEMA), were prepared via consecutive surface-initiated atom transfer radical polymerizations (SI-ATRPs) from a resist-micropatterned Si(100) wafer surface. The terminal hydroxyl groups on the side chains of PEGMA units in the P(PEGMA-co-PEGMEMA) microdomains were activated directly by 1,1'-carbonyldiimidazole (CDI) for the covalent coupling of human immunoglobulin (IgG) (as a model active protein). The resulting IgG-coupled PEG microdomains interact only and specifically with target anti-IgG, while the other PEG microregions effectively prevent specific and non-specific protein fouling. When extended to other active biomolecules, microarrays for specific and non-specific analyte interactions with a high signal-to-noise ratio could be readily tailored.     

pH dependence and protein selectivity of poly(ethyleneimine)/poly(acrylic acid) multilayers studied by in situ ATR-FTIR spectroscopy

The selective interaction between polyelectrolyte multilayers (PEM) consecutively adsorbed from poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAC) and a binary mixture containing concanavalin A (COA) and lysozyme (LYZ) based on electrostatic interaction is reported. The composition and structure of the PEM and the uptake of proteins were analyzed by in situ attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy, and the morphology and thickness were characterized by atomic force microscopy (AFM) and ellipsometry. The PEM dissociation degree and charge state and the protein adsorption were shown to be highly dependent on the outermost layer type and the pH in solution. High protein uptake was obtained under electrostatically attractive conditions. This was used to bind selectively one protein from a binary mixture of LYZ/COA. In detail it could be demonstrated that six-layered PEM-6 at pH = 7.3 showed a preferential sorption of positively charged LYZ, while at PEM-5 and pH = 7.3 negatively charged COA could be selectively bound. No protein sorption from the binary mixture was observed at pH = 4.0 for both PEM, when COA, LYZ, and the outermost PEI layer of PEM-5 were positively charged or the outermost PAC layer of PEM-6 was neutral. Furthermore, from factor analysis of the spectral data the higher selectivity was found for PEM-5 compared to PEM-6. Increasing the ionic strength revealed a drastic decrease in the selectivity of both PEM. Evidence was found that the proteins were predominantly bound at the surface and to a minor extent in the bulk phase of PEM. These results suggest possible working regimes and application fields of PEI/PAC multilayer assemblies related to the preparative separation of binary and multicomponent protein mixtures (biofluids, food) as well as to the design of selective protein-resistant surfaces.     

Hyperbranched poly(amino ester)s with different terminal amine groups for DNA delivery

Hyperbranched poly(amino ester)s containing tertiary amines in the core and primary, secondary, and tertiary amines in the periphery, respectively, were evaluated for DNA delivery in vitro. The same core structure facilitated the investigation on the effects of the terminal amine type on the properties of hyperbranched poly(amino ester)s for DNA delivery. The hydrolysis of the poly(amino ester)s was monitored using (1)H NMR. The results reflected that the terminal amine type had negligible effects on the hydrolysis rate but was much slower than that of linear poly(amino ester)s, probably due to the compact hyperbranched spatial structure preventing the accessibility of water. In comparison with PEI 25 K, the hyperbranched poly(amino ester)s showed much lower cytotoxicity in Cos7, HEK293, and HepG2 cells. Gel electrophoresis indicated that poly(amino ester)s could condense DNA efficiently, and the zeta potentials and sizes of the complexes formed with different weight ratios of hyperbranched poly(amino ester)s and DNA were measured. Remarkably, all the hyperbranched poly(amino ester)s showed DNA transfection efficiency comparable to PEI 25 K in Cos7, HEK293, and HepG2 cells regardless of the terminal amine type. Therefore, the terminal amine type had insignificant effects on the hydrolysis rate, cytotoxicity, DNA condensation capability, and in vitro DNA transfection efficiency of the hyperbranched poly(amino ester)s.     

Patterned biofunctional poly(acrylic acid) brushes on silicon surfaces

Protein patterning was carried out using a simple procedure based on photolithography wherein the protein was not subjected to UV irradiation and high temperatures or contacted with denaturing solvents or strongly acidic or basic solutions. Self-assembled monolayers of poly(ethylene glycol) (PEG) on silicon surfaces were exposed to oxygen plasma through a patterned photoresist. The etched regions were back-filled with an initiator for surface-initiated atom transfer radical polymerization (ATRP). ATRP of sodium acrylate was readily achieved at room temperature in an aqueous medium. Protonation of the polymer resulted in patterned poly(acrylic acid) (PAA) brushes. A variety of biomolecules containing amino groups could be covalently tethered to the dense carboxyl groups of the brush, under relatively mild conditions. The PEG regions surrounding the PAA brush greatly reduced nonspecific adsorption. Avidin was covalently attached to PAA brushes, and biotin-tagged proteins could be immobilized through avidin-biotin interaction. Such an immobilization method, which is based on specific interactions, is expected to better retain protein functionality than direct covalent binding. Using biotin-tagged bovine serum albumin (BSA) as a model, a simple strategy was developed for immobilization of small biological molecules using BSA as linkages, while BSA can simultaneously block nonspecific interactions.     

Use of poly(amido)amine dendrimers in prevention of early non-enzymatic modifications of biomacromolecules

Hyperglycaemia triggers the formation of both ‘early’ and advanced glycation end products, which are considered the major factors responsible for the complications of diabetes. Poly(amido)amine (PAMAM) dendrimers are relatively new class of materials with unique molecular structure predisposing them for the use as anti-glycation agents. The ability of poly(amido)amine (PAMAM) dendrimers G2 (MW 3256, 120 μmol/l) and G4 (MW 14215, 30 μmol/l) to inhibit the modification of proteins by high glucose (30 mmol/l, 37 °C, 72 h) was investigated using radiometric and spectrofluorometric assays. We monitored (a) non-enzymatic modifications of primary amino groups in BSA and polyamine compounds, and (b) the impact of anti-glycation agents on BSA conformation. Both PAMAM dendrimers and poly(l-lysine) (MW 70 kDa) effectively reduced BSA glycation, while undergoing the time-dependent modification themselves. Such a modification was a function of a number of available free amino groups per molecule, however, both dendrimers and poly(l-lysine) were equally effective in glucose scavenging. PAMAMs neither affected BSA conformation nor formed stable complexes with a protein, while non-glycated poly(l-lysine) significantly quenched BSA fluorescence. Our results encourage raising the hypothesis that PAMAM dendrimers may be considered effective and safe chemical competitors for non-enzymatic modification by glucose, thus confirming the earlier in vivo study showing the inhibition of protein modification in experimental diabetes in the presence of PAMAM dendrimers.     

Novel biodegradable poly(disulfide amine)s for gene delivery with high efficiency and low cytotoxicity

Novel biodegradable poly(disulfide amine)s with defined structure, high transfection efficiency, and low cytotoxicity were designed and synthesized as nonviral gene delivery carriers. Michael addition between N, N'-cystaminebisacrylamide (CBA) and three N-Boc protected diamines ( N-Boc-1,2-diaminoethane, N-Boc-1,4-diaminobutane, and N-Boc-1,6-diaminohexane) followed by N-Boc deprotection under acidic condition resulted in final cationic polymers with disulfide bonds, tertiary amine groups in main chains, and pendant primary amine groups in side chains. Polymer structures were confirmed by 1H NMR, and their molecular weights were in the range 3.3-4.7 kDa with narrow polydispersity (1.12-1.17) as determined by size exclusion chromatography (SEC). Acid-base titration assay showed that the poly(disulfide amine)s possessed superior buffering capacity to branched PEI 25 kDa in the pH range 7.4-5.1, which may facilitate the escape of DNA from the endosomal compartment. Gel retardation assay demonstrated that significant polyplex dissociation was observed in the presence of 5.0 mM DTT within 1 h, suggesting rapid DNA release in the reduction condition such as cytoplasm due to the cleavage of disulfide bonds. Genetic transfections mediated by these poly(disulfide amine)s were side-chain spacer length dependent. The poly(disulfide amine) with a hexaethylene spacer, poly(CBA-DAH), had comparable transfection efficiency to bPEI 25 kDa in the tested cell lines, i.e., 293T cells, Hela cells, and NIH3T3 cells. This same poly(disulfide amine) mediated 7-fold higher luciferase expression than bPEI 25 kDa in C2C12 cells (mouse myoblast cell line), a cell line difficult to transfect with many cationic polymers. Furthermore, MTT assay indicated that all three poly(disulfide amine)s/pDNA polyplexes were significantly less toxic than bPEI/pDNA complexes.     

Stability and nonfouling properties of poly(poly(ethylene glycol) methacrylate) brushes under cell culture conditions

This paper investigates the stability and nonfouling properties of poly(poly(ethylene glycol) methacrylate) (PPEGMA) brushes prepared by surface-initiated atom transfer radical polymerization from SiO(x) substrates modified with a trimethoxysilane-based ATRP initiator. At high chain densities, PPEGMA brushes were found to detach rapidly from glass or silicon substrates. Detachment of the PPEGMA brushes could be monitored with contact angle measurements, which indicated a decrease in the receding water contact angle upon detachment. Detachment of the PPEGMA brushes also resulted in an increase in nonspecific protein adsorption. The stability, and as a consequence the long-term nonfouling properties, of the PPEGMA brushes could be improved by tailoring the brush density and, to a lesser extent, the molecular weight of the polymer chains. By appropriate decrease of the grafting density, the stability of the brushes in cell culture medium could be improved from less than 1 to more than 7 days, without compromising the nonfouling properties.     

Dual-functional biomimetic materials: nonfouling poly(carboxybetaine) with active functional groups for protein immobilization

We introduce a dual-functional biocompatible material based on zwitterionic poly(carboxybetaine methacrylate) (polyCBMA), which not only highly resists protein adsorption/cell adhesion, but also has abundant functional groups convenient for the immobilization of biological ligands, such as proteins. The dual-functional properties are unique to carboxybetaine moieties and are not found in other nonfouling moieties such as ethylene glycol, phosphobetaine, and sulfobetaine. The unique properties are demonstrated in this work by grafting a polyCBMA polymer onto a surface or by preparing a polyCBMA-based hydrogel. PolyCBMA brushes with a thickness of 10-15 nm were grafted on a gold surface using the surface-initiated atom transfer radical polymerization method. Protein adsorption was analyzed using a surface plasmon resonance sensor. The surface grafted with polyCBMA very largely prevented the nonspecific adsorption of three test proteins, that is, fibrinogen, lysozyme, and human chorionic gonadotropin (hCG). The immobilization of anti-hCG on the surface resulted in the specific binding of hCG while maintaining a high resistance to nonspecific protein adsorption. Transparent polyCBMA-based hydrogel disks were decorated with immobilized fibronectin. Aortic endothelial cells did not bind to the polyCBMA controls, but appeared to adhere well and spread on the fibronectin-modified surface. With their dual functionality and biomimetic nature, polyCBMA-based materials are very promising for their applications in medical diagnostics, biomaterials/tissue engineering, and drug delivery.     

Synthesis and characterization of poly(N-hydroxyethylacrylamide) for long-term antifouling ability

Development of biomaterials with long-term biocompatibility, durability, and stability remains a critical challenge for biomedical devices. Here, we synthesize, characterize, and graft poly(N-(2-hydroxyethyl)acrylamide) (polyHEAA) onto both gold surfaces and gold nanoparticles (AuNPs) via surface-initiated atom transfer radical polymerization (SI-ATRP) to form a stable antifouling coating to resist nonspecific protein adsorption and bacterial attachment. Surface plasmon resonance (SPR) results demonstrate that all of polyHEAA brushes coated on the gold substrate at a wide range of film thickness of ~10-40 nm can achieve almost zero protein adsorption from undiluted blood plasma and serum for 1 h, while static bacteria assay results show that polyHEAA brushes prohibit long-term bacterial colonization by Staphylococcus epidermidis and Escherichia coli RP437 up to 3 days. Moreover, the polyHEAA-coated AuNPs with different diameters remain their hydrodynamic sizes unchanged in human blood plasma and serum for up to 7 days. All these data indicate that polyHEAA can serve as promising biomaterials with long-term biocompatibility and durability suitable for applications in complex biological media.     

Poly(glycidylmethacrylate) brushes generated on poly(VBC) beads by SI-ATRP technique: Hydrazine and amino groups functionalized for invertase adsorption and purification

Crosslinked-poly(vinylbenzylchloride), poly(VBC), beads were prepared by suspension polymerization and poly(glycidylmethacrylate) was grafted by surface-initiated-atom radical polymerization (SI-ATRP) technique. Epoxy groups of the grafted poly(GMA) were reacted with hydrazine and ammonia to create an affinity binding sites. The hydrazine and amine functionalized poly(VBC-g-GMA) beads were used as an affinity support for adsorption of invertase from solution and yeast crude extract. The influence of pH, equilibrium time, ionic strength and initial invertase concentration on the adsorption capacities of both hydrazine and amine functionalized beads has been investigated. Maximum invertase adsorptions onto hydrazine and amine functionalized beads, were 86.7 and 30.4 mg/g at pH 4.0 and 5.5, respectively. The experimental equilibrium data fitted well to the Temkin isotherm model. Finally, the hydrazine functionalized poly(VBC-g-GMA) beads were used for the purification of invertase from crude yeast extract in a batch system and the purity of the eluted invertase from the hydrazine functionalized beads was determined as 92% by HPLC from single step purification protocol.     

Amphiphilic core-shell nanocarriers based on hyperbranched poly(ester amide)-star-PCL: synthesis, characterization, and potential as efficient phase transfer agent

Amphiphilic biodegradable star-shaped polymer was conveniently prepared by the Sn(Oct)2-catalyzed ring opening polymerization of epsilon-caprolactone (CL) with hyperbranched poly(ester amide) (PEA) as a macroinitiator. Various monomer/initiator ratios were employed to vary the length of the PCL arms. (1)H NMR and FTIR characterizations showed the successful synthesis of star polymer with high initiation efficiency. SEC analysis using triple detectors, RI, light scattering, and viscosity confirmed the controlled manner of polymerization and the star architecture. Because of the hydrophilic PEA core and hydrophobic PCL shell, the obtained star polymers displayed inverted unimolecular micellar structure confirmed by dynamic light scattering. Three water soluble dyes, congo red, methyl orange, and bromophenol blue, were used to investigate the host-guest behavior of the micelles. It proved that the core-shell unimolecular reverse micelles were able to transport polar dyes from water to the organic phase with a high efficiency of up to 22.6 dyes per polymer, indicating a great potential of the micelles as drug carriers. The influence of arm length and core size on the load efficiency of the nanocarrier was also evaluated.     

Synthesis and properties of carboxymethylchitosan hydrogels modified with poly(ester-urethane)

Preparation and properties of carboxymethylchitosan (CMC) modified with polyurethane (PU) containing poly(ethylene adipate) (PEA) as a soft segment is described. Urethane prepolymer was first synthesized by the reaction of PEA with an excess of 1,6-hexamethylene diisocyanate (HDI) to terminate its ends with isocyanate functional groups, followed by chain extension reaction using ethylene glycol as a chain extender. Its chemical structure was characterized by ¹H NMR and FTIR, molecular weight by GPC, and thermal behavior by DSC. To prepare PU-modified CMC (CMC-PU), 1–60 wt% of PU were introduced into the CMC solution of THF:H₂O mixture (50:50 v/v) in the presence of 10 wt% of hexamethylene-1,6-di-(aminocarboxysulfonate) (HDA) to increase network density. Formation of the network structure was confirmed by investigating percent crosslinking and water swelling properties of CMC-PU compared to CMC network without PU. When percent of PU increased from 1 to 60 wt%, percent crosslinking of CMC-PU gradually increased up to 82%, whereas equilibrium water content (EWC) dropped and retained at 1000%. SEM showed microphase separation of PU (10–50 μm) thoroughly dispersed in CMC surface and in the bulk. In addition, CMC-PU exhibited a slight enhancement in toughness properties. Cytotoxicity and biocompatibility tests indicated that CMC-PU was non-toxic.     

Multiple functional hyperbranched poly(amido amine) nanoparticles: synthesis and application in cell imaging

The hyperbranched poly(amido amine) nanoparticles (HPAMAM NPs) with multiple functions, such as biodegradability, autofluorescence, and specific affinity, were successfully prepared by Michael addition dispersion polymerization of CBA, AEPZ, and N-galactosamine hydrochloride (or N-glucosamine hydrochloride) in a mixture of methanol/water. The resultant NPs displayed strong photoluminescence, high photostability, broad absorption, and emission (from 430 to 620 nm) spectra. The fluorescence from HPAMAM NPs may be attributed to the tertiary amine chromophore. The incubation results of the liver cancer cells, HepG2, with the NPs showed that the NPs are nontoxic and can be recognized by asialoglycoprotein receptors on the surface of HepG2 and then can be internalized. Therefore, they have potential applications in bioimaging and drug or gene delivery.     

UV-patterned poly(ethylene glycol) matrix for microarray applications

A versatile method to fabricate polymeric matrixes for microarray applications is demonstrated. Several different design strategies are presented where a variety of organic films, such as plastic polymers and self-assembled monolayers (SAMs) on planar silica and gold substrates, act as supports for the graft polymerization procedure. An ensemble of poly(ethylene glycol) methacrylate monomers are combined to obtain a matrix with desired properties: low nonspecific binding and easily accessible groups for postimmobilization of ligands. The free radical graft polymerization process occurs under irradiation with UV light in the 254-266 nm range, which offers the possibility to introduce patterns by means of a photomask. The arrays are created on inert and homogeneous coatings prepared either by graft polymerization of a methoxy-terminated PEG-methacrylate or self-assembly of a methoxy-terminated oligo(ethylene glycol) thiol. Carboxylic acid groups, introduced in the array spots either during graft polymerization or upon wet chemical conversion of hydroxyls, grant the capability to immobilize proteins and other molecules via free amine groups. Immobilization of fluorescent species as well as biotin followed by exposure to a fluorescently labeled antibody directed toward biotin display both excellent integrity of the spots and low nonspecific binding to the surrounding framework. Beside patterns of uniform height and size, an array of spots with varying thickness (a sort of gradient) is demonstrated. Such gradient samples enable us to address critical issues regarding the mechanism(s) behind spatially resolved free radical polymerization of methacrylates. It also offers a convenient route to optimize the matrix properties with respect to thickness, loading capacity, protein diffusion/penetration, and nonspecific binding.