Unmodified PEG Research Articles

Peptide-functionalized gold nanoparticles for boron neutron capture therapy with the potential to use in Glioblastoma treatment

Glioblastoma is a highly aggressive glioma with limited treatment options. Boron neutron capture therapy (BNCT) offers a promising approach for refractory cancers, utilizing boron-10 (10B) and thermal neutrons to generate cytotoxic particles. Effective BNCT depends on selective targeting and retention of 10B in tumors. Current BNCT drugs face issues with rapid clearance and poor tumor accumulation. To address this, we developed gold nanoparticles (AuNPs) functionalized with cyclic arginine-glycine-aspartic acid (cRGD) peptides as a nanocarrier for Sodium Mercaptododecaborate (BSH), resulting in AuNPs-BSH&PEG-cRGD. In vitro, AuNPs-BSH&PEG-cRGD increased 10B content in GL261 glioma cells by approximately 2.5-fold compared to unmodified AuNPs-BSH&PEG, indicating enhanced targeting due to cRGD's affinity for integrin receptor αvβ3. In a subcutaneous glioma mouse model, 6 h post-intratumoral administration, the 10B concentration in tumors was 17.98 μg/g for AuNPs-BSH&PEG-cRGD, significantly higher than 0.45 μg/g for BSH. The tumor-to-blood (T/B) and tumor-to-normal tissue (T/N) ratios were also higher for AuNPs-BSH&PEG-cRGD, suggesting improved targeting and retention. This indicates that AuNPs-BSH&PEG-cRGD may enhance BNCT efficacy and minimize normal tissue toxicity. In summary, this study provides a novel strategy for BSH delivery and may broaden the design vision of BNCT nano-boron capture agents.

Lipoic acid-mediated oral drug delivery system utilizing changes on cell surface thiol expression for the treatment of diabetes and inflammatory diseases.

Lipoic acid (LA), which has good safety and oral absorption, is obtained from various plant-based food sources and needs to be supplemented through human diet. Moreover, substances with a disulfide structure can enter cells through dynamic covalent disulfide exchange with thiol groups on the cell membrane surface. Based on these factors, we constructed LA-modified nanoparticles (LA NPs). Our results showed that LA NPs can be internalized into intestinal epithelial cells through surface thiols, followed by intracellular transcytosis via the endoplasmic reticulum-Golgi pathway. Further mechanistic studies indicated that disulfide bonds within the structure of LA play a critical role in this transport process. In a type I diabetes rat model, the oral administration of insulin-loaded LA NPs exhibited a more potent hypoglycemic effect, with a pharmacokinetic bioavailability of 5.42 ± 0.53%, representing a 1.6 fold enhancement compared to unmodified PEG NPs. Furthermore, a significant upregulation of surface thiols in inflammatory macrophages was reported. Thus, we turned our direction to investigate the uptake behavior of inflammatory macrophages with increased surface thiols towards LA NPs. Inflammatory macrophages showed a 2.6 fold increased uptake of LA NPs compared to non-inflammatory macrophages. Surprisingly, we also discovered that the antioxidant resveratrol facilitates the uptake of LA NPs in a concentration-dependent manner. This is mainly attributed to an increase in glutathione, which is involved in thiol uptake. Consequently, we employed LA NPs loaded with resveratrol for the treatment of colitis and observed a significant alleviation of colitis symptoms. These results suggest that leveraging the variations of thiol expression levels on cell surfaces under both healthy and diseased states through an oral drug delivery system mediated by the small-molecule nutrient LA can be employed for the treatment of diabetes and certain inflammatory diseases.

Catalyst-Free Synthesis of Covalent Adaptable Network (CAN) Polyurethanes from Lignin with Editable Shape Memory Properties.

Here a new strategy of catalyst-free direct synthesis of covalent adaptable network polyurethanes (LPUs) from lignin with editable shape memory effect is reported. Using unmodified lignin, PEG, and isocyanate under the condition of the isocyanate index less than 1.0 (NCO/OH<1.0), a variety of LPUs are obtained. When NCO/OH=0.8, a stable cross-linked network can be formed (ex. the gel content of LPU50-0.8 was 98±0.3 %). The activation energy (Ea ) value of LPUs is similar to that of polyhydroxyurethanes (PHUs), at around 110 kJ mol-1 . With an increase of lignin content, the LPUs show a transition from ductile fracture to brittle fracture mode. And the mechanical properties of LPUs are significantly enhanced after extrusion processing, with the maximum modulus reaching 649±26 MPa and the maximum toughness up to 9927±111 kJ m-3 . The improvement in mechanical properties is due to the homogenization of complex cross-linked network under the powerful external force of the extruder and the lignin that originally was free in the system participated in the exchange reactions. Moreover, LPUs can also be prepared continuously in one step by using an extruder as the reactor. In addition, LPU50-0.8 has an editable shape memory effect. This study develops a novel method for the synthesis of LPU from lignin with NCO/OH<1.0, showcasing new possibilities for value-added utilization of lignin, and expands the bio-based products portfolio from biomass feedstock to help meet future green manufacturing demands.

Development of Poor Cell Adhesive Immersion Precipitation Membranes Based on Supramolecular Bis-Urea Polymers.

A variety of biomedical applications requires tailored membranes; fabrication through a mix-and-match approach is simple and desired. Polymers based on supramolecular bis-urea (BU) moieties are capable of modular integration through directed non-covalent stacking. Here, it is proposed that non-cell adhesive properties can be introduced in polycaprolactone-BU-based membranes by the addition of poly(ethylene glycol) (PEG)-BU during immersion precipitation membrane fabrication, while unmodified PEG is not retained in the membrane. PEG-BU addition results in denser membranes with a similar pore size compared to pristine membranes, while PEG addition induces defect formation. Infrared spectroscopy and surface hydrophobicity measurements indicate that PEG-BU is retained during membrane processing. Additionally, PEG-BU incorporation successfully leads to poor cell adhesive surfaces. No evidence is observed to indicate PEG retention. The results obtained indicate that the BU system enables intimate mixing of BU-modified polymers after processing. Collectively, the results provide the first steps toward BU-based immersion precipitated supramolecular membranes for biomedical applications.

Stabilization of poly(ethylene glycol)-poly(ε-caprolactone) star block copolymer micelles via aromatic groups for improved drug delivery properties

HypothesisThe functionalization of poly(ethylene glycol)-poly(ε-caprolactone) (PEG-PCL) block copolymers with moieties allowing for core-crosslinking is expected to result in improved micellar stability and drug delivery properties. ExperimentsPEG-(PCL)8 star block copolymers were functionalized with pendant benzylthioether (BTE) groups by applying an anionic post-polymerization modification technique followed by photoradical thiol-yne addition of benzyl mercaptan. The micellar properties of PEG-(PCL)8 and PEG-(PCL-BTE)8 were studied and compared in terms of critical micelle concentration (CMC), size, morphology, drug loading and release and in vitro cytotoxicity. FindingsIn comparison with unmodified PEG-(PCL)8 micelles, PEG-(PCL-BTE)8 micelles exhibited a 15-fold lower CMC, a 15-fold smaller size and a 50% higher drug loading and encapsulation efficiency thanks to the presence of pendant benzyl groups which provide the possibility for micellar core-crosslinking via supramolecular π-π stacking and additional hydrophobic interactions. Whereas the PEG-(PCL)8 micelles showed significant aggregation during in vitro cytotoxicity experiments, the PEG-(PCL-BTE)8 micelles showed no signs of aggregation and were capable of solubilizing high concentrations of curcumin, resulting in a significant decrease in MCF-7 cell viability after 48 h. Their ease of synthesis combined with promising results regarding drug delivery make the PEG-(PCL-BTE)8 micelles appealing for application in the field of encapsulation.

Efficient Photocatalytic Activity of TiO2 Nanocrystals Modified with Organic Electron Donor and Barium Doping for Azo Group Decomposition Under UV Irradiation

Two kinds of surface-modified TiO2 photocatalysts, PEG–TiO2 nanocrystals and Ba–TiO2 nanocrystals, are prepared and characterized by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) analysis. The modified TiO2 nanocrystals are small particles with irregular shape and size below 10 nm. Reactive Orange 72, with a –N=N– group, is selected as a model dye. The photocatalytic activities of the modified TiO2 nanocrystals for redox reactions of the azo group under UV irradiation are compared and the mechanism of the reduction of the dye photocatalyst is discussed. The results show that the photocatalysts can efficiently degrade Reactive Orange 72 (50 mg/L) within 2 min. The dye is completely broken down into small molecular compounds. The Ba–TiO2 nanocrystals have oxygen vacancies that serve as internal SEDs, and shows stronger photocatalytic reactivity than that of the unmodified TiO2 nanocrystal and PEG–TiO2. The Ba–TiO2 nanocrystals show the fastest decolorization rate and the best maintained performance for five cycles. The surface-modified TiO2 nanocrystals have potential application in the environmental, photochemical, and photovoltaics fields.

Mono-PEGylation of Alpha-MMC and MAP30 from Momordica charantia L.: Production, Identification and Anti-Tumor Activity.

PEGylation is a well-established and effective strategy to decrease immunogenicity, which can increase the stability and in vivo half-life time. However, the generation of multi-site modified products is inevitable due to the lysine chemistry, which will bring difficulties in subsequent research, such as purification and quantification. Site-specific modification by mPEG-succinimidyl carbonate (mPEG-SC) is a widely used method for N-terminal conjugation. In this study, we used it for site-directed modification on two ribosome-inactivating proteins (RIPs), alpha-momorcharin (α-MMC) and momordica anti-HIV protein (MAP30), from Momordica charantia L. According to the optimization of previous modification conditions, we compared Macro-Cap SP with SP-Sepharose FF chromatography for separating the final mPEGylated RIPs. Two kinds of methods both can obtain homogenous mPEGylated RIPs which were identified by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), isoelectric focusing electrophoresis (IEF), and matrix-assisted laser desorption ionization-time of flight/time of flight (MALDI-TOF/TOF) analysis. We also used iodine staining method to detect the amount of unmodified PEG. Furthermore, the inhibition activity of both mPEGylated and non-PEGylated RIPs against human lung adenocarcinoma epithelial A549 cells was detected. All of the results suggested that the mPEGylated α-MMC/MAP30 might be potentially developed as new anti-tumor drugs.

Mechanically robust PEGDA–MSNs-OH nanocomposite hydrogel with hierarchical meso-macroporous structure for tissue engineering

Owing to their tissue-like elasticity, poly(ethylene glycol) (PEG)-based hydrogels are highly desirable as three-dimensional scaffolds for tissue regeneration. Also, their high permeability can mimic the native extracellular matrix. However, their applications are limited by their poor mechanical properties and bioinert nature, which restrict cell adhesion and spreading. This study aims to address both limitations by developing a novel hierarchical nanocomposite hydrogel (NC gel) composed of polyethylene glycol diacrylate (PEGDA) and hydroxyl mesoporous silica nanoparticles (MSNs-OH) via in situ free-radical polymerization. Structural and physicochemical characterization shows that MSNs-OH act as both reinforcing agents and adhesion sites in the hydrogel system, which significantly enhances mechanical properties and cellular affinity. Compared with the unmodified PEG hydrogels, which are fractured easily, MSNs-OH provide the PEG-based NC gels with flexibility due to interactions with PEGDA. Furthermore, the increased protein adsorption capability, the integration of hierarchical macro–mesoporous structure, as well as the introduction of silica, provide a favorable environment for the adhesion and spreading of rat marrow stem cells (RMSCs). These NC hydrogels show promise as scaffolds for tissue engineering.

Pseudopolyrotaxanes on Inorganic Nanoplatelets and their Supramolecular Hydrogels

In this paper, we demonstrate the first hybrid suprastructure of pseudopolyrotaxanes (PPRs) on clay nanoplatelets. Simple end-modification of poly(ethylene glycol) with pyridinium (PEG-N(+)) enabled the chains to form brushlike conformation on clay surfaces. Thus, the PEG chains were able to thread into the cavities of α-cyclodextrins (α-CDs), leading to hybrid PPR hydrogels. This was very different from the unmodified PEG chains, which were absorbed onto the clay surface and thus made the PPR formation impossible. The hydrogels made of this PPR-on-clay structure displayed a dynamic modulus 1 order of magnitude higher than those of the native PPR hydrogels. Furthermore, based on the competitive host-guest interactions, such hybrid hydrogels showed fully photoreversible sol-gel transition after a competitive guest containing azobenzene moiety was introduced.

Polymerizable superoxide dismutase mimetic protects cells encapsulated in poly(ethylene glycol) hydrogels from reactive oxygen species‐mediated damage

A polymerizable superoxide dismutase mimetic (SODm) was incorporated into poly(ethylene glycol) (PEG) hydrogels to protect encapsulated cells from superoxide-mediated damage. Superoxide and other small reactive oxygen species (ROS) can cause oxidative damage to donor tissue encapsulated within size exclusion barrier materials. To enzymatically breakdown ROS within biomaterial cell encapsulation systems, Mn(III) Tetrakis[1-(3-acryloxy-propyl)-4-pyridyl] porphyrin (MnTTPyP-acryl), a polymerizable manganese metalloporphyrin SOD mimetic, was photopolymerized with PEG diacrylate (PEGDA) to create functional gels. In unmodified PEG hydrogels, a significant reduction in metabolic activity was observed when encapsulated Min6 β-cells were challenged with chemically generated superoxide. Cells encapsulated within MnTPPyP-co-PEG hydrogels, however, demonstrated greatly improved metabolic activity following various superoxide challenges. Further, cells were encapsulated and cultured for 10 days within MnTPPyP-co-PEG hydrogels and challenged with superoxide on days 4, 6, and 8. At the conclusion of this study, cells in blank PEG hydrogels had no observable metabolic activity but when encapsulated in MnTPPyP-functionalized hydrogels, cells retained 60 ± 5% of the metabolic activity compared to untreated controls.

Development of a PEG Derivative Containing Hydrolytically Degradable Hemiacetals

Development of a PEG Derivative Containing Hydrolytically Degradable Hemiacetals

Injectable Biodegradable Poly(ethylene glycol)/RGD Peptide Hybrid Hydrogels for in vitro Chondrogenesis of Human Mesenchymal Stem Cells

In this study, an injectable and biodegradable poly(ethylene glycol) (PEG)/arginine-glycine-aspartic (RGD) peptide hybrid hydrogel has been synthesized and used as a biomimetic scaffold for encapsulation of human mesenchymal stem cells (hMSCs). Tetrahydroxyl PEG was functionalized with acrylate, and then reacted with thiol-containing peptide (RGD). Gelation occurred within 30 min with the addition of cells and PEG-dithiol via Michael addition. The hydrogels synthesized with a peptide concentration of 1.0-5.0 mM achieved significantly greater cell viability when compared to the hydrogels without the RGD peptide. However, the effect of RGD on chondrogenesis was found to be dose-dependent. Immunohistology studies demonstrated that hMSCs encapsulated in the hydrogel matrix with 1.0 mM RGD and TGF-β3 showed enhanced positive staining for aggrecan and type II collagen as compared to that with 5.0 mM RGD and unmodified PEG hydrogels. RT-PCR results further revealed that the cells in hydrogels with 1 mM RGD expressed significantly higher levels of type II collagen than those in PEG hydogels without RGD peptide. These findings have demonstrated that the PEG-RGD hydrogels can be a promising scaffold to deliver hMSCs for cartilage repair.

Hydrophobically modified poly(ethylene glycol) as reactive clays inhibitor additive in water‐based drilling fluids

AbstractAdsorption measurements and inhibition tests were used to investigate the mechanisms of shale stabilization by hydrophobically modified poly(ethylene glycol) (PEG). Commercially available PEG with a large range of molar masses and PEG diesters were adsorbed on smectite‐rich clay from saline solutions and the clay/polymer complexes obtained were characterized by thermogravimetric analysis and x‐ray diffraction. The adsorption isotherms obtained for all unmodified PEG showed low affinity for the clay surface, however they all accessed the interlamellar spaces of the clay and reduced the clay water content of the complexes obtained. The PEG macromolecules had their affinity for the clay strongly enhanced by the hydrophobic modification especially with dodecanoic acid and were intercalated into the clay matrix, reducing, in a more efficient way, the water uptake by the clay. Conventional rolling tests were performed to evaluate the effect of polymers on the clay cuttings integrity. Results show that under conditions promoting the adsorption of polymers on both external and interlayer clay surfaces, displacement of the water from the clay was obtained and dispersion and disintegration of clay cuttings were inhibited. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Potential of Hydrogels Based on Poly(Ethylene Glycol) and Sebacic Acid as Orthopedic Tissue Engineering Scaffolds

In this study, the bioactive effects of poly(ethylene glycol) (PEG) sebacic acid diacrylate (PEGSDA) hydrogels with or without RGD peptide modification on osteogenic differentiation and mineralization of marrow stromal cells (MSCs) were examined. In a separate experiment, the ability of PEGSDA hydrogel to serve as a delivery vehicle for bone morphogenetic protein 2 (BMP-2) was also investigated. As a scaffold, the attachment and proliferation of MSCs on PEGSDA hydrogel scaffolds with and without RGD peptide modification was similar to the control, tissue culture polystyrene. In contrast, cells were barely seen on unmodified PEG diacrylate (PEGDA) hydrogel throughout the culture period for up to 21 days. Osteogenic phenotypic expression such as alkaline phosphatase (ALP) of MSCs as well as mineralized calcium content were significantly higher on PEGSDA-based hydrogels than those on the control or PEGDA hydrogels. Potential use of PEGSDA scaffold as a delivery vehicle of osteogenic molecules such as BMP-2 was also evaluated. Initial burst release of BMP-2 from PEGSDA hydrogel scaffold (14.7%) was significantly reduced compared to PEGDA hydrogel scaffold (84.2%) during the first 3 days of a 21-day release period. ALP activity of an osteoblast was significantly higher in the presence of BMP-2 released from PEGSDA hydrogel scaffolds compared to that in the presence of BMP-2 released from PEGDA scaffolds, especially after 6 days of release. Overall, PEGSDA hydrogel scaffolds without further modification may be useful as orthopedic tissue engineering scaffolds as well as local drug carriers for prolonged sustained release of osteoinductive molecules.

Glucagon-Like Peptide-1 Functionalized PEG Hydrogels Promote Survival and Function of Encapsulated Pancreatic β-Cells

Encapsulating pancreatic islets in a semipermeable poly(ethylene glycol) (PEG) hydrogel membrane holds potential as an immuno-isolation barrier for the treatment of type 1 diabetes mellitus. The semipermeable PEG hydrogel not only permits free diffusion of nutrients, metabolic waste, and insulin produced from the encapsulated β-cells, but also provides a size-exclusion effect to prevent direct contact of entrapped islets to host immune cells and antibodies. However, the use of unmodified PEG hydrogels for islet encapsulation is not ideal, as there is no bioactive cue to promote the long-term survival and function of the encapsulated cells. Herein, we report the synthesis and characterization of a bioactive glucagon-like peptide 1 (GLP-1) analog, namely, GLP-1-cysteine or GLP-1C, and the fabrication of functional GLP-1 immobilized PEG hydrogels via a facile thiol−acrylate photopolymerization. The immobilization of bioactive GLP-1C within PEG hydrogels is efficient and does not alter the bulk hydrogel properties. Further, the GLP-1 immobilized PEG hydrogels enhance the survival and insulin secretion of encapsulated islets. Overall, this study demonstrates a strategy to modify PEG hydrogels with bioactive peptide moieties that can significantly enhance the efficacy of islet encapsulation.

Functional PEG–peptide hydrogels to modulate local inflammation inducedby the pro-inflammatory cytokine TNFα

Hydrogels are an important class of biomaterials for cell encapsulation and delivery, providing a physical barrier or “immuno-isolation” between the host tissue and encapsulated cells. The semi-permeable gel protects the encapsulated cells from host immune cells and/or antibody recognition while allowing facile diffusion of nutrients. However, a previously un-addressed problem is that highly permissive hydrogels cannot exclude the infiltration of soluble immune-mediators, such as pro-inflammatory cytokines that are highly expressed in wounded environments in vivo. When encountered with pro-inflammatory cytokines, encapsulated cells fail to perform their desired functions. Here, we report the synthesis, characterization, and application of peptide-functionalized, cytokine-antagonizing poly(ethylene glycol) (PEG) hydrogels capable of sequestering the pro-inflammatory cytokine, tumor necrosis factor α (TNFα). Results demonstrate that the survival, function, and differentiation of encapsulated cells (e.g., rat adrenal pheochromocytoma cells – PC12s, mouse pancreatic islets, and human mesenchymal stem cells or hMSCs) are significantly hindered in un-modified PEG hydrogels under in vitro TNFα treatments. In contrast, cells encapsulated in TNFα-antagonizing hydrogels are un-affected by the infiltrated TNFα. This study demonstrates the importance of controlling the availability of pro-inflammatory cytokines in highly permissive hydrogels.

Inverted pattern formation of cell microarrays on poly(ethylene glycol) (PEG) gel patterned surface and construction of hepatocyte spheroids on unmodified PEG gel microdomains

We present herein the novel technique for constructing inverted cell-adhesion patternes on PEG gel modified glass surfaces by photoirradiation using the same photomask and materials. The PEG gel micropatterns were prepared by a photolithographic technique using a photomask with 100 microm aligned cavities after spin-coating of a mixed solution of alpha,omega-dimethacryloyl-PEG (PEG-DMA) and a photoinitiator on glass surfaces. When methanol was used as a casting solvent for the spin-coating (Method A), the circular PEG gel domains with a diameter of 100 microm were fabricated on the surface, and as would be predicted, seeded bovine aortic endothelial cells (BAECs) adhered to the glass area on the constructed surface to form a BAECs sheet with 100 microm aligned cavity. In contrast, it was rather surprising for us that a complete inverted cell pattern was formed when the PEG gel pattern surface was prepared using methanol/water co-solvent (Method B). Furthermore, when hepatoma cancer cells were seeded on the constructed surface prepared by Method B, they formed a spherical multicellular aggregate (spheroid) on the unmodified PEG gel domains without feeder cells. In order to obtain information on this peculiar phenomenon, fluorescence-based protein adsorption experiments, contact angle measurements, and X-ray photospectroscopy (XPS) analysis were carried out.

The influence of the RGD peptide motif and its contextual presentation in PEG gels on human mesenchymal stem cell viability.

An investigation was undertaken into the method of delivery of RGD peptide motifs to adult human mesenchymal stem cells (hMSCs) encapsulated in poly(ethylene glycol) (PEG) hydrogel systems. Previous studies have shown that the viability of hMSCs encapsulated in bio-inert hydrogels, such as PEG-based gels, decreases over time. hMSCs are an adhesive-dependent cell type, requiring attachment sites to maintain their survival and function. The incorporation of tethered RGD peptide motifs was found to sustain a high level of hMSC survival in PEG gels. However, previous reports are largely limited to pendantly tethered RGD in gels; therefore, further investigation into hMSCs' affinity for and response to the contextual presentation of RGD was studied using varying methods of RGD attachment to the PEG gel, as well as delivery of soluble RGD peptides. Studies with encapsulated hMSCs showed that the constrained RGD peptide, bound via two links to the PEG gel, promoted approximately 60% cell survival, while tethering the RGD as a pendant group, bound via a single link to the PEG gel, promoted approximately 80% cell survival. Interestingly, incorporating a glycine spacer arm to the RGD pendant tether further enhanced survival to approximately 88%. Investigations with solubly delivered peptides resulted in a dramatic decrease in cell viability with time, eventually leading to survival that was similar to that of unmodified PEG gels. Integrin staining for alphavbeta3 and alpha4, as well as focal adhesion staining, correlates to the trends in hMSC survival for covalently-bound RGD motifs and a loss of viability for the solubly delivered peptide systems.

Trastuzumab−Polyethylenimine−Polyethylene Glycol Conjugates for Targeting Her2-Expressing Tumors

In this study, we describe the synthesis and characterization of a conjugate consisting of poly(ethylene glycol 2,000 Da)(10)-graft-poly(ethylene imine 25 kDa) (PEG-PEI) covalently coupled to Trastuzumab (Herceptin) via N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP) for specific gene delivery to Her2-expressing cell lines. The efficiency of DNA condensation was studied using an ethidium bromide exclusion assay and demonstrated negligible differences compared to PEG-PEI. Conjugate complex sizes were determined by dynamic light scattering to be in the range 130-180 nm. zeta potentials at different N/P ratios were close to neutral. Flow cytometry and confocal microscopy revealed efficient binding and uptake of Trastuzumab-PEI-PEG complexes using Her2-positive SK-BR-3 cells. In contrast, binding and uptake into Her2-negative OVCAR-3 cells was negligible. In good correlation with these findings, reporter gene expression using targeted complexes in SK-BR-3 cells was up to sevenfold higher than that of unmodified PEG-PEI complexes. With the use OVCAR-3 cells, no significant difference in expression efficiencies could be observed between conjugate and PEG-PEI complexes. Inhibition experiments with free Trastuzumab showed a significant decrease in reporter gene expression using SK-BR-3 cells but no decrease using OVCAR-3 cells, strongly supporting a specific Her2-receptor-mediated uptake mechanism. Our results suggest that Trastuzumab-PEI-PEG might be a promising new bioconjugate for targeted gene transfer to Her2-positive tumor cells in vivo.

A novel star PEG–derived surface coating for specific cell adhesion

In this study a novel approach for the coating and functionalization of substrates for cell culture and tissue engineering is presented. Glass, silicon, and titanium panes were coated with an ultrathin film (30 +/- 5 nm) of reactive star-shaped poly(ethylene glycol) prepolymers (Star PEG). Homogeneity of the films was checked by optical microscopy and scanning force microscopy. These coatings prevent unspecific protein adsorption as monitored by fluorescence microscopy and ellipsometry. In order to allow specific cell adhesion the films were modified with linear RGD peptides (gRGDsc) in different concentrations. After sterilization, fibroblast, SaOS, and human mesenchymal stem cells (hMSC) were seeded on these substrates. Cell adhesion, spreading, and survival was observed for up to 30 days on linear RGD peptide (gRGDsc)-modified coatings, whereas no cell adhesion could be detected on unmodified Star PEG layers. By variation of the RGD concentration within the film the amount of cells that became adhesive could be controlled. When differentiation conditions are used for cultivation of hMSCs the cells show the expression of osteogenic marker genes after 14 days which is comparable to cultivation on cell culture plastic. Thus, the Star PEG/RGD film did not negatively influence the differentiation process. The high flexibility of the system considering the incorporation of biologically active compounds opens a broad field of future experiments.