Keratin hydrogels support the sustained release of bioactive ciprofloxacin

An in-situ nitriding method has been developed to modify the outer surface and the pore walls of both open and closed pores of porous NiTi shape memory alloys (SMAs) as part of their sintering process. XRD and XPS examinations revealed that the modified layer is mainly TiN. The biocompatibility of the in-situ nitrided sample has been characterized by its corrosion resistance, cell adherence, and implant surgery. The in-situ nitrided porous NiTi SMAs exhibit much better corrosion resistance, cell adherence, and bone tissue induced capability than the porous NiTi alloys without surface modification. Furthermore, the released Ni ion content in the blood of rabbit is reduced greatly by the in-situ nitriding. The excellent biocompatibility of in-situ nitrided sample is attributed to the formation of the TiN layer on all the pore walls including both open and closed pores.     

Hyaluronic acid-based hydrogels crosslinked by copper-catalyzed azide-alkyne cycloaddition with tailorable mechanical properties

Biopolymers of the extracellular matrix are attractive starting materials for providing degradable and biocompatible biomaterials. In this study, hyaluronic acid-based hydrogels with tunable mechanical properties were prepared by the use of copper- catalyzed azide-alkyne cycloaddition (known as "click chemistry"). Alkyne-functionalized hyaluronic acid was crosslinked with linkers having two terminal azide functionalities, varying crosslinker density as well as the lengths and rigidity of the linker molecules. By variation of the crosslinker density and crosslinker type, hydrogels with elastic moduli in the range of 0.5-4 kPa were prepared. The washed materials contained a maximum of 6.8 mg copper per kg dry weight and the eluate of the gel crosslinked with diazidostilbene did not show toxic effects on L929 cells. The hyaluronic acid-based hydrogels have potential as biomaterials for cell culture or soft tissue regeneration applications.     

Perlecan domain I-conjugated, hyaluronic acid-based hydrogel particles for enhanced chondrogenic differentiation via BMP-2 release

We have developed a biomimetic growth factor delivery system that effectively stimulates the chondrogenic differentiation of the cultured mesenchymal stem cells via the controlled presentation of bone morphogenetic protein-2 (BMP-2). Hyaluronic acid (HA)-based, microscopic hydrogel particles (HGPs) with inherent nanopores and defined functional groups were synthesized by an inverse emulsion polymerization technique. Recombinantly produced, heparan sulfate (HS)-bearing perlecan domain I (PlnDI) was covalently immobilized to HA HGPs (HGP–P₁) via a flexible poly(ethylene glycol) (PEG) linker through the lysine amines in the core protein of PlnDI employing reductive amination. Compared to HGP without PlnDI, HGP–P₁ exhibited significantly (p < 0.05) higher BMP-2 binding capacity and distinctly different BMP-2 release kinetics. Heparitinase treatment increased the amount of BMP-2 released from HGP–P₁, confirming the HS-dependent BMP-2 binding. While BMP-2 was released from HGPs with a distinct burst release followed by a minimal cumulative release, its release from HGP–P₁ exhibited a minimal burst release followed by linear release kinetics over 15 days. The bioactivity of the hydrogel particles was evaluated using micromass culture of multipotent mesenchymal stem cells (MSCs), and the chondrogenic differentiation was assessed by the production of glycosaminoglycan, aggrecan and collagen type II. Our results revealed that BMP-2 loaded HGP–P₁ stimulates more robust cartilage specific ECM production as compared to BMP-2 loaded HGP, due to the ability of HGP–P₁ to potentiate BMP-2 and modulate its release with a near zero-order release kinetics. The PlnDI-conjugated, HA HGPs provide an improved BMP-2 delivery system for stimulating chondrogenic differentiation in vitro, with potential therapeutic application for cartilage repair and regeneration.     

Polyanhydrides for controlled release of bioactive agents

This report is a review of the development of a drug delivery system based on biorodible polyanhydrides. With the water labile anhydride linkage, a wide range of matrix degradation and drug release rates can be obtained from these drug-carriers. In addition to monolithic formulations, the feasibility of an injectable system by microencapsulation is demonstrated. The possibility of enhancing the release externally by an ultrasonic source has also been explored. The polymers tested showed good tissue biocompatibility and their breakdown products showed no adverse toxicological effects. Preliminary in vivo results confirmed the efficacy of these devices.     

Heparin-decorated, hyaluronic acid-based hydrogel particles for the controlled release of bone morphogenetic protein 2

We are interested in developing hydrophilic particulate systems that are capable of sequestering growth factors, regulating their release and potentiating their biological functions. To this end heparin (HP)-decorated, hyaluronic acid (HA)-based hydrogel particles (HGPs) were synthesized using an inverse emulsion polymerization technique employing divinyl sulfone as the crosslinker. By varying the feed composition of the aqueous phase the amount of HP integrated in the particles can be systematically tuned. The resulting microscopic particles are spherical in shape and contain nanosized pores suitable for growth factor encapsulation. The covalently immobilized HP retained its ability to bind bone morphogenetic protein-2 (BMP-2) specifically, and its release kinetics can be adjusted by tuning the particle composition. Compared with pure HA particles the hybrid HA/HP HGPs show a higher BMP-2 loading capacity. While BMP-2 was released from HA HGPs with a significant initial burst, a near zero order release kinetics was observed from HA/HP hybrid particles with an optimized heparin content of 0.55 μg per mg HGPs. The ability of HA/HP hybrid particles to present BMP-2 in a controlled manner, combined with the innate bioactivity of HA, induced robust and consistent chondrogenic differentiation of murine mesenchymal stem cells, as shown by up-regulation of the mRNA levels of chondrogenic markers and the production of cartilage-specific extracellular matrix components. The simplicity of the particle synthesis, combined with the defined biological activities of the constituent building blocks, renders the HP-decorated, HA-based hydrogel particle system an attractive candidate for the sustained release of BMP-2, possibly for cartilage repair and regeneration.     

Controlled release of bioactive TGF-beta 1 from microspheres embedded within biodegradable hydrogels

Transforming growth factor-beta1 (TGF-beta1) is of great relevance to cartilage development and regeneration. A delivery system for controlled release of growth factors such as TGF-beta1 may be therapeutic for cartilage repair. We have encapsulated TGF-beta1 into poly(DL-lactide-co-glycolide) (PLGA) microspheres, and subsequently incorporated the microspheres into biodegradable hydrogels. The hydrogels are poly(ethylene glycol) based, and the degradation rate of the hydrogels is controlled by the non-toxic cross-linking reagent, genipin. Release kinetics of TGF-beta1 were assessed using ELISA and the bioactivity of the released TGF-beta1 was evaluated using a mink lung cell growth inhibition assay. The controlled release of TGF-beta1 encapsulated within microspheres embedded in scaffolds is better controlled when compared to delivery from microspheres alone. ELISA results indicated that TGF-beta1 was released over 21 days from the delivery system, and the burst release was decreased when the microspheres were embedded in the hydrogels. The concentration of TGF-beta1 released from the gels can be controlled by both the mass of microspheres embedded in the gel, and by the concentration of genipin. Additionally, the scaffold permits containment and conformation of the spheres to the defect shape. Based on these in vitro observations, we predict that we can develop a microsphere-loaded hydrogel for controlled release of TGF-beta1 to a cartilage wound site.     

Thermo-responsive hydrogels with N-isopropylacrylamide/acrylamide interpenetrating networks for controlled drug release

Series of thermo-sensitive hydrogels (PNAs) based on N-isopropylacrylamide/acrylamide interpenetrating polymer networks were synthesized via in situ free-radical polymerization. Poly (ethylene glycol diacrylate) and poly (ε-caprolactone diacrylate) were synthesized as macro-cross-linkers due to their excellent biocompatibilities. The macro-cross-linkers and hydrogels were characterized by ¹H NMR and FT-IR, respectively. The interior morphology of the hydrogels was observed by scanning electron microscopy. The swelling ratios at different temperatures and the swelling/deswelling kinetics of the hydrogels were studied. Their volume phase transition temperatures were also measured by differential scanning calorimetry characterization. The results indicated that the PNA hydrogels had uniform macroporous structures, and they not only had considerable swelling ratios, but also exhibited rapid swelling/deswelling kinetics and response sensitivities. In addition, the weight ratio of AAm/NIPAAm also affected the swelling performance and phase transition temperature of hydrogels, and its value less than 5% was the optimal proportion to achieve excellent comprehensive properties. Levofloxacin lactate and Naproxen were selected as drugs and simulated in vitro condition release, and the drug release results showed that the PNA hydrogels behaved fast release performance.     

Retention and activity of BMP-2 in hyaluronic acid-based scaffolds in vitro.

Bone morphogenetic protein-2 (BMP-2) delivered in a suitable implantable matrix has the potential to repair local skeletal defects by inducing new bone formation from undifferentiated pluripotent stem cells resident in host tissue. In this study, we examined in vitro the potential of a derivatized hyaluronic acid (Hyaff-11) scaffold as a delivery vehicle for recombinant human BMP-2 (rhBMP-2) in bone and cartilage repair therapies. Hyaff-11 scaffolds were fabricated using a phase inversion/particulate leaching method and soak-loaded with rhBMP-2. In vitro release kinetics of rhBMP-2, demonstrated using enzyme-linked immunosorbant assay and alkaline phosphatase (ALP) assay revealed a slow, sustained rhBMP-2 release during 28 days, with a cumulative release of 31.82% of the initial rhBMP-2 loaded. rhBMP-2 was released in bioactive form as demonstrated by ALP induction of pluripotent cell line, C3H10T1/2 (T1/2), down the osteoblast lineage when incubated with the release supernatants. rhBMP-2 retention in Hyaff-11 scaffolds was greater than that from collagen gels, which released most of the initially loaded rhBMP-2 by 14 days. rhBMP-2-loaded Hyaff-11 scaffolds were also seeded with T1/2 cells and evaluated at 3, 7, 14, and 28 days for viability and expression of osteoblast phenotype. Cells remained viable throughout the study and expressed a time- and dose-dependent ALP and osteocalcin expression in the rhBMP-2 groups. Based on these observations, Hyaff-11 scaffolds may be suitable delivery systems for rhBMP-2 in bone/cartilage repair because of their ability to retain rhBMP-2, release low levels of bioactive rhBMP-2 to the local environment in a sustained manner, and stimulate differentiation of pluripotent stem cells.     

Drug-binding hydrogels of hyaluronic acid functionalized with beta-cyclodextrin

Hyaluronic acid (HA) hydrogels are attractive materials for biomedical applications because they are porous, water-swelling, biocompatible, biodegradable, and resistant to non-specific cell adhesion. A limitation of HA hydrogels is that incorporation of bioactive drugs can be restricted by low solubility of drug within the hydrogel environment. Our goal was to synthesize HA hydrogels that bind drug through hydrophobic interactions as a method for increasing drug loading. We functionalized photocrosslinked HA hydrogels with a methacryloyl derivative of beta-cyclodextrin (betaCD). betaCD is a molecular "basket" with a hydrophilic exterior and a hydrophobic cavity. Inclusion complexes are formed when betaCD hosts all or part of a hydrophobic drug within the cavity. HA hydrogels functionalized with methacryloyl-betaCD monomer gained the property of inclusion complexation which greatly enhanced the uptake of a model hydrophobic drug, hydrocortisone. Pre-incubation of the hydrogels with adamantane carboxylic acid (ACA) inhibited hydrocortisone uptake by competition for betaCD cavities. In addition, control hydrogels of HA functionalized with alphaCD monomer were not efficient at hydrocortisone uptake because the alphaCD cavity is too small for efficient complexation. These experiments confirmed that the betaCD monomer enhances drug loading by the mechanism of inclusion complexation. Drug-binding HA-betaCD hydrogels may be further engineered to create HA-based biomaterials with a built in drug delivery capability.     

Highly porous bioresorbable scaffolds with controlled release of bioactive agents for tissue-regeneration applications

Highly porous poly(dl-lactic-co-glycolic acid) films with controlled release of horseradish peroxidase (HRP) as a model protein have been successfully developed and studied. These films, which are prepared by freeze-drying inverted emulsions, are designed for use in tissue-regeneration applications. The effects of the emulsion’s formulation and host polymer’s characteristics on the film’s microstructure and HRP release profile over 4 weeks were investigated. A dual pore size population is characteristic for most films, with large 12–18 μm pores and small 1.5–7 μm pores, and porosity in the range of 76–92%. An increase in the polymer content and its initial molecular weight, organic/aqueous (O:A) phase ratio and lactic acid content, or a decrease in the HRP content, all resulted in a decreased burst effect and a more moderate release profile. A simultaneous change in two or three of these formulation parameters (compared to a reference formulation) resulted in a synergistic effect on the HRP release profile. A constant HRP release rate was achieved when a composite film was used. Human gingival fibroblast adhesion to the films indicated good biocompatibility. Appropriate selection of the emulsion’s parameters can therefore yield highly porous films with the desired protein-release behavior which can serve as scaffolds for bioactive agents in tissue-regeneration applications.     

Strong binding of bioactive BMP-2 to nanocrystalline diamond by physisorption

Nano-crystalline diamond (NCD)-coated surfaces were efficiently functionalized with bone morphogenetic protein-2 (BMP-2) by means of physisorption. Due to their randomly oriented texture, NCD-coated surfaces appear to bind complex molecules firmly. Applying various highly sensitive analytical methods, the interaction was found extremely stable. The strength of the experimentally measured adherence between BMP-2 and NCD was further corroborated by theoretical calculations. Oxygen treatment rendered NCD hydrophilic by the appearance of surface oxygen containing groups. This particular NCD surface exhibited even higher binding energies towards BMP-2 than the hydrophobic surface, and this surface was also favoured by cultured cells. Most importantly in this context, bound BMP-2 was found fully active. When cultured on BMP-2-treated NCD, osteosarcoma cells strongly up-regulated alkaline phosphatase, a specific marker for osteogenic differentiation. Hence, this simple method will allow generating highly versatile surfaces with complex biomimetic coatings, essentials for novel medical devices and implants as well as for innovative scaffolds in tissue engineering.     

Novel etherified locust bean gum-alginate hydrogels for controlled release of glipizide

On many occasions, homopolysaccharide hydrogel networks alone are not suitable for controlled drug delivery. In this study, interpenetrating networks (IPNs) of sodium alginate (ALG) and etherified locust bean gum (ELBG) were developed through ionotropic gelation with Al³⁺ ions, tested for glipizide release, and were compared with homopolymer hydrogel networks. The degree of reticulation in IPNs was explained by the neutralization equivalent, tensile strength measurement, and drying kinetics of drug-free hydrogels. IPNs afforded a maximum of 94.40?±?0.35% drug entrapment efficiency and exhibited slower drug release profiles up to 8?h. Al³⁺-ALG network almost completed the release of embedded drug in 3.5?h; however, the homopolymer Al³⁺-ELBG network discharged their content at a slow, uniform rate up to 8?h like the IPNs. All the networks appeared spherical under scanning electron microscope. In all cases, a faster drug release rate was assumed in phosphate buffer (pH 7.4) than in KCl/HCl buffer (pH 1.2) solution. The pH-responsive swelling of the beads was responsible for the variable drug release rate in different media. NonFickian diffusion mechanism was operative for the transport of drug from the IPNs. Moreover, IPNs gained appreciation for their better mechanical strength (63.79?±?1.59?MPa) than Al³⁺-ELBG network. Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, and X-ray diffraction analyses indicated a compatible environment for drug encapsualtion and release from the IPNs. The drug release curves of Al³⁺-ELBG and IPNs were found similar to a reference product. Hence, Al³⁺-ELBG and IPNs could be useful in controlling diabetes over longer periods.     

Synthesis, characterization and controlled drug release of thermosensitive IPN-PNIPAAm hydrogels

A method was developed to prepare thermosensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogels with an interpenetrating polymer network (IPN) structure for the purpose of improving its mechanical properties, response rate to temperature and sustained release of drugs. Although the differential scanning calorimetry data exhibited similarly lower critical solution temperature (LCST) between IPN- and non-IPN-PNIPAAm hydrogels, an increase in the glass transition temperature (Tg) of the IPNs relative to the normal PNIPAAm hydrogel was observed. In addition, the mechanical properties of the IPNs were greatly improved when compared with the normal PNIPAAm hydrogel. The interior morphology of the IPN-PNIPAAm hydrogels was revealed by scanning electron microscopy (SEM); the IPN hydrogels showed a fibrillar-like porous network structure that normal PNIPAAm did not have. Furthermore, by measuring the temperature dependence of the swelling ratio and deswelling kinetics, these IPN hydrogels also exhibited improved intelligent characteristics (e.g., controllable faster response rate) that depended on the composition ratio of the two network components. From the applications viewpoint, the effects of a shrinking-reswelling cycle around the LCST on the properties of the IPN hydrogels were examined to determine if these properties would be stable for potential applications. Bovine serum albumin was chosen as the model protein for examining its release from the IPNs at different temperatures. The release data suggested that an improved controlled release could be achieved by the IPN-PNIPAAm hydrogels without losing their intelligent properties.     

Hyaluronic acid-based hydrogels as 3D matrices for in vitro evaluation of chemotherapeutic drugs using poorly adherent prostate cancer cells

The current investigation aimed to develop a biomimetic, three-dimensional (3D) culture system for poorly adherent bone metastatic prostate cancer cells (C4-2B) for use as an in vitro platform for anti-cancer drug screening. To this end, hyaluronic acid (HA) derivatives carrying complementary aldehyde (HAALD) and hydrazide (HAADH) groups were synthesized and characterized. In situ encapsulation of C4-2B cells was achieved by simple mixing of HAALD and HAADH in the presence of the cells. Unlike two-dimensional (2D) monolayer culture in which cells adopt an atypical spread morphology, cells residing in the HA matrix formed distinct clustered structures which grew and merged, reminiscent of real tumors. Anti-cancer drugs added to the media surrounding the cell/gel construct diffused into the gel and killed the embedded cells. The HA hydrogel system was used successfully to test the efficacy of anti-cancer drugs including camptothecin, docetaxel, and rapamycin, alone and in combination, including specificity, dose and time responses. Responses of cells to anti-neoplastics differed between the 3D HA hydrogel and 2D monolayer systems. We suggest that the data obtained from 3D HA systems is superior to that from conventional 2D monolayers as the 3D system better reflects the bone metastatic microenvironment of the cancer cells.     

Injectable glycosaminoglycan hydrogels for controlled release of human basic fibroblast growth factor

Synthetic hydrogel mimics of the extracellular matrix (ECM) were created by crosslinking a thiol-modified analog of heparin with thiol-modified hyaluronan (HA) or chondroitin sulfate (CS) with poly(ethylene glycol) diacrylate (PEGDA). The covalently bound heparin provided a crosslinkable analog of a heparan sulfate proteoglycan, thus providing a multivalent biomaterial capable of controlled release of basic fibroblast growth factor (bFGF). Hydrogels contained >97% water and formed rapidly in <10min. With as little as 1% (w/w) covalently bound heparin (relative to total glycosaminoglycan content), the rate of release of bFGF in vitro was substantially reduced. Total bFGF released increased with lower percentages of heparin; essentially quantitative release of bFGF was observed from heparin-free hydrogels. Moreover, the hydrogel-released bFGF retained 55% of its biological activity for up to 28 days as determined by a cell proliferation assay. Finally, when these hydrogels were implanted into subcutaneous pockets in Balb/c mice, neovascularization increased dramatically with HA and CS hydrogels that contained both bFGF and crosslinked heparin. In contrast, hydrogels lacking bFGF or crosslinked heparin showed little increase in neovascularization. Thus, covalently linked, heparin-containing glycosaminoglycan hydrogels that can be injected and crosslinked in situ constitute highly promising new materials for controlled release of heparin-binding growth factors in vivo.     

Implantable controlled release devices for BMP-7 delivery and suppression of glioblastoma initiating cells

Designing therapeutic devices capable of manipulating glioblastoma initiating cells (GICs) is critical to stop tumor recurrence and its associated mortality. Previous studies have indicated that bone morphogenetic protein-7 (BMP-7) acts as an endogenous suppressor of GICs, and thus, it could become a treatment for this cancer. In this work, we engineer an implantable microsphere system optimized for the controlled release of BMP-7 as a bioinspired therapeutic device against GICs. This microsphere delivery system is based on the formation of a heparin-BMP-7 nanocomplex, first coated with Tetronic^® and further entrapped in a biodegradable polyester matrix. The obtained microspheres can efficiently encapsulate BMP-7, and release it in a controlled manner with minimum burst effect for over two months while maintaining protein bioactivity. Released BMP-7 showed a remarkable capacity to stop tumor formation in a GICs cell culture model, an effect that could be mediated by forced reprogramming of tumorigenic cells towards a non-tumorigenic astroglial lineage.     

Sustained release of BMP-2 in a lipid-based microtube vehicle

Sustained release systems have been developed for the use of growth factors in tissue engineering applications. However, many of these systems continue to have limitations associated with low loading efficiencies and reduced biological activity after release. In this paper, we utilized a lipid-based microtube system for the sustained release of BMP-2. The lipid microtubes were fabricated using a self-assembly method, in order to avoid the use of harsh organic solvents that may damage the protein. BMP-2 was loaded into the microtubes by rehydrating dried microtubes in the protein solution. The loading efficiency and release kinetics of BMP-2 in the microtubes were measured using in vitro immunoassays. Loading efficiency was found to be dependent on microtube concentration. The potential for this system to deliver biologically active BMP-2 was assessed using the alkaline phosphatase assay and von Kossa staining on human mesenchymal stem cell cultures. The results demonstrate that the lipid microtube system is able to provide sustained delivery of biologically active BMP-2 and thereby induce osteogenic differentiation.     

Synthesis and controlled release behaviour of dextran bioactive esters by direct reaction of dextran with the potassium salts of bioactive carboxylic acids

This work deals with the coupling of model bioactive carboxylic acids (1-naphthylacetic acid, 2-(6-methoxy-2-naphthyl)propionic acid (naproxen) and nicotinic acid) to dextran by direct reaction with their potassium salts using pyridine/sulfonyl chloride as activating agent. The structure of the resulting polymeric derivatives was determined by means of ¹H and ¹³C NMR spectroscopy. The influence of the pyridine concentration, the type of sulfonyl chloride and the temperature on the reaction of dextran with potassium 1-naphthyl acetate was evaluated. The activation energy was found to be 65,7 kJ/mol. ¹³C NMR spectra at 75,4 MHz of partially modified dextran with 1-naphthyl acetate groups were studied in order to evaluate the selectivity of the reaction between dextran and potassium 1-naphthyl acetate. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C2 > C4 > C3. The hydrolysis in the heterogeneous phase of some dextran polymers partially modified with 1-naphthyl acetate groups shows that the release of the bioactive compound is dependent on the hydrophilic character of the polymer as well as the pH value of the medium.     

Hypoxia-induced angiogenesis is increased by the controlled release of deferoxiamine from gelatin hydrogels

The objective of this study is to design biodegradable hydrogels for the controlled release of deferoxiamine (DFO) and evaluate their biological activity. When the DFO was added to human umbilical vein endothelial cells cultured in 5.0% O₂, the level of hypoxia-inducible factor-1α and vascular endothelial growth factor significantly increased compared with that without DFO. The expression of angiogenesis-related genes was accordingly increased by the DFO addition. An aqueous solution of mixed gelatin and DFO was freeze-dried, and dehydrothermally treated at 140 °C for 24 h to prepare a gelatin hydrogel incorporating DFO. In the release test with phosphate-buffered saline solution (PBS) at 37 °C, an initial DFO release of 60% was observed, followed by no release. When placed in PBS containing collagenase, the hydrogel was enzymatically degraded with time, and consequently released DFO in a degradation-dependent manner. After the hydrogel incorporating DFO was injected intramuscularly into a mouse model of hind limb ischemia, the number of new blood vessels formed was significantly higher than that with free DFO and DFO-free hydrogel. It is concluded that the DFO-containing hydrogel shows promising for inducing angiogenesis locally.     

MMP-2 sensitive, VEGF-bearing bioactive hydrogels for promotion of vascular healing

We sought to develop bioactive hydrogels to facilitate arterial healing, e.g., after balloon angioplasty. Toward this end, we developed a new class of proteolytically sensitive, biologically active polyethylene glycol (PEG)-peptide hydrogels that can be formed in situ to temporarily protect the arterial injury from blood contact. Furthermore, we incorporated endothelial cell-specific biological signals with the goal of enhancing arterial reendothelialization. Here we demonstrate efficient endothelial cell anchorage and activation on PEG hydrogel matrices modified by conjugation with both the cell adhesive peptide motif RGD and an engineered variant of vascular endothelial growth factor (VEGF). By crosslinking peptide sequences for cleavage by MMP-2 into the polymer backbone, the hydrogels became sensitive to proteolytic degradation by cell-derived matrix metalloproteinases (MMPs). Analysis of molecular hallmarks associated with endothelial cell activation by VEGF-RGD hydrogel matrices revealed a 70% increase in production of the latent MMP-2 zymogen compared with PEG-peptide hydrogels lacking VEGF. By additional provision of transforming growth factor beta1 (TGF-beta1) within the PEG-peptide hydrogel, conversion of the latent MMP zymogen into its active form was demonstrated. As a result of MMP-2 activation, strongly enhanced hydrogel degradation by activated endothelial cells was observed. Our data illustrate the critical importance of growth factor activities for remodeling of synthetic biomaterials into native tissue, as it is desired in many applications of regenerative medicine. Functionalized PEG-peptide hydrogels could help restore the native vessel wall and improve the performance of angioplasty procedures.