The new (challenging) role of academia in biomaterial translational research and medical device development.

With the ever-changing landscape of translational research, the medical device and pharmaceutical industries increasingly license technologies with the added value of clinical and/or pre-clinical data rather than those in earlier stages of development. Universities have the potential to fill the gap in product development from academic laboratories through enhanced student training and increased implementation of some development and manufacturing activities that are traditionally found only in the private sector. A development roadmap is described from initial product feasibility through commercialization in the context of efficient development practices. The specific challenges in the design and development of biomaterial-based medical devices are described in the context of this development path with an emphasis on unique challenges for academic laboratories.

Elevation of CXCR3-binding chemokines in urine indicates acute renal-allograft dysfunction.

A noninvasive urinary test that diagnoses acute renal allograft dysfunction would benefit renal transplant patients. We aimed to develop a rapid urinary diagnostic test by detecting chemokines. Seventy-three patients with renal allograft dysfunction prompting biopsy and 26 patients with stable graft function were recruited. Urinary levels of CXCR3-binding chemokines, monokine induced by IFN-gamma (Mig/CXCL9), IFN-gamma-induced protein of 10 kDa (IP-10/CXCL10), and IFN-inducible T-cell chemoattractant (I-TAC/CXCL11), were determined by a particle-based triplex assay. IP-10, Mig and I-TAC were significantly elevated in renal graft recipients with acute rejection, acute tubular injury and BK virus nephritis. Using 100 pg/mL as the threshold level, both IP-10 and Mig had diagnostic value (sensitivity 86.4%; specificity 91.3%) in differentiating acute graft dysfunction from other clinical conditions. In terms of monitoring the response to antirejection therapy, this urinary test is more sensitive and predictive than serum creatinine. These results indicate that this rapid test is clinically useful.

Synthesis and physicochemical analysis of interpenetrating networks containing modified gelatin and poly(ethylene glycol) diacrylate.

The interrelated effects of gelatin modification, content, and poly(ethylene glycol) molecular weight on the melting temperature, surface hydrophilicity, tensile properties, swelling/degradation, and drug-release kinetics of a novel interpenetrating network (IPN) system containing gelatin and poly(ethylene glycol) diacrylate were evaluated. Gelatin content had a large effect on the IPN melting temperature and Delta H. Modifying gelatin with ethylenediaminetetraacetic acid and/or monomethoxy poly(ethylene glycol) monoacetate ester as well as increasing poly(ethylene glycol) diacrylate molecular weight increased the surface hydrophilicity. Increasing the gelatin weight percent increased the IPN elasticity at room temperature. When buffer and elevated temperature were present in the testing environment, the elasticity of all IPNs tested decreased. IPNs showed an enhanced elasticity and strength when compared with glutaraldehyde-fixed gelatin hydrogels. The extent of IPN swelling and degradation was increased by increasing the gelatin content or by modifying gelatin. The time to complete sample degradation was longer for IPNs when compared with gelatin crosslinked with glutaraldehyde. Modifications to the IPN system increased the maximum percent of chlorhexidine digluconate released from the IPNs. The rate of complete drug release was slower from IPNs than from glutaraldehyde-fixed gelatin matrices. A wide range of IPN physicochemical properties was obtained through formulation changes and chemical modifications.

Cell interaction with protein-loaded interpenetrating networks containing modified gelatin and poly(ethylene glycol) diacrylate.

The effects of modification to an interpenetrating network (IPN) system composed of gelatin and poly(ethylene glycol) diacrylate were characterized by protein release kinetics, fibroblast adhesion, and in vivo host response. The maximum cumulative percent of parvalbumin released from various IPN formulations ranged from 17.6+/-3.2% to 56.9+/-35.4% over 2-96h. Despite modifying gelatin with ethylenediaminetetraacetic dianhydride and/or monomethoxy poly(ethylene glycol) monoacetate ester or increasing the gelatin content, the largest amount of parvalbumin released occurred within 24h, prior to material bulk degradation. Over the time period evaluated, little (i.e. <1%) of the basic fibroblast growth factor (bFGF) loaded into the IPNs evaluated was released, independent of modifications made to the IPN formulation. Fibroblast adhesion to IPNs with or without loaded bFGF was quantified. The adherent fibroblast density on the IPNs was significantly lower than that of TCPS controls at all times independent of the IPN formulation tested and bFGF loading. Select IPN formulations elicited a comparable level of acute and chronic inflammatory response in vivo when compared with the gelatin and poly(ethylene glycol) diacrylate starting materials. IPNs provide a minimal cell-active surface that could be employed as delivery matrices and for further bioconjugation to mediate specific cellular response.

Engineering endogenous inflammatory cells as delivery vehicles.

Leukocytes are central in directing host inflammatory and immune processes; therefore, leukocyte response to biomaterials is extremely important. Although several leukocyte-derived molecules are used clinically, the long-term efficacy of treatments involving the systemic administration of these bioactive agents has yet to be demonstrated. Hence, the localized delivery of selected cytokines and growth factors produced by endogenous leukocytes is desirable and may have potential therapeutic values in the fundamental processes of tissue healing, growth regulation, and biocompatibility. The specificity and diversity of ligand-receptor interactions offer an attractive method in manipulating cellular behavior. Therefore, a more detailed understanding of the interplay between ligands and cell membrane receptors must be obtained. We designed interleukin-1-derived biomimetic agonists and antagonists to study and modulate leukocyte function in vitro. Selected agonists increased GM-CSF release by adherent human blood-derived macrophages in the presence of the natural IL1beta antagonist, namely IL1ra. Furthermore, IL1-derived biomimetic antagonists neutralized the ability of IL1beta in increasing the release of GM-CSF by adherent macrophages. We employed similar methodologies to elucidate the molecular mechanisms of integrin and extracellular matrix interaction in regulating leukocyte function. Oligopeptides were designed based on the functional structure of fibronectin and grafted on to a polymer network containing polyethyleneglycols. Macrophage adhesion was independent of the peptide identity that contained sequence RGD, PHSRN, PRRARV, or combinations thereof in an integrin-dependent fashion in vitro. However, integrin-dependent FBGC formation in vitro was highly dependent on both RGD and PHSRN in a single peptide formulation and with a specific orientation. From our intracellular signaling studies in vitro, protein tyrosine and serine/threonine kinases were found important in integrin signaling leading to macrophage adhesion mediated by fibronectin-integrin association. Furthermore, RGD and PHSRN appear to be significant in mediating this receptor-ligand association resulting in the necessary signaling characteristic for macrophage adhesion and the subsequent development. Our in vivo results showed that peptide identity played a minimal role in modulating the host inflammatory response and adherent macrophage density. RGD-containing peptides mediated rapid FBGC formation by 4 days of implantation by significantly increasing both the number of macrophages that participate in the cell fusion process and the rate of cell fusion. Both RGD and PHSRN domains were important in mediating FBGC formation at later implantation periods. These findings represent a mechanistic correlation between the role of protein functional architectures in ligand-receptor recognition and the post-ligation signaling events that control cellular behavior in vitro and in vivo.

In vivo biocompatibility of gelatin-based hydrogels and interpenetrating networks.

The in vivo host response to two gelatin-based hydrogel systems of varying crosslinking modalities and loaded with the anti-inflammatory agent dexamethasone sodium phosphate was investigated. Either gelatin was chemically crosslinked with glutaraldehyde, or polyethyleneglycol diacrylate was photopolymerized around gelatin to form interpenetrating networks. The subcutaneous cage implant system was utilized to determine differential leukocyte concentrations in the inflammatory exudate surrounding the materials as indices for biocompatibility and drug efficacy in vivo. Most of the crosslinked gelatin-based materials, either via glutaraldehyde fixation or interpenetrating network formation, elicited stronger inflammatory responses than either of the starting materials, gelatin and polyethyleneglycol diacrylate. In general, dexamethasone delayed and intensified the inflammatory response. The loss of material mass did not correlate directly with the degree of cellular inflammatory response, but increased with longer implantation time and decreased with more extensive fixation.