Fluorescence based detection of polychlorinated biphenyls (PCBs) in water using hydrophobic interactions.

Despite increasing controls in their production and disposal, persistent organic pollutants in water, even at concentrations below parts per million, represent an ongoing environmental health risk. Despite this concern, the detection of these compounds in water sources rely upon expensive, time consuming approaches that do not permit frequent monitoring and evaluation. In this work, a new fluorescence-based technique is presented for the detection of polychlorinated biphenyls (PCBs) in water. Benzopyrene (BaP) fluorescence was shown to increase with trace concentrations of aromatic organic pollutants. BaP forms a hydrophobic complex with PCBs, which has allowed for the successful detection of pollutants including PCB-126, PCB-153 and PCB-118. To determine the selectivity and robustness of this response, the impact of pH, ionic strength and humic acid to mimic surface water conditions is explored. While suppression of the signal was seen, these factors' impact on the detection of PCBs was minor, suggesting that a potential sensing strategy can be developed through this interaction. It is seen that the number and location of chlorine atoms are important along with the geometric orientation of molecule's structure.

Engineered silica nanocarriers as a high-payload delivery vehicle for antioxidant enzymes.

Antioxidant enzymes for the treatment of oxidative stress-related diseases remain a highly promising therapeutic approach. As poor localization and stability have been the greatest challenges to their clinical translation, a variety of nanocarrier systems have been developed to directly address these limitations. In most cases, there has been a trade-off between the delivered mass of enzyme loaded and the carrier's ability to protect the enzyme from proteolytic degradation. One potential method of overcoming this limitation is the use of ordered mesoporous silica materials as potential antioxidant enzyme nanocarriers. The present study compared the loading, activity and retention activity of an anti-oxidant enzyme, catalase, on four engineered mesoporous silica types: non-porous silica particles, spherical silica particles with radially oriented pores and hollow spherical silica particles with pores oriented either parallel to the hollow core or expanded, interconnected bimodal pores. All these silica types, except non-porous silica, displayed potential for effective catalase loading and protection against the proteolytic enzyme, pronase. Hollow particles with interconnected pores exhibit protein loading of up to 50 wt.% carrier mass, while still maintaining significant protection against proteolysis.

Synthesis and characterization of CREKA-targeted polymers for the disruption of fibrin gel matrix propagation.

Recently, efforts to control the propagation of the fibrin gel matrix (FGM) are under investigation as a means of limiting the formation of post-surgical adhesions (PSAs). A series of polymeric biomaterials based on block co-polymers of methacrylic acid (MA) and methoxypolyethylene glycol methacrylate (PEGMA) have been synthesized and characterized in order to study the impact of molecular architecture on the performance of these materials in suppressing FGM development. A robust synthetic strategy has been developed to facilitate the well controlled variation of numerous structural properties, including the relative size of each polymer block, the total polymer length, and the length of poly(ethylene glycol) (PEG) chain length, and to incorporate the fibrin-targeting pentapeptide cysteine-arginine-glutamic acid-lysine-alanine (CREKA). Preliminary investigations, based on quartz crystal microgravimetry (QCM), indicate the importance of molecular architecture in modulating the FGM propagation from model surfaces.

Vascularization of PEG-grafted macroporous hydrogel sponges: a three-dimensional in vitro angiogenesis model using human microvascular endothelial cells.

Vascular tissue can penetrate implants that have an interconnected porous structure. The extent of vascularization is heavily dependent on a number of factors, including the nature of the material as well as the size and porosity of the implant's pore morphology. Currently, it is still not clear what mechanisms are controlling this response. In this work, in vitro human microvascular endothelial cell (HMVEC) experiments employed in angiogenesis research have been adapted as a screening technique for biomaterial vascularization. Hydrogels composed of poly(2-hydroxy ethyl methacrylate) (PHEMA) containing poly(ethylene glycol) (PEG) grafts were capable of supporting in vitro tubule formation. The sizes and lengths of tubules were dependent upon the porosity of the polymer network and pore sizes. When compared to the pure PHEMA sponges, PEG-grafted networks possessed a more lattice-type structure, with greater pore interconnection. As a result, these polymers were better suited to supporting tubule formation.

Evaluation of porous networks of poly(2-hydroxyethyl methacrylate) as interfacial drug delivery devices.

Long-term implantable drug delivery devices are desirable to achieve rapid and reliable delivery of bioactive substances to the body. The limitation of most implantable devices is the resulting chronic inflammatory response and fibrous encapsulation of the implant, which prevents effective drug delivery for prolonged periods. One method of overcoming this problem is the addition of an intermediary that could prevent capsule formation. Biocompatible materials with interconnected pore structures greater than 8-10 microm have been shown to support the ingrowth and maintenance of vascularized tissue. In this investigation, we evaluate the efficacy of using porous hydrogel sponges for the tissue interface in an implantable drug delivery device. Porous networks of poly(2-hydroxyethyl methacrylate) (PHEMA) were synthesized using a thermally initiated free-radical solution polymerization. To characterize the microstructure of the PHEMA networks, scanning electron microscopy and mercury porosimetry were used. By altering the solvent fraction in the reaction mixture, PHEMA sponges were synthesized with interconnected pores ranging in size from from 6 to 15 microm with porosities of 55% to 87%. Following the in vitro evaluation, sponges were attached to the distal end of a 20-gauge catheter tubing, and implanted subcutaneously and intraperitoneally. After 5 months implantation, insulin was infused into the devices from external pumps and rapid insulin absorption was observed in conjunction with dramatic lowering of blood glucose levels. From histological evaluation of explanted devices, we observed highly vascularized tissue surrounding the mesenteric implants. These results indicate that it may be possible to use PHEMA sponges for a tissue intermediary for long-term implantable drug delivery devices.