Biomedical subjects

Simon W Leppard

Publications and source records attributed to Simon W Leppard.

3 recordsLinked to original sources

PubMed2006

Comparative in vitro evaluation of microspherical embolisation agents.

This study describes the comparative performance of four commercially available microspherical embolisation products: Embosphere, Embogold, Contour SE and Bead Block. A series of in vitro evaluations were designed to assess the mechanical and biological characteristics of these biomaterials. Size distribution analysis revealed sieving techniques used to fractionate the embolics produced similar size distributions. The forces required to compress Embosphere, Embogold and Bead Block were in the range 21-27.5 kPa. Contour SE was significantly more compressible at approximately 5 kPa. However, recoverability of Contour SE required several minutes in contrast to the other products, a phenomenon attributed to its macroporous structure. When time taken to reach and remain in suspension was studied, results showed that the products quickly reached equilibrium with contrast agent. Bead Block was maintained in suspension for twice as long as the other products. Catheter deliverability was assessed and found to be dependent upon both microsphere and catheter, the best combination being Bead Block delivered via the Progreat catheter. Both the blood contacting SEM and plasma coagulation time showed none of the products were pro-thrombic or pro-coagulatory, each producing comparable results. Small differences in physical properties such as compressibility, could play an important role in delivery and effectiveness of vessel blockage. Currently all products are used routinely in clinical practice.

Acrylic Resins↗

PubMed2006

DC bead: in vitro characterization of a drug-delivery device for transarterial chemoembolization.

PURPOSE: The purpose of this investigation is to present the in vitro characterization and detailed drug-loading procedure for DC Bead, a microsphere product that can be loaded with chemotherapeutic agents for embolization. MATERIALS AND METHODS: DC Bead is an embolic microsphere product that is capable of being loaded with anthracycline drugs such as doxorubicin just before administration in a transarterial chemoembolization (TACE) procedure. Beads can be loaded from solutions prepared from doxorubicin powder or the doxorubicin HCl formulation. In this evaluation, bead sizes were measured by optical microscopy with video imaging. Gravimetric analysis demonstrated the effect of drug loading on bead water content, and its consequent impact on bead compressibility was determined. The subsequent deliverability of the beads was assessed by mixing the beads with contrast medium and saline solution and passing the beads through an appropriately sized microcatheter. A T-cell apparatus was used to monitor the in vitro elution of the drug from the beads over a period of 24 hours in various elution media. RESULTS: DC Bead spheres could be easily loaded with doxorubicin to a recommended level of 25 mg/mL of hydrated beads by immersion of the beads in the drug solution for 10-120 minutes depending on microsphere size. Other commercial embolic microspheres were shown not to load doxorubicin to the same extent or release it in the same fashion and were considered unsuitable for local drug delivery. Maximum theoretic capacity for DC Bead was approximately 45 mg/mL. Increase in doxorubicin loading resulted in a concomitant decrease in water content and consequential increase in bead resistance to compression force. Drug loading also resulted in a decrease in the average size of the beads, which was dependent on bead size and drug dose. This did not impact bead delivery at any drug loading level to a maximum of 37.5 mg/mL. Beads 100-700 microm in size could be delivered through 2.7-F microcatheters, whereas the 700-900-microm range required 3-F catheters. Modeling of the kinetics of drug elution from the beads in vitro at a loading dose of 25 mg/mL yielded calculated half-lives of 150 hours for the 100-300-microm range to a maximum of 1,730 hours for the 700-900-microm size range, which was dependent on the ionic strength of the elution medium. For comparison, there was a rapid loss of drug from an unstable Lipiodol emulsion with a half-life of approximately 1 hour. CONCLUSIONS: DC Bead can be loaded with doxorubicin to provide an accurate dosage of drug per unit volume of beads. Drug elution is dependent on ion exchange with the surrounding environment and is controlled and sustained, unlike the rapid separation of the drug from Lipiodol. Drug loading has no impact on the handling and deliverability of the beads, making them suitable for superselective TACE.

Antibiotics, Antineoplastic↗

PubMed2005

Phosphorylcholine is favorable for antibody production from hybridoma cells.

Growth of antibody-secreting hybridomas requires special conditions such as serum-free defined media containing growth factors and vitamins. However, the surface on which these cells can proliferate has been shown to play an important role. Phosphorylcholine (PC)-based polymers are zwitterionic compounds with nonbiofouling properties. These polymers are characterized by having reduced protein absorption properties. Our aim was to determine whether well-established hybridoma cell lines were able to proliferate and produce measurable amounts of monoclonal antibodies when grown on PC-polymer-coated surfaces. Comparative experiments using four well-known hybridoma cell lines (PAb421, PAb246, PAb1801 which recognize p53, and PAb280 which recognizes SV40 small t antigen) grown on PC-polymer-coated, uncoated, and two commercially available tissue culture plates showed that PC-polymer-coated plates were more efficient than uncoated plates in sustaining cell growth and monoclonal antibody production/secretion as defined by growth assays and ELISA. Also, results demonstrated that PC-polymer-coated plates were able to perform better than commercially available plates. These observations suggest that PC polymers could be used as an alternative, efficient surface coating to grow hybridoma cell lines and allow detectable antibody secretion.

Antibodies, Monoclonal↗