Structural instability of plasmid biopharmaceuticals: challenges and implications.

The global increase in the number of applications involving therapeutic plasmid DNA (pDNA) is creating a need for large amounts of highly stable and purified molecules. One of the main obstacles during the developmental stages of a new therapeutic DNA molecule involves tackling a wide array of structural instability events occurring in/with pDNA and therefore assuring its structural integrity. This review focuses on major instability determinants in pDNA.

The role of probe-probe interactions on the hybridization of double-stranded DNA targets onto DNA-modified magnetic microparticles.

In this work, we have studied the effect of different probe lengths and surface densities on the hybridization of a 181-bp polymerase chain reaction product to probes tethered onto magnetic microparticles. Hybridization was shown to be favored by longer probes but only at probe surface densities where probe-to-probe interactions are absent. From these results, a simple rule was inferred for determining maximum surface densities above which hybridization signals decreased.

Development of a polysulfone hollow fiber vascular bio-artificial pancreas device for in vitro studies.

A system for vascular hollow fiber bio-artificial pancreas development, optimization and in vitro testing was implemented and operated in a simple and fully described manner, allowing other researchers to test a variety of experimental conditions (different biomaterials, biologic tissue, addition of proteins or other adjuvants). In this work, a polysulfone hollow fiber was used as bioprotective material. Two different cell sources were co-immobilized with agarose microspheres in and experimented with the membrane device: rat islets of Langerhans and mouse beta-TC-3 insulinoma cells.

Recent patents on bacterial proteins as potential anticancer agents.

While most anticancer agents are small molecular weight compounds that inhibit specific steps in the pathways contributing to cancer growth, or monoclonal antibodies that target specific antigens hyper-expressed in cancer cells, recent efforts have also been directed towards bacterial pathogens that are known to allow cancer regression. Consequently, patents that cover the construction or characterization of specific bacteria, with or without additional cloned genes, are available. This review is, however, focused on patents that claim bacterial proteins as potential anticancer agents.

Prediction of diffusion coefficients of plasmids.

The ability to predict diffusion coefficients is important in the design, analysis, and operation of plasmid downstream processing operations such as membrane and fixed-bed chromatography. A correlation is proposed to predict the diffusion coefficient, D, of supercoiled plasmid DNA molecules in dilute solutions on the basis of the molecular weight, M, or size. Experimental data (18 points) collected from the literature confirmed the proposed variation of D with plasmid molecular weight as D proportional, variant M(-2/3), for molecules within the 1,800-287,100 base-pair range.

Membrane-assisted extractive bioconversions.

This chapter summarizes the use of membrane reactors in extractive bioconversions as process integration systems leading to in situ product recovery. Several membrane reactor configurations are analyzed, taking into account the type of bioconversion, biocatalyst type and location (either in the aqueous phase or in the membrane), membrane chemistry and morphology, solvent (extractant) type and its biocompatibility. Modeling of liquid-liquid extractive membrane bioreactors operation is also analyzed considering kinetics and mass-transfer aspects.