PROPERTIES OF KAOLINITE AS A FUNCTION OF ITS PARTICLE SIZE*

This investigation was undertaken to ascertain whether or not certain properties of kaolinite are definite functions of particle size. The studies were carried out on carefully fractionated, single-base kaolinite. The following properties of these fractions were measured: (a) base-exchange capacity, (b) permeability, (c) heat of wetting, (d) thermal conduct, and (e) drying shrinkage. Base-exchange capacity, heat of wetting, and drying shrinkage are not simple functions of the measured particle size of kaolinite because of the unpredictable physical characteristics and habits of the crystalline aggregates. The first three properties named are each linear functions of the other. These properties are independent of the physical groupings of the kaolinite crystals and therefore cannot be predicted from measured particle size except in the case of the finest fractions. Permeability is dependent both on apparent surface and true surface. Thermal-analysis curves may be useful as a rough guide to clay properties.     

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PEGylated Cationic Serum Albumin for Boosting Retroviral Gene Transfer

Retroviral vectors are common tools for introducing genes into the genome of a cell. However, low transduction rates are a major limitation in retroviral gene transfer, especially in clinical applications. We generated cationic human serum albumin (cHSA) protected by a shell of poly(ethylene glycol) (PEG); this significantly enhanced retroviral gene transduction with potentially attractive pharmacokinetics and low immunogenicity. By screening a panel of chemically optimized HSA compounds, we identified a very potent enhancer that boosted the transduction rates of viral vectors. Confocal microscopy revealed a drastically increased number of viral particles attached to the surfaces of target cells. In accordance with the positive net charge of cationic and PEGylated HSA, this suggests a mechanism of action in which the repulsion of the negatively charged cellular and viral vector membranes is neutralized, thereby promoting attachment and ultimately transduction. Importantly, the transduction‐enhancing PEGylated HSA derivative evaded recognition by HSA‐specific antibodies and macrophage activation. Our findings hold great promise for facilitating improved retroviral gene transfer.