A dry powder aerosol drug delivery system was designed with both nano- and microstructure to maximize the protein loading via surface adsorption and to facilitate delivery to the deep lung, respectively. Ovalbumin was employed as a model protein to adsorb to and controllably flocculate DOTAP-coated PLG nanoparticles into “nanoclusters” possessing low density microstructure. The mechanism of nanoparticle flocculation was probed by evaluating the effects of ionic strength, shear force, and protein concentration on the geometric and aerodynamic diameters of the nanoclusters as well as the protein adsorption efficiency. Salt ions were found to compete with ovalbumin adsorption to nanoparticles and facilitate flocculation; therefore, formulation of nanoclusters for inhaled drug delivery may require the lowest possible ionic strength to maximize protein adsorption. Additional factors, such as shear force and total protein–particle concentration can be altered to optimize nanocluster size, suggesting the possibility of regional lung delivery. Immediate release of ovalbumin was observed, and native protein structure upon release was confirmed by circular dichroism and fluorescence spectroscopy studies. Controlled flocculation of nanoparticles may provide a useful alternative to spray drying when formulating dry powders for pulmonary or nasal administration of protein therapeutics or antigens.

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The two preceding articles in this series 1 have shown that the daily addition of a pint (473 cc.) equivalent of evaporated milk to the diets of children in an institution (one group receiving irradiated and the other nonirradiated milk) produced a measurable increase of growth in height and weight and in ossification of the bones in the wrists as compared with that of the control group given the regular institutional diet. The present study deals with the progress of dental caries in the same groups of children during the same period. LITERATURE A number of workers have reported a striking arrest of dental caries as a result of different types of dietary supplement. Since their findings have been reviewed many times (Hanke,2 1934) they will be only briefly The expenses of this investigation were defrayed in part by the Irradiated Evaporated MilkInstitute.