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Protein-based nanoparticles have gained interest for traversing different biological (e.g., systemic or microenvironmental, etc.) barriers and enabling targeted drug delivery. Silk protein-based nanoparticles are useful and versatile drug delivery systems for sustained and controlled release due to their biocompatibility, biodegradability, accessible chemistries, and ability to stabilize different drugs and other biomolecules. In the present study, silk nanoparticles (SNPs) were engineered using a nanoprecipitation technique with tight control over size (∼45–250 nm diameter) and low polydispersity index by altering variables including stirring speed, reaction bath temperature, silk molecular weight (MW), and silk concentration. Of these variables, stir speed was the most significant contributor toward particle size control. SNPs with positive or negative surface charges and decoration of SNPs with surface antigens were also demonstrated. New mechanistic insights into control of SNP size, cellular uptake using glioblastoma as a model, surface characteristics, and the entrapment of a small-molecule drug (doxorubicin) within the particles were addressed. These insights expand the potential utility of SNPs for medical, environmental, and food applications. [ABSTRACT FROM AUTHOR]

The theoretical and experimental studies of silica formation are conducted utilizing biological and model organic additives to understand the roles of hydroxyl-containing biomolecules in biosilicification. The results demonstrate that in aqueous systems, the effect of hydroxyl-containing additives is negligible.

A study on the silk fibroin sol-gel transitions is conducted by monitoring the process under various physicochemical conditions with optical spectroscopy at 550 nm. No detectable changes in the protein secondary structure are found up to about 15% gelation, indicating that these early stages of gelation are not accompanied by the formation of [beta]-sheets.

Caffeic acid is used as a model compound to study surface-induced orientation and subsequent biocatalysis reactions on the nanometer length scale under environmentally friendly reaction conditions. The result demonstrates the important capability of obtaining regioselective control in dip pen nanolithography (DPN)-patterned nanosystems using surface-mediated reaction control and the resulting structures lead to new opportunities for improved function in areas of molecular recognition, conductivity and related applications.

The nerve growth factor (NGF) receptor is a complex of two proteins, gp75 and the tyrosine kinase TrkA. Using fluorescence recovery after photobleaching, we have studied the diffusion properties of the TrkA receptor. For PC 12 cells that express both gp75 and TrkA, TrkA was relatively immobile with only 28 [+ or -] 1% of receptor molecules free to diffuse with D = (3.64 [+ or -] 0.23) x [10.sup.-9] [cm.sup.2]/s. Addition of NGF decreased the mobile fraction to 21 [+ or -] 1% with D = (4.11 [+ or -] 0.18) x [10.sup.-9] [cm.sup.2]/s. Using the Sf9 baculovirus expression system, we were able to study TrkA in the absence and presence of gp75. On Sf9 cells, TrkA showed a mobile fraction of 46 [+ or -] 2% with D = (2.64 [+ or -] 0.21) x [10.sup.-9] [cm.sup.2]/s in the absence of gp75 and 43 [+ or -] 2% with D = (2.31 [+ or -] 0.25) x [10.sup.-9] [cm.sup.2]/s in its presence. Thus, gp75 did not alter TrkA mobility. Addition of NGF to the medium approximately halved the mobile fraction for TrkA in both the absence and presence of gp75. However, using a kinase-deficient mutant of TrkA, we found that ligand-induced immobilization requires an active kinase in the absence of gp75 but not in its presence. In addition, using point mutations at specific TrkA autophosphorylation sites, we determined that mobility is controlled by multiple phosphorylation sites, but the SHC binding site at Y490 may be particularly important for ligand-induced immobilization of TrkA. Therefore, two mechanisms lead to NGF- induced immobilization of TrkA - the first resulting from autophosphorylation of TrkA and the second occurring through TrkA's association with gp75.

An easy one-pot biocatalytic synthesis of unique biodegradable amphiphilic oligomers was developed. The selectivity of various kinds of lipases and the general applicability of the technique was shown through the screening of several commercial lipases and two very different monomer/enzyme systems. This method allows the formation of chains with sugar headgroups without protection-deprotection strategies.

A study aimed at examining the dependence of trinitrotoluene (TNT) and metabolites binding on several affecting factors is presented. The TNT's binding activity with dissolved humic acid (HA) is observed through a series of experiments that included equilibrium dialysis and HPLC quantification. The results of the experiments suggested that the binding between pollutants TNT to HA at different levels are governed by several factors such as pH, ionic strength, ligand structure, temperature, and incubation time.

A novel technique for the trace analysis of metal ions Zn(II), Be(II), and Bi(III) in bulk solutions is discussed. This technique involves the generation of a chemiluminescence signal from alkaline phosphatase catalyzed hydrolysis of a phosphate derivative of 1,2-dioxetane. Zn(II) can be determined by two methods, reactivation of the alkaline phosphatase apoenzyme and inhibition of the native enzyme. Be(II) and Bi(III) can be determined quantitatively by inhibition of the native enzyme. Subppb to ppm level detection of Zn(II), Be(II), and Bi(III) has been achieved. Initial studies with mixed metals are also reported. The technique described is rapid and sensitive and can be readily applied to the microassay of heavy metal ions.

Construction, cloning, and expression of the synthetic genes encoding recombinant spider silk proteins is presented. The repetitive units in the synthetic genes were patterned after sequences identified from native dragline silk proteins. These sequences were transformed to DNA sequences to maximize expression levels in Escherichia coli, which were used as building blocks for the construction. These synthetic spider silks were seen to have significant beta-sheet structure.