We present herein details pertaining to the preparation of bioconjugates of colloidal gold with aspartic protease from the fungus Aspergillus saitoi (F-prot) and their characterization and enzymatic activity. Simple mixing of the colloidal gold and protein solutions under protein-friendly conditions (pH = 3) followed by centrifugation (to remove uncomplexed gold nanoparticles and protein molecules) results in the formation of the fungal protease-gold nanoparticle conjugates. The protein-gold nanoparticle bioconjugate was redispersed in buffer solution and indicated the formation of efficient bioconjugates with intact native protein structures. The bioconjugates in solution were characterized by UV-vis spectroscopy, fluorescence spectroscopy, and biocatalytic activity measurements while drop-dried bioconjugate films on Si (111) substrates were characterized by scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), and X-ray diffraction (XRD) measurements. Microscopy images do show some aggregate formation, but the intactness of the native structure of the enzyme in the bioconjugate material was verified by fluorescence and biocatalytic activity measurements. The enzyme retains substantial biocatalytic activity in the bioconjugate material and was comparable to that of free enzyme in solution.

A novel approach to sensitive and rapid antigen detection is described. In the presence of a specific antigen, quantum dot-antibody conjugates rapidly self-assemble into agglomerates that are typically more than 1 order of magnitude larger than their individual components. The size distribution of the agglomerated colloids depends on, among other things, the relative concentration of quantum dot conjugates and antigen molecules. Quantum dot agglomerates mediated by antigen recognition were characterized by measuring their light scattering and fluorescence characteristics in an unmodified flow cytometer. Protein antigens angiopoietin-2 and mouse IgG were detected to sub-picomolar concentrations using this method. This simple technique enables the potential simultaneous detection of multiple antigenic biomarkers directly from physiological media and could be used for early detection and frequent screening of cancers and other diseases.

No abstract

No abstract

Luminescent polymer based metallogels have gained considerable interest due to their wide range of applications in the fields of tissue engineering, drug delivery, sensing, and optical systems. One of the...