Low molecular weight, high affinity targeting ligands for use in therapeutics and diagnostics systems

Antibodies are a rapidly developing class of molecules used in the treatment inflammatory diseases and cancers as well as in diagnostic systems. However, there are major limitations associated with the use of antibodies including specificity for only one type of disease, the lack of uptake in solid tumors, the immunogenicity of the molecule, non-specific uptake of antibodies into normal organs, reduced binding if derivatized and difficulty with production and purification. The most troublesome problem, however, is the loss of specificity through epitope mutation. As an alternative to antibody therapeutics, design of a high affinity low molecular weight molecule which reduces the aforementioned issues could revolutionize therapeutics and diagnostics by circumventing these problems while still providing selectivity. Surface epitopes are continually mutating without harming or altering functions in the cell and subsequently become undetectable by antibodies. Thus targeting surface receptors vital to cell survival with high affinity, low molecular weight ligands represent a unique method for use in therapeutics and diagnostics. There are several low molecular weight, high affinity ligands which could achieve these goals; however, few have been used therapeutically and fewer have been used in diagnostic assays. Here we present the use of several low molecular weight, high affinity ligands for use in cancer and inflammatory disease therapeutics and bacterial diagnostics systems. First, we designed a label free biosensor, employing a peptide sequence identified from a phage display library, capable of detecting as few as 34 anthrax causing Bacillus anthracis spores. Secondly, we have developed a flow cytometry based diagnostic system for the detection of Pseudomonas aeruginosa employing the siderophore, pyoverdine. Through simple conjugation to a latex microsphere, we were able to specifically detect as few as 10e4 bacteria/mL. Lastly, we prepared a folate conjugated verrucarin A prodrug designed to specifically target folate receptor expressing cancer cells and activated macrophages. The conjugate was found to be cytotoxic to human KB cells and murine RAW cells with IC50s of 70 nM and 4 nM respectively. Using this concept, we can develop a new class of therapeutic and diagnostic systems not limited to potentially mutable surface molecules

Detection of Folate Binding Protein with Enhanced Sensitivity Using a Functionalized Quartz Crystal Microbalance Sensor

In this report, we describe the development of a quartz crystal microbalance biosensor for detection of folate binding protein (FBP). Using a simple folate—BSA conjugate absorbed onto a Au-coated quartz sensor, a detection limit of 30 nM was achieved. Binding of FBP to the sensor surface could be blocked at concentrations as high as 1 uM with a 100-fold excess of folic acid, indicating the specificity of the folate—FBP interaction and the absence of nonspecific binding to the functionalized surface. Moreover, capture could be achieved in the presence of blood serum, making the assay amendable to the analysis of bodily fluids. Further signal enhancement based on an anti-FBP antibody and protein-A-coated gold nanosphere sandwich assay extended the detection limit to 50 pM (~3 orders-of-magnitude improvement). Given the overexpression of FBP in certain malignancies and inflammatory disorders, we expect the methodology described here to be useful to detect FBP as a possible biomarker for disease diagnosis