Next-Generation Noncompetitive Nanosystems Based on Gambogic Acid: In silico Identification of Transferrin Receptor Binding Sites, Regulatory Shelf Stability, and Their Preliminary Safety in Healthy Rodents.

A major challenge in drug delivery is to enhance the transport of drugs across biological barriers, such as the small intestine, the blood-brain barrier, and the blood-retinal/ocular barrier, and to effectively reach the site of action while minimizing the systemic impact. In recent years, piggybacking cell surface receptors have been considered a viable strategy for active drug delivery across the biological barriers. However, the ligands used to target drugs to plasma membrane receptors often have to compete against endogenous ligands, thereby limiting their binding to the cell surface and their transport across barriers. To address this problem, gambogic acid (GA) was identified as a noncompetitive ligand specific to the transferrin receptor (TfR), a receptor present on various barriers. However, the binding sites of the GA on TfR remain unknown, an essential step toward establishing structure-activity relationships. In silico binding site prediction tools, blind docking, and molecular docking simulation confirm that the GA binding site on the TfR is independent of the transferrin-bound iron binding sites. The GA-conjugated polyesters were processed into nanoparticles suitable for drug delivery applications that possess excellent storage stability under regulatory conditions. Traditionally, GA has been used as an anticancer compound that warrants safety assessment. The preliminary studies in healthy rodents on 10-repeated oral doses show no adverse effects. This work will generate paradigm shifting, new knowledge in the field of nanomedicines using unique noncompetitive nanosystems that do not compete with endogenous transferrin.

Digital light-directed synthesis. A microarray platform that permits rapid reaction optimization on a combinatorial basis.

Solution reactions using photogenerated reagents (Gao, X.; Yu, P.; LeProust, E.; Sonigo, L.; Pellois, J. P.; Zhang, H. J. Am. Chem. Soc. 1998, 120, 12698) are a potentially powerful means for combinatorial parallel synthesis of addressable molecular microarrays. In this report, we demonstrate that this chemistry permits combinatorial screening of reaction conditions on a microarray platform. Using this method of optimization and our reaction apparatus, efficient photogenerated acids and reaction conditions suitable for removal of the acid labile protection group on 5'-O of nucleotides are identified in a short period of time. The chemistry platform demonstrated opens new avenues for rapid, simultaneous investigation of multiple reactions using different reagents and reaction parameters directly on a solid support (e.g., a glass plate). The combinatorial screening method described may be extended to include general organic reactions employing photogenerated and conventional reagents as well as a microarray reaction device. This should be especially valuable for efficient synthesis of addressable organic compound libraries.

Peptide synthesis based on t-Boc chemistry and solution photogenerated acids.

Solution reactions using photogenerated reagents (PGRs) (Gao, X.; Yu, P. Y.; Leproust, E.; Sonigo, L.; Pellois, J. P.; Zhang, H. J. Am. Chem. Soc. 1998, 120, 12698) are developed for parallel synthesis of addressable, combinatorial molecular microarrays. To advance the PGR chemistry for general chemical conversions, light-controlled synthesis of peptides, which employs photogenerated acids (PGAs) and/or in combination with photosensitizers for deprotection of N-t-Boc group, is demonstrated. These reactions were performed on resin and glass plates and conveniently monitored by HPLC analysis (reactions on resin) and fluorescence emission after coupling the deprotected NH(2) group with 4(5)-carboxyfluorescein. These results demonstrate the potential of the PGA chemistry for parallel synthesis of addressable peptide libraries on a microarray platform.