Jason N. Payne

Two prototype molecules are shown to exhibit chemically triggered release of a chromophore as molecular payload or triggered release of the host molecule cucurbit[7]uril.

The high sensitivity and functional group selectivity of surface-enhanced Raman scattering (SERS) make it an attractive method for enzyme sensing, but there is currently a severe lack of enzyme substrates that release SERS reporter molecules with favorable detection properties. We find that 2-mercaptopyridine-3-carbonitrile (o-MPN) and 2-mercaptopyridine-5-carbonitrile (p-MPN) are highly effective as SERS reporter molecules that can be captured by silver or gold nanoparticles to give intense SERS spectra, each with a distinctive nitrile peak at 2230 cm^–1. p-MPN is a more sensitive reporter and can be detected at low nanomolar concentrations. An assay validation study synthesized two novel substrate molecules, Glc-o-MPN and Glc-p-MPN, and showed that they can be cleaved efficiently by β-glucosidase (K_m = 228 and 162 μM, respectively), an enzyme with broad industrial and biomedical utility. Moreover, SERS detection of the released reporters (o-MPN or p-MPN) enabled sensing of β-glucosidase activity and β-glucosidase inhibition. Comparative experiments using a crude almond flour extract showed that the presence of β-glucosidase activity could be confirmed by SERS detection in a much shorter time period (>10 time shorter) than by UV–vis absorption detection. It is likely that a wide range of enzyme assays and diagnostic tests can be developed using 2-mercaptopyridine-carbonitriles as SERS reporter molecules.

Background: Phloridzin, an antidiabetic and antineoplastic agent usually found in fruit trees, is a dihydrochalcone constituent that has a clinical/pharmaceutical significance as a sodium-glucose linked transport 2 (SGLT2) inhibitor. While the aglycone metabolite of phloridzin, phloretin, displays a reduced capacity of SGLT2 inhibition, this nutraceutical displays enhanced antineoplastic activity in comparison to phloridzin. Purpose: The objective of this study was to develop gold nanoparticle (AuNP) mediated delivery of phloridzin and phloretin and explore their anticancer mechanism through conjugation of the dihydrochalcones and the AuNP cores. Methods: Phloridzin and phloretin conjugated AuNPs (Phl-AuNP and Pht-AuNP) were synthesized in single-step, rapid, biofriendly processes. The synthesized AuNPs morphology was characterized via transmission electron microscopy and ultraviolet-visible spectroscopy. The presence of phloridzin or phloretin was confirmed using scanning electron microscopy-energy dispersive x-ray spectroscopy. The percentage of organic component (phloridzin/phloretin) onto AuNPs surface was characterized using thermogravimetric analysis. Assessment of the antineoplastic potency of the dihydrochalcones conjugated AuNPs against cancerous cell lines (HeLa) was accomplished through monitoring via flow cytometry. Results: The functionalized AuNPs were synthesized via a single-step method that relied only upon the redox potential of the conjugate itself and required no toxic chemicals. The synthesized Phl-AuNPs were found to be in the size range of 15±5 nm, whereas the Pht-AuNP were found to be 8±3 nm, placing both conjugated AuNPs well within the size range necessary for successful pharmaceutical applications. These assays demonstrate a significant increase in the cancerous cell toxicities as a result of the conjugation of the drugs to AuNPs, as indicated by the 17.45-fold increase in the efficacy of Pht-AuNPs over pure phloretin, and the 4.49-fold increase in efficacy of Phl-AuNP over pure phloridzin. Conclusion: We report a simple, biofriendly process using the reducing and capping potential of the dihydrochalcones, phloridzin and phloretin, to synthesize stable AuNPs that have promising futures as potential antineoplastic agents.

With a sharp increase in the cases of multi-drug resistant (MDR) bacteria all over the world, there is a huge demand to develop a new generation of antibiotic agents to fight against them. As an alternative to the traditional drug discovery route, we have designed an effective antibacterial agent by modifying an existing commercial antibiotic, kanamycin, conjugated on the surface of gold nanoparticles (AuNPs). In this study, we report a single-step synthesis of kanamycin-capped AuNPs (Kan-AuNPs) utilizing the combined reducing and capping properties of kanamycin. While Kan-AuNPs have increased toxicity to a primate cell line (Vero 76), antibacterial assays showed dose-dependent broad spectrum activity of Kan-AuNPs against both Gram-positive and Gram-negative bacteria including Kanamycin resistant bacteria. Further, a significant reduction in the minimum inhibitory concentration (MIC100) of Kan-AuNPs was observed when compared to free kanamycin against all the bacterial strains tested. Mechanistic studies using transmission electron microscopy and fluorescence microscopy indicated that at least part of Kan-AuNPs increased efficacy may be through disrupting the bacterial envelope, resulting in the leakage of cytoplasmic content and the death of bacterial cells. Results of this study provide critical information about a novel method for the development of antibiotic capped AuNPs as potent next-generation antibacterial agents.