In vivo evaluation of riboflavin receptor targeted fluorescent USPIO in mice with prostate cancer xenografts.

Riboflavin (Rf) receptors bind and translocate Rf and its phosphorylated forms (e.g. flavin mononucleotide, FMN) into cells where they mediate various cellular metabolic pathways. Previously, we showed that FMN-coated ultrasmall superparamagnetic iron oxide (FLUSPIO) nanoparticles are suitable for labeling metabolically active cancer and endothelial cells in vitro. In this study, we focused on the in vivo application of FLUSPIO using prostate cancer xenografts. Size, charge, and chemical composition of FLUSPIO were evaluated. We explored the in vitro specificity of FLUSPIO for its cellular receptors using magnetic resonance imaging (MRI) and Prussian blue staining. Competitive binding experiments were performed in vivo by injecting free FMN in excess. Bio-distribution of FLUSPIO was determined by estimating iron content in organs and tumors using a colorimetric assay. AFM analysis and zeta potential measurements revealed a particulate morphology approximately 20-40 nm in size and a negative zeta potential (-24.23 ± 0.15 mV) in water. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry data confirmed FMN present on the USPIO nanoparticle surface. FLUSPIO uptake in prostate cancer cells and human umbilical vein endothelial cells was significantly higher than that of control USPIO, while addition of excess of free FMN reduced accumulation. Similarly, in vivo MRI and histology showed specific FLUSPIO uptake by prostate cancer cells, tumor endothelial cells, and tumor-associated macrophages. Besides prominent tumor accumulation, FLUSPIO accumulated in the liver, spleen, lung, and skin. Hence, our data strengthen our hypothesis that targeting riboflavin receptors is an efficient approach to accumulate nanomedicines in tumors opening perspectives for the development of diagnostic and therapeutic systems. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available for this article at 10.1007/s12274-016-1028-7 and is accessible for authorized users.

Mechanistic profiling of the siRNA delivery dynamics of lipid-polymer hybrid nanoparticles.

Understanding the delivery dynamics of nucleic acid nanocarriers is fundamental to improve their design for therapeutic applications. We investigated the carrier structure-function relationship of lipid-polymer hybrid nanoparticles (LPNs) consisting of poly(DL-lactic-co-glycolic acid) (PLGA) nanocarriers modified with the cationic lipid dioleoyltrimethyl-ammoniumpropane (DOTAP). A library of siRNA-loaded LPNs was prepared by systematically varying the nitrogen-to-phosphate (N/P) ratio. Atomic force microscopy (AFM) and cryo-transmission electron microscopy (cryo-TEM) combined with small angle X-ray scattering (SAXS) and confocal laser scanning microscopy (CLSM) studies suggested that the siRNA-loaded LPNs are characterized by a core-shell structure consisting of a PLGA matrix core coated with lamellar DOTAP structures with siRNA localized both in the core and in the shell. Release studies in buffer and serum-containing medium combined with in vitro gene silencing and quantification of intracellular siRNA suggested that this self-assembling core-shell structure influences the siRNA release kinetics and the delivery dynamics. A main delivery mechanism appears to be mediated via the release of transfection-competent siRNA-DOTAP lipoplexes from the LPNs. Based on these results, we suggest a model for the nanostructural characteristics of the LPNs, in which the siRNA is organized in lamellar superficial assemblies and/or as complexes entrapped in the polymeric matrix.

Imaging dehydration kinetics of a channel hydrate form of the HIV-1 attachment inhibitor prodrug BMS-663068.

An analysis of the free acid form of the HIV-1 attachment inhibitor prodrug BMS-663068-01 revealed a reversible moisture sorption event in the 42%-46% relative humidity (RH) range. An existing single-crystal analysis indicated that these observations were due to the formation of a nonstoichiometric channel hydrate. This effect was reproducible on repeated cycles, suggesting that the material's structural integrity was not compromised because of the interconversion process. Small, reversible, and predictable changes in the atomic structure were observed by solid-state nuclear magnetic resonance (ssNMR). Atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM) could discern changes in surface topography as a function of RH. Surface cracks were visible at 25% RH, most of which disappeared at 60% RH. This change was reversible on reducing the RH, with cracks reappearing in the same locations. A reduction in surface roughness was seen at high humidity, which was consistent with the uptake of moisture causing surface swelling. The observations by AFM/ESEM were consistent with the atomic alterations seen with ssNMR. Changes in unit cell dimensions are not uncommon with channel hydrates as the crystal lattice expands or contracts when the crystal structure absorbs/desorbs water, but concomitant, reversible surface morphology property changes have not been widely reported.

Characterising the surface adhesive behavior of tablet tooling components by atomic force microscopy.

PURPOSE: The aim of this study is to develop an atomic force microscopy (AFM) based approach to study the adhesive forces between tabletting punches and model formulation ingredients, that can ultimately be used to understand and predict issues such as sticking during tabletting compression. METHODS: Adhesive interactions were studied between single lactose particles and coated tablet punches. The adhesion was measured at varying relative humidities (RHs) and the influence of surface roughness was investigated. Roughness parameters were measured with AFM imaging and a modeling approach used to predict the influence of roughness on adhesion. RESULTS: Surface roughness was found to play a significant role in the observed lactose-punch adhesion and the variation of this adhesion across the punch surface. Such differences between punches can be correlated to observations from industrial use. Adhesion forces were spatially mapped to identify "hot spots" of high adhesion. A modeling approach can predict the relative adhesion of different surfaces from roughness data. The adhesion was also significantly affected by RH, for one type of punch causing a greater than 3? increase in adhesion between 30 and 60% RH. Interestingly, different punches showed different RH-adhesion behavior, relating to their hydrophilicity. CONCLUSIONS: The work introduces a new method for screening tablet punch materials and tabletting conditions. Important factors to be considered when evaluating adhesive interactions in tablet compression have been highlighted. Correlations are observed between AFM adhesion results and tabletting behavior during manufacture. This provides a promising basis for a predictive approach toward combating tabletting issues.