Quantitative Label-Free Chemical Imaging of PLGA Nanoparticles in Cells and Tissues with Single-Particle Sensitivity.

Nanomedicine has brought significant advancements to healthcare by utilizing nanotechnology in medicine. Despite much promise, the further development of nanocarriers for clinical use has been hindered by a lack of understanding and visualization of nano-bio interactions. Conventional imaging methods have limitations in resolution, sensitivity, and specificity. This study introduces a label-free optical approach using stimulated Raman scattering (SRS) microscopy to image poly(lactic-co-glycolic acid) (PLGA) nanocarriers, the most widely used polymeric nanocarrier for delivery therapeutic agents, with single-particle sensitivity and quantification capabilities. A unique Raman peak was identified for PLGA ester, enabling generalized bio-orthogonal bond imaging. We demonstrated quantitative SRS imaging of PLGA nanocarriers across different biological systems from cells to animal tissues. This label-free imaging method provides a powerful tool for studying this prevalent nanocarrier and quantitatively visualizing their distribution, interaction, and clearance in vivo.

Intracellular Localization Studies of the Luminescent Analogue of an Anticancer Ruthenium Iminophosphorane with High Efficacy in a Triple-Negative Breast Cancer Mouse Model.

The potential of ruthenium(II) compounds as an alternative to platinum-based clinical anticancer agents has been unveiled after extensive research for over 2 decades. As opposed to cisplatin, ruthenium(II) compounds have distinct mechanisms of action that do not rely solely on interactions with DNA. In a previous report from our group, we described the synthesis, characterization, and biological evaluation of a cationic, water-soluble, organometallic ruthenium(II) iminophosphorane (IM) complex of p-cymene, ([(η6-p-cymene)Ru{(Ph3P═N-CO-2N-C5H4)-κ-N,O}Cl]Cl (1 or Ru-IM), that was found to be highly cytotoxic against a panel of cell lines resistant to cisplatin, including triple-negative breast cancer (TNBC) MDA-MB-231, through canonical or caspase-dependent apoptosis. Studies on a MDA-MB-231 xenograft mice model (after 28 days of treatment) afforded an excellent tumor reduction of 56%, with almost negligible systemic toxicity, and a favored ruthenium tumor accumulation compared to other organs. 1 is known to only interact weakly with DNA, but its intracellular distribution and ultimate targets remain unknown. To gain insight on potential mechanisms for this highly efficacious ruthenium compound, we have developed two luminescent analogues containing the BOPIPY fluorophore (or a modification) in the IM scaffold with the general structure of [(η6-p-cymene)Ru{(BODIPY-Ph2P═N-CO-2-NC5H4)-κ-N,O}Cl]Cl {BODIPY-Ph2P = 8-[(4-diphenylphosphino)phenyl]-4,4-dimethyl-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene (3a) and 4,4-difluoro-8-[4-[[2-[4-(diphenylphosphino)benzamido]ethyl]carbamoyl]phenyl]-1,3,5,7-tetramethyl,2,6-diethyl-4-bora-3a,4a-diaza-s-indacene (3b)}. We report on the synthesis, characterization, lipophilicity, stability, luminescence properties, and cell viability studies in the TNBC cell line MDA-MB-231, nonmalignant breast cells (MCF10a), and lung fibroblasts (IMR-90) of the new compounds. The ruthenium derivative 3b was studied by fluorescence confocal microscopy. These studies point to a preferential accumulation of the compound in the endoplasmic reticulum, mitochondria, and lysosomes. Inductively coupled plasma optical emission spectrometry (ICP-OES) analysis also confirms a greater ruthenium accumulation in the cytoplasmic fraction, including endoplasmic reticulum and lysosomes, and a smaller percentage of accumulation in mitochondria and the nucleus. ICP-OES analysis of the parent compound 1 indicates that it accumulates preferentially in the mitochondria and cytoplasm. Subsequent experiments in 1-treated MDA-MB-231 cells demonstrate significant reactive oxygen species generation.

Length of hydrocarbon chain influences location of curcumin in liposomes: Curcumin as a molecular probe to study ethanol induced interdigitation of liposomes.

Using fluorescence quenching of curcumin in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes by brominated derivatives of fatty acids, the location of curcumin has been studied, which indicates length of hydrocarbon chain has an effect on the location of curcumin in liposomes. Change of fluorescence intensity of curcumin with temperature in the presence of liposomes helps to estimate the phase transition temperature of these liposomes, thus, influence of cholesterol on liposome properties has been studied using curcumin as a molecule probe. The cooperativity due to the interactions between the hydrocarbon chains during melting accelerates the phase transition of DPPC liposomes in the presence of high percentage of cholesterol whereas high percentage of cholesterol generates a rather rigid DMPC liposome over a wide range of temperatures. We used ethanol to induce interdigitation between the hydrophobic chains of the lipids and studied this effect using curcumin as fluorescence probe. As a result of interdigitation, curcumin fluorescence is quenched in liposomes. The compact arrangement of the acyl chains prevents curcumin from penetrating deep near the midplane. In the liquid crystalline phase ethanol introduces a kind of order to the more fluid liposome, and does not leave space for curcumin to be inserted away from water.

Dibenzonaphthyridinones: Heterocycle-to-Heterocycle Synthetic Strategies and Photophysical Studies.

A heterocycle-to-heterocycle strategy is presented for the preparation of highly fluorescent and solvatochromic dibenzonaphthyridinones (DBNs) via methodology that leads to the formation of a tertiary, spiro-fused carbon center. A linear correlation between the results of photophysical experiments and time dependent density functional theory calculations was observed for the λ(max) of excitation for DBNs with varying electronic character.

Green synthesis of curcumin conjugated nanosilver for the applications in nucleic acid sensing and anti-bacterial activity.

Silver nanoparticles (Ag NPs) are often synthesized by chemical and physical methods. Natural and non-toxic molecules are recently being replaced for nanoparticles preparation. In this paper we have used curcumin, which interacts with Ag+ and subsequently synthesizes silver nanoparticles. Further continuation of the reaction often makes aggregation and forms dark brown/black silver oxide. Presence of glycerol in the reaction mixture gives mono-disperse curcumin conjugated Ag NPs, which can be made stable by capping with polyvinylpyrolidone (PVP). XRD data confirm that curcumin conjugated Ag NPs are crystalline in nature with a mean crystalline size of 13.27 nm. The Ag NPs are spherical and in the range of 10-50 nm though their hydrodynamic radius is found to be higher, ∼294 nm, due to polyvinylpyrolidone capping and aggregation of nanoparticles in solution. The production of curcumin conjugated Ag NPs follows first order kinetics and the effect of curcumin concentration during formation of Ag NPs indicates a linear enhancement in the production of Ag NPs with an increase in concentration of curcumin. These curcumin conjugated silver nanoparticles show anti-bacterial activity and can successfully determine nucleic acid (DNA and RNA) in the concentration range 100-1000 ng/mL with a linear regression coefficient >0.997 using Resonance Rayleigh Scattering spectra.

Ionic liquid expedites partition of curcumin into solid gel phase but discourages partition into liquid crystalline phase of 1,2-dimyristoyl-sn-glycero-3-phosphocholine liposomes.

The hydrolysis of curcumin in alkaline and neutral buffer conditions is of interest because of the therapeutic applicability of curcumin. We show that hydrolysis of curcumin can be remarkably suppressed in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes. The fluorescence of curcumin sensitively detects the phase transition temperature of liposomes. However, at greater concentrations, curcumin affects the phase transition temperature, encouraging fusion of two membrane phases. The interaction of curcumin with DMPC is found to be strong, with a partition coefficient value of Kp = 2.78 × 10(5) in the solid gel phase, which dramatically increases in the liquid crystalline phase to Kp = 1.15 × 10(6). The importance of ionic liquids as green solvents has drawn interest because of their toxicological effect on human health; however, the impact of ionic liquids (ILs) on liposomes is not yet understood. The present study establishes that ILs such as 1-methyl-3-octylimidazolium chloride (moic) affect the permeability and fluidity of liposomes and thus influence parition of curcumin into DMPC liposomes, helping in the solid gel phase but diminishing in the liquid crystalline phase. The Kp value of curcumin does not change appreciably with moic concentration in the solid gel state but decreases with moic concentration in the liquid crystalline phase. Curcumin, a rotor sensitive to detect phase transition temperature, is applied to investigate the influence of ionic liquids such as 1-methyl-3-octylimidazolium chloride, 1-buytl-3-methyl imadazolium tetrafluoroborate, and 1-benzyl-3-methyl imidazolium tetrafluoroborate on DMPC liposome properties. 1-Methyl-3-octylimidazolium chloride lowers the phase transition temperature, but 1-buytl-3-methyl imidazolium tetrafluoroborate and 1-benzyl-3-methyl imidazolium tetrafluoroborate do not perceptibly modify the phase transition temperature; rather, they broaden the phase transition.

Effect of curcumin on liposome: curcumin as a molecular probe for monitoring interaction of ionic liquids with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine liposome.

Recent increase and wider use of ionic liquids (ILs) for various applications has drawn attention to their toxicological consequence on human health. The present study explores effects of three different kinds of widely used ILs, such as 1-methyl-3-octylimidazolium chloride, 1-buytl-3-methyl imadazolium tetrafluoroborate and 1-benzyl-3-methyl imidazolium tetrafluoroborate, on liposome properties of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) by applying curcumin as molecular probe. Fluorescence intensity of curcumin is reported as a novel rotor which is sensitive to viscosity and thus the fluidity of the solvent. It follows a linear relationship of log fluorescence vs viscosity as proposed by Förster-Hoffmann equation. Curcumin binds strongly to liposome. At low concentration, the lipophilic drug curcumin does not appreciably influence the phase transition temperature of DPPC but as concentration reaches high levels significantly depresses the phase transition temperature. ILs diminish membrane fluidity. 1-methyl-3-octylimidazolium chloride disorders membrane properties by lowering the phase transition as is observed for higher concentration of curcumin, but 1-buytl-3-methyl imidazolium tetrafluoroborate and 1-benzyl-3-methyl imidazolium tetrafluoroborate do not modify phase transition temperature perceptibly; rather they broaden the phase transition at low molar concentration ratio. The three different kinds of ILs under study behave similarly at a high IL:DPPC ratio (1:2), while they behave differently at lower ratios (1:10-1:5).