Interactions of functionalized dextran-coated liposomes with vascular smooth muscle cells

Development of Ulvan-Containing Liposomes as Antibacterial Drug Delivery Platforms

Liposomes, due to their safety profile and targeting ability, are among the most studied nanocarriers as antimicrobial delivery systems. However, due to lack of stability and the non-specific interaction of liposomes with cells and proteins, their use is relatively limited. Aiming to overcome these drawbacks, it was envisaged that incorporation of ulvan, a bioactive marine sulfated polysaccharide isolated from green algae, in liposomes could improve their physicochemical properties and overall stability. Thus, we initially studied the interactions of ulvan with neutral, negatively, and positively charged lipids using Differential Scanning Calorimetry and subsequently, based on the obtained results, we prepared the respective ulvan–containing neutral and charged liposomes, where ulvan interacts with both lipid chains and polar groups in the liposomal bilayer. In a further step, we entrapped in the liposomes fusidic acid, used as a model antibacterial drug, and proceeded with the evaluation of their antibacterial activity against Staphylococcus aureus. The physicochemical properties (size and ζ-potential), stability, morphology, and entrapment efficiency of the prepared liposomal formulations were determined.

Dextran functionalization enhances nanoparticle-mediated siRNA delivery and silencing

Understanding the endocytosis and intracellular trafficking of short interfering RNA (siRNA) delivery vehicle complexes remains a critical bottleneck in designing siRNA delivery vehicles for highly active RNA interference (RNAi)-based therapeutics. In this study, we show that dextran functionalization of silica nanoparticles enhanced uptake and intracellular delivery of siRNAs in cultured cells. Using pharmacological inhibitors for endocytotic pathways, we determined that our complexes are endocytosed via a previously unreported mechanism for siRNA delivery in which dextran initiates scavenger receptor-mediated endocytosis through a clathrin/caveolin-independent process. Our findings suggest that siRNA delivery efficiency could be enhanced by incorporating dextran into existing delivery platforms to activate scavenger receptor activity across a variety of target cell types.

Carbohydrate nanocarriers in biomedical applications: functionalization and construction

Carbohydrates are used to functionalize or construct nanocarriers for biomedical applications – specific targeting, biocompatibility, stealth effect, biodegradability.

Cellular Uptake and Intracellular Cargo Release From Dextran Based Nanogel Drug Carriers

Nanogels (NG) hold great promise as a drug delivery platform. In this work, we examine the potential of lysozyme-dextran nanogels (LDNG) as drug carriers in vitro using two cell lines: a model target tissue, human umbilical cord vein endothelial cells (HUVEC) and a model of the mononuclear phagocyte system (phorbol 12-myristate 13-acetate (PMA)-stimulated THP-1 cells). The LDNG (∼100 nm) were prepared with rhodamine-label dextran (LRDNG) via Maillard reaction followed by heat-gelation reaction and were loaded with a fluorescent probe, 5-hexadecanoylaminofluorescein (HAF), as a mock drug. Epifluorescence microscopy confirmed rapid uptake of LRDNG by HUVEC. Although LysoTracker Green staining indicated a lysosomal fate for LRDNG, the mock drug cargo (HAF) diffused extensively inside the cell within 15 min. Flow cytometry and confocal microscopy indicated slow uptake of LRDNG in PMA-stimulated THP-1 cells, with only 41% of cells containing LRDNG after 24 h exposure. Finally, 24 h exposure to LRDNG did not affect the viability of either cell type at the dose studied (20 μg/ml). At a higher dose (200 μg/ml), LRDNG resulted in a marked loss of viability of HUVEC and THP-1, measuring 30% and 38%, respectively. Collectively, our results demonstrate the great potential of LRDNG as a drug delivery platform, combining simple production, rapid uptake and cargo release in target cells with "stealth" properties and low cytotoxicity.

Bimolecular integrin-ligand interactions quantified using peptide-functionalized dextran-coated microparticles

Integrins play a key role in cell-cell and cell-matrix interactions. Artificial surfaces grafted with integrin ligands, mimicking natural interfaces, have been used to study integrin-mediated cell adhesion. Here we report the use of a new chemical engineering technology in combination with single-molecule nanomechanical measurements to quantify peptide binding to integrins. We prepared latex beads with covalently-attached dextran. The beads were then functionalized with the bioactive peptides, cyclic RGDFK (cRGD) and the fibrinogen γC-dodecapeptide (H12), corresponding to the active sites for fibrinogen binding to the platelet integrin αIIbβ3. Using optical tweezers-based force spectroscopy to measure non-specific protein-protein interactions, we found the dextran-coated beads nonreactive towards fibrinogen, thus providing an inert platform for biospecific modifications. Using periodate oxidation followed by reductive amination, we functionalized the bead-attached dextran with either cRGD or H12 and used the peptide-grafted beads to measure single-molecule interactions with the purified αIIbβ3. Bimolecular force spectroscopy revealed that the peptide-functionalized beads were highly and specifically reactive with the immobilized αIIbβ3. Further, the cRGD- and H12-functionalized beads displayed a remarkable interaction profile with a bimodal force distribution up to 90 pN. The cRGD-αIIbβ3 interactions had greater binding strength than that of H12-αIIbβ3, indicating that they are more stable and resistant mechanically, consistent with the platelet reactivity of RGD-containing ligands. Thus, the results reported here describe the mechanistic characteristics of αIIbβ3-ligand interactions, confirming the utility of peptide-functionalized latex beads for the quantitative analysis of molecular recognition.

Formulation and optimization of piroxicam proniosomes by 3-factor, 3-level Box-Behnken design

The aim of this study was to investigate the combined influence of 3 independent variables in the preparation of piroxicam proniosomes by the slurry method. A 3-factor, 3-level Box-Behnken design was used to derive a second-order polynomial equation and construct contour plots to predict responses. The independent variables selected were molar ratio of Span 60:cholesterol (X(1)), surfactant loading (X(2)), and amount of drug (X(3)). Fifteen batches were prepared by the slurry method and evaluated for percentage drug entrapment (PDE) and vesicle size. The transformed values of the independent variables and the PDE (dependent variable) were subjected to multiple regression to establish a full-model second-order polynomial equation. F was calculated to confirm the omission of insignificant terms from the full-model equation to derive a reduced-model polynomial equation to predict the PDE of proniosome-derived niosomes. Contour plots were constructed to show the effects of X(1), X(2) and X(3) on the PDE. A model was validated for accurate prediction of the PDE by performing checkpoint analysis. The computer optimization process and contour plots predicted the levels of independent variables X(1), X(2), and X(3) (0, -0.158 and -0.158 respectively), for maximized response of PDE with constraints on vesicle size. The Box-Behnken design demonstrated the role of the derived equation and contour plots in predicting the values of dependent variables for the preparation and optimization of piroxicam proniosomes.

Stability study of stavudine-loaded O-palmitoyl-anchored carbohydrate-coated liposomes

The purpose of this study was to evaluate the physicochemical stability of carbohydrate-anchored liposomes. In the present study, carbohydrate (galactose, fucose, and mannose) was palmitoylated and anchored on the surface of positively charged liposomes (PL). The stabilities of plain neutral liposomes (NL), PL, and O-palmitoyl carbohydrate-anchored liposomes were determined. The effects of storage conditions (4 degrees C +/- 2 degrees C, 25 degrees C +/- 2 degrees C/60% +/- 5% relative humidity [RH], or 40 degrees C +/- 2 degrees C/75% +/- 5% RH for a period of 10, 20, and 30 days) were observed on the vesicle size, shape, zeta potential, drug content, and in vitro ligand agglutination assay by keeping the liposomal formulations in sealed amber-colored vials (10-mL capacity) after flushing with nitrogen. The stability of liposomal formulations was found to be temperature dependent. All the liposomal formulations were found to be stable at 4 degrees C +/- 2 degrees C up to 1 month. Storage at 25 degrees C +/- 2 degrees C/60% +/- 5% RH and 40 degrees C +/- 2 degrees C/75% +/- 5% RH adversely affected uncoated liposomal formulations. Carbohydrate coating of the liposomes could enhance the stability of liposomes at 25 degrees C +/- 2 degrees C/60% +/- 5% RH and 40 degrees C +/- 2 degrees C/75% +/- 5% RH.

Physico-chemical characterization of polysaccharide-coated nanoparticles

A series of amphiphilic copolymers (PCL-DEX) made of poly(epsilon-caprolactone) (PCL) side chains grafted onto a dextran (DEX) backbone, was used to modify the surface of PCL nanoparticles. PCL-DEX nanoparticles were prepared by a technique derived from emulsion-solvent evaporation. The purpose of the present study was to investigate the DEX coating (quantification, conformation, mobility) in order to better understand particle surface-protein interactions. The DEX coating was deeply examined using different complementary methods: zeta potential measurement, specific degradation of the DEX shell by dextranase, energy-filtering transmission electron microscopy coupled to image-spectrum electron energy-loss spectroscopy, electronic paramagnetic resonance, high performance size exclusion chromatography as well as nonspecific bovine serum albumin adsorption. All our data together supported a core-shell structure of the nanoparticles, DEX moieties constituting the external coating. The amount of DEX located on the nanoparticle surface was estimated to 70%. The organisation of the shell including chains density and mobility was found to be dramatically influenced by DEX molar mass. The steric repulsion conferred by the presence of DEX at the surface of the nanoparticles decreased the adsorption of albumin. The nanoparticle-protein interaction was, however, greatly influenced by the polysaccharide conformation onto the surface.

Polysaccharide-decorated nanoparticles

Surface modified colloidal carriers such as nanoparticles are able to modulate the biodistribution of the loaded drug when given intravenously, but also to control the absorption of drugs administered by other routes. This review presents the different strategies to coat the surface of polymeric as well as inorganic nanoparticles with polysaccharides. Various physicochemical and biological methods have been described to demonstrate such surface modification. The medical applications, mainly in imaging cancer, of polysaccharide-coated nanoparticles are presented, including their abilities to increase the blood circulation time and to target specific tumoral tissues. It has been shown that these coatings allow also to improve drug absorption via nasal or ocular pathways, due the mucoadhesive and/or permeability enhancer properties of the polysaccharides. Finally, the ability of polysaccharide-coated nanoparticles to deliver DNA or oligonucleotides will be discussed.

Interactions of heparin with human skin cells: Binding, location, and transdermal penetration

The development of new materials for tissue engineering of skin substitutes requires an increasing knowledge of their interactions with human skin cells. Since carbohydrate recognition is involved in numerous biologic processes, including skin regeneration, the aim of this study was to identify sugar receptors expressed at the surface of human dermic and epidermic cells. Binding of fluorescent sugar-polyhydroxyethylacrylamide derivatives was analyzed by flow cytofluorimetry on cultured human skin fibroblasts, keratinocytes, and melanocytes. We observed that these three cell types express a membrane receptor specific for GlcNAc6S. Since the polysaccharide heparin contains this sugar moiety, we further investigated the interactions of heparin with skin cells. We analyzed the in vitro cell binding and ex vivo diffusion with the Franz cell of heparin and of two other polysaccharides of similar molecular weight, dextran and chondroitin sulfate. We found evidence of the preferential binding of heparin on keratinocytes and its high transcutaneous penetration of skin. Altogether, our results describe the affinity of heparin for human skin cells and suggest it may be an excellent candidate for use in the skin delivery of drugs or cosmetics and also as an active component in engineered skin.

Photodynamic therapy of skin cancers: sensitizers, clinical studies and future directives

Photodynamic therapy (PDT) is a new modality of skin cancer treatment. It involves the administration of photosensitizing drugs which, when localized in tumor tissue can produce its destruction by absorbing an adequate dose of light of an appropriate wavelength. A large number of photosensitizing agents have been tested in PDT experiments. Topical application of 5-aminolevulinic acid (5-ALA) followed by light irradiation is the most commonly used method. 5-ALA is a prodrug converted in situ via the heme cycle into protoporphyrin IX, an effective photosensitizer agent. Treatment of nonmelanoma skin cancers by PDT has met with varying degrees of success. In the case of 5-ALA, this therapy's main limitation is the poor penetration of 5-ALA into skin, due to hydrophilic and charge characteristics. However, the efficacy of 5-ALA-PDT may be improved by (a) development of adequate drug delivery systems; (b) use of enhancers of PpIX production and accumulation in target tissue, and (c) modifications of the 5-ALA molecule. Optimal timing, light sources, doses, and number of applications are also important factors for topical 5-ALA therapy and must be well defined. The aim of this review is to highlight recent progress in 5-ALA-PDT of skin cancer, and to present ways holding promise for its improvement.