Polyelectrolyte complexes of chitosan and hyaluronic acid or carboxymethylpullulan and their aminoguaiacol derivatives with biological activities as potential drug delivery systems.

Polyelectrolyte complexes (PECs) were elaborated from chitosan as cationic polymer and carboxy-methylpullulan (CMP), hyaluronic acid (HA) and their derivatives grafted with aminoguaiacol (G) with different degrees of substitution (DSGA) with the aim of obtaining nanogels for drug delivery. For each couple of polysaccharides, the charge ratios giving the smaller size with the lower PDI were selected to produce PECs. CMP_CHIT and CMP-G_CHIT PECs had smaller sizes (220-280 nm) than HA_CHIT and HA-G_CHIT PECs (280-390 nm). PECs were stable at 4 °C during 28 days at pH 5. In phosphate buffer saline (PBS) at pH 7.4, at 4 °C, a better stability of PECs based on CMP-G derivatives was observed. The hydrophobic associations between aminoguaiacol groups (highlighted by measurements of pyrene fluorescence) led to a better PECs' stabilization in PBS. The PECs' antioxidant and antibacterial activities were demonstrated and related to the DSGA. Diclofenac and curcumin were used as drug models: their loading reached 260 and 53 µg/mg PEC, respectively. The release of diclofenac in PBS at 37 °C followed a quasi-Fickian diffusion mechanism with release constant between 0.88 and 1.04 h-1. The curcumin release followed a slow linear increase in PBS/EtOH (60/40 V/V) with an effect of DSGA.

Using Targeted Nano-Antibiotics to Improve Antibiotic Efficacy against Staphylococcus aureus Infections.

The poor bioavailability of antibiotics at infection sites is one of the leading causes of treatment failure and increased bacterial resistance. Therefore, developing novel, non-conventional antibiotic delivery strategies to deal with bacterial pathogens is essential. Here, we investigated the encapsulation of two fluoroquinolones, ciprofloxacin and levofloxacin, into polymer-based nano-carriers (nano-antibiotics), with the goal of increasing their local bioavailability at bacterial infection sites. The formulations were optimized to achieve maximal drug loading. The surfaces of nano-antibiotics were modified with anti-staphylococcal antibodies as ligand molecules to target S. aureus pathogens. The interaction of nano-antibiotics with the bacterial cells was investigated via fluorescent confocal microscopy. Conventional tests (MIC and MBC) were used to examine the antibacterial properties of nano-antibiotic formulations. Simultaneously, a bioluminescence assay model was employed, revealing the rapid and efficient assessment of the antibacterial potency of colloidal systems. In comparison to the free-form antibiotic, the targeted nano-antibiotic exhibited enhanced antimicrobial activity against both the planktonic and biofilm forms of S. aureus. Furthermore, our data suggested that the efficacy of a targeted nano-antibiotic treatment can be influenced by its antibiotic release profile.

Antibody-Conjugated Nanocarriers for Targeted Antibiotic Delivery: Application in the Treatment of Bacterial Biofilms.

Conventional antibiotic treatment is in most cases insufficient to eradicate biofilm-related infections, resulting in high risk of treatment failure and recurrent infections. Recent studies have shown that novel methods of antibiotic delivery can improve clinical outcomes and reduce the emergence of antibiotic resistance. The objectives of this work were to develop and evaluate a targeting nanocarrier system that enables effective delivery of antimicrobial drugs to Staphylococcus aureus, a commonly virulent human pathogen. For this purpose, we first prepared a formulation of polymeric nanoparticles (NPs) suitable for encapsulation and sustained release of antibiotics. A specific antibody against S. aureus was used as a targeting ligand and was covalently immobilized onto the surface of nanoparticulate materials. It was demonstrated that the targeting NPs preferentially bound S. aureus cells and presented an elevated accumulation in the S. aureus biofilm. Compared to free-form antibiotic, the antibiotic-loaded targeting NPs significantly enhanced in vitro bactericidal activity against S. aureus both in planktonic and biofilm forms. Using a mouse infection model, we observed improved therapeutic efficacy of these antibiotic-loaded NPs after a single intravenous administration. Taken together, our studies show that the targeting nanoparticulate system could be a promising strategy to enhance the biodistribution of antibiotics and thereby improve their efficacy.

Polysaccharides against Viruses: Immunostimulatory Properties and the Delivery of Antiviral Vaccines and Drugs.

Because viruses still represent a significant threat to human and animal health worldwide, the development of effective weapons against viral infections remains a top priority for the biopharmaceutical industry. This article reviews the dietary and pharmaceutical applications of polysaccharides (PS), first of all chitosan, in the prevention and treatment of viral diseases, focusing more particularly on solid or gel micro/nanoparticulate systems. The intrinsic antiviral activity of PS and their immunostimulatory effects, implemented in animal and human diets, are first surveyed. Then the review discusses the potential of PS-based particles as carriers of antiviral drugs and vaccines, with emphasis on the adjuvant potency of PS in solid vaccine formulations. The gap between the abundance of academic studies in this area and the lack of actual antiviral formulations dispensed to human patients is underlined, notwithstanding a number of branded products on the market.

Retention properties of hydrophobically end-capped poly(ethylene glycol)s on a beta-cyclodextrin support.

High-performance liquid chromatography (HPLC) was used to examine the retention behavior of monomethoxypoly(ethylene glycol)s bearing one hydrophobic naphthyl end group (Nap-MPEG) on beta-cyclodextrin polymer (poly-beta-CD) immobilized on a silica support, under isocratic elution conditions and using water as mobile phase. Studies of retentions and theoretical plate heights H were conducted at infinite dilution by comparing the behavior of Nap-MPEGs having different molecular weight (750, 1000 and 5000 g/mol). The larger is its molecular size, the lower is the retention of the polymer. The linear increase of H with mobile phase velocity reveals slow mass-transfer kinetics arising from the restricted diffusion into the pores of the support. The complexation constants between the Nap-MPEGs and beta-CD in solution (around 500M(-1)) were determined from the decrease of retention observed by adding increasing concentrations of hydroxypropyl beta-CD into the eluent. The peak profiles in mass-overload conditions were studied by fitting a model based upon bi-Langmuir kinetics which assumes a non-uniform support having two types of binding sites and apparent adsorption rate constants are used to describe mass-transfer kinetics. A three-parameter adsorption equilibrium isotherm was sufficient to account for the modifications of peak shapes observed when increasing amounts of polymer were injected. This result indicates an interaction with a heterogeneous poly-beta-CD support mainly composed of low affinity groups, non-saturable in the range of polymer concentration studied. An upper limit was estimated for the equilibrium constant (<1000 M(-1)) characterizing the affinity of Nap-MPEG for the non-saturable sites of the poly-beta-CD support. Large affinity constants (8-9 x 10(4)M(-1)) were found for the interaction of Nap-MPEGs with a small percentage of active sites.

Immobilization of a (dextran-adamantane-COOH) polymer onto beta-cyclodextrin-modified silica.

Adamantane-modified compounds are known to form stable complexes with beta-cyclodextrins (beta-CD) by host-guest interactions. In this study, the inclusion complex formed between beta-CD cavities and the adamantane group was evaluated for the elaboration of a cation-exchange support. The synthesis of the chromatographic supports involved three steps: (i) a polymer of beta-CD was grafted to diol-modified silica, (ii) a dextran polymer was modified by both adamantane groups and ionizable COOH functions, (iii) the dextran derivative (Ad-Dex-COOH) was bound to the chromatographic support by complexation between the adamantane groups of the dextran and beta-CD cavities of the support. The polymer immobilization on the beta-CD support was successful as the resulting support exhibited weak cation-exchange properties. The stationary phase was easy to prepare under mild conditions (aqueous media, room temperature) and was quite stable when using aqueous mobile phases. The chromatographic behaviour of model proteins was studied in isocratic elution by examining the effect of salt concentration in the buffer on retention. A mixed retention mode was found for lysozyme, revealing both electrostatic and hydrophobic interactions with the stationary phase.

Determination of binding constants of hydrophobically end-capped poly(ethylene glycol)s with beta-cyclodextrin by affinity capillary electrophoresis.

The formation of inclusion complexes between methoxypoly(ethylene glycol)s (MPEG)s bearing one hydrophobic group (phenyladamantyl) per chain and beta-cyclodextrin (beta-CD) was studied by capillary electrophoresis (CE). The effect of highly sulphated beta-CD (HS-beta-CD) on the migration behaviour of the phenyladamantyl-modified MPEG (MPEG-PhAd) analyte was investigated. It was established that the interaction between the modified PEG and beta-CD involved a 1:1 stoichiometry. Non-linear regression and three usual linearization methods (y-reciprocal, x-reciprocal and double reciprocal) were employed to estimate the binding constants. It was demonstrated that the binding constants were similar (around 400 M(-1)) for two MPEG-PhAd having different chain lengths (2000 and 5000 g/mol).