Giacomo Fontana

Amoxicillin-loaded polyethylcyanoacrylate nanoparticles: Influence of PEG coating on the particle size, drug release rate and phagocytic uptake

Polyethyleneglycol (PEG)-coated polyethylcyanoacrylate (PECA) nanoparticles loaded with amoxicillin were prepared and the influence of the PEG coating on the particle size, zeta potential, drug release rate and phagocytic uptake by murine macrophages was studied. Experimental results show that this colloidal drug delivery system could be useful for intravenous or oral administration. The profile of amoxicillin release from PECA nanoparticles system was studied under various conditions similar to those of some corporeal fluids. In all these experiments, amoxicillin release in the free form was studied by HPLC analysis. Experimental results showed that at pH 7.4 drug release rises when molecular weight of PEG added to polymerization medium increases; in human plasma on the contrary drug release is reduced as molecular weight of PEG rises. Phagocytosis was evaluated by incubating amoxicillin-loaded PECA nanoparticles with murine macrophages and determining the amount of phagocytized nanoparticles by dosing the amoxicillin present inside the macrophages. The results of this study showed significative differences between nanoparticles prepared in the presence or in the absence of PEG and demonstrated that the PEG coating reduces the macrophages uptake. These results suggest that nanoparticles prepared in the presence of PEG are stealth carriers, which could be an injectable colloidal system able to avoid MPS recognition after intravenous injection. Experimental data of drug release at pH 1.1 and in the presence of urease, taking into account the mucoadhesive properties of polyalkylcyanoacrylate nanoparticles and the activity of the amoxicillin versus Helicobacter pylori, suggest moreover that the colloidal drug delivery system obtained in our laboratory could be useful for the treatment of diseases caused by H. pylori by peroral administration.

Ocular Tolerability and In Vivo Bioavailability of Poly(ethylene glycol) (PEG)‐Coated Polyethyl‐2‐Cyanoacrylate Nanosphere‐Encapsulated Acyclovir

Acyclovir-loaded polyethyl-2-cyanoacrylate (PECA) nanospheres were prepared by an emulsion polymerization process in the micellar phase and characterized. The influence of the presence of nonionic surfactant as well as other substances [i.e., 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) and poly(ethylene glycol) (PEG)], on formulation parameters and loading capacity was investigated. In particular, the presence of PEG resulted in an increase of mean size and size distribution. To obtain PEG-coated PECA nanospheres with a mean size of < 200 nm, Pluronic F68 at concentrations > 1.5% (w/v) should be used during preparation. The presence of PEG also resulted in a change in zeta potential, from -25.9 mV for uncoated nanospheres to -12.2 mV for PEG-coated PECA nanospheres. The presence of HP-beta-CyD elicited an increase of nanosphere size and size distribution, but zeta potential was not influenced. In vitro drug release from nanospheres was determined in both phosphate buffer (pH 7.4) and plasma. The presence of HP-beta-CyD and PEG did not influence the acyclovir release rate in plasma. In the case of release in phosphate buffer, PEG-coated nanospheres showed a slower release. Ocular tolerability of PEG-coated PECA nanospheres was evaluated by the in vivo Draize test. This colloidal carrier was well tolerated, eliciting no particular inflammation at the level of the various ocular structures. In vivo ocular bioavailability was evaluated by instilling 50 microL of the acyclovir-loaded nanospheres only once in the conjunctival sac of rabbit eyes. At various time intervals, aqueous humour acyclovir content was determined by high-performance liquid chromatography. Acyclovir-loaded PEG-coated PECA nanospheres were compared with an aqueous solution of the drug and a physical mixture of acyclovir nanospheres. The acyclovir-loaded PEG-coated PECA nanospheres showed a significant (p < 0.001) increase of drug levels (25-fold) in aqueous humor compared with the free drug or the physical mixture. This finding is probably due to an improved ocular mucoadhesion of PEG-coated PECA nanospheres.

Preparation, characterization and in vitro antimicrobial activity of ampicillin-loaded polyethylcyanoacrylate nanoparticles

In this paper, the experimental conditions for preparing ampicillin-loaded polyethylcyanoacrylate (PECA) nanoparticles are described. The effects of drug concentration and surfactant type in the polymerization medium on the particle size distribution and loading capacity were studied. The results of these studies show that only the type of surfactant has an impact on the nanoparticle dimensions. The release rate of ampicillin from PECA nanoparticles at pH 7.4 (extracellular value pH) performed either with and without esterases, show that the drug release is considerably increased in the presence of these exzymes. The results of drug release study at pH 1.1 (simulated gastric juice) are very interesting. This study has evidenced that the 70% of ampicillin is released quickly, while the remaining fraction is firmly incorporated in nanoparticles. The released ampicillin is quickly degraded in acid medium while the entrapped fraction is protected from acid degradation and afterwards, when nanoparticles reach the small intestine, can be readily released in the presence of esterases. This result could be exploited for the oral administration of the ampicillin-PECA system. Finally, studies of antimicrobial activity of prepared systems evidenced that ampicillin-loaded PECA nanoparticles exhibit an activity equal or higher than the free drug.

Hydrophilic and Hydrophobic Polymeric Derivatives of Anti-Inflammatory Agents Such as Alclofenac, Ketoprofen, and Ibuprofen

Macromolecular prodrugs of a hydrophilic polymer [α,β-poly( N- hydroxyethyl)-DL-aspartamide (PHEA)] was used as a drug carrier. Three poly- (HEA)-NSAID adducts were studied: poly(HEA)-Alclofenac, poly(HEA)-Keto profen, and poly(HEA)-Ibuprofen. Prodrugs with different drug content were synthesized both as water-soluble and water-insoluble agents. Hydrolysis of water-soluble adducts in a simulated gastric juice was studied.

Solid Lipid Nanoparticles Containing Tamoxifen Characterization and In Vitro Antitumoral Activity

Solid lipid nanoparticles (SLNs) containing tamoxifen, a nonsteroidal antiestrogen used in breast cancer therapy, were prepared by microemulsion and precipitation techniques. Tamoxifen loaded SLNs seem to have dimensional properties useful for parenteral administration, and in vitro plasmatic drug release studies demonstrated that these systems are able to give a prolonged release of the drug in the intact form. Preliminary study of antiproliferative activity in vitro, carried out on MCF-7 cell line (human breast cancer cells), demonstrated that SLNs, containing tamoxifen showed an antitumoral activity comparable to free drug. The results of characterization studies and of in vitro antiproliferative activity strongly support the potential application of tamoxifen-loaded SLNs as a carrier system at prolonged release useful for intravenous administration in breast cancer therapy.

Phea-graft-polybutylmethacrylate copolymer microparticles for delivery of hydrophobic drugs

Polymeric microparticles encapsulating two model hydrophobic drugs, beclomethasone dipropionate (BDP) and flutamide (FLU) were prepared by using the high pressure homogenization-solvent evaporation method starting from a oil-in-water emulsion. For the preparation of polymeric microparticles a α,β-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA) graft copolymer with comb like structure was properly synthesized via grafting from atom transfer radical polymerization (ATRP) technique, by using two subsequent synthetic steps. In the first step a polymeric multifunctional macroinitiator was obtained by the conjugation of a proper number of 2-bromoisobutyryl bromide (BIB) residues to the PHEA side chains, obtaining the PHEA-BIB copolymer. PHEA-BIB copolymer was then used as macroinitiator for the polymerization via ATRP of the hydrophobic monomer such as butyl methacrylate (BMA) to obtain the α,β-poly(N-2-hydroxyethyl)-D,L-aspartamide-co-(N-2-ethylen-isobutyrate)-graft-poly(butyl methacrylate) copolymer (PHEA-IB-p(BMA)). Spherical microparticles with 1-3 microns diameter were prepared. Microparticles loaded with BDP or FLU were also prepared. In vitro mucoadhesion and enzymatic degradation studies evidenced bioadhesive properties and biodegradability of prepared microparticles, while release studies showed a different release profiles for the two loaded drugs: BDP was totally released from nanoparticles until 24h in pulmonary mimicking conditions; differently a slower FLU release rate was observed in gastro-intestinal mimicking conditions. The in vitro cytotoxicity activity was assessed using 16HBE and Caco-2 cell lines. Results showed that exposure of both cell lines to BDP-loaded microparticles do not inhibited the cell growth; on the contrary FLU-loaded microparticles inhibited the cell growth, in particular of the Caco-2 cancer cell line, in a concentration- and time-dependent manner. Finally, uptake studies demonstrated that BDP-loaded microparticles and FLU-loaded microparticles effectively increased uptake of loaded drugs in a time-dependent manner, respectively on 16HBE and Caco-2 cell lines.

Preparation and Characterization of Solid Lipid Nanoparticles Containing Cloricromene

This article describes the development of solid lipid nanoparticles (SLN) as colloidal carriers for cloricromene. Nanoparticles were prepared by the microemulsion or precipitation technique. In vitro drug release profile from SLN was studied under various experimental conditions mimicking some body fluids. The drug release rate of drug at pH 7.4 and human plasma is high. In plasma, after 15 min, about 70% of drug was released. The cloricromene that was not released within 4 hr was found in the SLN. This result suggests that this colloidal system could be useful for targeted drug delivery to the central nervous system after intravenous administration.

Macromolecular prodrug of diflunisal. II. Investigations of in vitro release and of photochemical behaviour

Abstract A macromolecular conjugate between the α,β-poly(2-hydroxyethyl)- dl -aspartamide (PHEA) and diflunisal (DFN), a known antiinflammatory drug. (PHEA-DFN) containing 16% (w/w) of drug, has been already shown to be able to release the free drug in the intact form in simulated gastric juice (Giammona et al., 1994). Hydrolysis studies at pH 5.5 (pH value of endosomal compartments) and pH 7.4 (pH value of extracellular fluids) show that intact free drug is released from the conjugate. It is demonstrated that esterase enzymes are able to cleave the ester bonds between drug molecules and polymeric backbone; moreover by using human plasma as source of enzymes a slow hydrolysis kinetics at the stationary state has been found. In addition, when DFN is covalently linked to PHEA, the photohemolysis process occurring when red blood cells are irradiated by UV light in the presence of free drug disappears completely. The same result is obtained with other two polymer conjugates between PHEA and antiinflammatory drugs such as ketoprofen (KPN) and naproxen (NAP). This suggests the ability of PHEA to protect these drugs from the alteration induced by UV light. This effect seems to be independent on the molecular mechanism of the photochemical reaction.