Adriana Ganem-Rondero

Preparation and characterization of solid lipid nanoparticles containing cyclosporine by the emulsification-diffusion method.

Solid lipid nanoparticles (SLNs) have been used for carrying different therapeutic agents because they improve absorption and bioavailability. The aim of the study was to prepare lipidic nanoparticles containing cyclosporine (CyA) by the emulsification-diffusion method and to study their physicochemical stability. Glyceryl behenate (Compritol® ATO 888) and lauroyl macrogolglycerides (Gelucire® 44/14) were used as carrier materials. Nanoparticles with good stability were obtained with Gelucire®, while it was difficult to obtain stable systems with Compritol®. Systems with Gelucire® were characterized by particle size, Z-potential, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), entrapment efficiency and in vitro release. Particle size and Z-potential were evaluated for at least three months. With a high CyA content (≥60 mg) in Gelucire® SLNs, variations in size were greater and particle size also increased over time in all batches; this effect may have been caused by a probable expulsion of the drug due to the lipid’s partial rearrangement. While the Z-potential decreased 10 mV after three months, this effect may be explained by the superficial properties of the drug that make the molecules to be preferably oriented at the solid-liquid interface, causing a change in the net charge of the particle. SEM confirmed size and shape of the nanoparticles. DSC studies evidenced that CyA affects the lipid structure by a mechanism still unknown. The entrapment efficiency was higher than 92%, and CyA release from SLNs was relatively fast (99.60% in 45 min).

Anti-biofilm activity of chitosan gels formulated with silver nanoparticles and their cytotoxic effect on human fibroblasts.

The development of multi-species biofilms in chronic wounds is a serious health problem that primarily generates strong resistance mechanisms to antimicrobial therapy. The use of silver nanoparticles (AgNPs) as a broad-spectrum antimicrobial agent has been studied previously. However, their cytotoxic effects limit its use within the medical area. The purpose of this study was to evaluate the anti-biofilm capacity of chitosan gel formulations loaded with AgNPs, using silver sulfadiazine (SSD) as a standard treatment, on strains of clinical isolates, as well as their cytotoxic effect on human primary fibroblasts. Multi-species biofilm of Staphylococcus aureus oxacillin resistant (MRSA) and Pseudomonas aeruginosa obtained from a patient with chronic wound infection were carried out using a standard Drip Flow Reactor (DFR) under conditions that mimic the flow of nutrients in the human skin. Anti-biofilm activity of chitosan gels and SSD showed a log-reduction of 6.0 for MRSA when chitosan gel with AgNPs at a concentration of 100 ppm was used, however it was necessary to increase the concentration of the chitosan gel with AgNPs to 1000 ppm to get a log-reduction of 3.3, while the SSD showed a total reduction of both bacteria in comparison with the negative control. The biocompatibility evaluation on primary fibroblasts showed better results when the chitosan gels with AgNPs were tested even in the high concentration, in contrast with SSD, which killed all the primary fibroblasts. In conclusion, chitosan gel formulations loaded with AgNPs effectively prevent the formation of biofilm and kill bacteria in established biofilm, which suggest that chitosan gels with AgNPs could be used for prevention and treatment of infections in chronic wounds. The statistic significance of the biocompatibility of chitosan gel formulations loaded with AgNPs represents an advance; however further research and development are necessary to translate this technology into therapeutic and preventive strategies.

Transdermal iontophoresis of dexamethasone sodium phosphate in vitro and in vivo: Effect of experimental parameters and skin type on drug stability and transport kinetics

The aim of this study was to investigate the cathodal iontophoresis of dexamethasone sodium phosphate (DEX-P) in vitro and in vivo and to determine the feasibility of delivering therapeutic amounts of the drug for the treatment of chemotherapy-induced emesis. Stability studies, performed to investigate the susceptibility of the phosphate ester linkage to hydrolysis, confirmed that conversion of DEX-P to dexamethasone (DEX) upon exposure to samples of human, porcine and rat dermis for 7 h was limited (82.2+/-0.4%, 72.5+/-4.8% and 78.6+/-6.0% remained intact) and did not point to any major inter-species differences. Iontophoretic transport of DEX-P across dermatomed porcine skin (0.75 mm thickness) was studied in vitro as a function of concentration (10, 20, 40 mM) and current density (0.1, 0.3, 0.5 mA cm(-2)) using flow-through diffusion cells. Increasing concentration of DEX-P from 10 to 40 mM resulted in a approximately 4-fold increase in cumulative permeation (35.65+/-23.20 and 137.90+/-53.90 microg cm(-2), respectively). Good linearity was also observed between DEX-P flux and the applied current density (i(d); 0.1, 0.3, 0.5 mA cm(-2); J(DEX) (microg cm(2) h(-1))=237.98 i(d)-21.32, r(2)=0.96). Moreover, separation of the DEX-P formulation from the cathode compartment by means of a salt bridge - hence removing competition from Cl(-) ions generated at the cathode - produced a 2-fold increase in steady-state iontophoretic flux (40 mM, 0.3 mA cm(-2); 20.98+/-7.96 and 41.82+/-11.98 microg cm(-2) h(-1), respectively). Pharmacokinetic parameters were determined in Wistar rats (40 mM DEX-P; 0.5 mA cm(-2) for 5h with Ag/AgCl electrodes and salt bridges). Results showed that DEX-P was almost completely converted to DEX in the bloodstream, and significant DEX levels were achieved rapidly. The flux across rat skin in vivo (1.66+/-0.20 microg cm(-2) min(-1)), calculated from the input rate, was not statistically different from the flux obtained in vitro across dermatomed porcine skin (1.79+/-0.49 microg cm(-2) min(-1)). The results suggest that DEX-P delivery rates would be sufficient for the management of chemotherapy-induced emesis.

Human growth hormone: New delivery systems, alternative routes of administration, and their pharmacological relevance

The availability of recombinant human growth hormone (GH) has broadened its range of clinical applications. Approved indications for GH therapy include treatment of growth hormone deficiency (in children and in adults), Turner syndrome, Prader-Willi syndrome, chronic renal insufficiency and more recently, idiopathic short stature in children, AIDS-related wasting and fat accumulation associated with lipodystrophy in adults. Therapy with GH usually begins at a low dose and is gradually titrated to obtain optimal efficacy while minimizing side effects. It is usually administered on a daily basis by subcutaneous injection, since this was considered to impact upon patient compliance, extended-release GH preparations were developed and new delivery platforms - e.g., auto-injectors and needle-free devices - were introduced in order to improve not only compliance and convenience but also dosing accuracy. In addition, alternative less invasive modes of administration such as the nasal, pulmonary and transdermal routes have also been investigated. Here, we provide an overview of the different technologies and routes of GH administration and discuss the principles, limitations and pharmacological profiles for each approach.

Using transdermal iontophoresis to increase granisetron delivery across skin in vitro and in vivo: Effect of experimental conditions and a comparison with other enhancement strategies

The objectives of the study were (i) to investigate the effect of experimental parameters on the iontophoretic transport of granisetron, (ii) to identify the relative contributions of electromigration (EM) and electroosmosis (EO), (iii) to determine the feasibility of delivering therapeutic amounts of drug for the treatment of chemotherapy-induced nausea and vomiting and (iv) to test the in vitro results in a simple animal model in vivo. Preliminary in vitro studies using aqueous granisetron formulations investigating the effect of drug concentration (5, 10, 20 and 40 mM) and current density (0.1, 0.2, 0.3 mA cm(-2)) were performed using porcine ear skin. As expected, cumulative delivery in vitro at the 20 and 40 mM concentrations was significantly greater than that at 5 and 10mM, which were not statistically different (p<0.05). Increasing the applied current density from 0.1 to 0.3 mA cm(-2) resulted in a approximately 4.2-fold increase in iontophoretic flux. Furthermore, in the absence of Na(+) in the formulation, no dependence of iontophoretic flux on drug concentration was reported (at a granisetron concentration of 40 mM, the transport rate was 2.93+/-0.62 microg cm(-2)min(-1)). Co-iontophoresis of acetaminophen was used to show that EM was the predominant transport mechanism accounting for 71-86% of total granisetron delivery. In vivo studies in Wistar rats (40 mM granisetron; application of 0.3 mA cm(-2) for 5h with Ag/AgCl electrodes and salt bridges) showed an average iontophoretic input rate (k(input)) of 0.83+/-0.26 microg min(-1) and a maximum plasma concentration (C(max)) of 0.092+/-0.004 microg ml(-1). Based on these results and given the known pharmacokinetics, transdermal iontophoresis could achieve therapeutic drug levels for the management of chemotherapy-induced emesis using a reasonably sized (4-6 cm(2)) patch.

Single Emulsion-Solvent Evaporation Technique and Modifications for the Preparation of Pharmaceutical Polymeric Nanoparticles

In recent years, there has been an increased interest in using nanoparticles for drug delivery and pharmaceutical development. Nanoparticles can offer significant advantages over the conventional drug delivery systems in terms of high drug loading, stability and specificity, controlled release capability, and the ability to deliver both hydrophilic and hydrophobic drug molecules through various routes of administration. This review article focuses on the use of the single emulsion solvent evaporation method, the first method proposed for the preparation of polymeric nanoparticles, and modifications that have been developed over the years to improve the results obtained with this technique.

Controlled transdermal iontophoresis for poly-pharmacotherapy: Simultaneous delivery of granisetron, metoclopramide and dexamethasone sodium phosphate in vitro and in vivo

Iontophoresis has been used to deliver small molecules, peptides and proteins into and across the skin. In principle, it provides a controlled, non-invasive method for poly-pharmacotherapy since it is possible to formulate and to deliver multiple therapeutic agents simultaneously from the anodal and cathodal compartments. The objective of this proof-of-principle study was to investigate the simultaneous anodal iontophoretic delivery of granisetron (GST) and metoclopramide (MCL) and cathodal iontophoresis of dexamethasone sodium phosphate (DEX-P). In addition to validating the hypothesis, these are medications that are routinely used in combination to treat chemotherapy-induced emesis. Two preliminary in vitro studies using porcine skin were performed: Study 1 - effect of formulation composition on anodal co-iontophoresis of GST and MCL and Study 2 - combined anodal iontophoresis of GST (10mM) and MCL (110 mM) and cathodal iontophoresis of DEX-P (40 mM). The results from Study 1 demonstrated the dependence of GST/MCL transport on the respective drug concentrations when co-iontophoresed at 0.3 mA·cm(-2). Although they possess similar physicochemical properties, MCL seemed to be a more efficient charge carrier (JMCL=0.0591∗CMCLvs JGST=0.0414∗CGST). In Study 2, MCL permeation was markedly superior to that of GST (2324.83 ± 307.85 and 209.83 ± 24.84 μg·cm(-2), respectively); this was consistent with the difference in their relative concentrations; DEX-P permeation was 336.94 ± 71.91 μg·cm(-2). The in vivo studies in Wistar rats (10mM GST, 110 mM MCL and 40 mM DEX-P (0.5 mA·cm(-2) for 5h with Ag/AgCl electrodes and salt bridges) demonstrated that significant drug levels were achieved rapidly for each drug. This was most noticeable for dexamethasone (DEX) where relatively constant plasma levels were obtained from the 1 to 5h time-points; DEX-P was not detected in the plasma since it was completely hydrolyzed to the active metabolite. The calculated input rates in vivo (k01) for GST, MCL and DEX were 0.45 ± 0.05, 3.29 ± 0.48 and 1.97 ± 0.38 μg·cm(-2) · min(-1), respectively. The study confirmed that iontophoresis provided a controlled method for the simultaneous administration of multiple therapeutic agents and that it could be of use for poly-pharmacotherapy in general and more specifically that it was able to deliver different drugs used in the treatment of chemotherapy-induced emesis.

Comparing metoclopramide electrotransport kinetics in vitro and in vivo

The purpose of this work was to investigate the transdermal iontophoretic delivery of metoclopramide and to determine (i) the dependence of electrotransport on current density and drug concentration, (ii) the relative contributions of electromigration and electroosmosis and (iii) the feasibility of administering therapeutic amounts of drug, using a drug-sparing iontophoretic configuration. Iontophoretic delivery of metoclopramide (MCL) across dermatomed porcine ear skin was investigated in vitro as a function of concentration (10, 20, 40, 80 and 100mM) and current density (0.1, 0.2 and 0.3mAcm(-2)) using vertical flow-through diffusion cells. In vivo studies were performed in Wistar rats (40mM MCL, 0.3mAcm(-2), 5h); the anodal and drug formulation compartments were separated by a salt bridge. Cumulative delivery in vitro after 7h of current application (40mM MCL; 0.3mAcm(-2)) in the absence of electrolyte was 624.45+/-99.45microgcm(-2) (flux - 2.55+/-0.35microgcm(-2)min(-1)). There was a linear relationship between flux and both current density and drug concentration. Co-iontophoresis of acetaminophen confirmed that electromigration was the major transport mechanism (accounting for approximately 80% of MCL delivery). Electroosmotic inhibition, albeit modest, was only observed at the highest MCL concentration (100mM). Although the delivery rate observed in vivo in male Wistar rats (1.21+/-0.55microgcm(-2)min(-1)) was lower than that observed in vitro, the results suggest that drug input rates would be sufficient to achieve therapeutic levels in humans using non-invasive transdermal iontophoresis.

Sucrose Esters as Transdermal Permeation Enhancers

Surfactants are widely used excipients in topical formulations, not only for their solubilizing and emulsifying properties but also for their well-known capacity to enhance drug permeation. Although nonionic surfactants are frequently chosen because of their mild effect on the skin, they share a low efficacy as permeation enhancers. Among nonionic surfactants, sucrose fatty acid esters (SEs) have awoken the interest of different research groups due to their interesting properties, such as biodegradability, nontoxicity, low irritation to the skin, and their ability to form liquid crystals and microemulsions (among other systems). Furthermore, as described in this chapter, SEs have shown a good capacity to enhance the transcutaneous transport of drugs. Their enhancing ability depends on different factors such as the physicochemical properties of the drug, the type of SEs, and the characteristics of the vehicle or the delivery system. This chapter gathers information about the studies related to SEs as transdermal penetration enhancers.

Preparation and characterization of mucoadhesive nanoparticles of poly (methyl vinyl ether-co-maleic anhydride) containing glycyrrhizic acid intended for vaginal administration.

Abstract Traditional vaginal preparations reside in the vaginal cavity for relatively a short period of time, requiring multiple doses in order to attain the desired therapeutic effect. Therefore, mucoadhesive systems appear to be appropriate to prolong the residence time in the vaginal cavity. In the current study, mucoadhesive nanoparticles based on poly(methyl vinyl ether-co-maleic anhydride) (PVM/MA) intended for vaginal delivery of glycyrrhizic acid (GA) (a drug with well-known antiviral properties) were prepared and characterized. Nanoparticles were generated by a solvent displacement method. Incorporation of GA was performed during nanoprecipitation, followed by adsorption of drug once nanoparticles were formed. The prepared nanoparticles were characterized in terms of size, Z-potential, morphology, drug loading, interaction of GA with PVM/MA (by differential scanning calorimetry) and the in vitro interaction of nanoparticles with pig mucin (at two pH values, 3.6 and 5; with and without GA adsorbed). The preparation method led to nanoparticles of a mean diameter of 198.5 ± 24.3 nm, zeta potential of −44.8 ± 2.8 mV and drug loading of 15.07 ± 0.86 µg/mg polymer. The highest mucin interaction resulted at pH 3.6 for nanoparticles without GA adsorbed. The data obtained suggest the promise of using mucoadhesive nanoparticles of PVM/MA for intravaginal delivery of GA.