ABSTRACT
Lipid-based particulate delivery systems have been extensively investigated in the last decade for both pharmaceutical and cosmetic skin application although their translocation across the skin is not yet clarified. The aim of this paper was to investigate on humans the ability of solid lipid nanoparticles (SLN) and solid lipid microparticles (SLM) to penetrate the outermost stratum corneum (SC) and to be modified upon contact with the cutaneous components by using the Tape Stripping Test coupled with the energy dispersive X-ray (EDX) analysis. SLN and SLM were prepared by the melt emulsification technique and loaded with nanosized titanium dioxide (TiO2) to become identifiable by means of X-ray emission. Following human skin application, the translocation of the particulate systems was monitored by the analysis of twelve repetitive stripped tapes using non-encapsulated metal dioxide as the control. Intact SLN as well as non-encapsulated TiO2 were recorded along the largest SC openings until the 12th stripped tape suggesting the intercluster region as their main pathway. Evidences of a concurrent biodegradation process of the lipid matrix, as the result of SLN interaction with the lipid packing between the corneocyte clusters, were found in the deepest SC layers considered. On the contrary, SLM were retained on the skin surface without undergoing biodegradation so preventing the leaching and the subsequent SC translocation of the loaded TiO2.
Subject(s)
Epidermis/metabolism , Lipids/administration & dosage , Metal Nanoparticles/administration & dosage , Titanium/administration & dosage , Adult , Female , Humans , Lipids/chemistry , Metal Nanoparticles/chemistry , Microscopy, Electron, Scanning , Middle Aged , Skin Absorption , Spectrometry, X-Ray Emission , Titanium/chemistry , Young AdultABSTRACT
Fluorescent calcium alginate/chitosan microparticles, prepared using a spray-drying technique followed by crosslinking reactions with calcium ions and chitosan, were assayed in-vivo for polymyxin B (PMB) oral toxicity, uptake by Peyer's patches and PMB oral absorption. A single PMB dose (300 mg kg(-1)), loaded in microparticles or dissolved in water, was administered to rats by oral gavage under fasted and fed conditions. By monitoring incidence of mortality, animal behaviour, clinical signs and abnormality in several organs, PMB in water solution was found lethal at a dose lower than the LD50 (790 mg kg(-1)) in the fasted state and toxic for the gastrointestinal tract in the fed state. However, no signs of acute toxicity at the level of the gastrointestinal tract were observed when animals were administered PMB loaded in microparticles under fasted and fed conditions. A lower PMB dose (125 mg kg(-1)), loaded in microparticles or dissolved in water, was given to rats in a fed state to determine PMB levels in Peyer's patches, urine and serum as well as to detect the loaded microparticles inside Peyer's patches for three days after dosing. Abnormalities were observed at gut level only when PMB was dosed in a water solution. Detectable antibiotic levels in Peyer's patches and urine as well as more constant PMB serum concentrations were provided by dosing PMB loaded in microparticles. Therefore, the use of alginate/chitosan microparticles to target the lymphatic system could improve safety when administering PMB orally.
Subject(s)
Drug Carriers/chemistry , Gastric Mucosa/metabolism , Lymphoid Tissue/metabolism , Polymyxin B/pharmacokinetics , Administration, Oral , Alginates/chemistry , Animals , Anti-Bacterial Agents/administration & dosage , Anti-Bacterial Agents/pharmacokinetics , Anti-Bacterial Agents/toxicity , Biological Transport , Chitosan/chemistry , Dose-Response Relationship, Drug , Dyspnea/chemically induced , Gastrointestinal Hemorrhage/chemically induced , Glucuronic Acid/chemistry , Hemorrhagic Disorders/chemically induced , Hexuronic Acids/chemistry , Male , Microscopy, Confocal , Microscopy, Fluorescence/methods , Microscopy, Video/methods , Microspheres , Particle Size , Polymyxin B/chemistry , Polymyxin B/toxicity , Rats , Rats, Sprague-Dawley , Toxicity Tests, Acute/methodsABSTRACT
A crosslinked alginate microparticle system for the targeting to the lymphatic system by Peyer's patches (PP) uptake was designed in order to improve the oral absorption of Polymyxin B (PMB). To verify mucoadhesion and PP uptake, microparticles labelled with fluorescein isothiocyanate (FITC) were prepared by spray-drying technique and crosslinking reactions with calcium ions and chitosan (CS), in vitro characterized and assayed by an ex vivo method. Microparticles showed a size less then 3 microm, an antibiotic loading level of 11.86 +/- 0.70%, w/w, a sustained drug release behaviour in simulated gastro-intestinal (GI) fluids and a preserved biological activity throughout the manufacture. The ex vivo study was performed by a perfusion method on intestinal tracts of just sacrificed adult rats. The recovered samples were analysed by epifluorescence microscope for mucoadhesion and PP uptake and by microbiological analysis for antibiotic activity preservation, providing evidence of mucoadhesion at the level of both PP and non-PP epithelium, uptake by PP and PMB microbiological activity in PP tissue. Furthermore, the study revealed the involvement of transport pathways across villous enterocytes.
