In vitro studies of amikacin-loaded human carrier erythrocytes.

Erythrocyte-encapsulated antibiotics have the potential to provide an effective therapy against intracellular pathogens. The advantages over the administration of free antibiotics include a lower systemic dose, decreased toxicity, a sustained delivery of the antibiotic at higher concentrations to the intracellular site of pathogen replication, and increased efficacy. In this study, the encapsulation of amikacin by human carrier erythrocytes prepared using a hypo-osmotic dialysis was investigated. The effects of the initial amikacin dialysis concentration and hypo-osmotic dialysis time on the encapsulation efficiency of amikacin were determined, and the osmotic fragility and hematologic parameters of amikacin-loaded carrier erythrocytes were measured. The efficiency of amikacin entrapment by carrier erythrocytes was dependent on the initial dialysis concentration of the drug. Statistically significant differences in the osmotic fragility profiles between control and carrier erythrocytes were observed, which were dependent on the hypo-osmotic dialysis time and on the dialysis concentration of amikacin. Mean hematologic parameters were evaluated and compared with unloaded, native erythrocytes; the mean corpuscular volume (MCV) of amikacin-loaded carrier erythrocytes was statistically significant smaller. Amikacin demonstrated a sustained release from loaded erythrocytes over a 48-h period, which suggests a potential use of the erythrocyte as a slow systemic-release system for antibiotics.

Encapsulation and in vitro evaluation of amikacin-loaded erythrocytes.

The aim of our present work was to establish the effect of the osmolality of the hypotonic buffer on the encapsulated amount and the in vitro properties of Amikacin-loaded erythrocytes. Amikacin was encapsulated in rat erythrocytes using a hypotonic dialysis method with hypotonic buffers of different osmolalities with mean values around 90 and 150 mOsm/kg. Morphological examination of the ghost erythrocytes was accomplished using scanning electron microscopy (SEM). The osmotic fragility of normal and loaded erythrocytes was tested using hypotonic solutions. Evaluation of the hematological parameters of the control and loaded erythrocytes was carried out using a hematology system analyzer. Amikacin release from loaded erythrocytes was tested in autologous plasma at 37 degrees C over a 24-h period. The quantification of Amikacin in loaded erythrocytes and in autologous plasma was performed using an HPLC technique. A higher osmotic fragility of loaded erythrocytes was observed using a low osmolality buffer. Some hematological parameters showed statistically significant differences between the loaded erythrocytes obtained using two buffers of different osmolalities with respect to untreated erythrocytes. According to our results, Amikacin carrier erythrocytes obtained by hypotonic dialysis using a low osmolality buffer (90 mOsm/kg) should afford a good encapsulation yield, appropriate morphological properties, and sustained release in vitro.

Drug, enzyme and peptide delivery using erythrocytes as carriers.

Erythrocytes are potential biocompatible vectors for different bioactive substances, including drugs. These can be used successfully as biological carriers of drugs, enzymes and peptides. There are currently diverse methods that permit drug encapsulation in erythrocytes with an appropriate yield. The methods most commonly employed are based on a high-haematocrit dialysis procedure, mainly hypo-osmotic dialysis. Erythrocytes loaded with drugs and other substances allow for different release rates to be obtained. Encapsulation in erythrocytes significantly changes the pharmacokinetic properties of drugs in both animals and humans, enhancing liver and spleen uptake and targeting the reticulo-endothelial system (RES). Amongst other applications, erythrocytes have been used for drug-targeting the RES with aminoglycoside antibiotics; the selective transport to certain organs and tissues of certain antineoplastic drugs, such as methotrexate, doxorubicine, etoposide, carboplatin, etc.; the encapsulation of angiotensin-converting enzyme (ACE) inhibitors, systemic corticosteroids, the encapsulation of new prodrugs with increased duration of action, etc. Erythrocytes are also attractive systems in the sense of their potential ability to deliver proteins and therapeutic peptides. Thus, erythrocytes have been used for the transport of enzymes destined for the correction of metabolic alterations as l-asparaginase, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (AlDH) among others. Erythrocytes have been used successfully as carriers of anti-HIV peptides, such as AZT, nucleoside analogues, antisense oligonucleotides, antineoplastic peptides, erythropoietin, interleukin 3, etc. Amongst other applications, mention may be made of paramagnetic erythrocytes, encapsulation of MRI contrast agents or the study of the metabolism of the red cell. Although erythrocytes have been applied with different uses in human medicine, their deployment is still very limited due to difficulties involving storage, its exposure to contamination and the absence of a validated industrial procedure for its preparation.