Design, Synthesis, and Evaluation of a Liposaccharide Drug Delivery Agent: Application to the Gastrointestinal Absorption of Gentamicin

Feasibility Study for the Rectal Route of Administration for Gentamicin Evaluated in the Neonatal Minipig Model

Neonatal infections are a major cause of newborn mortality in low- and middle-income countries, particularly in areas without access to inpatient care. To address this, the World Health Organization developed guidelines for delivering simplified antibiotic regimens (oral amoxicillin and intramuscular gentamicin) in outpatient settings to young infants with suspected serious bacterial infection when referral is not feasible. However, there are still limitations to access, as the regimen requires a health care provider trained in giving intramuscular injections to infants. To provide a needle-free, simplified alternate to intramuscular delivery, PATH investigated the feasibility of the rectal administration of gentamicin. Potential formulations were screened by in vitro testing, and 2 liquid enema formulations and a cocoa butter suppository were developed and evaluated in a preclinical study of the rectal uptake of gentamicin in a neonatal minipig model. Sera samples from the control group, dosed by intramuscular injection, resulted in expected sera concentrations of gentamicin, but no gentamicin was detected in the sera of groups rectally dosed with the test formulations. The results of this study did not provide evidence to support the therapeutic feasibility of rectally absorbed gentamicin.

Synthesis, characterization and in vitro evaluation of amphiphilic ion pairs of erythromycin and kanamycin antibiotics with liposaccharides

The hydrophilic ion paring strategy (HIP) is a method explored to improve the cell/tissue uptake of poorly adsorbed drugs and to optimize their physico-chemical characteristics. In this context, we here describe the synthesis of some ion pairs of two model cationic antibiotics, erythromycin (ERY) and kanamycin A (KAN), with liposaccharides having different levels of lipophilicity and charge. The formation of drug-liposaccharide complexes was confirmed by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) analysis. The effect of the amphiphilic liposaccharide moieties on the antimicrobial activity of ERY and KAN was assessed by measuring the minimal inhibitory concentration (MIC) of the compounds against a panel of bacterial strains that were susceptible or resistant to the parent antibiotics. The ion pairing did not depress the in vitro antibiotic activity, although no lowering of MIC values was registered. The experimental findings would motivate the future investigation of this ion pairing strategy in drug design, for instance allowing improvement of the encapsulation efficiency of hydrophilic antibiotics in lipid-based nanocarriers, or changing their in vivo biodistribution and pharmacokinetic profile.

Preparation and Microbiological Evaluation of Amphiphilic Kanamycin-Lipoamino Acid Ion-Pairs

Amphiphilic ion-pairs of kanamycin (KAN) were prepared by evaporation of a water-ethanol co-solution of KAN base and a lipoamino acid bearing a 12-carbon atoms alkyl side chain (LAA12), at different molar ratios. Infrared spectroscopy confirmed the structure of ion-pairs, while differential scanning calorimetry (DSC) and powder X-ray diffractometry (PXRD) studies supported the formation of new saline species with a different crystalline structure than the starting components. The solubility pattern shown in a range of both aqueous and organic solvents confirmed that the ion-pairs possess an amphiphilic character. The LAA12 counter-ion showed not to improve the antibacterial activity of KAN, suggesting that such chemical strategy is not able to favor the penetration of this drug inside the bacteria cells. Nevertheless, a slight improving, i.e., a one-fold dilution, was observed in E. coli. The present study can also serve as the basis for a further evaluation of LAA ion-pairing of antibiotics, as a means to improve the loading of hydrophilic drugs into lipid-based nanocarriers.

Niosomes from glucuronic acid-based surfactant as new carriers for cancer therapy: preparation, characterization and biological properties

Niosomes are vesicular systems composed of surfactant molecules, claimed to be used as drug delivery carriers thanks to their physico-chemical and biological properties. The aim of this work was to design niosomes obtained with a surfactant synthesized from glucuronic acid. Doxorubicin and 5FU were used as model drugs. Niosomes were prepared with different ratios between surfactant and cholesterol, and characterized in terms of size, morphology, drugs entrapment efficiency and in vitro releases, to identify the optimal formulation to be used in pharmaceutical fields. In addition, the hemolytic activity of all formulations have been also evaluated. Results showed that dodecylglucuronamide surfactant was able to produce vesicular systems with or without the presence of cholesterol. Niosomes resulted regular in size and shape and they have been found to encapsulate and release in a controlled manner both doxorubicin and 5-fluorouracil. Hemolytic tests showed that the capability of disrupting erythrocyte only depend on the size of colloidal aggregates. Finally, our formulations could be potentially used as antitumoral delivery systems in anticancer therapy.

Amphiphilic erythromycin-lipoamino acid ion pairs: characterization and in vitro microbiological evaluation

A series of amphiphilic ion pairs of erythromycin (ERY) with lipoamino acids (LAAs) were produced. The ion pairs were prepared by evaporation of a water/ethanol co-solution of the drug and LAA bearing an alkyl side chain of 10-16 carbon atoms. For the sake of comparison, equimolar physical mixtures were prepared by triturating ERY and the LAA in the absence of any solvent. FTIR spectroscopy confirmed the structure of ion pairs, while differential scanning calorimetry and powder X-ray diffractometry were used to assess the formation of new saline species. The solubility pattern of the coevaporates in different aqueous and organic solvents confirmed their amphiphilic properties. ERY-LAA ion pairs were submitted to an in vitro microbiological assay against different bacterial strains, both susceptible and resistant to macrolides. The presence of the LAA moiety was shown not altering the antibacterial spectrum of activity of the drug. These results can be the basis for a further evaluation of ERY-LAA ion pairs as a mean to improve the penetration of the drug inside bacterial cells and to optimize the loading of ERY in lipid-based nanocarriers.

Enabling the intestinal absorption of highly polar antiviral agents: ion-pair facilitated membrane permeation of zanamivir heptyl ester and guanidino oseltamivir

Antiviral drugs often suffer from poor intestinal permeability, preventing their delivery via the oral route. The goal of this work was to enhance the intestinal absorption of the low-permeability antiviral agents zanamivir heptyl ester (ZHE) and guanidino oseltamivir (GO) utilizing an ion-pairing approach, as a critical step toward making them oral drugs. The counterion 1-hydroxy-2-naphthoic acid (HNAP) was utilized to enhance the lipophilicity and permeability of the highly polar drugs. HNAP substantially increased the log P of the drugs by up to 3.7 log units. Binding constants (K(11(aq))) of 388 M(-1) for ZHE-HNAP and 2.91 M(-1) for GO-HNAP were obtained by applying a quasi-equilibrium transport model to double-reciprocal plots of apparent octanol-buffer distribution coefficients versus HNAP concentration. HNAP enhanced the apparent permeability (P(app)) of both compounds across Caco-2 cell monolayers in a concentration-dependent manner, as substantial P(app) (0.8-3.0 x 10(-6) cm/s) was observed in the presence of 6-24 mM HNAP, whereas no detectable transport was observed without counterion. Consistent with a quasi-equilibrium transport model, a linear relationship with slope near 1 was obtained from a log-log plot of Caco-2 P(app) versus HNAP concentration, supporting the ion-pair mechanism behind the permeability enhancement. In the rat jejunal perfusion assay, the addition of HNAP failed to increase the effective permeability (P(eff)) of GO. However, the rat jejunal permeability of ZHE was significantly enhanced by the addition of HNAP in a concentration-dependent manner, from essentially zero without HNAP to 4.0 x 10(-5) cm/s with 10 mM HNAP, matching the P(eff) of the high-permeability standard metoprolol. The success of ZHE-HNAP was explained by its >100-fold stronger K(11(aq)) versus GO-HNAP, making ZHE-HNAP less prone to dissociation and ion-exchange with competing endogenous anions and able to remain intact during membrane permeation. Overall, this work presents a novel approach to enable the oral delivery of highly polar antiviral drugs, and provides new insights into the underlying mechanisms governing the success or failure of the ion-pairing strategy to increase oral absorption.

Design, synthesis and biological evaluation of novel lipoamino acid-based glycolipids for oral drug delivery

A series of lipoamino acid-based glycolipids were synthesised. Suitably derivatised lipoamino acid derivatives were prepared and conjugated to monosaccharides (including glycosyl azides, isothiocyanates, thiols and sulphones) to yield novel O-, N-, S- and C-linked glycolipids in good yields. Their potential to improve the oral absorption of piperacillin is reported.

Lipidation and glycosylation of a T cell antigen receptor (TCR) transmembrane hydrophobic peptide dramatically enhances in vitro and in vivo function

A T cell antigen receptor (TCR) transmembrane sequence derived peptide (CP) has been shown to inhibit T cell activation both in vitro and in vivo at the membrane level of the receptor signal transduction. To examine the effect of sugar or lipid conjugations on CP function, we linked CP to 1-aminoglucosesuccinate (GS), N-myristate (MYR), mono-di-tripalmitate (LP1, LP2, or LP3), and a lipoamino acid (LA) and examined the effects of these compounds on T cell activation in vitro and by using a rat model of adjuvant-induced arthritis, in vivo. In vitro, antigen presentation results demonstrated that lipid conjugation enhanced CP's ability to lower IL-2 production from 56.99%+/-15.69 S.D. observed with CP, to 12.08%+/-3.34 S.D. observed with LA. The sugar conjugate GS resulted in only a mild loss of in vitro activity compared to CP (82.95%+/-14.96 S.D.). In vivo, lipid conjugation retarded the progression of adjuvant-induced arthritis by approximately 50%, whereas the sugar conjugated CP, GS, almost completely inhibited the progression of arthritis. This study demonstrates that hydrophobic peptide activity is markedly enhanced in vitro and in vivo by conjugation to lipids or sugars. This may have practical applications in drug delivery and bioavailability of hydrophobic peptides.

Polycationic lipophilic-core dendrons as penetration enhancers for the oral administration of low molecular weight heparin

Two polycationic lipophilic-core carbohydrate-based dendrons 2a-b and five polycationic lipophilic-core peptide dendrons 3-6, containing four arginine or lysine terminal residues, were synthesized and then tested in rats as penetration enhancers for the oral delivery of low molecular weight heparin. Better results were obtained with dendrons containing terminal lysine residues than terminal arginine. A significant anti-factor Xa activity was obtained when low molecular weight heparin was coadministered with dendron 5.

Strategies to improve oral drug bioavailability

Efforts to improve oral drug bioavailability have grown in parallel with the pharmaceutical industry. As the number and chemical diversity of drugs has increased, new strategies have been required to develop orally active therapeutics. The past two decades have been characterised by an increased understanding of the causes of low bioavailability and a great deal of innovation in oral drug delivery technologies, marked by an unprecedented growth of the drug delivery industry. The advent of biotechnology and consequent proliferation of biopharmaceuticals have brought new challenges to the drug delivery field. In spite of the difficulties associated with developing oral forms of this type of therapeutics, significant progress has been made in the past few years, with some oral proteins, peptides and other macromolecules currently advancing through clinical trials. This article reviews the approaches that have been successfully applied to improve oral drug bioavailability, primarily, prodrug strategies, lead optimisation through medicinal chemistry and formulation design. Specific strategies to improve the oral bioavailability of biopharmaceuticals are also discussed.