Abstract
To develop proliposome formulations to improve the oral bioavailability of l-glutathione (GSH), GSH-loaded proliposomes were prepared using the granule method. Mannitol was selected as an effective excipient to achieve the desired particle size, entrapment efficiency (EE), and solubility for oral delivery of the final formulation. To evaluate the effect of surface charge of proliposomes on the oral bioavailability of GSH, negative (F1–F4) and positive proliposomes (F5–F9) were prepared. Particle size of F1 and F5 was 167.8 ± 0.9 and 175.9 ± 2.0 nm, and zeta potential of F1 and F5 was –8.1 ± 0.7 and 21.1 ± 2.0 mV, respectively. Encapsulation efficiency of F1 and F5 was 58.6% and 54.7%, respectively. Considering their particle size, zeta potential, and EE, the proliposomes F1 and F5 were adopted as the optimal formulations for further experiments. Solid state characterization of the proliposomes confirmed lipid coating on the surface of mannitol. The release of GSH from F1 and F5 formulations was prolonged until 24 h and pH independent. The total antioxidant capacity of GSH was concentration-dependent and maintained after formulation of GSH proliposomes. Circular dichroism spectroscopy confirmed that the molecular structure of GSH was maintained in the proliposome formulations. GSH proliposomes exhibited no significant changes in particle size and zeta potential for 4 weeks. An oral bioavailability study in rats revealed that F5 exhibited 1.05-, 1.08-, and 1.11-fold higher bioavailability than F1, commercial capsule formulation, and pure GSH, respectively. In conclusion, the prepared GSH proliposomes enhanced the poor bioavailability of GSH and prolonged its duration of action.
Highlights
Usage of conventional chemical substances is limited when the treatment or disease condition has complex mechanisms (Ahmad et al, 2017)
The granulation method was chosen for this study because of its simplicity and efficiency, and it was modified to prepare GSH proliposomes
The particle size and zeta potential of the reconstituted liposomes depended on the amount of the lipids
Summary
Usage of conventional chemical substances is limited when the treatment or disease condition has complex mechanisms (Ahmad et al, 2017) For these unmet needs, development of biopharmaceuticals using in vivo mechanisms was initiated and soon became the core technology of drug development (Gavrilescu & Chisti, 2005). Peptide drugs have advantages of high potency, efficacy, stability, and selectivity They have disadvantages of short half-life, low cell-membrane permeability, and poor oral bioavailability due to gastric and enzymatic degradation (Ahmad et al, 2017; Mohtashamian & Boddohi, 2017). L-Glutathione (GSH) is a water-soluble tripeptide composed of amino acids such as glutamine, cysteine, and glycine (Townsend et al, 2003). It is the most abundant intracellular low-molecular-weight peptide containing a thiol group (Meng et al, 2009). In Parkinson’s disease, the amount of early GSH is reduced by 40%, and only 2% of its normal state is available (Sian et al, 1994)
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