Przemysław Żmuda, Khaidakov B, Krasowska M, Katarzyna Czapska, Dobkowski M, Guzowski J, et al. 2024 Bioavailability of liposomal vitamin C in powder form: a randomized, double-blind, cross-over trial.
Overview
This lecture covers a clinical trial evaluating the bioavailability and properties of liposomal vitamin C in powder form compared to non-liposomal vitamin C, focusing on formulation, stability, and pharmacokinetic outcomes.
Vitamin C: Functions and Challenges
- Vitamin C (ascorbic acid) acts as a strong antioxidant, protecting biomolecules from oxidation and supporting immune function.
- It is a cofactor in hormone, carnitine, and collagen synthesis and helps with iron absorption.
- Humans can't synthesize vitamin C and must obtain it from the diet.
- Vitamin C is unstable and degrades when exposed to heat, light, oxygen, and certain metals.
Liposomal Encapsulation: Rationale and Production
- Encapsulation in liposomes protects vitamin C from degradation and improves bioavailability.
- Liposomes are made from biocompatible phospholipids and can shield active substances from environmental stress.
- Traditional liposome production uses organic solvents, which have drawbacks; this study used a solvent-free method.
- The powder formulation was created by spray-drying a liposomal suspension with maltodextrin.
Characterization of Liposomal Vitamin C Powder
- Scanning electron microscopy showed intact microcapsules with vitamin C liposomes inside.
- Liposomes had a mean particle size of ~262 nm (span = 0.500), indicating a uniform, stable product.
- High absolute zeta potential (–41.44 mV) suggested strong colloidal stability.
In Vitro Bioavailability Assessment
- The Caco-2 cell model, simulating human intestinal absorption, showed liposomal vitamin C had 22.28% higher bioavailability than the non-liposomal form (p < 0.05).
Clinical Trial Design and Results
- Randomized, double-blind, cross-over trial with 9 healthy adult volunteers.
- Each participant received both 1000 mg doses of non-liposomal and liposomal vitamin C after a washout period.
- Blood vitamin C levels were measured at multiple intervals up to 24 hours post-dose.
Key Clinical Findings
- Liposomal vitamin C had a 30% higher area under the curve (AUC) than non-liposomal (p < 0.05).
- Blood concentrations at 10 h and 24 h were significantly higher with the liposomal form.
- Maximum plasma concentration (Cmax) was higher for liposomal form but not statistically significant.
- Time to maximum concentration (Tmax) was similar between formulations.
Limitations and Future Directions
- Small sample size; results are promising but need confirmation in larger studies.
- Further research should assess long-term effects and broader applicability.
Key Terms & Definitions
- Bioavailability — the proportion of a nutrient that enters the bloodstream and is available for use.
- Liposomal — refers to a drug or nutrient encapsulated within a vesicle made of a lipid bilayer.
- Zeta potential — a measure of the stability of colloidal dispersions; values >30 mV indicate good stability.
- AUC (Area Under the Curve) — reflects total drug/nutrient exposure over time in pharmacokinetics.
- Cmax — the maximum concentration of a substance in blood after administration.
- Tmax — the time it takes to reach Cmax.
- Span — a measure of particle size distribution width.
Action Items / Next Steps
- Review the advantages and challenges of liposomal delivery for unstable nutrients.
- Understand basic pharmacokinetic concepts (AUC, Cmax, Tmax).
- Prepare for further readings on encapsulation technologies and clinical trial design.