Folic Acid-Anchored PEGgylated Phospholipid Bioconjugate and Its Application in a Liposomal Immunodiagnostic Assay for Folic Acid

A folic acid-anchored, poly(ethylene glycol)-linked (PEGgylated) phospholipid and an immunoaffinity chromatographic column were prepared and employed to develop a liposomal immunodiagnostic assay for the direct determination of folic acid (FA) in this study. Distearoylphosphatidylethanolamine-poly(ethylene glycol)(2000)-folic acid (DSPE-PEG(2000)-FA) was synthesized through carbodiimide-mediated coupling of FA and DSPE-PEG(2000)-amine and characterized using thin layer chromatography, I H nuclear magnetic resonance spectroscopy, and electrospray ionization-mass spectrometry. Liposomal biolabels were constructed using the synthesized DSPE-PEG(2000)-FA in conjunction with other phospholipids. A stationary phase having affinity for FA was prepared by covalently linking purified anti-FA monoclonal antibodies onto N-hydroxysuccinimide-activated Sepharose beads, which were subsequently packed into a 1.9 cm diameter polypropylene column. The calibration curve for FA had a linear range from 10(-8) to 10(-4) M. The limit of detection was 6.8 ng (equivalent to 500 mu L of 3.1 x 10(-8) M FA). The elution buffer (35% methanol in Tris buffered saline containing 0.1% Tween 20) also served as the regeneration buffer, which allowed the same column to be used for up to 50 times without any observable loss of reactivity. The immunoaffinity chromatographic column was reusable and capable of concentrating analytes from sample solution; in conjunction with folic acid-sensitized liposomal biolabels, however, they hold great potential as sensitive immunoaffinity assays for the determination for FA. To confirm the feasibility of using this system in the analysis of real samples, the folic acid contents of three over-the-counter vitamin supplements were tested. The recoveries of folic acid of 90-112% for these three samples were obtained, suggesting contents that were consistent with the information obtained from their nutritional facts panels

Dynamic Probing of Nanoparticle Stability In Vivo: A Liposomal Model Assessed Using In Situ Microdialysis and Optical Imaging

Nanoparticle-mediated drug delivery and controlled release has been a vigorous research area in contemporary nanomedicine. The in vivo stability of nanoparticle delivered on site is a prerequisite for the design of drug-controlled release by any means. In this study, the first methodology comprised of microdialysis and optical imaging to assess the liposome stability in vivo is reported. Macroscopically, we demonstrated the DPPG liposomes with negative surface charge fast accumulated in the rat liver upon their i.v. administration using optical imaging. Microscopically, the concurrent analysis of fluorescent molecules leaching from the liposomes, in situ sampled using microdialysis probe, provides the dynamic information of stability of DPPG liposomes locus in quo. The current combination of in situ microdialysis and optical imaging possesses a great potential for use as a platform technology to evaluate the nanoparticle stability and the bioavailability of drug payload released on targeted site in vivo