Sunil Mahor

Targeted brain delivery of AZT via transferrin anchored pegylated albumin nanoparticles

Hydrophilic drugs/peptides have poor cross Blood–brain permeability. Various drug delivery systems with diverse surfacial characteristics have been reported for effective translocation of drugs across Blood–brain barrier. In present investigation, the potential of engineered albumin nanoparticles was evaluated for brain specific delivery after intravenous administration. Long circulatory PEGylated albumin nanoparticles encapsulating water-soluble antiviral drug azidothymidine (AZT) were prepared by ultra-emulsification method using chemical cross-linking by glutaraldehyde. Surface of the PEGylated nanoparticles was modified by anchoring transferrin as a ligand for brain targeting. Nanoparticles were characterized for their size, polydispersity, surfacial charge, drug loading and in vitro drug release. Fluorescence studies revealed the enhanced uptake of transferrin-anchored nanoparticles in the brain tissues when compared with unmodified nanoparticles. In vivo evaluation was carried out on albino rats to evaluate tissue distribution of engineered nanoparticles after intravenous administration. A significant (*P < 0.01) enhancement of brain localization of AZT was observed for transferrin anchored pegylated albumin nanopariticles (Tf-PEG-NPs). Hence, the specific role of transferrin ligand on nanoparticles for brain targeting was confirmed.

Liposomes modified with cyclic RGD peptide for tumor targeting.

Cyclic RGD peptide anchored sterically stabilized liposomes (RGD-SL) were investigated for selective and preferential presentation of carrier contents at angiogenic endothelial cells overexpressing αvβ3 integrins on and around tumor tissue and thus for assessing their targetabilty. Liposomes were prepared using distearoylphosphatidylcholine (DSPC), cholesterol and distearoylphosphatidylethanolamine–polyethyleneglycol–RGD peptide conjugate (DSPE–PEG–RGD) in a molar ratio 56:39:5. The control RAD peptide anchored sterically stabilized liposomes (RAD-SL) and liposome with 5 mol% PEG (SL) without peptide conjugate which had similar lipid composition were used for comparison. The average size of all liposome preparations prepared was approximately 105 nm and maximum drug entrapment was 10.2±1.1%. In vitro endothelial cell binding of liposomes exhibited 7-fold higher binding of RGD-SL to HUVEC in comparison to the SL and RAD-SL. Spontaneous lung metastasis and angiogenesis assays show that RGD peptide anchored liposomes are significantly (p<0.01) effective in the prevention of lung metastasis and angiogenesis compared to free 5-FU, SL and RAD-SL. In therapeutic experiments, 5-FU, SL, RGD-SL and RAD-SL were administered intravenously on day 4 at the dose of 10 mg 5-FU/kg body weight to B16F10 tumor bearing BALB/c mice resulting in effective regression of tumors compared with free 5-FU, SL and RAD-SL. Results indicate that cyclic RGD peptide anchored sterically stabilized liposomes bearing 5-FU are significantly (p<0.01) active against primary tumor and metastasis than the non-targeted sterically stabilized liposomes and free drug. Thus cyclic RGD peptide anchored sterically stabilized liposomes hold potential of targeted cancer chemotherapeutics.

Tetanus toxoid‐loaded transfersomes for topical immunization

Topical immunization is a novel immunization strategy by which antigens and adjuvants are applied topically to intact skin to induce potent antibody and cell‐mediated responses. Among various approaches for topical immunization, the vesicular approach is gaining wide attention. Proteineous antigen alone or in combination with conventional bioactive carriers could not penetrate through the intact skin. Hence, specially designed, deformable lipid vesicles called transfersomes were used in this study for the non‐invasive delivery of tetanus toxoid (TT). Transfersomes were prepared and characterized for shape, size, entrapment efficiency and deformability index. Fluorescence microscopy was used to investigate the mechanism of vesicle penetration through the skin. The immune stimulating activity of these vesicles was studied by measuring the serum anti‐tetanus toxoid IgG titre following topical immunization. The immune response was compared with the same dose of alum adsorbed tetanus toxoid (AATT) given intramuscularly, topically administered plain tetanus toxoid solution, and a physical mixture of tetanus toxoid and transfersomes again given topically. The results indicated that the optimal transfersomal formulation had a soya phosphatidylcholine and sodium deoxycholate ratio of 85:15%, w/w. This formulation showed maximum entrapment efficiency (87.34±3.81%) and deformability index (121.5±4.21). An in‐vivo study revealed that topically administered tetanus toxoid‐loaded transfersomes, after secondary immunization, elicited an immune response (anti‐TT‐IgG) comparable with that produced by intramuscular AATT. Fluorescence microscopy revealed the penetration of transfersomes through the skin to deliver the antigen to the immunocompetent Langerhans cells.

Estrogen(s) and Analogs as a Non-Immunogenic Endogenous Ligand in Targeted Drug/DNA Delivery

The maximum therapeutic potentials of pharmacologically active molecules are generally not attained due to their non specific delivery. Ligands associated with drug or delivery system through which it is delivered provide navigation and direction to the carrier system(s) so as to reach and release bioactive(s) at the desired site of action in a optimum therapeutic concentration vis a vis minimizing the undesired side effects associated with non specific delivery. Many ligands employed and implicated in targeted drug delivery have been reportedly found to be mild to strong immunogenic. Hence, their potential utility is considered to be compromised in achieving concept of magic bullet. Therefore endogenous ligand (bio self molecules) based drug/DNA delivery may be a better alternative they being biocomponents so are non-immunogenic and biocompatible per se. Estrogens and their receptors are over expressed in the several pathophysiological conditions including cardiovascular, osteoarthritis and cancer of prostate and ovaries etc. The selective high density of such portal may be utilized for targeting such estrogen receptor rich sites. The several scientific communities from various fields of specialization of science have explored estrogen(s) and their analogs for the purpose of targeting of bioactive(s) either by preparing estrogen-drug conjugates of using estrogens as site-directing ligands attached with various carrier system(s). This review presents an exhaustive account of how hormones especially estrogens and their derivatives could be used for site-specific delivery of bioactive(s), as diagnostic agents and also the future prospects of these bioligands in controlled and targeted clinical pharmacology. Estrogen-drug conjugates and various carrier systems that utilized estrogens as ligands for site-specific delivery have been reviewed and are discussed in detail.

Hepatitis B surface protein docked vesicular carrier for site specific delivery to liver.

The intrinsic liver tropism of liposomes can be augmented by the addition of targeting features such as the incorporation of hepatotropic elements of the hepatitis viruses. Hepatitis B virus is known to infect hepatocytes after viremia by asialoglycoprotein receptor mediated uptake. However, the specificity of hepatitis B virus surface protein (HBsAg) towards hepatocytes has confronting reports. In the present study, we evaluated the functional ability of HBsAg to be employed as a ligand for targeting hepatocytes. We prepared 14C labeled small unilamellar vesicles (SUVs) composed of egg PC/Cholesterol/N-glutarylphosphatidylethanolamine (NGPE) in a 60:30:10 molar ratio. HBsAg was covalently linked to SUVs using a water-soluble carbodiimide (EDC) mediated conjugation with NGPE. In vitro cell binding and uptake studies revealed that bioprotein docked carrier system was efficiently taken up by HepG2 cells by the receptor mediated endocytosis. The biodistribution behaviour of plain and HBsAg coated liposomes was also examined followed by intravenous injection. The study revealed that almost 75% of the radioactivity was recovered in the liver after 4 h of injection that was nearly three-fold greater in magnitude than the plain liposomes. Further, fractionation of liver into liver parenchymal cells (PC) and non-parenchymal cells confirmed the preferential localization of the HBsAg coated liposomal carrier in the parenchymal cells.