Synthetic polymannose as a drug carrier: synthesis, toxicity and anti-fungal activity of polymannose-amphotericin B conjugates.

Polymannose (PM) having a weight-average molar mass (Mw) of 30-53 kDa was synthesized by the polycondensation of mannose using phosphorous acid as the catalyst and characterized by various techniques such as NMR, IR, GPC and polarimetry. 2D NMR results confirmed the presence of (1 â†’ 6)-linked α-D-mannose residues as backbone with O-3 and O-2 substituted linear or branched chains in PM. Amphotericin B (AmB) was conjugated to periodate-oxidized PM through Schiff's linkages at 20 wt% concentration. The AmB-PM conjugates were highly soluble in phosphate buffered saline (180-250 mg/mL), exhibited negligible hemolytic potential to human erythrocytes even at a concentration of 200 µg/mL (equivalent to ~40 µg/mL AmB) and were non-toxic to human embryonic kidney (HEK293T) cells even at a concentration of 250 µg/mL (equivalent to ~50 µg/mL AmB). The minimum inhibitory concentration of the AmB-PM conjugates against C. albicans, C. parapsilosis and C. neoformans was in the range of 0.5-1.0 µg/mL. Mannose receptors are widely expressed on myeloid cells such as macrophages, neutrophils, and dendritic cells. Therefore, apart from treating fungal infections, AmB-PM conjugates also may have therapeutic potential for the treatment of macrophage-associated diseases such as leishmaniasis where mannose receptors are overexpressed.

Amphotericin B-albumin conjugates: Synthesis, toxicity and anti-fungal activity.

Amphotericin B (AmB), a hydrophobic drug with negligible aqueous solubility was conjugated to bovine serum albumin (BSA) via amide bond coupling to give 6 to 8 wt% drug payload. The resulting conjugate was characterized using SDS-PAGE and UV-visible, FTIR and CD spectroscopy. The conjugate was water-soluble to the extent of 150 mg/ml, was non-toxic to HEK 293 T cells at a concentration of 500 µg/ml (equivalent to ~30 µg AmB) and showed hemolysis of <5% at 200 µg/ml (equivalent to ~12 µg AmB) against human erythrocytes in vitro. In vitro release studies at 37 °C demonstrated steady release of AmB up to 20% from the conjugate with little burst effect in phosphate buffered saline whereas thrice the amount was released in human plasma in 72 h. AmBisome® used as a reference showed a very similar release profile in plasma. The conjugate exhibited potential anti-fungal activity against yeast strains such as C. albicans, C. neoformans and C. parapsilosis with the minimum inhibitory concentration (MIC) equivalent to AmB ranging from 0.7 to 1.1 µg/ml while AmBisome® and AmB alone showed the MIC between 0.78 and 1.5 and 0.53-0.78 µg/ml respectively. Although AmB has been conjugated to various natural and synthetic polymers to improve its solubility and reduce its toxicity, the results obtained in this study using the model protein BSA as a carrier point to the possibility of taking this pro-drug approach to human clinical use using human serum albumin (HSA) as the carrier, since HSA has emerged as a versatile drug carrier for treating diabetes and cancer and improving the pharmacokinetic profile of many drugs with US FDA approving HSA as a drug carrier for the anti-cancer drug paclitaxel (Abraxane®) for human use.

Identification of unprecedented anticancer properties of high molecular weight biomacromolecular complex containing bovine lactoferrin (HMW-bLf).

With the successful clinical trials, multifunctional glycoprotein bovine lactoferrin is gaining attention as a safe nutraceutical and biologic drug targeting cancer, chronic-inflammatory, viral and microbial diseases. Interestingly, recent findings that human lactoferrin oligomerizes under simulated physiological conditions signify the possible role of oligomerization in the multifunctional activities of lactoferrin molecule during infections and in disease targeting signaling pathways. Here we report the purification and physicochemical characterization of high molecular weight biomacromolecular complex containing bovine lactoferrin (≥250 kDa), from bovine colostrum, a naturally enriched source of lactoferrin. It showed structural similarities to native monomeric iron free (Apo) lactoferrin (∼78-80 kDa), retained anti-bovine lactoferrin antibody specific binding and displayed potential receptor binding properties when tested for cellular internalization. It further displayed higher thermal stability and better resistance to gut enzyme digestion than native bLf monomer. High molecular weight bovine lactoferrin was functionally bioactive and inhibited significantly the cell proliferation (p<0.01) of human breast and colon carcinoma derived cells. It induced significantly higher cancer cell death (apoptosis) and cytotoxicity in a dose-dependent manner in cancer cells than the normal intestinal cells. Upon cellular internalization, it led to the up-regulation of caspase-3 expression and degradation of actin. In order to identify the cutting edge future potential of this bio-macromolecule in medicine over the monomer, its in-depth structural and functional properties need to be investigated further.

Aptamer-based therapeutics of the past, present and future: from the perspective of eye-related diseases.

Aptamers have emerged as a novel and powerful class of biomolecules with an immense untapped potential. The ability to synthesise highly specific aptamers against any molecular target make them a vital cog in the design of effective therapeutics for the future. However, only a minutia of the enormous potential of this dynamic class of molecule has been exploited. Several aptamers have been studied for the treatment of eye-related disorders, and one such strategy has been successful in therapy. This review gives an account of several eye diseases and their regulatory biomolecules where other nucleic acid therapeutics have been attempted with limited success and how aptamers, with their exceptional flexibility to chemical modifications, can overcome those inherent shortcomings.

Targeted multimodal liposomes for nano-delivery and imaging: an avenger for drug resistance and cancer.

Understanding the cellular target structure and thereby proposing the best delivery system to achieve sustained release of drugs has always been a significant area of focus in biomedical research for translational benefits. Specific targeting of the receptors expressed on the target cell represents an effective strategy for increasing the pharmacological efficacy of the administered drug. Liposomes offer enhanced conveyance as a potential carrier of biomacromolecules such as anti-cancer proteins, drugs and siRNA for targeting tumour cell death. Commonly used liposomal constructs for various therapies are Doxil, Myocet, DepoCyt and Abraxanes. However, recent strategy of using multifunctional liposomes for the sustained release of drugs with increased plasma residence time and monoclonal antibody-based targeting of tumours coupled with imaging modalities have attracted enormous scientific attention. The ability of liposomes coated with specific ligands such as Apo-E derived RGD R9 and Tat peptide, to reverse the conceptualisation of drug resistance and cross the blood brain barrier, provides promising future for their use as an efficient drug delivery system. By outlining the recent advancements and innovations in the established concept of liposomal drug delivery, this review will focus on the multifunctional liposomes as an emerging novel lipid based drug delivery system.

Targeting hepatitis B virus and human papillomavirus induced carcinogenesis: novel patented therapeutics.

Viral infections leading to carcinogenesis tops the risk factors list for the development of human cancer. The decades of research has provided ample scientific evidence that directly links 10-15% of the worldwide incidence of human cancers to the infections with seven human viruses. Moreover, the insights gained into the molecular pathogenetic and immune mechanisms of hepatitis B virus (HBV) and human papillomavirus (HPV) viral transmission to tumour progression, and the identification of their viral surface antigens as well as oncoproteins have provided the scientific community with opportunities to target these virus infections through the development of prophylactic vaccines and antiviral therapeutics. The preventive vaccination programmes targeting HBV and high risk HPV infections, linked to hepatocellular carcinoma (HCC) and cervical cancer respectively have been recently reported to alter age-old cancer patterns on an international scale. In this review, with an emphasis on HBV and HPV mediated carcinogenesis because of the similarities and differences in their global incidence patterns, viral transmission, mortality, molecular pathogenesis and prevention, we focus on the development of recently identified HBV and HPV targeting innovative strategies resulting in several patents and patent applications.