Amit K. Jain

Toxicity of Multiwalled Carbon Nanotubes with End Defects Critically Depends on Their Functionalization Density

Carboxylated carbon nanotubes stand as the most promising nanovectors for biomedical and pharmaceutical applications due to their ease of covalent conjugation with eclectic functional molecules including therapeutic drugs, proteins, and oligonucleotides. In the present study, we attempt to investigate how the toxicity of acid-oxidized multiwalled carbon nanotubes (MWCNTs) can be tweaked by altering their degree of functionalization and correlate the toxicity trend with their biodistribution profile. In line with that rationale, mice were exposed to 10 mg/kg of pristine (p) and acid-oxidized (f) MWCNTs with varying degrees of carboxylation through a single dose of intravenous injection. Thereafter, extensive toxicity studies were carried out to comprehend the short-term (7 day) and long-term (28 day) impact of p- and various f-MWCNT preparations on the physiology of healthy mice. Pristine MWCNTs with a high aspect ratio, surface hydrophobicity, and metallic impurities were found to induce significant hepatotoxicity and oxidative damage in mice, albeit the damage was recovered after 28 days of treatment. Conversely, acid-oxidized carboxylated CNTs with shorter lengths, hydrophilic surfaces, and high aqueous dispersibility proved to be less toxic and more biocompatible than their pristine counterparts. A thorough scrutiny of various biochemical parameters, inflammation indexes, and histopathological examination of liver indicated that toxicity of MWCNTs systematically decreased with the increased functionalization density. The degree of shortening and functionalization achieved by refluxing p-MWCNTs with strong mineral acids for 4 h were sufficient to render the CNTs completely hydrophilic and biocompatible, while inducing minimal hepatic accumulation and inflammation. Quantitative biodistribution studies in mice, intravenously injected with Tc-99m labeled MWCNTs, clearly designated that clearance of CNTs from reticuloendothelial system (RES) organs such as liver, spleen, and lungs was critically functionalization density dependent. Well-individualized MWCNTs with shorter lengths (<500 nm) and higher degrees of oxidation (surface carboxyl density >3 μmol/mg) were not retained in any of the RES organs and rapidly cleared out from the systematic circulation through renal excretion route without inducing any obvious nephrotoxicity. As both p- and f-MWCNT-treated groups were devoid of any obvious nephrotoxicity, CNTs with larger dimensions and lower degrees of functionalization, which fail to clear out from the body via renal excretion route, were thought to be excreted via biliary pathway in faeces.

Carbon nanotubes and their toxicity

The vital need of studying the toxicological profile of carbon nanotubes (CNTs) has emerged from the rapidly enhancing utility of CNTs in the field of nanobiology and drug delivery. This review highlights the vivid aspect of CNTs’ toxicity comprising of in-vitro to in-vivo toxicological profile vis-à-vis the various potential routes of CNTs exposure. The article also underlines the various surface modifications on carbon nanotubes and its role in imparting biocompatibility to the CNTs, further suggesting their utility as a safer delivery module for bioactives.

Adapalene loaded solid lipid nanoparticles gel: An effective approach for acne treatment

Salient features such as controlled release, target ability, potential of penetration, improved physical stability, low cost compared to phospholipids, and ease of scaling-up makes solid lipid nanoparticles (SLNs) a viable alternative to liposomes for effective drug delivery. Adapalene (ADA) is a second generation retinoid effective in treating various dermatologic disorders such as Acne vulgaris with a few noticeable dose-mediated side effects. The present study was aimed at developing and characterizing ADA loaded SLNs for effective topical delivery. The formulated SLN system was characterized for particle size, poly dispersity index, entrapment efficiency and drug release properties. The resultant formulation (ADA loaded SLNs incorporated into carbopol hydrogel) was evaluated for in vitro drug release, skin permeation and bio-distribution, rheological behaviour, and texture profile analysis. The SLNs based ADA gel has shown its potential in targeting skin epidermal layer, and reducing systemic penetration. The developed system can avoid systemic uptake of ADA in skin layers, and can localize drug in skin epidermis as confirmed by rat skin model. Our results advocate potential of SLNs as a novel carrier for topical delivery of ADA in topical therapeutic approaches. This study open new avenues for drug delivery which better meets the need of anti-acne research.

Carbohydrate-conjugated multiwalled carbon nanotubes: development and characterization

UNLABELLED This work presents a novel cascade of chemical functionalization of multiwalled carbon nanotubes (MWCNTs) through chemical modification by a carbohydrate, D-galactose. Galactose-conjugated or galactosylated MWCNTs were synthesized involving the sequential steps of carboxylation, acylation, amine modification, and finally, galactose conjugation. The modification of MWCNTs with galactose was investigated by elemental analysis, x-ray diffraction analysis, Fourier transform-infrared spectroscopy, Raman spectroscopy, and zeta potential measurements, at every sequential step of functionalization. Size and surface characteristics of chemically modified MWCNTs were monitored by transmission electron microscopy and scanning electron microscopy. That galactosylation improved the dispersibility of MWCNTs in aqueous solvents was confirmed by investigation of their dispersion characteristics at different pH values. Thus, the galactosylated MWCNTs as developed could be used for delivery of different bioactive(s) as well as active ligand (galactose)-based targeting to hepatic tissue. FROM THE CLINICAL EDITOR This work presents a novel cascade of functionalization of multiwalled carbon nanotubes (MWCNTs) through chemical modification by a carbohydrate. Galactosylation improves the dispersibility of MWCNTs in aqueous solvents. The galactosylated MWCNTs could be used for delivery of different bioactive(s) as well as active ligand-based targeting to hepatic tissue.

Galactose engineered solid lipid nanoparticles for targeted delivery of doxorubicin

The present investigation reports the preparation, optimization, and characterization of surface engineered solid lipid nanoparticles (SLNs) encapsulated with doxorubicin (DOX). Salient features such as biocompatibility, controlled release, target competency, potential of penetration, improved physical stability, low cost and ease of scaling-up make SLNs viable alternative to liposomes for effective drug delivery. Galactosylation of SLNs instructs some gratifying characteristic, which leads to the evolution of promising delivery vehicles. The impendence of lectin receptors on different cell surfaces makes the galactosylated carriers admirable for targeted delivery of drugs to ameliorate their therapeutic index. Active participation of some lectin receptors in immune responses to antigen overlaid the application of galactosylated carriers in delivery of antigen and immunotherapy for treatment of maladies like cancer. These advantages revealed the promising potential of galactosylated carriers in each perspective of drug delivery. The developed DOX loaded galactosylated SLNs formulation was found to have particle size 239 ± 2.40 nm, PDI 0.307 ± 0.004, entrapment efficiency 72.3 ± 0.9%. Higher cellular uptake, cytotoxicity, and nuclear localization of galactosylated SLNs against A549 cells revealed higher efficiency of the formulation. In a nutshell, the galactosylation strategy with SLNs could be a promising approach in improving the delivery of DOX for cancer therapy.

A synergistic approach of adapalene-loaded nanostructured lipid carriers, and vitamin C co-administration for treating acne

Abstract The present study documents the fabrication and characterization of a topically applicable gel loaded with nanostructured lipid carriers (NLCs) of adapalene (ADA) and vitamin C (ascorbyl-6-palmitate [AP]). The NLCs were prepared by high pressure homogenization (HPH) method followed by incorporation into AP loaded gel. The fabricated system was characterized for size, poly dispersity index, entrapment efficiency (EE) and in vitro drug release properties, and was further investigated for skin compliance, skin transport characteristics (skin permeation and bio-distribution), rheological behavior, texture profile analysis and anti-acne therapeutic potential against testosterone-induced acne in male Wistar rats. The NLC-based formulation improved targeting of the skin epidermal layer and reducing systemic penetration. The co-administration of vitamin C led to an adjunct effect in acne therapy in physiological conditions. In brief, the present results suggest the potential of NLCs as a novel carrier for the dermal delivery of ADA and also the synergistic effect of vitamin C in topical therapeutics.

5-Aminolevulinic acid coated microneedles for photodynamic therapy of skin tumors

This study evaluated the potential of coated microneedles for improved dermal delivery of 5-aminolevulinic acid (5-ALA), which naturally gets converted by cells of the tissue in to a photosensitizer called protoporphyrin IX (PPIX). Microneedle patches containing 57 microneedles were coated with 5-ALA using an in-house developed micro-precision dip coater. The coating process was optimized to achieve higher 5-ALA loading on microneedles and a high delivery efficiency into porcine cadaver skin. Using 5 dips with 25% w/v 5-ALA solution, a mass of about 350μg of 5-ALA was coated per patch, which gave a delivery efficiency of about 90% in porcine cadaver skin. Bright-field and scanning electron microscopy established that coatings of 5-ALA on microneedles of the patch were uniform. In vivo dermal pharmacokinetics showed that delivery of just 350μg of 5-ALA using coated microneedles led to about 3.2-fold higher PPIX formation after 4h, as compared to topical application of 20% w/w 5-ALA in a conventional cream formulation (25mg cream). Furthermore, with use of coated microneedles, PPIX was observed in deeper regions of the skin (~480μm) as compared to topical 5-ALA cream formulation (~150μm). The potential of PPIX for photodynamic therapy was tested in vivo. After light exposure (633nm; 118J/cm(2)), PPIX got photosensitized, and due to higher initial amount of PPIX in the coated microneedle group, about twice the amount of PPIX was photobleached compared to topical cream application. Finally, even with a lower dose of just 1.75mg 5-ALA, coated microneedles suppressed the growth of subcutaneous tumors by ~57%, while a topical cream containing 5mg of 5-ALA did not suppress the tumor volume and led to tumor growth comparable to the untreated control group. Overall, the strategy of delivering 5-ALA using coated microneedles could be a promising approach for photodynamic therapy of skin tumors.

Cationic bovine serum albumin (CBA) conjugated poly lactic-co-glycolic acid (PLGA) nanoparticles for extended delivery of methotrexate into brain tumors

Current strategies for the treatment of brain tumors have been hindered primarily by the presence of the highly lipophilic, insurmountable blood–brain barrier (BBB). The purpose of the current research is to investigate the efficiency of the engineered biocompatible polymeric nanoparticles (NPs) as drug delivery vehicles to bypass the BBB and enhance the biopharmaceutical attributes of anti-metabolite methotrexate (MTX) encapsulated NPs. The NPs were prepared by the solvent diffusion method, using cationic bovine serum albumin (CBA), and were characterized for physicochemical parameters, such as particle size, polydispersity index, and zeta-potential, while the surface modification was confirmed by FTIR, and NMR spectroscopy. The developed NPs exhibited the zestful relocation of FITC tagged NPs across the BBB in albino rats. Further, hemolytic studies confirmed them to be non-toxic and biocompatible, as compared to free MTX. The in vitro cytotoxicity assay of our engineered NPs on HNGC1 tumor cells proved the superior uptake in tumor cells, and elicited a potent cytotoxic effect, compared to plain NPs and the free MTX solution. The outcomes of the study evidently indicate the prospect of CBA conjugated poly (D,L-lactide-co-glycolide) (PLGA) NPs loaded with MTX in a brain cancer bomber, with the amplified capability to circumvent the BBB.

Advances in oral delivery of anti-cancer prodrugs

ABSTRACT Introduction: Most anticancer drugs have poor aqueous solubility and low permeability across the gastrointestinal tract. Furthermore, extensive efflux by P-glycoproteins (P-gp) in the small intestine also limits the efficient delivery of anticancer drugs via oral route. Area covered: This review explores the prodrug strategy for oral delivery of anticancer drugs. Different categories of oral anticancer prodrugs along with recent clinical studies have been comprehensively reviewed here. Furthermore, novel anticancer prodrugs such as polymer-prodrugs and lipid-prodrugs have been discussed in detail. Finally, various nanocarrier-based approaches employed for oral delivery of anticancer prodrugs have also been discussed. Expert opinion: Premature degradation of anticancer prodrugs in the gastrointestinal tract could lead to variable pharmacokinetics and undesired toxicity. Despite their increased aqueous solubility, the oral bioavailability of several anticancer prodrugs are limited by their poor permeability across the gastrointestinal tract. These limitations can be overcome by the use of functional excipients (polymers, lipids, amino acids/dipeptides), which are specifically absorbed via transporters and receptor-mediated endocytosis. Oral delivery of anticancer prodrugs using nanocarrier-based drug delivery system is a recent development; however it should be justified based on the comparative advantages of encapsulating prodrug in a nanocarrier versus the use of anticancer prodrug molecule itself.

Influence of salivary washout on drug delivery to the oral cavity using coated microneedles: An in vitro evaluation

The objective of this study was to determine whether in buccal tissues, after insertion and removal of coated microneedles, the presence of saliva over the insertion site can lead to loss of the deposited drug, and if saliva can influence in vitro permeation of the drug across the tissue. Microneedles were coated with sulforhodamine (SRD), which was used as a model drug, and inserted in to porcine buccal mucosa in vitro. Fluorescence microscopy was used to study microneedle coating quality and the diffusion of SRD through the mucosa. Permeation experiments were conducted for simulated dynamic or static salivary flow by adding 100μL/h or 100, 200 or 300μL of phosphate buffered saline (PBS) in the donor compartment of the Franz diffusion cells, into which buccal tissue after insertion of SRD-coated microneedles was placed. Microscopy showed that microneedles were uniformly coated with SRD and that SRD was successfully delivered in to the mucosa. Some SRD remained in the tissue even after 24h, despite presence of PBS on top of the coated microneedle insertion site. It was found that salivary washout can result in loss of drug that has been deposited in oral cavity mucosal tissues using coated microneedles, and presence of fluid over the coated microneedle insertion site can increase flux across the tissue. Thus, it is advisable to include salivary flow during in vitro studies related to the use of coated microneedles for drug delivery to the oral cavity in order to not obtain misleading results.