Pharmaceutical Nanotechnology - Volume 1, Issue 2, 2013

Nowadays, nanosuspension is a growing approach for pharmaceutical product development due to several unique properties applicable in pharmaceutical field. This article reviews the physical and chemical stability of nanosuspensions, their mechanism, and the factors which affect the stability. Some common factors responsible for nanosuspensions instability and few significant strategies used to overcome the stability problem are also discussed.

Current neuroimaging techniques in experimental medicine and clinical diagnosis are limited by low resolution and restricted image depth. Fluorescence in vivo imaging using near-infrared-emitting nanostructures, including nanocrystal quantum dots (QDs) can overcome these limitations. The objective of the present study was to establish if nanocrystals are suitable for repeated live imaging of deep structures (500 μm) in the intact animal. Intranasal instillation of QDs (5 μL) in mice with unilateral cortical microlesions resulted in marked QD accumulation at the microlesion site in the brain. Glial cell activation in response to the local devascularization played a key role in the uptake of QDs. The majority of QDs were taken up by activated microglia, whereas astroglia played a smaller role in this process. Progression and regression of the lesion upon therapeutic interventions were determined in real-time. Intranasal administration of antiinflammatory nanotherapeutics (micelle-incorporated nimodipine or minocycline) was effective in preventing lesion progression as evidenced by the smaller lesion volumes compared to the untreated controls. Moreover, lesion reduction was accompanied by significantly improved motor function. Near-infrared fluorescence imaging using nanocrystals is a valuable addition to current neuropathological methods for the diagnosis of cerebral microlesions and eventually other neurodegenerative diseases, both in experimental models and eventually in humans.

We have synthesized two types of nanoparticles (NPs) for controlled, localized delivery of platelet-derived growth factor (PDGF). One type is based on a liposome formulation; another type is based on a biodegradable polymer formulation. Liposome NPs have high PDGF loading and loading efficiency. With similar small particle size and size distribution, PLGA-m-PEG-PDGF NPs have lower PDGF loading and loading efficiency. It allows for controlled release of PDGF over a long period (e.g., up to 42 days). Based on an electrochemical process which uses electrolysis of water and isoelectric focusing of collagen, we also fabricated aligned collagen fibers which can incorporate the above formulated NPs as well as non-encapsulated (free) PDGF. The loading of NPs inside collagen fibers was confirmed by using fluorescence microscope, scanning electron microscope, and optical microscope. Cell proliferation study confirmed that both types of collagen-NP fibers are biocompatible and can enhance the proliferation of adipose derived stem cells in the short term. Our research demonstrated that two different NP formulations, as well as free PDGF can be loaded inside collagen to form aligned collagen-NP fibers, which can be used to enhance the proliferation of stem cells for connective tissue repair and regeneration (e.g., tendon).

9-Nitrocamptothecin (9-NC) is an efficient antitumor reagent with poor drug-to-lipid entrapment (1:72) in the conventional liposomes formulation. In order to improve the encapsulation and therapeutic efficacy, PEGylated cholesterol (Chol-PEG) was introduced into the 9-NC loaded liposomes formulation by pH gradient encapsulation method. Comparing with conventional composition, 9-NC/lipid molar ratio was increased from 1:72 up to 1:6 in the Chol-PEG based liposomes with uniform size distribution (~120 nm). PEGylated formulation showed obvious lower IC50 value than 9-NC solution (from > 50μmol/L to 5.5 μmol/L on breast cancer 4T1 cells, while from > 50μmol/L to 25.4 μmol/L on hepatoma HepG2 cells) in cytotoxicity measurement. The safety of PEGylated 9-NC liposomes formulation was also illustrated in ex vivo hemolysis test. The enhanced tumor inhibition efficiency of PEGylated 9-NC liposomes was confirmed from tumor-bearing BALB/c mice model using same dosage of 9-NC solution as control (from 28.6% to 70.1% in tumor inhibition). These results suggest that this Chol-PEG based liposome formulation may serve as a promising nanoscale platform for 9-NC controlled delivery.

Need for novel, innovative strategies for developing antibiotics is becoming a necessity due to an increasing number of rapidly evolving micro-organismal threats. Antibiotic encapsulated gold nanoparticles (GNPs) are one such strategy showing promise. We report the development of ampicillin encapsulated gold nanoparticles (Amp-GNPs) that possess highly effective, dose dependant antibacterial activity. In this method, ampicillin molecules have been coated on individual GNPs which can then serve as drug carrier devices. Our method for synthesizing Amp-GNPs is an entirely ecofriendly, single step reaction taking place in an aqueous buffer. Following characterization of Amp-GNPs, we find them to be ˜15 nm in diameter and spherical in shape. We have tested the antibacterial activity of Amp-GNPs against multiple strains of bacteria, both Gram-positive and Gram-negative, and have found Amp-GNPs to be highly efficient against all tested strains. By examining the mechanism of Amp-GNPs antibacterial activity, it was determined that Amp-GNPs disrupt the bacterial cells membrane when coming into contact with the cells, thus disturbing the cell equilibrium, leading to cell lysis or necrosis. Amp-GNPs have been shown to exhibit significant potential and ability to enter the medical field’s arsenal to fight infectious disease.

Finasteride, lipophilic 5-α reductase inhibitor was selected as a model drug to evaluate in-vivo iontophoretic transdermal delivery of novel lipid-based vesicular carriers (invasomes). The study included three protocols. The protocol I involved formulation of invasomes with terpenes (limonene, carvone and nerolidol) using Taguchi robust design for optimization. Invasomes were characterized for vesicular shape, size, zeta potential, entrapment efficiency and percutaneous permeation. The vesicles were found to be unilamellar, spherical in shape with size ranging from 4.54±0.30μm to 13.00±0.20μm. They possessed negative charge and entrapment efficiency (58.23±0.41% to 84.56±0.25 %). Formulation IF1 containing lipophilic terpene limonene (0.5%) enhanced permeation by 21.17 fold when compared with control (aqueous solution). The optimized invasomal formulation was checked for the enhanced permeation using the iontophoretic technique in second protocol. Two factors three level Taguchi robust design was used for optimizing the current density and pulse-on/off ratio. Formulation INF9 (0.5 mA/cm2, 3:1 pulse on/off ratio) enhanced flux by 25.83 fold when compared with control. In protocol III in-vivo studies of optimized iontophoretic invasomal formulation in the form of gel were performed on rabbits and compared with oral suspension. Plasma samples were analyzed by LCMS and pharmacokinetic parameters were calculated. AUC and T1/2 were increased by 3.03 times and 1.34 times respectively showing effective transdermal delivery. Histopathological studies of the optimized formulation (INF9) on rat skin revealed changes in dermis indicating the effect of ethanol and terpenes present in invasomes. These results indicated invasomes as effective vesicular carriers for iontophoretic transdermal delivery of finasteride.

Nanomaterials have been utilized in biomedical applications for many years because of their unique properties such as quantum confinement, surface plasmon resonance, and superparamagnetism. These applications are expected to advance diagnosis and therapeutics. Fluorescent nanomaterials, such as quantum dots (QDs), were exalted in biological imaging and tracking, and trended to replace protein-based probes. Our previous investigation indicated that cellpenetrating peptides (CPPs) are a promising delivery system that can translocate materials efficiently in a noncovalent manner. In this study, we demonstrate that arginine-rich CPPs can noncovalently complex with QDs and significantly raise efficiency of cellular entry. We further examined their mechanisms of cellular penetrations, subcellular localizations, and cytotoxicity. Importantly, CPP/QD complexes were not toxic at the level of efficient transduction. Collectively, our study provided an insight that CPPs can facilitate the delivery of nanomaterials into cells. Various compositions of CPPs are a major factor affecting uptake routes and efficiency for drug delivery applications.