Mohd Abul Kalam

Recent developments in l-asparaginase discovery and its potential as anticancer agent

L-Asparaginase (EC3.5.1.1) is an enzyme, which is used for treatment of acute lymphoblastic leukaemia (ALL) and other related blood cancers from a long time. This enzyme selectively hydrolyzes the extracellular amino acid L-asparagine into L-aspartate and ammonia, leading to nutritional deficiencies, protein synthesis inhibition, and ultimately death of lymphoblastic cells by apoptosis. Currently, bacterial asparaginases are used for treatment purpose but offers scepticism due to a number of toxicities, including thrombosis, pancreatitis, hyperglycemia, and hepatotoxicity. Resistance towards bacterial asparaginase is another major disadvantage during cancer management. This situation attracted attention of researchers towards alternative sources of L-asparaginase, including plants and fungi. Present article discusses about potential of L-asparaginase as an anticancer agent, its mechanism of action, and adverse effects related to current asparaginase formulations. This article also provides an outlook for recent developments in L-asparaginase discovery from alternative sources and their potential as a less toxic alternative to current formulations.

Development of chitosan nanoparticles coated with hyaluronic acid for topical ocular delivery of dexamethasone

The present study involved design of dexamethasone-sodium phosphate (DEX) loaded mucoadhesive chitosan nanoparticles for topical ocular delivery to improve its precorneal retention and corneal permeability. The chitosan-sodium tripolyphosphate nanoparticle (CS-NPs) was developed through ionotropic-gelation technique. The developed CS-NPs were coated with hyaluronic-acid (HA) to make discrete, free-flowing NPs and to improve their mucoadhesive characteristics. The particle-size, zeta-potential and polydispersity-index were determined by Malvern-Zetasizer. The average size of the CS-NPs ranged from 305.25±14.29nm (without HA-coating and before freeze-drying) to 400.57±15.23nm (HA-coated and after freeze-drying). Due to the polyanionic nature of HA, reversing of zeta-potentials from +32.55±4.15 to -33.74±3.45 was observed. Polydispersity-indices varied from 0.178±0.067 (before freeze-drying of HA-coated F2) to 0.427±0.028 (after freeze-drying of HA-coated F2). The encapsulation and loading capacity of around 72.95% and 14.51% respectively were found in optimized CS-NPs. In simulated tear fluid 75.84% cumulative amount of released drug was detected and the in-vitro release results suggested the mechanism of drug release was Fickian-diffusion type. The clarity, pH, refractive index, surface tension and viscosity of the suspensions of DEX-CS-NPs were found promising for ocular use. Stability study on nanoparticles revealed no significant changes were observed in particle-size, encapsulation, drug release and physicochemical characteristics at 25°C for 3-months storage.

Part II: Enhancement of transcorneal delivery of gatifloxacin by solid lipid nanoparticles in comparison to commercial aqueous eye drops.

This study describes corneal permeation of gatifloxacin from solid lipid nanoparticle (SLN) through the cornea and its effect on corneal hydration level. The aqueous humor levels of gatifloxacin after single topical instillation in Gate(®) Eyedrops and positively charged SLN-C were determined. A 3.37-fold increase in the relative bioavailability was observed with the SLN-C (AUC0→∞ 2.192 μg mL(-1) h) (AUC, area under the curve) as compared to Gate(®) Eyedrops (AUC0→∞ 0.651 μg mL(-1) h). The t1/2 of drug in SLN-C exhibited a 2.34-fold higher than Gate(®) Eyedrops seem to be significantly increased (p > 0.05), Cmax of gatifloxacin from SLN-C showed 1.09-fold higher concentration as compared to Gate(®) Eyedrops. The results suggested that SLNs could enhance ocular bioavailability of gatifloxacin and prolong its residence time in the eyes. Moreover, no signs of ocular irritation were seen with the SLN formulations, indicating their relative safety compared to the marketed drops.

Part I: Development and optimization of solid-lipid nanoparticles using Box–Behnken statistical design for ocular delivery of gatifloxacin†

This study aims to improve gatifloxacin bioavailability to the eye using solid-lipid nanoparticles (SLN). Cationic SLNs were prepared by o/w-microemulsion method using stearylamine. The generated formulations were optimized by three-factor, three-level Box-Behnken statistical design. The independent variables were the lipid(mix) concentration (X1), poloxamers-188 (X2), and sodium-taurocholate (X3), while the dependent variables were drug release (Y1), encapsulation efficiency (EE) (Y2), and particle size (Y3 ) with applied constraints of maximizing drug release and EE and minimizing particle size. Response surface plots were drawn, statistical validity of the polynomials was established, optimized formulations were selected by feasibility and grid search, and the optimization process was validated. Particle size, polydispersity index, and zeta-potentials were measured by photon correlation spectroscopy. Particles morphology was evaluated by transmission electron microscopy. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WXRD) studies were performed to characterize state of drug and lipid modification. SLN size was (250-305 nm) and zeta-potential (29-36 mV) after 3-month storage. Entrapment efficiencies were 46.58 and 78.55%, and loading efficiencies were 29.60 and 20.70 for SLN-C and SLN-D, respectively. DSC and WXRD analyses showed low-crystalline SLN and amorphous drug dispersion in SLN. In vitro release data were fitted to release kinetics equations, where the release pattern was found to follow Korsmeyer-Peppas model.

Optimizing indomethacin-loaded chitosan nanoparticle size, encapsulation, and release using Box–Behnken experimental design

Indomethacin chitosan nanoparticles (NPs) were developed by ionotropic gelation and optimized by concentrations of chitosan and tripolyphosphate (TPP) and stirring time by 3-factor 3-level Box-Behnken experimental design. Optimal concentration of chitosan (A) and TPP (B) were found 0.6mg/mL and 0.4mg/mL with 120min stirring time (C), with applied constraints of minimizing particle size (R1) and maximizing encapsulation efficiency (R2) and drug release (R3). Based on obtained 3D response surface plots, factors A, B and C were found to give synergistic effect on R1, while factor A has a negative impact on R2 and R3. Interaction of AB was negative on R1 and R2 but positive on R3. The factor AC was having synergistic effect on R1 and on R3, while the same combination had a negative effect on R2. The interaction BC was positive on the all responses. NPs were found in the size range of 321-675nm with zeta potentials (+25 to +32mV) after 6 months storage. Encapsulation, drug release, and content were in the range of 56-79%, 48-73% and 98-99%, respectively. In vitro drug release data were fitted in different kinetic models and pattern of drug release followed Higuchi-matrix type.

The potential application of hyaluronic acid coated chitosan nanoparticles in ocular delivery of dexamethasone.

This study investigates in-vitro transcorneal permeation on excised-rabbit cornea and its effect on corneal hydration-level, in-vivo ocular irritation, tear and aqueous humor dexamethasone-sodium-phosphate (DEX) concentration after topical administration of chitosan-nanoparticles (CS-NPs), hyaluronan-coated-CS-NPs (HA-CS-NPs) and DEX-aqueous-solution in rabbit eyes. The permeation parameters and irritation results indicated the ocular safety of NPs. The developed UPLC-method was successfully applied for DEX quantification in tears and aqueous-humors. Tear samples were collected and DEX-concentration was analyzed by UPLC. A statistically significantly (p<0.05) high DEX-concentration in the inferior conjunctival-sulcus from NPs treated eyes was found as compared to DEX-solution treated eyes. Similarly, DEX-concentration in aqueous-humor was estimated. The drug was detected sufficiently high in aqueous-humor till 24h following topical administration of NPs. The NPs have shown significantly (p<0.05) higher bioavailability of DEX compared to DEX-solution. About 1.83- and 2.14-fold higher AUC0-24h was observed with the CS-NPs and HA-CS-NPs, respectively compared to DEX-solution. The reason for higher tear concentration and higher bioavailability of DEX from uncoated and HA-coated CS-NPs was assumed due to their prolonged precorneal-retention because of highly mucoadhesive characteristics of CS and HA. Moreover, presence of HA on CS-NPs, speed-up cellular-uptake by receptor-mediated-endocytosis could be another reason for enhanced bioavailability.

Delivery of gatifloxacin using microemulsion as vehicle: formulation, evaluation, transcorneal permeation and aqueous humor drug determination.

Abstract The successful ophthalmic delivery system is reliant on the diminution in the precorneal loss of drugs by increasing the corneal contact time and increasing the transcorneal permeability, which may enhance the bioavailability of drug to the eyes. The objective of this investigation was to develop and evaluate the potential of microemulsions of gatifloxacin with respect to the conventional eye drops of gatifloxacin. Oil-in-water microemulsions were prepared with different concentrations of oil, surfactant and co-surfactant using aqueous titration method. All formulations showed circular shape droplets, displayed an average droplet size ranged between 51 and 74 nm and absolute zeta potential values ranged from 15 to 24 mV, with optimum physicochemical characteristics suitable for eye. The optimized microemulsion possessed good stability, showed greater adherence to corneal surface and good permeation of gatifloxacin in the anterior chamber of the eye, resulting in a twofold increase in gatifloxacin concentration than the conventional dosage form. Hence, the optimized microemulsions showed increased intraocular penetration and enhance ocular bioavailability of gatifloxacin.

Effect of cryoprotection on particle size stability and preservation of chitosan nanoparticles with and without hyaluronate or alginate coating

The aim of the present study was to determine the effect of different cryoprotectants and their concentration on the physicochemical characteristics of chitosan nanoparticles (CS-NPs). The effect of coating of CS-NPs with hyaluronic acid (HA) and alginic acid (ALG) before and after lyophilization was also evaluated. The ionic gelation method was used for the preparation of NPs and six different types of cryoprotectants (sucrose, glucose, trehalose, mannitol, polyethylene glycol-2000, and polyethylene glycol-10,000) were investigated at 5%, 10%, 20%, and 50% concentration levels. Coating of CS-NPs with HA and their protection with high amount of cryoprotectants indicated better particle size stability. Samples that were lyophilized without cryoprotectants resulted in an increase in average size due to high agglomeration. All cryoprotectants with varying amount provided some sort of size stability for the NPs except for the PEG-10,000 which had no protective effect at higher concentrations. Sucrose and trehalose sugars were found to have the highest protective effect with HA coated and uncoated CS-NPs. In conclusion, using cryoprotectants along with surface coating, the CS-NPs could achieve the desired physicochemical characteristics for a prolonged duration.

Biological investigation of a supersaturated self-nanoemulsifying drug delivery system of Piper cubeba essential oil

Piper cubeba essential oil (PCEO) is used in many ailments but its mechanism of action is not very well reported especially in the case of pain and inflammation. Therefore, in this work, the mechanism of its anti-inflammatory activity alone and as a supersaturated self-nanoemulsifying drug delivery system (S-SNEDDS) was evaluated. S-SNEDDS formulations of PCEO were developed by an aqueous phase titration method. Thermodynamically stable S-SNEDDSs were characterized based on their droplet size, polydispersity index, zeta potential, viscosity, refractive index, % transmittance and surface morphology. Based on the best physicochemical parameters, the S-SNEDDS F1 was selected for biological investigations in rats. The dose of pure PCEO was 400 mg kg−1 body weight while the S-SNEDDS F1 was administered in two different doses i.e. 40 mg kg−1 and 80 mg kg−1 body weight. The results of this work indicated that pretreatment of PCEO and the S-SNEDDS F1 reduced the exudate volume and polymorphonuclear cell number significantly. Moreover, the levels of MPO, NO and proinflammatory cytokines (TNF-α and IL-β) were also reduced by PCEO and the S-SNEDDS F1 and this observation was also supported by histological observation. The results of the S-SNEDDS F1 were superior compared to PCEO alone even at significantly lower doses. These results indicate the potential of a developed S-SNEDDS in enhancing the therapeutic efficacy of PCEO.

Oral bioavailability enhancement and hepatoprotective effects of thymoquinone by self-nanoemulsifying drug delivery system

Thymoquinone (TQ) is a poorly water soluble bioactive compound which shows poor oral bioavailability upon oral administration. Due to poor aqueous solubility and bioavailability of TQ, various self-nanoemulsifying drug delivery systems (SNEDDS) of TQ were developed and evaluated for enhancement of its hepatoprotective effects and oral bioavailability. Hepatoprotective and pharmacokinetic studies of TQ suspension and TQ-SNEDDS were carried out in rat models. Different SNEDDS formulations of TQ were developed and thermodynamically stable TQ-SNEDDS were characterized for physicochemical parameters and evaluated for drug release studies via dialysis membrane. Optimized SNEDDS formulation of TQ was selected for further evaluation of in vivo evaluation. In vivo hepatoprotective investigations showed significant hepatoprotective effects for optimized TQ-SNEDDS in comparison with TQ suspension. The oral administration of optimized SNEDDS showed significant improvement in in vivo absorption of TQ in comparison with TQ suspension. The relatively bioavailability of TQ was enhanced 3.87-fold by optimized SNEDDS in comparison with TQ suspension. The results of this research work indicated the potential of SNEDDS in enhancing relative bioavailability and therapeutic effects of natural bioactive compounds such as TQ.