Development, Characterization, and Evaluation of SLN-Loaded Thermoresponsive Hydrogel System of Topotecan as Biological Macromolecule for Colorectal Delivery

BACKGROUND

Chemotherapeutic drugs cause severe toxicities if administered unprotected, without proper targeting, and controlled release. In this study, we developed topotecan- (TPT-) loaded solid lipid nanoparticles (SLNs) for their chemotherapeutic effect against colorectal cancer. The TPT-SLNs were further incorporated into a thermoresponsive hydrogel system (TRHS) (TPT-SLNs-TRHS) to ensure control release and reduce toxicity of the drug. Microemulsion technique and cold method were, respectively, used to develop TPT-SLNs and TPT-SLNs-TRHS. Particle size, polydispersive index (PDI), and incorporation efficiency (IE) of the TPT-SLNs were determined. Similarly, gelation time, gel strength, and bioadhesive force studies of the TPT-SLNs-TRHS were performed. Additionally, in vitro release and pharmacokinetic and antitumour evaluations of the formulation were done.

RESULTS

TPT-SLNs have uniformly distributed particles with mean size in nanorange (174 nm) and IE of ~90%. TPT-SLNs-TRHS demonstrated suitable gelation properties upon administration into the rat's rectum. Moreover, drug release was exhibited in a control manner over an extended period of time for the incorporated TPT. Pharmacokinetic studies showed enhanced bioavailability of the TPT with improved plasma concentration and AUC. Further, it showed significantly enhanced antitumour effect in tumour-bearing mice as compared to the test formulations.

CONCLUSION

It can be concluded that SLNs incorporated in TRHS could be a potential source of the antitumour drug delivery with better control of the drug release and no toxicity.

Assessment of thyroid function in pesticide formulators

Thirty male pesticide formulators exposed to the dust and liquid formulation of endosulfan, quinalphos, chlorpyriphos, monocrotophos, lindane, parathion, phorate, and fenvalerate and 20 comparable control subjects from the same area of study were examined for the evaluation of thyroid function tests. The level of TSH was elevated (about 28%) in pesticide formulators as compared to a control group, but the increase was statistically insignificant. Based on the individual TSH measurement, 3 of 30 formulators had isolated elevated levels of TSH and seem to have acquired sub-clinical hypothyroidism; five had TSH values slightly elevated to the upper boarder line (4.03 muIU/ml); and the majority of formulators (N= 22) had TSH values in the normal range varying from 1.29 to 3.9 muIU/ml. Total T3 was suppressed significantly (P< 0.01) in formulators, while marginal decrease (about 7%) was noticed in T4 level. This study indicated thyroid function impairment in few pesticide formulators.

A simple chemical method for the oxidation of beta-hydroxybutyrate; application of the method for the estimation of ketone bodies

A simple one-step method employing potassium persulphate as an oxidising agent in presence of catalyst, Ag2+, for the oxidation of beta-hydroxybutyrate (beta-OHB) to acetoacetate (AcAc) has been developed and standardized. Under the condition of assay, beta-OHB (0.079-0.395 microM) was quantitatively transformed to AcAc. The reaction linearity was observed from 0.079 to 0.634 microM. Optimum conditions were: pH, 6.2; temp., 40 degrees C; persulphate saturation, 40% and catalyst, 1.82 mM. Under the experimental condition, no reversal of inhibition caused by chloride (22.96 mM) was observed at Ag+ concentrations (9.09 and 18.18 mM), while higher conc. of Ag+ (27.27 mM) caused significant reversal of inhibition (about 60%). The maximum reversal of inhibition was achieved at Ag+ (36.36 mM). The level of ketone bodies, when estimated by the present method, was greatly enhanced during starvation period and about 2- and 12-fold higher level of ketone bodies was observed (compared to control) in rats fasted for 24 and 48 hr respectively.

Spectral evidence for the oxidation of beta-hydroxybutyrate to acetoacetate: diminution of spectra by glucose and chloride

Chemical oxidation of beta-hydroxybutyrate (beta-OHB) to acetoacetate (AcAc) has been carried out by a simple and new method employing potassium persulphate as an oxidising agent. Under the conditions of assay, beta-OHB (0.079-0.395 microM) was instantaneously oxidised to AcAc and the authenticity of the oxidised product was proved by absorption spectroscopy. A common absorption maxima at about 446 nm was observed in all the spectra recorded for the product (AcAc-complex) obtained after the oxidation of beta-OHB (0.079-0.395 microM) to AcAc followed by coupling with diazotized p-nitroaniline. This absorption maxima was almost equal to that obtained for AcAc-complex using AcAc as reference standard. It implies that AcAc formed by the chemical oxidation of beta-OHB is identically similar to the AcAc used as reference standard for the study. This fact was further strengthened when absorption spectra, recorded either individually or in combination (mixed-type), exhibited a single peak with a common absorption maxima at about 446 nm. Absorption spectra was found to be partially diminished by glucose (1.77 microM) and chloride (17.1 microM), while almost complete diminution of absorption spectra was observed at higher concentration of glucose (8.88 microM) and chloride (51.3 microM).

Colorimetric assay of 2,2-bis(4-chlorophenyl)acetic acid (DDA) in urine

2,2-Bis(4-chlorophenyl) acetic acid (DDA) was extracted from acidified urine at pH 2 by benzene. It was complexed by partitioning with crystal violet in acetic to yield a blue color which was quantitated at 610 nm. Its identity was confirmed by paper chromatographic separation. The DDA excretion in nine subjects ranged from 0.024 to 0.130 microgram/ml with a mean of 0.065 while that determined by gas chromatography ranged from 0.038 to 0.120 with a mean of 0.069.