Safety of nanosuspensions in drug delivery

A reversible decomposition approach for the formation of injectable, excipient-free, self-assembling nanocrystals

A chemical procedure to generate excipient-free SN38 nanocrystals with greater efficacy and less toxicity than CPT-11.

Silver sulfadiazine nanosuspension-loaded thermosensitive hydrogel as a topical antibacterial agent

Background

Silver sulfadiazine (AgSD) is widely employed as an antibacterial agent for surface burn management. However, the antibacterial activity of AgSD was restrained because of the lower drug solubility and possible cytotoxicity.

Objective

This study aimed to formulate stable silver sulfadiazine/nanosuspensions (AgSD/NSs) with improved AgSD solubility and prepare a suitable carrier for AgSD/NS delivery. Nanotechnology was used to overcome the low drug dissolution rate of AgSD, while the new carrier loaded with AgSD/NS was assumed to decrease the possible cytotoxicity, enhance antibacterial activity, and promote wound healing.

Methods

AgSD/NSs were prepared by high pressure homogenization method. Poloxamer 407-based thermoresponsive hydrogels were prepared by cold method as carriers of AgSD/NS to obtain AgSD/NS-loaded thermoresponsive hydrogel. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to measure the physicalchemical properties of AgSD/NSs and AgSD/NS-loaded gel. The cytotoxicity of the AgSD/NS-loaded gel was evaluated using methyl thiazolyltetrazolium assay with L929 mouse fibroblast cell lines. In vitro antibacterial activities of AgSD/NSs and AgSD/NS loaded gel were also measured.

Results

Stable AgSD/NSs with an average particle size of 369 nm were formulated while 1.5% P407 was selected as a stabilizer. The optimized AgSD/NS thermoresponsive hydrogel exhibited the gelation temperature of approximately 30°C. A significant improvement in solubility was observed for AgSD nanoparticles (96.7%) compared with AgSD coarse powders (12.5%). The results of FTIR and XRD revealed that the physicochemical properties of AgSD/NS were reserved after incorporating into the hydrogel. The cell viability after incubation with AgSD/NS-loaded thermoresponsive hydrogel improved from 60.7% to 90.6% compared with incubation with AgSD/NS directly. Drug release profiles from the thermoresponsive hydrogel increased compared with the commercial AgSD cream, implying less application frequency of AgSD cream clinically. In vitro antibacterial studies manifested that AgSD nanocrystallization significantly enhanced the antibacterial activity compared with the AgSD coarse powder.

Conclusion

The combination of AgSD nanosuspensions and thermoresponsive hydrogel effectively improved the AgSD antibacterial activity and decreased the cytotoxicity. This study also suggested that a poloxamer thermoresponsive hydrogel could be used as a delivery system for other nanocrystals to decrease possible nanotoxicity.

Comb-like PEG-containing polymeric composition as low toxic drug nanocarrier

BACKGROUND

Development of biocompatible multifunctional polymeric drug carriers is crucial in modern pharmaceutics aimed to create "smart" drugs. The high potential of the PEGylated comb-like polymeric nanocarrier (PNC) in delivering both traditional and experimental drugs to tumor cells in vitro and in vivo has been demonstrated previously. In the present study, we investigated the general toxicity of polyethylene glycol (PEG) processed with both covalent and non-covalent attachments of PEG to compose a comb-like polymer that behaves like a simple chain of n monomers decorated with swollen side chains. The PNC possesses properties of a water-soluble surfactant containing methyl-terminated PEG side branches in some monomer units attached covalently to the carbon chain backbone.

RESULTS

We have demonstrated that the synthesized PNC possesses weak toxic effects toward human leukemia cells (HL-60 and Jurkat lines), as well as toward hepatocellular (HepG2), colon (HCT116) and breast (MCF-7) tumor cell lines. Additionally, after a long period (20 days) of intraperitoneal administration, the PNC had no significant toxic effects in laboratory white mice (470 mg/kg body mass in 1 ml) and Wistar rats (440 mg/kg body mass in 10 ml).

CONCLUSION

The developed PNC we studied can be qualified as a compound of grade 4 toxicity (low toxicity substance). The reduced toxicity of this PNC in combination with its improved bioavailability and previously detected capability to enhance cytotoxicity toward tumor cells in vitro and potential tumor treatment effects in vivo suggests its potential as a safe drug delivery platform for treating various diseases, especially cancer.

A novel albumin wrapped nanosuspension of meloxicam to improve inflammation-targeting effects

Background

The objective of this study was to develop a more bio-available and safe nanosuspension of meloxicam (MX), which could dramatically improve inflammation targeting.

Methods and results

MX-loaded bovine serum albumin (BSA) nanosuspensions were prepared using acid–base neutralization in aqueous solution and the prepared nanosuspensions were characterized. The results obtained showed that the prepared nanosuspensions had a narrow size distribution with a mean particle size of 78.67±0.22 nm, a polydispersity index of 0.133±0.01, and a zeta potential of −11.87±0.91 mV. The prepared MX nanosuspensions were spherically wrapped by BSA with a smooth surface as shown by transmission electron microscopy. Stability studies showed that the nanosuspensions were physically stable at 4°C with a shelf life of at least 6 months. In the in vitro dissolution test, the MX-loaded BSA nanosuspension (MX-BSA-NS) exhibited sustained release. In addition, an in vivo pharmacokinetic study in rats following intravenous injection showed that the half-life (t_1/2), mean residence time (MRT), and area under the concentration–time curve (AUC_0–∞) of MX-BSA-NS was increased by 169.83%, 150.13%, and 148.80%, respectively, in comparison with MX conventional solution (MX solution). Furthermore, results from inflammation targeting studies showed that the concentration of MX increased significantly in inflamed tissues but was reduced in normal tissues compared with the MX solution group after injection of MX-BSA-NS.

Conclusion

The prepared MX-BSA-NS significantly increased the inflammation-targeting properties and bioavailability of MX, suggesting its potential as a promising formulation for the targeted drug delivery of MX in future clinical applications.

Nanosuspensions of a new compound, ER-β005, for enhanced oral bioavailability and improved analgesic efficacy

Estrogen receptor-β005 (ER-β005) is a novel compound developed by our group; however, its application has been greatly hindered due to its low solubility. A nanosuspension of insoluble drugs is a nanoscale colloidal dispersion that has extremely higher drug-loading compared with other nanomedicines. In this study, nanosuspensions of ER-β005 (Nano-ER-β005) stabilized by a food protein, β-casein (β-CN), were prepared via an antisolvent-precipitation method to improve oral absorption and thus promote therapeutic efficacy. Nano-ER-β005, which has a diameter of 110nm and drug-loading of 50%, was developed. Analyses of fluorescence and circular dichroism (CD) spectra demonstrated a strong interaction between β-CN and drug particles in Nano-ER-β005, indicating that β-CN is a potent nanosuspension stabilizer. The oral bioavailability of Nano-ER-β005 was 1.6-fold greater than that of raw drug particles. Additionally, ER-β005 was confirmed to have a strong therapeutic effect against pain reactions in animal models, and inhibition of this effect was significantly increased with Nano-ER-β005 treatment. In conclusion, by using β-CN as a stabilizer, nanosuspensions of ER-β005 were developed and oral absorption was enhanced. Moreover, ER-β005 is a powerful drug that inhibits pain reactions, and its therapeutic efficacy was markedly increased in the Nano-ER-β005.

Feasibility of USPIOs for T1-weighted MR molecular imaging of tumor receptors

USPIOs having a superior T₁ contrast effect could only be used for T₂-weighted, but not for T₁-weighted MR tumor receptor imaging.