Advances in nanoparticle and organic formulations for prolonged controlled release of auxins

Plant hormones have been well known since Charles Darwin as signaling molecules directing plant metabolism. Their action and transport pathways are at the top of scientific interest and were reviewed in many research articles. Modern agriculture applies phytohormones as supplements to achieve desired physiological plant response. Auxins are a class of plant hormones extensively used for crop management. Auxins stimulate the formation of lateral roots and shoots, seed germination, while extensively high concentrations of these chemicals act as herbicides. Natural auxins are unstable; light or enzyme action leads to their degradation. Moreover, the concentration dependant action of phytohormones denier one-shot injection of these chemicals and require constant slow additive of supplement. It obstructs the direct introduction of auxins. On the other hand, delivery systems can protect phytohormones from degradation and provide a slow release of loaded drugs. Moreover, this release can be managed by external stimuli like pH, enzymes, or temperature. The present review is focused on three auxins: indole-3-acetic, indole-3-butyric, and 1-naphthaleneacetic acids. We collected some examples of inorganic (oxides, Ag, layered double hydroxides) and organic (chitosan, organic formulations) delivery systems. The action of carriers can enhance auxin effects via protection and targeted delivery of loaded molecules. Moreover, nanoparticles can act as nano fertilizers, intensifying the phytohormone effect, providing slow controlled release. So delivery systems for auxins are extremely attractive for modern agriculture opening sustainable management of plant metabolism and morphogenesis.

One-pot synthesis of acid-degradable polyphosphazene prodrugs for efficient tumor chemotherapy

In order to improve the therapeutic efficacy and reduce the side effects of anticancer drugs, stimuli-responsive and biodegradable drug-delivery systems have attracted significant attention in the past three decades. Herein, we report acid-responsive and degradable polyphosphazene nano-prodrugs synthesized via a one-pot cross-linking reaction of 4-hydroxybenzhydrazide-modified doxorubicin (BMD) with hexachlorocyclotriphosphazene (HCCP). The phenol groups in the as-synthesized BMD exhibited a high reactivity towards HCCP and in the presence of a basic catalyst the determined drug loading ratio of the nanoparticles, denoted as HCCP-BMD, was up to 85.64%. Interestingly, the hydrazone bonds in BMD and the skeleton of polyphosphazene tended to break down in acidic environments, and the antitumor active drug DOX was found to be released in an acidic tumor microenvironment (pH ∼ 6.8 for extracellular, and pH ∼ 5.0 for endosomes and lysosomes). The resulting HCCP-BMD prodrug exhibited high cytotoxicity to HeLa cells and could effectively suppress tumor growth, with negligible damage to normal tissues. We therefore believe that this acid- degradable polyphosphazene prodrug may offer great potential in various biomedical fields.

Soluplus-Mediated Diosgenin Amorphous Solid Dispersion with High Solubility and High Stability: Development, Characterization and Oral Bioavailability

Background and Purpose

The traditional Chinese medicine, diosgenin (Dio), has attracted increasing attention because it possesses various therapeutic effects, including anti-tumor, anti-infective and anti-allergic properties. However, the commercial application of Dio is limited by its extremely low aqueous solubility and inferior bioavailability in vivo. Soluplus, a novel excipient, has great solubilization and capacity of crystallization inhibition. The purpose of this study was to prepare Soluplus-mediated Dio amorphous solid dispersions (ASDs) to improve its solubility, bioavailability and stability.

Methods

The crystallization inhibition studies were firstly carried out to select excipients using a solvent shift method. According to solubility and dissolution results, the preparation methods and the ratios of drug to excipient were further optimized. The interaction between Dio and Soluplus was characterized by differential scanning calorimetry (DSC), fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (PXRD) and molecular docking. The pharmacokinetic study was conducted to explore the potential of Dio ASDs for oral administration. Furthermore, the long-term stability of Dio ASDs was also investigated.

Results

Soluplus was preliminarily selected from various excipients because of its potential to improve solubility and stability. The optimized ASDs significantly improved the aqueous solubility of Dio due to its amorphization and the molecular interactions between Dio and Soluplus, as evidenced by dissolution test in vitro, DSC, FT-IR spectroscopy, SEM, PXRD and molecular docking technique. Furthermore, pharmacokinetic studies in rats revealed that the bioavailability of Dio from ASDs was improved about 5 times. In addition, Dio ASDs were stable when stored at 40°C and 75% humidity for 6 months.

Conclusion

These results indicated that Dio ASDs, with its high solubility, high bioavailability and high stability, would open a promising way in pharmaceutical applications.

Acid-Responsive and Biologically Degradable Polyphosphazene Nanodrugs for Efficient Drug Delivery

To enhance the therapeutic effects and reduce the damage to normal tissues in cancer chemotherapy, it is indispensable to develop drug delivery carriers with controllable release and good biocompatibility. In this work, acid-responsive and degradable polyphosphazene (PPZ) nanoparticles were synthesized by the reaction of hexachlorotripolyphosphonitrile (HCCP) with 4-hydroxy-benzoic acid (4-hydroxy-benzylidene)-hydrazide (HBHBH) and anticancer drug doxorubicin (DOX). The controlled release of DOX could be realized based on the acid responsiveness of acylhydrazone in HBHBH. Experimental results showed that polyphosphazene nanoparticles remained stable in the body's normal fluids (pH ∼ 7.4), while they were degraded and controllable release of DOX in an acidic environment such as tumors (pH ∼ 6.8) and lysosome and endosome (∼5.0) in cancer cells In particular, the doxorubicin (DOX)-loading ratio was fair high and could be tuned from 10.6 to 52.6% by changing the dosing ratio of DOX to HBHBH. Meanwhile, the polyphosphazene nanodrugs showed excellent toxicity to tumor cells and reduced the side effect to normal cells both in vitro and in vivo due to their enhanced permeability and retention (EPR) effect and pH-sensitive degradation properties. Therefore, the constructed pH-sensitive drug delivery system has great potential for cancer chemotherapy.