Understanding the kinetic mixing between liquid crystalline nanoparticles and agrochemical actives.

The use of liquid crystalline nanoparticles as potential agrochemical delivery agents or adjuvant systems is gaining traction due to the possibility that the systems can enhance penetration of the active and increase adhesion of the formulation to the leaf, increasing overall efficacy and decreasing the harmful environmental impact. However the interaction between liquid crystalline nanoparticles and active products is not well understood. Using small angle X-ray scattering we investigated the structural changes that occur to liquid crystalline nanoparticles upon addition of three common herbicides, 2,4-D 2-ethylhexyl ester, bromoxynil octanoate and haloxyfop-p-methyl ester active agrochemicals in the form of emulsions. It was found that the hydrophobic herbicides induced structural changes to varying degrees when pre-mixed with liquid crystalline forming lipids (phytantriol and glycerol monooleate) and also during dynamic mixing as emulsions.

Correction to: Lessons learned in the development of sustained release penicillin drug delivery systems for the prophylactic treatment of rheumatic heart disease (RHD).

Jürgen B. Bulitta's name was misspelled in the original version of the article. It is correct as reflected here. The original article has been revised.

Lessons learned in the development of sustained release penicillin drug delivery systems for the prophylactic treatment of rheumatic heart disease (RHD).

The current prophylactic treatment to prevent rheumatic heart disease requires four-weekly intramuscular injection of a suspension of the poorly soluble benzathine salt form of penicillin G (BPG) often for more than 10 years. In seeking to reduce the frequency of administration to improve adherence, biodegradable polymer matrices have been investigated. Poly(lactide-co-glycolide) (PLGA)-based in situ forming precursor systems containing N-methyl-2-pyrrolidone as solvent and PLGA-based monolithic implants for surgical implantation containing BPG were developed. Long-term release studies indicated low and plateaued release of penicillin G, but continual favourable release profiles for the benzathine counterion, indicating degradation of the polymer and generation of acidic microenvironment being detrimental to penicillin stability. In order to avoid the issue of the acidic product, poly(caprolactone)(PCL) implants were also investigated, with favourable penicillin G release behaviour being achieved, and slow release over 180 days. However, when taking into account the mass of polymer, and the total dose of drug calculated from literature pharmacokinetic parameters for penicillin G, we concluded that an implant size of over 7 g would still be required. This may preclude clinical deployment of a polymer matrix type delivery system for this indication in children and adolescents. Therefore, we have learned that biodegradable PLGA-type systems are not suitable for development of sustained release BPG treatments and that although the PCL system provides favourable release behaviour, the total size of the implant may still present a hurdle for future development.

Tristearin as a Model Cuticle for High-Throughput Screening of Agricultural Adjuvant Systems.

The widely varied compositions and structures of plant cuticles create problems in the identification of suitable model systems for laboratory testing of adjuvants. We have compared the behavior of an extracted cuticle wax with tristearin, a well characterized crystalline triglyceride, which we propose as a model cuticle for ranking new adjuvant systems for their propensity to disrupt the cuticle barrier. The interaction of adjuvant products and their components with the extracted cuticle wax and tristearin was determined using differential scanning calorimetry and small angle X-ray scattering approaches. The interaction of the additive with tristearin caused a concentration-dependent change in the crystallite level, and correlated between the extracted wax and tristearin. Tristearin was subsequently used to compare the effectiveness of a range of adjuvant products and their major components. This approach has utility to quantify the effects of adjuvant components and enable more judicious selection of adjuvant candidates to progress to plant trials.

Kinetic Resolution of the Interactions between Agrochemical Products and Adjuvant Systems upon Mixing.

The addition of an adjuvant to a pesticide usually occurs in a mix-tank, before spray application to the crop. Their interaction is potentially crucial to overall efficacy but has received little attention from a physical-chemical perspective. Study was undertaken by laser diffraction, Raman spectroscopy, and small-angle X-ray scattering to resolve these physical processes. It was shown that migration of the pesticide into the adjuvant droplet occurred in all cases studied. The level of transfer was dependent upon adjuvant level, adjuvant solubility, and surfactant level. For suspension pesticides, dissolution of crystallites within the droplet occurred to a degree limited by solubility. The results directly demonstrate the transfer of the pesticide into the adjuvant carrier. This indicates that for emulsion-based pesticides, application to the target is likely as a homogeneously mixed droplet, whereas for suspension pesticides, solubility may limit transfer and dissolution, leading to heterogeneity in the applied particles.

Fast, long-range electron-transfer reactions of a "blue" copper protein coupled non-covalently to an electrode through a stilbenyl thiolate monolayer.

A self-assembled monolayer (SAM), formed by the insitu saponification of a stilbenyl thioacetate on a gold electrode, yields fast electron transfer (ET)(the exchange rate at zero driving force exceeds 1600 s-1) with adsorbed molecules of the blue copper protein, azurin, over a distance exceeding 15 angstroms .