Pyrazinoic acid-Poly(malic acid) biodegradable nanoconjugate for efficient intracellular delivery

Poly(malic acid) Nanoconjugates of Pyrazinoic Acid for Lung Delivery in the Treatment of Tuberculosis

Tuberculosis (TB) remains a major global infection, and TB treatments could be improved by site-specific targeting with delivery systems that allow tissue and cell uptake. To increase the drug concentration at the target sites following lung delivery, polymeric nanoconjugates based on biodegradable poly(malic acid) were designed. Pyrazinoic acid (POA), the active moiety of pyrazinamide─a first-line antituberculosis drug─was covalently bound to poly(malic acid) using a hydrophobic linker at mole ratios of 25%, 50%, and 75%. Three linkers, hexanediol, octanediol, and decanediol, were considered. Independently of the linker or ratio, all the conjugates were able to self-assemble, forming nanoconjugates (NCs) in water with 130-190 nm in diameter. Pyrazinoic acid could be released in a controlled manner without any burst release effect. Its kinetics can be adjusted by modifying the grafting ratio and linker length. No cytotoxicity was observed on RAW 264.7 macrophages up to ∼14 μg/mL of POA. In addition, the nanoconjugates were efficiently taken up by these cells over 5 h. Thanks to their high loading capacity and modulable release profiles, these nanoconjugates hold great promise for more effective treatment of tuberculosis.

Poly(malic acid)-budesonide nanoconjugates embedded in microparticles for lung administration

To improve the therapeutic activity of inhaled glucocorticoids and reduce potential side effects, we designed a formulation combining the advantages of nanoparticles, which have an enhanced uptake by alveolar cells, allow targeted delivery and sustained drug release, as well as limited drug systemic passage, with those of microparticles, which display good alveolar deposition. Herein, a polymer-drug conjugate, poly(malic acid)-budesonide (PMAB), was first synthesized with either 11, 20, 33, or 43 mol% budesonide (drug:polymer from 1:8 to 3:4), the drug creating hydrophobic domains. The obtained conjugates self-assemble into nanoconjugates in water, yielding excellent drug loading of up to 73 wt%, with 80-100 nm diameters. In vitro assays showed that budesonide could be steadily released from the nanoconjugates, and the anti-inflammatory activity was preserved, as evidenced by reduced cytokine production in LPS-activated RAW 264.7 macrophages. Nanoconjugates were then embedded into microparticles through spray-drying with L-leucine, forming nano-embedded microparticles (NEMs). NEMs were produced with an aerodynamic diameter close to 1 µm and a density below 0.1 g.cm-3, indicative of a high alveolar deposition. NEMs spray-dried with the less hydrophobic nanoconjugates, PMAB 1:4, were readily dissolved in simulated lung fluid and were chosen for in vivo experiments to study pharmacokinetics in healthy rats. As it was released in vivo from NEMs, sustained distribution of budesonide was obtained for 48 h in lung tissue, cells, and lining fluid. With high loading rates, modulable release kinetics, and low cytotoxicity, these nanoconjugates delivered by NEMs are promising for the more efficient treatment of pulmonary inflammatory diseases.

Kinetic Modelling of the Coproduction Process of Fumaric and Malic Acids by Rhizopus arrhizus NRRL 1526

The production of organic acids by biotechnological processes has experienced a notable impulse with the advent of first and second generation biorefineries and the need of searching for renewable and sustainable feedstock, such as biomass. Fumaric acid is a promising biomonomer for polyamide production and a well-known acidulant and preservative in food and feed industries. Malic acid is a well-known food acidulant with a high market share. The biotechnological Fumaric and Malic acid production via fungi of the Rhizopus genus is being explored nowadays as a process for the valorization of food and food-related waste to obtain food ingredients and key platform chemicals of the so-called biochemical biorefinery. In this work, a preliminary study is performed to find reproducible conditions for the production of the acids by Rhizopus arrhizus NRRL 1526 by controlling fungi morphology and inoculum conditions. Afterwards, several production runs are performed to obtain biomass, glucose, and acid concentration data at different processing time values. Finally, an unstructured, unsegregated model including a logistic-type equation for biomass and potential-type equations for the substrate and the products is fitted to experimental data. We find that the production of the organic acids is mainly non-associated with fungal growth.