Trunk Injection of Citrus Trees with a Polymeric Nanobactericide Reduces Huanglongbing Severity Caused by Candidatus Liberibacter asiaticus

Huanglongbing (HLB) is a disease caused by the phloem- limited Candidatus Liberibacter asiaticus (CLas) that affects the citrus industry worldwide. To date, only indirect strategies have been implemented to eradicate HLB. Included among these is the population control of the psyllid vector (Diaphorina citri), which usually provides inconsistent results. Even though strategies for direct CLas suppression seem a priori more promising, only a handful of reports have been focused on a confrontation of the pathogen. Recent developments in polymer chemistry have allowed the design of polycationic self-assembled block copolymers with outstanding antibacterial capabilities. Here, we report the use of polymeric nano-sized bactericide particles (PNB) to control CLas directly in the phloem vasculature. The field experiments were performed in Rioverde, San Luis Potosí, and is one of the most important citrusproducing regions in Mexico. An average 52% reduction in the bacterial population was produced when PNB was injected directly into the trunk of 20 infected trees, although, in some cases, reduction levels reached 97%. These results position PNB as a novel and promising nanotechnological tool for citrus crop protection against CLas and other related pathogens.

Thermo-responsive polymer catalysts for polyester recycling processes: Switching from homogeneous catalysis to heterogeneous separations

Inspired by the endless versatility offered by functional polymer materials in terms of modulating and imprinting diverse chemical, physical, and/or biological properties, we developed and screened a family of polymer...

All-Aqueous, Surfactant-Free, and pH-Driven Nanoformulation Methods of Dual-Responsive Polymer Nanoparticles and their Potential use as Nanocarriers of pH-Sensitive Drugs

All-aqueous, surfactant-free, and pH-driven nanoformulation methods to generate pH- and temperature-responsive polymer nanoparticles (NPs) are described. Copolymers comprising a poly(methyl methacrylate) (PMMA) backbone with a few units of 2-(dimethylamino)ethyl methacrylate (DMAEMA) are solubilized in acidic buffer (pH 2.0) to produce pH-sensitive NPs. Copolymers of different molar mass (2.3-11.5 kg mol^-1 ) and DMAEMA composition (7.3-14.2 mol%) are evaluated using a "conventional" pH-driven nanoformulation method (i.e., adding an aqueous polymer solution (acidic buffer) into an aqueous non-solvent (basic buffer)) and a robotized method for pH adjustment of polymer dispersions. Dynamic light scattering, zeta-potential (ζ), and sedimentation-diffusion analyses suggest the formation of dual-responsive NPs of tunable size (from 20 to 110 nm) being stable for at least 28 days in the pH and temperature intervals from 2.0 to 6.0 and 25 to 50 °C, respectively. Ultraviolet-visible spectroscopic experiments show that these NPs can act as nanocarriers for the pH-sensitive dipyridamole drug, expanding its bioavailability and potential controlled release as a function of pH and temperature. These approaches offer alternative strategies to prepare stimuli-responsive NPs, avoiding the use of harmful solvents and complex purification steps, and improving the availability of biocompatible polymer nanoformulations for specific controlled release of pH-sensitive cargos.

Bioconjugation of papain with poly(N-vinylpyrrolidone): NMR characterization and study of its enzymatic activity

A poly(vinylpyrrolidone) end-functionalized with a carboxylic acid group (PVP–CO2H) was synthesized by reversible addition-fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) polymerization mediated by 4-(O-ethylxanthyl)methyl benzoic acid. The molecular weight of the as-synthesized PVP–CO2H was estimated through UV–vis spectroscopy (Mn(UV–vis) = 7322 g/mol), gel permeation chromatography (GPC) (Mn(GPC) = 8670 g/mol), and 1H NMR, (Mn(NMR) = 8207 g/mol). The values obtained were close with the theoretical molecular weight (Mn(th) = 7925 g/mol). Subsequently, the preformed PVP–CO2H was activated to produce N-succinimidyl poly(vinylpyrrolidone) (PVP–NHS). This precursor was covalently coupled to papain to produce bioconjugate PVP–papain. The functional group modifications in the PVP chain-end were observed by the variations in the chemical shift values by 1H and 13C NMR and FTIR analysis at each step of the synthesis. The molecular weight of the PVP–papain was obtained by SEC–HPLC and suggests that, on average, four or five chains of PVP–CO2H were attached to one papain molecule. Compared with papain, the PVP–papain exhibited significantly improved catalytic activity, pH, and thermal stability. Additionally, the storage studies showed that the catalytic activity of PVP–papain was about 79% versus the native enzyme (29%), and this activity was maintained even when it was stored for 25 days.

Combinations of Antimicrobial Polymers with Nanomaterials and Bioactives to Improve Biocidal Therapies

The rise of antibiotic-resistant microorganisms has become a critical issue in recent years and has promoted substantial research efforts directed to the development of more effective antimicrobial therapies utilizing different bactericidal mechanisms to neutralize infectious diseases. Modern approaches employ at least two mixed bioactive agents to enhance bactericidal effects. However, the combinations of drugs may not always show a synergistic effect, and further, could also produce adverse effects or stimulate negative outcomes. Therefore, investigations providing insights into the effective utilization of combinations of biocidal agents are of great interest. Sometimes, combination therapy is needed to avoid resistance development in difficult-to-treat infections or biofilm-associated infections treated with common biocides. Thus, this contribution reviews the literature reports discussing the usage of antimicrobial polymers along with nanomaterials or other inhibitors for the development of more potent biocidal therapies.

Thermosensitive spontaneous gradient copolymers with block- and gradient-like features

Amphiphilic gradient copolymers with thermoresponsive properties were synthesized in one pot via RAFT copolymerization.

Opportunities for dual RDRP agents in synthesizing novel polymeric materials

Dual RDRP agents provide access to new polymeric materials by combining ATRP, NMP, and RAFT polymerization without end group transformations.

Alkoxyamine-functionalized latex nanoparticles through RAFT polymerization-induced self-assembly in water

Alkoxyamine-functionalized latex nanoparticles were obtained through RAFT polymerization-induced self-assembly in water using poly(acrylic acid) macroRAFT carrying alkoxyamine moieties.

New dialkoxyamine-trithiocarbonate for the synthesis of multiblock copolymers through in tandem RAFT/NMP

A new strategy for synthesizing multiblock copolymers comprising polystyrene, polyacrylates, poly(N-isopropylacrylamide), etc. is described.