Laser weeding of common weed species.

The massive use of herbicides since the 1950s has resulted in increasing problems with herbicideresistant weeds and pollution of the environment, including food, feed, and water. These side effects have resulted in political pressures to reduce herbicide application. The European Commission aims to reduce the use and risk of chemicals and more hazardous pesticides in the EU. Therefore, new weed control methods are in demand. Laser weeding might be an alternative to replace or supplement herbicides and other weed control methods in an Integrated Weed Management (IPM) strategy. This work aimed to investigate how increasing laser energy affected common weeds when the apical meristem was exposed to irradiation at the early stages of development. A 50 W thulium-doped fibre laser with a diameter of 2 mm and a wavelength of 2 µm was used. The highest efficacy of laser irradiation was achieved when the grass weed (Alopecurus myosuroides) had one leaf and the dicot species were at the cotyledon stage. There was a large difference between the species' susceptibility to irradiation probably caused by differences in morphology and growth habit. At the 4-leaf stage, most of the species regrew after irradiation. Laser weeding may be a solution to replace or supplement other weed control methods in some crops, but in general the weeds must be irradiated when they are at the cotyledon to 2-leaf stage to avoid regrowth.

Laser weeding: opportunities and challenges for couch grass (Elymus repens (L.) Gould) control.

Laser weeding may contribute to less dependency on herbicides and soil tillage. Several research and commercial projects are underway to develop robots equipped with lasers to control weeds. Artificial intelligence can be used to locate and identify weed plants, and mirrors can be used to direct a laser beam towards the target to kill it with heat. Unlike chemical and mechanical weed control, laser weeding only exposes a tiny part of the field for treatment. Laser weeding leaves behind only ashes from the burned plants and does not disturb the soil. Therefore, it is an eco-friendly method to control weed seedlings. However, perennial weeds regrow from the belowground parts after the laser destroys the aerial shoots. Depletion of the belowground parts for resources might be possible if the laser continuously kills new shoots, but it may require many laser treatments. We studied how laser could be used to destroy the widespread and aggressive perennial weed Elymus repens after the rhizomes were cut into fragments. Plants were killed with even small dosages of laser energy and stopped regrowing. Generally, the highest efficacy was achieved when the plants from small rhizomes were treated at the 3-leaf stage.

Nanoformulation of fibrinogen by thermal stabilization of its electrostatic complexes with hyaluronic acid.

The formulation of well-defined and stable fibrinogen-based nanoparticles (NPs) without the use of any chemical reaction or any toxic organic solvent is reported. Electrostatic interaction between hyaluronic acid (HA) and fibrinogen (Fbg) leads to well-defined complexes at acidic pH which however readily dissolve at neutral pH. On the other hand, when thermal treatment is applied on the pre-formed complexes NPs keep their integrity. Circular dichroism indicates that the protein's native secondary conformation in the final NPs is not affected by the formulation. The tendency of the complexes to aggregate at elevated ionic strengths is greatly suppressed after the application of the temperature treatment protocol. This characteristic is even more pronounced at neutral pH and it is connected to the enhanced surface charge of the NPs. The encapsulation of the hydrophobic compound curcumin causes only weak secondary aggregation. This work shows that the ability of Fbg to self-assemble upon thermal treatment can be effectively used to stabilize Fbg nanoformulations inside complexes with polysaccharides.

Reorganizations inside thermally stabilized protein/polysaccharide nanocarriers investigated by small angle neutron scattering.

We use small angle neutron scattering (SANS) to characterize the internal morphology of nanoparticles (NPs) formed by the complexation between chondroitin sulfate (CS) and bovine serum albumin (BSA) and subsequent stabilization by thermal treatment. We demonstrate that SANS can quantify the internal rearrangements and protein morphology alterations upon thermal treatment and solution conditions variations. A three-level Guinier/power-law hierarchical model identifies BSA globules, interconnected clusters of globules and higher aggregates. The effect of temperature treatment which causes protein denaturation and ß-sheet inter-globular associations is captured by the model at the relevant length scales 1-100 nm. Furthermore, the nanogel behavior of the thermally treated CS/BSA NPs, which up to this moment had been characterized by light scattering, is elucidated. Loading of the nutraceutical compound ß-carotene (ß-C) is revealed to occur at the outer regions of the NPs. This study demonstrates that the combination of SANS and a hierarchical model for data analysis may provide very useful insights for nanocarriers which are based on polysaccharide/protein complexes and aim at biomedical applications and the food industry.

Association and Internal Morphology of Self-Assembled HPPhOx/BSA Hybrid Nanoparticles in Aqueous Solutions.

We investigate the formation of hybrid polyelectrolyte/protein nanoparticles by associations between aggregates of partially hydrolyzed poly(2-phenyl-2-oxazoline) (HPPhOx) and bovine serum albumin (BSA) in aqueous solutions. Light scattering experiments show that at conditions of low salt, BSA creates interaggregate bridges and increases the size of the HPPhOx nanoparticles. At high salt contents, breaking of aggregates leads to well-defined nanoparticles. The interior of the formed nanoparticles is probed by small-angle neutron scattering. At low salt, diffuse arrangements are observed, whereas at high salt concentration, scattering is dominated by well-defined hydrophobic domains enhanced by the incorporation of BSA. This system shows that the combination of hydrophobic and electrostatic interactions in random-amphiphilic-polyelectrolyte/protein complexes can be used to determine the properties of self-assembled hybrid multifunctional nanoparticles.

Tuning the solution organization of cationic polymers through interactions with bovine serum albumin.

The interactions of bovine serum albumin (BSA) with aggregates of cationic polymers, i.e. quaternized poly(chloromethyl styrene) chains (QIm-PCMS), in aqueous solutions are investigated using small angle neutron scattering on length scales relevant to the size of BSA. The arrangement of the macromolecular chains within their aggregates is consistent with a blob description of overlapping chains that contain hydrophobic domains. The local conformations depend on the salt content as in typical linear polyelectrolytes. Although the hydrophobic content of the cationic polymers does not cause measurable local morphology differences, the interactions with BSA are enhanced in the case of the not fully quaternized polymer. The secondary structure of BSA is critically compromised by the interaction with the quaternized polymers as the signature of the alpha helix conformation is lost. The complexation with BSA and the resulting enhancement of interchain associations on higher length scales are verified using dynamic light scattering experiments. This study demonstrates the ability to tune the polyelectrolyte/protein interactions and polyelectrolyte chain-chain associations by modifying the hydrophobic content of the polyelectrolytes.