Polysaccharides

Colletotrichum species are among the most destructive phytopathogens worldwide, with appressorium-mediated penetration representing a critical stage in host infection. Targeting this morphogenetic transition offers a promising strategy for sustainable disease control by interfering with the infection process rather than solely inhibiting fungal growth. In this study, chitosan–κ-carrageenan nanoparticles (CS–κ-CRG) without and with lysozyme (CS–κ-CRG/Lz) were synthesized, characterized, and evaluated for their ability to inhibit appressorium formation in Colletotrichum siamense, a strain exhibiting low sensitivity to chitosan. The nanoparticles showed monodisperse size distributions, with hydrodynamic diameters of 503 and 333 nm for CS–κ-CRG and CS–κ-CRG/Lz, respectively, positive surface charges of approximately +26 mV, spherical morphology, and a lysozyme encapsulation efficiency of 63%. Both formulations significantly reduced conidial viability and delayed germination, inducing morphological alterations such as conidial swelling, hyphal deformation, and vacuolization. Fluorescence microscopy using calcofluor white and propidium iodide revealed disturbances in cell wall organization and loss of membrane integrity. Both nanomaterials markedly affected appressorium development in a concentration- and formulation-dependent manner. Notably, CS–κ-CRG/Lz showed stronger suppression of appressorium formation, whereas at 200 µg·mL⁻¹, CS–κ-CRG nanoparticles stimulated appressorium formation, suggesting that sublethal nanoparticle stress may trigger compensatory or hyper-pathogenic responses. These findings highlight the potential and complexity of utilizing chitosan-based nanomaterials for phytopathogen management and emphasize the importance of mechanistic and dose–response evaluations before field application.

Wormlike micelles (WLMs) of surfactants with rheological properties highly responsive to pH are of growing interest for various applications. The present paper proposes an approach to enhance their rheological properties and make the pH-response more pronounced. It consists of the incorporation of a percolated network of cellulose nanocrystals (CNCs) into the solution of entangled WLMs. To provide pH-responsiveness, potassium oleate was used as a surfactant. Rheological studies demonstrated that CNCs increase the viscosity and storage modulus by one order of magnitude. This effect was attributed to the interaction of WLMs with nanocrystals and the formation of entanglements of WLMs with percolated CNCs. Moreover, added CNCs make the pH-response stronger. The lowering of pH from 10.1 to 9.7 leads to a sharp drop in viscosity by ca. 2000 Pa·s, which is much higher than the decrease in viscosity of the WLM solution without CNCs. According to SANS data, the drop in viscosity is due to the transformation of WLMs into vesicles. It occurs as a result of the protonation of surfactant carboxylic groups decreasing surface charge on the micelles. In the presence of CNCs, the transition pH shifts to an alkaline medium, indicating that CNCs promote vesicle formation. Also, CNCs cause some of the vesicles to aggregate with each other, as follows from dynamic light scattering and optical microscopy data. Both observations suggest an interaction between CNCs and vesicles, which is supported by ITC data. These findings are valuable for the research and development of high-performing surfactant-based products.

Polysaccharide-based microparticles have emerged as suitable carriers and stabilizers of active substances, showing potential to stabilize bioactive compounds during storage and gastrointestinal digestion, thereby improving their bioaccessibility and bioavailability. This narrative review provides a comprehensive overview of the main polysaccharides employed as wall materials, including starch, maltodextrin, alginate, pectin, inulin, chitosan, and gum Arabic, and discusses how structural interactions and physicochemical properties can positively influence the microencapsulation of polyphenols and pigments. The principles and main findings of the main microencapsulation techniques, including spray-drying, freeze-drying, extrusion, emulsification, and coacervation, are briefly described. Polysaccharides can entrap both hydrophilic and hydrophobic compounds through physical interactions, forming a barrier around the nucleus or binding to the bioactive compound. Intermolecular binding between polysaccharides in the wall matrix, polyphenols, and pigments in the nucleus can confer up to 90% encapsulation efficiency, primarily governed by hydrogen bonds and electrostatic interactions. The mixture of wall polysaccharides in the microparticles synthesis favors the encapsulation solubility, storage stability, bioaccessibility, and bioactivity of the microencapsulate compounds. Clinical trials regarding the bioefficacy of polyphenols and pigments loaded in polysaccharide microparticles are scarce and require further evidence to reinforce the use of this technology.