Spray Dried Inulin–Sodium Carboxymethylcellulose Microcarriers with Solid-to-Colloidal Transition: Development for Foliar Delivery of Polyphenol-Rich Extract

Abstract

This study reports on the development of a carbohydrate-based spray-dried microparticulate system (F-CHES) conceived for the stabilization and foliar delivery of polyphenol-rich plant extracts for sustainable phyto defense applications. Chestnut spiny bur (CHES) extract, with demonstrated anti-fungal activity against phytopathogens, was micro-encapsulated via spray-drying in a polysaccharide matrix, composed primarily of inulin (INU DP ∼15), sodium carboxymethylcellulose (CMC) and low amount of sodium lauryl sulfate (SLS 0.05% w/v), engineered to improve extract processability, water compatibility, stability and functional performance. Structural characterization by semi-solid (HRMAS) and solid-state (CPMAS) NMR revealed polysaccharide matrix–extract interactions that influenced the internal organization and component distribution within microparticles. The integration of high-resolution analytical techniques was also essential for standardizing the production process. The optimized F-CHES 0.8 micropowder, containing 1.5% w/v of CHES extract, 5% INU, 0.8% Na-CMC, showed a process yield (70.42 ± 2.42%) and high encapsulation efficiency (98.58%). The formulation ensured chemical stability over 12 weeks (active compound retention ≥94.86%), and displayed favorable morphological and physicochemical properties, including hydrodynamic diameter of 0.55 µm and ζ-potential of –37.2 mV. Interestingly, upon dispersion in water, the microparticles converted into a colloidal state and the resulting dispersion can form stable transparent coating on leaf surface suited for foliar delivery.

Highlights

Introduction

In recent years, the design of functional microparticulate carriers based on carbohydrate matrices still arouses high interest as an advanced tool for the stabilization and controlled delivery of bioactive natural products (Liu et al., 2018). Polysaccharides, due to their biocompatibility, chemical versatility, and film-forming ability, are particularly suitable as encapsulating agents. Most carbohydrate-based encapsulation systems developed to date rely on high-molecular-weight wall-forming agents, such as maltodextrins, gums, or starches, to form single- or multi-polymer matrices (Ghiorghita et al., 2024; Zabot et al., 2022; Sansone et al., 2023). The strategic combination of polysaccharides with distinct physicochemical properties to fine-tune delivery performance and improve system stability is one of the most promising and actively explored technological approaches. In this context, a binary system based on inulin (INU) and sodium carboxymethylcellulose (CMC), which can offer complementary physicochemical properties, has not yet been systematically investigated for microencapsulation of polyphenol-rich botanical extracts. Prior studies have demonstrated the value of INU in carrying thermolabile actives (Mensink et al., 2015a, 2015b) and the film-forming properties of CMC are well recognized in controlled-release systems (Rahman et al., 2021). INU, a prebiotic fructan with polymerization degree between 10 and 60, exhibits excellent solubility, water compatibility, and low-temperature processability (Mensink et al., 2015a, 2015b). When combined with high-molecular-weight or film-forming polysaccharides, it improves matrix flexibility and coating behavior (Sansone et al., 2023). CMC, a linear, water-soluble, anionic cellulose derivative is widely used in food and pharmaceutical applications due to its stabilizing, thickening, and film-forming properties (Rahman et al., 2021). Its –OH and –COOH groups facilitate hydrogen bonding and electrostatic interactions with phenolics (Ghiorghita et al., 2024), while acting as a rheological modifier to promote colloidal system formation in water (Chalah et al., 2022). In this study, INU-CMC combination was studied not only as binary polysaccharide carrier for unstable and sticky polyphenol-rich extracts but also for the potentiality to convert microparticles from solid-to-colloidal state in aqueous dispersion, a characteristic required for agricultural spray foliar application in plant protection. As the bioactive model, we also selected an extract from Castanea sativa Mill. spiny burs (CHES), a sustainable extract from agro-industrial waste. Rich in hydrolysable tannins and phenolic acids, CHES has shown antifungal activity against Alternaria alternata, Fusarium solani, and Botrytis cinerea (Esposito et al., 2019). However, hydroalcoholic natural extracts poor solubility and sensitivity to degradation can limit their applicability in open-field conditions (Esposito et al., 2021; Sansone et al., 2023). Spray drying, due to its scalability, low cost, and versatility, is widely used to encapsulate thermolabile phytochemicals in dry forms suitable for storage and reconstitution (Sansone et al., 2023; Rajabi et al., 2025). The design of efficient spray-dried microparticles with wall systems able to protect the core material, favor dispersion, and to enhance deposition on plant surfaces, is essential for transforming such extracts into field-ready formulations (Ding et al., 2020). In this context, the present study focuses on the development and physicochemical characterization of F-CHES, a spray-dried engineered INU–CMC microcarrier system for CHES encapsulation, with potential application in sustainable plant protection. The system was designed to confer structural stability in solid form, enabling a solid-to-colloidal transition in water and promoting uniform foliar coverage for an effective antifungal application after spraying. The formulation was optimized to balance INU (5% w/v) and CMC (0.5–1% w/v), ensuring both spray-drying processability and re-dispersibility of the powder in water.

To further improve dispersion of hydrophobic polyphenols in the aqueous feed, Sodium Lauryl Sulfate (SLS, 0.05% w/v) was added, in line with prior studies demonstrating its ability to improve solubility and processability of poorly water-soluble compounds in carbohydrate-based spray-dried microspheres (Lee et al., 2001). SLS, as a surface-active agent, may be able to enhance the dispersion to reduce interfacial tension during spray drying process and decrease particle size (Maher et al., 2023; Chaudhari & Dugar, 2017)). Despite being synthetic, SLS is broadly used for its proven amphiphilic efficiency in formulation science (Maher et al., 2023). Beyond its technological design, in the effort to align with and the principles of sustainable agriculture and the goals of eco-compatible crop protection under Integrated Pest Management (IPM) strategies (Cenobio-Galindo et al., 2024), sustainable bio-based materials, biodegradable polysaccharides, green solvents, a phenolic extract derived from agro-industrial wastes and a dry-to-colloid delivery approach were used.

The designed system was thoroughly characterized via Semi-solid (HRMAS) and solid-state (CPMAS) NMR spectroscopy for molecular-level interactions and process standardization, Laser Light Scattering (LLS) and Scanning Electron Microscopy (SEM) for evaluating particle morphology and dry-state dimensions, Dynamic Light Scattering (DLS) and ζ-potential analysis to assess colloidal behavior in water. Moreover, a preliminary morphological assessment of leaf coating behavior was carried out.

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Materials

Solvents and Standards: Methanol (HPLC-grade), ethanol (96% v/v), and quercetin 3-O-β-D-glucoside standard were purchased from VWR Chemicals (France). HPLC-grade water was obtained from Clean Consult International S.p.A. (Lodi Vecchio, Lombardia, Italy).

Polymers and Surfactants: inulin from chicory (Cichorium intybus L.) with linear chains of D-fructose, linked together with β-(2-1) bonds and characterized by the presence of a terminal glucose residue; Degree of polymerization (DP≈ 15, quantity of linked fructose), low molecular weight (< 3000 Da). Sodium carboxy methyl cellulose – cellulose derivative, anionic linear glucose homopolymer with glucopyranose units linked by β-1,4glycosidic bonds (carboxymethyl groups (-CH₂-COOH) bond to the hydroxyl groups of the glucopyranose units); average degree of substitution (DS, average number of CH2COO-Na groups per monomer) 1.15–1.45; average MW ≈ 90000 g/mol (90 kDa); Viscosity: 50-200 mPa.s (25°C, 1% aqueous solution) purchased from Sigma Aldrich. Sodium lauryl sulfate (SLS, Natrium Laurylsulfuricum, 90% USP), anionic surface activator was provided by ACEF Spa (Fiorenzuola D’Arda, PC, Italy).

Chestnut Spiny Burs Extract (CHES): A hydroalcoholic (aqueous ethanol 50%, v/v) extract from dried chestnut burs (Castanea sativa) was prepared as described by Esposito et al., 2019. Briefly, 50 g of dried burs were homogenized in 2500 mL of 50% aqueous ethanol using an Ultra-Turrax T-25 (IKA, Germany) at 10,000 rpm for 4 min. After orbital shaking at 45 °C and 300 rpm for 30 min, the mixture was filtered (45 μm sieve) under vacuum. Ethanol was removed using a Büchi R-210 rotavapor (Buchi Italia srl, Milan, Italy), and the remaining aqueous phase was lyophilized (Alpha 1–2 LD freeze dryer, Martin Christ, Germany) to produce a dry powder (yield ≈ 11.6% w/w) (Esposito et al., 2019).

Rita Patrizia Aquino, Teresa Mencherini, Pierluigi Mazzei, Tiziana Esposito, Francesco Del Prete, Francesca Fortunato, Giacomo Pepe, Giulia Auriemma, Francesca Sansone, Spray Dried Inulin–Sodium Carboxymethylcellulose Microcarriers with Solid-to-Colloidal Transition: Development for Foliar Delivery of Polyphenol-Rich Extract, Carbohydrate Polymer Technologies and Applications, 2025, 101023, ISSN 2666-8939, https://doi.org/10.1016/j.carpta.2025.101023.