Facile spray-drying assembly of uniform microencapsulates with tunable core-shell structures and controlled release properties

Fabrication and functional application of zein-based core-shell structures: A review

Core-shell structures exhibit a number of distinct absorptive properties that make them attractive tools for use in a range of industrial contexts including pharmaceuticals, biotechnology, cosmetics, and food/agriculture. Several recent studies have focused on the development and fabrication of zein-based core-shell structures for a range of functional material deliveries. However, no recent review article has evaluated the fabrication of such core-shell structures for food-based applications. In this paper, we therefore survey current approaches to fabricating different zein-based platforms including particles, fibers, films, and hydrogels that have appeared in a variety of functionally relevant applications. In addition, we highlight certain challenges and future research directions in this field, thereby providing a novel perspective on zein-based core-shell structures.

Gas-Phase Functionalization of Phytoglycogen Nanoparticles and the Role of Reagent Structure in the Formation of Self-Limiting Hydrophobic Shells

A suite of acyl chloride structural isomers (C6H11OCl) was used to effect gas-phase esterification of starch-based phytoglycogen nanoparticles (PhG NPs). The surface degree of substitution (DS) was quantified using X-ray photoelectron spectroscopy, while the overall DS was quantified using 1H NMR spectroscopy. Gas-phase modification initiates at the NP surface, with the extent of surface and overall esterification determined by both the reaction time and the steric footprint of the acyl chloride reagent. The less sterically hindered acyl chlorides diffuse fully into the NP interior, while the branched isomers are restricted to the near-surface region and form self-limiting hydrophobic shells, with shell thicknesses decreasing with increasing steric footprint. These differences in substitution were also reflected in the solubility of the NPs, with water solubility systematically decreasing with increasing DS. The ability to separately control both the surface and overall degree of functionalization and thereby form thin hydrophobic shells has significant implications for the development of polysaccharide-based biopolymers as nanocarrier delivery systems.

Multifunctional, Hybrid Materials Design via Spray-Drying: Much more than Just Drying

Spray-drying is a popular and well-known "drying tool" for engineers. This perspective highlights that, beyond this application, spray-drying is a very interesting and powerful tool for materials chemists to enable the design of multifunctional and hybrid materials. Upon spray-drying, the confined space of a liquid droplet is narrowed down, and its ingredients are forced together upon "falling dry." As  detailed in this article, this enables the following material formation strategies either individually or even in combination: nanoparticles and/or molecules can be assembled; precipitation reactions as well as chemical syntheses can be performed; and templated materials can be designed. Beyond this, fragile moieties can be processed, or "precursor materials" be prepared. Post-treatment of spray-dried objects eventually enables the next level in the design of complex materials. Using spray-drying to design (particulate) materials comes with many advantages-but also with many challenges-all of which are outlined here. It is believed that multifunctional, hybrid materials, made via spray-drying, enable very unique property combinations that are particularly highly promising in myriad applications-of which catalysis, diagnostics, purification, storage, and information are highlighted.

Advances in spray-dried probiotic microcapsules for targeted delivery: a review

Probiotics have gained significant attention owing to their roles in regulating human health. Recently, spray drying has been considered as a promising technique to produce probiotic powders due to its advantages of high efficiency, cost-saving, and good powder properties. However, the severe environmental conditions from drying and digestion can significantly reduce cell viability, resulting in poor bioaccessibility and bioavailability of live cells. Therefore, there is a need to develop effective targeted delivery systems using spray drying to protect bacteria and to maintain their physiological functions in the targeted sites. This review highlights recent studies about spray-dried targeted delivery vehicles for probiotics, focusing on key strategies to protect bacteria when encountering external stresses, the formation mechanism of particles, the targeted release and colonization mechanisms of live cells in particles with different structures. Advances in the targeted delivery of live probiotics via spray-dried vehicles are still in their early stages. To increase the possibilities for industrialization and commercialization, functional improvement of microcapsules in terms of protection, targeted release, and colonization of bacteria, as well as the effect of spray drying on bacterial physiological functions in the host, need to be further investigated.

Cyclosporine A-Loaded Ternary Solid Dispersion Prepared with Fine Droplet Drying Process for Improvement of Storage Stability and Oral Bioavailability

This study aimed to develop a cyclosporine A (CsA)-loaded ternary solid dispersion (tSD/CsA) to improve the storage stability of a solid dispersion (SD) system and the oral absorbability of CsA. Hydroxypropyl cellulose (HPC) and hydroxypropyl methylcellulose acetate succinate (HPMCAS) were selected as carrier materials of tSD, and tSD/CsA was prepared with a fine droplet drying process, a powderization technology that employs an inkjet head. The physicochemical properties of tSD/CsA were evaluated in terms of morphology, storage stability, dissolution behavior, and mucoadhesive property. After the oral administration of CsA samples (10 mg-CsA/kg) to rats, the plasma concentration of CsA was monitored to estimate oral absorbability. tSD/CsA comprised uniform shriveled particles with a diameter of 3.4 mm and span factor of 0.4, which is a parameter to estimate the particle size distribution. Although HPC-based binary SD showed marked aggregation of the particles after storage under 40 °C/75% relative humidity, there were no significant aggregations of tSD/CsA, due to the relatively low hygroscopic property of HPMCAS. The pH-dependent release of CsA with improved dissolution was observed in tSD/CsA. In the in vitro mucoadhesive evaluation using a mucin disk, tSD/CsA exhibited a better mucoadhesive property than HPC-based SD, possibly leading to prolonged retention of tSD particles in the gastrointestinal tract after oral administration. Orally-dosed tSD/CsA in rats resulted in significantly improved oral absorption of CsA, as evidenced by a 27-fold higher bioavailability than amorphous CsA. tSD/CsA may be a promising dosage option to improve the storage stability of a SD system and the biopharmaceutical properties of CsA.

A Platform Approach to Protein Encapsulates with Controllable Surface Chemistry

The encapsulation of proteins into core-shell structures is a widely utilised strategy for controlling protein stability, delivery and release. Despite the recognised utility of these microstructures, however, core-shell fabrication routes are often too costly or poorly scalable to allow for industrial translation. Furthermore, many scalable routes rely upon emulsion-techniques implicating denaturing or environmentally harmful organic solvents. Herein, we investigate core-shell protein encapsulation through single-feed, aqueous spray drying: a cheap, industrially ubiquitous particle-formation technology in the absence of organic solvents. We show that an excipient’s preference for the surface of the spray dried particle is well-predicted by its hydrodynamic diameter (Dh) under relevant feed buffer conditions (pH and ionic strength) and that the predictive power of Dh is improved when measured at the spray dryer outlet temperature compared to room temperature (R2 = 0.64 vs. 0.59). Lastly, we leverage these findings to propose an adaptable design framework for fabricating core-shell protein encapsulates by single-feed aqueous spray drying.

Development of curcumin loaded core-shell zein microparticles stabilized by cellulose nanocrystals and whey protein microgels through interparticle interactions

Novel multilayered core-shell microparticles were developed to deliver curcumin using positively charged zein microparticles coated with negatively charged cellulose nanocrystals (CNCs) and positively charged whey protein microgels (WPMs) at pH 4. Different levels of WPMs (0.10%-1.50%, w/v) were utilized to regulate the structure, stability, and in vitro digestion of curcumin loaded zein-CNC core-shell microparticles. The size of zein-CNC-WPM core-shell microparticles ranged from 2087.7 to 2928.2 nm. The electrostatic attraction and hydrogen bonding were mainly involved in the assembly of the core-shell microparticles through particle-particle interactions. The microstructure of the core-shell microparticles was dependent on the level of the WPM. When its appropriate level was adopted (0.50%-1.00%, w/v), the WPM formed a protective shell for zein-CNC-WPM core-shell microparticles. The retention rate of curcumin in the core-shell microparticles increased by 47.56% and 32.79% during light and thermal treatment, respectively. Excess microgels facilitated the bridging aggregation and formation of a network structure on the particle surface, which further reduced their stability and greatly restricted the curcumin release. The potential of nanosized protein microgels was explored to stabilize and modulate the physicochemical properties of multilayered core-shell microparticles through interparticle interactions.

Structural design of zein-cellulose nanocrystals core-shell microparticles for delivery of curcumin

The novel core-shell microparticles were fabricated to deliver curcumin by using hydrophobic zein microparticles as the core and hydrophilic cellulose nanocrystals (CNCs) as the shell. Different concentrations (0.10-1.50%, w/v) of CNCs were utilized to regulate the microstructure, physicochemical stability, and in vitro digestion of the core-shell microparticles. The size of the microparticles ranged from 1017.3 to 3663.7 nm. Electrostatic attraction and hydrophobic interactions were responsible for the assembly of zein-CNCs core-shell microparticles. The microstructure of the microparticles was dependent on the CNCs level. The retention rate of curcumin in the core-shell microparticles was increased by 76.41% after UV radiation. Furthermore, the rise of CNCs level delayed the release of curcumin from the microparticles in gastrointestinal tract and reduced its bioaccessibility. The potential of utilizing hydrophilic nanoparticles was explored to stabilize hydrophobic microparticles through interparticle interactions, which was useful to develop the novel core-shell microparticles for the application in functional foods.

Structured micro/nano materials synthesized via electrospray: a review

The development of synthetic methods for micro/nano materials with precisely controlled structures, morphologies, and local compositions is of great importance for the advancement of modern nanotechnology. The electrospray method is a "platform" approach for the preparation of a broad range of micro-/nanostructures; electrospray is simple and scalable. This review summarizes recent research on the micro-/nanostructures prepared via the electrospray route. These include spherical structures (e.g. simple, porous, Janus, and core-shell particles), non-spherical structures (e.g. red blood cell-like and spindle-like particles, multi-compartment microrods, 2D holey nanosheets, and nanopyramids), and assembled structures. The experimental details, underlying physical/chemical principles, and key benefits of these structures are comprehensively discussed. The effects and importance of nozzle design, properties of feeding solutions (e.g. concentration of solute, polymer additives, solvent/nonsolvent combinations), working environment (e.g. temperature and humidity), and types of collection media are highlighted.

Solid lipid nanoparticles self-assembled from spray dried microparticles

We report the self-assembly of drug-loaded solid lipid nanoparticles (SLNs) from spray dried microparticles comprising poly(vinylpyrrolidone) (PVP) loaded with glyceryl tristearate (GTS) and either indomethacin (IMC) or 5-fluorouracil (5-FU). When the spray dried microparticles are added to water, the PVP matrix dissolves and the GTS and drug self-assemble into SLNs. The SLNs provide a non-toxic delivery platform for both hydrophobic (IMC) and hydrophilic (5-FU) drugs. They show extended release profiles over more than 24 h, and in permeation studies the drug cargo is seen to accumulate inside cancer cells. This overcomes major issues with achieving local intestinal delivery of these active ingredients, in that IMC permeates well and thus will enter the systemic circulation and potentially lead to side effects, while 5-FU remains in the lumen of the small intestine and will be secreted without having any therapeutic benefit. The SLN formulations are as effective as the pure drugs in terms of their ability to induce cell death. Our approach represents a new and simple route to the fabrication of SLNs: by assembling these from spray-dried microparticles on demand, we can circumvent the low storage stability which plagues SLN formulations.

Spray-drying water-based assembly of hierarchical and ordered mesoporous silica microparticles with enhanced pore accessibility for efficient bio-adsorption

The fast and scalable spray-drying-assisted evaporation-induced self-assembly (EISA) synthesis of hierarchically porous SBA-15-type silica microparticles from a water-based system is demonstrated. The SBA-15-type silica microparticles has bowl-like shapes, uniform micro-sizes (∼90 µm), large ordered mesopores (∼9.5 nm), hierarchical meso-/macropores (20-100 nm) and open surfaces. In the synthesis, soft- and hard-templating approaches are combined in a single rapid drying process with a non-ionic tri-block copolymer (F127) and a water-insoluble polymer colloid (Eudragit RS, 120 nm) as the co-templates. The RS polymer colloid plays three important roles. First, the RS nanoparticles can be partially dissolved by in-situ generated ethanol to form RS polymer chains. The RS chains swell and modulate the hydrophilic-hydrophobic balance of F127 micelles to allow the formation of an ordered mesostructure with large mesopore sizes. Without RS, only worm-like mesostructure with much smaller mesopore sizes can be formed. Second, part of the RS nanoparticles plays a role in templating the hierarchical pores distributed throughout the microparticles. Third, part of the RS polymer forms surface "skins" and "bumps", which can be removed by calcination to enable a more open surface structure to overcome the low pore accessibility issue of spray-dried porous microparticles. The obtained materials have high surface areas (315-510 m² g^-1) and large pore volumes (0.64-1.0 cm³ g^-1), which are dependent on RS concentration, HCl concentration, silica precursor hydrolysis time and drying temperature. The representative materials are promising for the adsorption of lysozyme. The adsorption occurs at a >three-fold faster rate, in a five-fold larger capacity (an increase from 20 to 100 mg g^-1) and without pore blockage compared with the adsorption of lysozyme onto spray-dried microparticles of similar physicochemical properties obtained without the use of RS.

All-Natural Food-Grade Hydrophilic-Hydrophobic Core-Shell Microparticles: Facile Fabrication Based on Gel-Network-Restricted Antisolvent Method

Hydrophilic-hydrophobic core-shell microparticles are highly appealing for a variety of industrial applications (foods, pharmaceutics, cosmetics, biomedicines, etc.) owing to their unique properties of moisture resistance and controlled release. However, the fabrication of such structured microparticles proves to be nontrivial due to the difficulty in assembling two materials of distinctly different hydrophilicities and hydrophobicities. This paper reports a facile method to fabricate hydrophilic-hydrophobic core-shell microparticles using all-natural food-grade polysaccharides and proteins, based on a novel principle of gel-network-restricted antisolvent precipitation. Immersion of microgel beads prepared from hydrophilic polysaccharides (i.e., alginates, κ-carrageenan, agarose) into a hydrophobic protein solution (i.e., zein in 70% aqueous ethanol) enables slow and controllable antisolvent precipitation of a protein layer around the microbead surface, leading to the formation of a hydrophilic-hydrophobic core-shell structure. The method applies to various gelling systems and can easily tailor the particle size and shell thickness. The resulting freeze-dried microparticles demonstrate restricted swelling in water, improved moisture resistance, and sustained release of encapsulants, with great potential in applications such as protection of unstable and/or hygroscopic compounds and delivery and controlled release of drugs, bioactives, flavors, etc. The method is rather universal and can be extended to prepare more versatile core-shell structures using a large variety of hydrophilic and hydrophobic materials.

Fabrication of Electrospun Polymer Nanofibers with Diverse Morphologies

Fiber structures with nanoscale diameters offer many fascinating features, such as excellent mechanical properties and high specific surface areas, making them attractive for many applications. Among a variety of technologies for preparing nanofibers, electrospinning is rapidly evolving into a simple process, which is capable of forming diverse morphologies due to its flexibility, functionality, and simplicity. In such review, more emphasis is put on the construction of polymer nanofiber structures and their potential applications. Other issues of electrospinning device, mechanism, and prospects, are also discussed. Specifically, by carefully regulating the operating condition, modifying needle device, optimizing properties of the polymer solutions, some unique structures of core⁻shell, side-by-side, multilayer, hollow interior, and high porosity can be obtained. Taken together, these well-organized polymer nanofibers can be of great interest in biomedicine, nutrition, bioengineering, pharmaceutics, and healthcare applications.

Fe3O4@SiO2mesoporous spheres as Fe(ii) donors loaded with artemisinin and a photosensitizer to alleviate tumor hypoxia in PDT for enhanced anticancer therapy

Fe₃O₄@SiO₂as an Fe(ii) donor loaded with artemisinin and photosensitizer to alleviate hypoxia in PDT showed excellent anticancer activity.

Low density, good flowability cyclodextrin-raffinose binary carrier for dry powder inhaler: anti-hygroscopicity and aerosolization performance enhancement

BACKGROUND

The hygroscopicity of raffinose carrier for dry powder inhaler (DPI) was the main obstacle for its further application. Hygroscopicity-induced agglomeration would cause deterioration of aerosolization performance of raffinose, undermining the delivery efficiency.

METHODS

Cyclodextrin-raffinose binary carriers (CRBCs) were produced by spray-drying so as to surmount the above issue. Physicochemical attributes and formation mechanism of CRBCs were explored in detail. The flow property of CRBCs was examined by FT4 Powder Rheometer. Hygroscopicity of CRBCs was elucidated by dynamic vapor sorption study. Aerosolization performance was evaluated by in vitro deposition profile and in vivo pharmacokinetic profile of CRBC based DPI formulations.

RESULTS

The optimal formulation of CRBC (R₄) was proven to possess anti-hygroscopicity and aerosolization performance enhancement properties. Concisely, the moisture uptake of R₄ was c.a. 5% which was far lower than spray-dried raffinose (R₀, c.a. 65%). R₄ exhibited a high fine particle fraction value of 70.56 ± 0.61% and it was 3.75-fold against R₀. The pulmonary and plasmatic bioavailability of R₄ were significantly higher than R₀ (p < 0.05).

CONCLUSION

CRBC with anti-hygroscopicity and aerosolization performance enhancement properties was a promising approach for pulmonary drug delivery, which could provide new possibilities to the application of hygroscopic carriers for DPI.

Polymerization-Induced Phase Separation Formation of Structured Hydrogel Particles via Microfluidics for Scar Therapeutics

Excessive scar formation can form disabling contractures that result in a debilitating psychological outcome. Sustainable hydrophobic corticosteroid release in vivo is essential to regulate the wound healing process. Functional hydrogel particles are widely applied for sustainable release. However, due to the limited aqueous solubility of hydrophobic compounds, most of the corticosteroid is released from the hydrogels within seconds, causing undesirable scar formation and recurrence. In this study, a novel polymerization-induced phase separation is investigated to form well-defined polyethylene glycol diacrylate (PEGDA) core/alginate shell structured hydrogel particles using microfluidics without toxic organic solvents. Based on their wettability preference, hydrophobic corticosteroid-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles are compartmentalized in the PEGDA core during polymerization to control the corticosteroid release. The distribution of the PLGA nanoparticles is precisely regulated by the phase separation boundary and characterized using a fluorescent dye. The thickness of the shell and partition coefficients are determined using the UV intensity and irradiation period. Upon encapsulation of the PLGA nanoparticles within the poly(PEGDA) core, a long-term corticosteroid treatment is developed and effective scar therapeutic outcomes are evaluated using both in vitro and in vivo models.

Technological solutions for encapsulation

Encapsulation offers broad scope of applications. It can be used to deliver almost everything from advanced drugs to unique consumer sensory experiences; it could be also employed as a protection system or a sensing material. This cutting-edge technology undergoes rapid growth in both academic and industrial conditions. Research in this matter is continuing to find a new application of microcapsules as well as to improve the methods of their fabrication. Therefore, in this review, we focus on the art of the encapsulation technology to provide the readers with a comprehensive and in-depth understanding of up-to-day development of microcapsule preparation methods. Our goal is to help identify the major encapsulation processes and by doing so maximize the potential value of ongoing research efforts.

Aerosol-Assisted Fast Formulating Uniform Pharmaceutical Polymer Microparticles with Variable Properties toward pH-Sensitive Controlled Drug Release

Microencapsulation is highly attractive for oral drug delivery. Microparticles are a common form of drug carrier for this purpose. There is still a high demand on efficient methods to fabricate microparticles with uniform sizes and well-controlled particle properties. In this paper, uniform hydroxypropyl methylcellulose phthalate (HPMCP)-based pharmaceutical microparticles loaded with either hydrophobic or hydrophilic model drugs have been directly formulated by using a unique aerosol technique, i.e., the microfluidic spray drying technology. A series of microparticles of controllable particle sizes, shapes, and structures are fabricated by tuning the solvent composition and drying temperature. It is found that a more volatile solvent and a higher drying temperature can result in fast evaporation rates to form microparticles of larger lateral size, more irregular shape, and denser matrix. The nature of the model drugs also plays an important role in determining particle properties. The drug release behaviors of the pharmaceutical microparticles are dependent on their structural properties and the nature of a specific drug, as well as sensitive to the pH value of the release medium. Most importantly, drugs in the microparticles obtained by using a more volatile solvent or a higher drying temperature can be well protected from degradation in harsh simulated gastric fluids due to the dense structures of the microparticles, while they can be fast-released in simulated intestinal fluids through particle dissolution. These pharmaceutical microparticles are potentially useful for site-specific (enteric) delivery of orally-administered drugs.

Formation of nano-structured core–shell micro-granules by evaporation induced assembly

Nano-structured spherical micro-granules of core–shell morphology have been realized by utilizing the contrasting interfacial interaction of two different types of nano-particles with liquid solvent.

Facile, continuous and large-scale production of core–shell HMX@TATB composites with superior mechanical properties by a spray-drying process

Core–shell HMX@TATB composites with low shell content and compact shell structure were fabricated via a facile and effective spray-drying technique.

Self-assembly of colloidal nanoparticles inside charged droplets during spray-drying in the fabrication of nanostructured particles

Studies on self-assembly of colloidal nanoparticles during formation of nanostructured particles by spray-drying methods have attracted a large amount of attention. Understanding the self-assembly phenomenon allows the creation of creative materials with unique structures that may offer performance improvements in a variety of applications. However, current research on the self-assembly of colloidal nanoparticles have been conducted only on uncharged droplet systems. In this report, we first investigated the self-assembly processes of charged colloidal nanoparticles in charged droplets during spray-drying. Silica nanoparticles and polystyrene spheres are used as a model system. To induce a positive or a negative charge on the droplets, we used an electrospray method. Repulsive and attractive interactions between charged colloidal nanoparticles and droplet surface are found to control the self-assembly of colloidal nanoparticles inside the charged droplet. Interestingly, self-assembly of colloidal nanoparticles inside charged droplets under various processing parameters (i.e., droplet charge, droplet diameter, and surface charge, size, and composition of colloidal nanoparticles) allows the formation of unique nanostructured particles, including porous and hollow particles with control over the internal structure, external shape, number of hollow cavities, and shell thickness, in which this level of control cannot be achieved using conventional spray-drying method.