Tuning Microcapsule Shell Thickness and Structure with Silk Fibroin and Nanoparticles for Sustained Release

5-Fluorouracil/curcumin loaded silk fibroin hydrogel for the adjuvant therapy in colorectal cancer

This study employed silk fibroin (SF) as a carrier material to encapsulate curcumin (CUR) and 5-fluorouracil (5-FU), forming a highly effective drug-loaded hydrogel. The process involved mixing SF solution containing 5-FU with curcumin solution dissolved in acetone (AC), leading to the formation of composite drug-loaded nanospheres with particle sizes ranging from 77.87 nm to 299.22 nm, demonstrated enhanced permeability and retention (EPR) effects, enabling passive targeting of solid tumors. After the formation of the nanospheres, they were dispersed into a solution containing SF and polyethylene glycol (PEG). Following gelation and PEG removal, a SF hydrogel loaded with 5-FU and CUR (5-FU/CUR@SF hydrogel) was obtained. Results indicated that the 5-FU/CUR@SF hydrogel exhibited excellent drug release properties, with 5-FU and CUR achieving sustained release of 59.66 ± 3.76 % and 47.94 ± 5.03 %, respectively, over a 400-h of sustainable releasing period. Human colorectal cancer cell line (HT-29) and normal human colon epithelial cell line (NCM-460) were cultured with the 5-FU/CUR@SF hydrogel, resulting an apoptosis rate of only 17.38 ± 1.98 % for NCM-460 cells, whereas the apoptosis rate for HT-29 cells significantly increased to 72.31 ± 2.18 %, and its cell viability dropped to 59.77 ± 0.55 %. These findings suggest that the 5-FU/CUR@SF hydrogel exhibits low cytotoxicity toward normal NCM-460 cells, while exerting significant and sustained inhibitory effects on HT-29 cancer cells. In conclusion, the SF-based drug-loaded composite hydrogel holds great potential as a novel adjuvant therapeutic strategy for the treatment of CRC.

Enhanced Anti-inflammatory Effects of Diclofenac Delivered Orally via Polyvinylpyrrolidone K30/Silk Fibroin Nanoparticles in a Murine Model of Carrageenan-Induced Paw Edema

Diclofenac has a relatively low oral bioavailability (50-60 %) and is quickly metabolized with a half-life of less than 1 h. Therefore, the oral therapeutic effect of diclofenac is not optimal. This research developed polyvinylpyrrolidone K30-functionalized silk fibroin nanoparticles as an effective delivery system for diclofenac (FNPs-PVP-DC). The FNPs-DC and FNPs-PVP-DC were formulated by two methods of adsorption and solvent exchange. Depending on the formulation factors, the obtained particles exhibited different properties of nano-scale sizes (400-800 nm), narrow size distribution, negatively charged surfaces (-17 to -19 mV), high PVP K30 incorporation (23 %-50 %), pHpzc of ~6.6, and appropriate chemical interactions. Interestingly, particles formulated by the adsorption method showed low drug encapsulation efficiencies of <15 %, whereas the solvent exchange method yielded moderate results of ~40 %. The FNPs-DC possessed aggregated patterns, while the FNPs-PVP-DC were more uniformly distributed. All formulations limited diclofenac release (<20 %) under gastric conditions and sustained its release in the intestinal environment. In in-vivo carrageenan-induced paw edema mice model, the FNPs-PVP-DC demonstrated a 20-30 % higher anti-inflammatory effect and a faster onset of action (within 1 h) compared to pure diclofenac at the same dose (5 mg/kg). These findings suggest that FNPs-PVP-DC have promising potential as novel oral anti-inflammatory products.

Facile Preparation of Silica/Tannic Acid/Zein Microcapsules Templated from Non-Aqueous Pickering Emulsions and their Application in Cargo Protection

Microcapsules have attracted significant attention in academia and industry due to their unique properties for protecting and controlling the release of active substances. However, based on water-insoluble biopolymers, developing a straightforward approach to prepare microcapsules with improved biocompatibility and functional shells remains a great challenge. In this study, zein, a water-insoluble protein, is employed to prepare robust microcapsules facilely using oil-in-aqueous ethanol Pickering emulsions as templates. First, the emulsion template is stabilized by hydrophobic silica nanoparticles with in situ surface modification of tannic acid. The zein is then precipitated at the interface in a controlled manner using antisolvent approach to obtain silica/tannic acid/zein (STZ) microcapsules. It is found that the concentration of zein and the presence of tannic acid played a significant role in the formation of STZ microcapsules with well-defined morphology and a robust shell. The uniform deposition of zein on the surface of template droplets is facilitated by the interactions between tannic acid and zein via hydrogen bond and electrostatic force. Finally, the resulting STZ microcapsules showed super resistance to ultraviolet (UV) radiation and high temperature for the unstable, lipophilic, and active substance of β-carotene.

Salting-out effect-mediated size-control of protein nanoparticles towards controllable microstructures for sustained release of eugenol

Size and monodispersity of solid particles are essential to their structuring behaviors at biphasic interfaces. However, delicate control over biomolecular nanoparticle sizes is challenging. In this study, we prepared monodisperse rice protein (RP) nanoparticles by neutralizing RP solutions (pH 12.0) using combined treatments of cationic exchange resins (CERs) and HCl. CERs absorbed Na+ by releasing H+ without producing salt during neutralization. By compromising the usages of CERs and HCl when preparing RPs, the generation of NaCl can be delicately tailored, leading to controllable nanoparticle sizes from 20 nm to 30 nm. By mixing these nanoparticles with eugenol in an aqueous solution, the nanoparticles accommodated eugenol in their cores due to inward diffusion. Furthermore, such eugenol-contained nanoparticles with different sizes demonstrated tunable releases of eugenol due to size-dependent capillary forces, which can be harnessed for suppression of microbial growth on fruit with prolonged effective eugenol concentration.

Recent advances of silk fibroin materials: From molecular modification and matrix enhancement to possible encapsulation-related functional food applications

Silk fibroin materials are emergingly explored for food applications due to their inherent properties including safe oral consumption, biocompatibility, gelatinization, antioxidant performance, and mechanical properties. However, silk fibroin possesses drawbacks like brittleness owing to its inherent specific composition and structure, which limit their applications in this field. This review discusses current progress about molecular modification methods on silk fibroin such as extraction, blending, self-assembly, enzymatic catalysis, etc., to address these limitations and improve their physical/chemical properties. It also summarizes matrix enhancement strategies including freeze drying, spray drying, electrospinning/electrospraying, microfluidic spinning/wheel spinning, desolvation and supercritical fluid, to generate nano-, submicron-, micron-, or bulk-scale materials. It finally highlights the food applications of silk fibroin materials, including nutraceutical improvement, emulsions, enzyme immobilization and 3D/4D printing. This review also provides insights on potential opportunities (like safe modification, toxicity risk evaluation, and digestion conditions) and possibilities (like digital additive manufacturing) in functional food industry.

Novel antimicrobial and self-healing dental resin to combat secondary caries and restoration fracture

OBJECTIVE

Dental resin composites have been the most popular materials for repairing tooth decay in recent years. However, secondary caries and bulk fracture are the major hurdles that affect the lifetime of dental resin composites. This current study synthesized a novel antimicrobial and self-healing dental resin containing nanoparticle-modified self-healing microcapsules to combat secondary caries and restoration fracture.

METHODS

Multifunctional dental resins containing 0-20% nanoparticle-modified self-healing microcapsules were prepared. The water contact angle, antimicrobial properties, mechanical properties, cell toxicity, and self-healing capability of the dental resins were tested.

RESULTS

A novel multifunctional dental resin was synthesized. When the microcapsule mass fraction was 10%, the resin presented a strong bacteriostasis rate (80.3%) and excellent self-healing efficiency (66.1%), while the hydrophilicity, mechanical properties, and cell toxicity were not affected.

SIGNIFICANCE

The novel antimicrobial self-healing dental resin is a promising candidate for use in clinical practice, which provides a simple and highly efficient strategy to combat secondary caries and restoration fracture. This novel dental resin also gives the inspiration to prolong the service life of dental restorations.

Stimuli-responsive silk fibroin for on-demand drug delivery

Stimuli-responsive "smart" hydrogel biomaterials have attracted great attention in the biomedical field, especially in designing novel on-demand drug delivery systems. As a handful natural biomaterial approved by US Food and Drug Administration, silk fibroin (SF) has unique high temperature resistance as well as tunable structural composition. These properties make it one of the most ideal candidates for on-demand drug delivery. Meanwhile, recent advances in polymer modification and nanomaterials have fostered the development of various stimuli-responsive delivery systems. Here, we first review the recent advance in designing responsive SF-based delivery systems in different stimulus sources. These systems are able to release mediators in a desired manner in response to specific stimuli in active or passive manners. We then describe applications of these specially designed responsive delivery systems in wound healing, tumor therapy, as well as immunomodulation. We also discuss the future challenges and prospects of stimuli-responsive SF-based delivery systems.

A Bone-Penetrating Precise Controllable Drug Release System Enables Localized Treatment of Osteoporotic Fracture Prevention via Modulating Osteoblast-Osteoclast Communication

Improving local bone mineral density (BMD) at fracture-prone sites of bone is a clinical concern for osteoporotic fracture prevention. In this study, a featured radial extracorporeal shock wave (rESW) responsive nano-drug delivery system (NDDS) is developed for local treatment. Based on a mechanic simulation, a sequence of hollow zoledronic acid (ZOL)-contained nanoparticles (HZNs) with controllable shell thickness that predicts various mechanical responsive properties is constructed by controlling the deposition time of ZOL and Ca²⁺ on liposome templates. Attributed to the controllable shell thickness, the fragmentation of HZNs and the release of ZOL and Ca²⁺ can be precisely controlled with the intervention of rESW. Furthermore, the distinct effect of HZNs with different shell thicknesses on bone metabolism after fragmentation is verified. In vitro co-culture experiments demonstrate that although HZN2 does not have the strongest osteoclasts inhibitory effect, the best pro-osteoblasts mineralization results are achieved via maintaining osteoblast-osteoclast (OB-OC) communication. In vivo, the HZN2 group also shows the strongest local BMD enhancement after rESW intervention and significantly improves bone-related parameters and mechanical properties in the ovariectomy (OVX)-induced osteoporosis (OP) rats. These findings suggest that an adjustable and precise rESW-responsive NDDS can effectively improve local BMD in OP therapy.

Microencapsulation of High-Content Actives Using Biodegradable Silk Materials

There is a compelling need across several industries to substitute non-degradable, intentionally added microplastics with biodegradable alternatives. Nonetheless, stringent performance criteria in actives' controlled release and manufacturing at scale of emerging materials hinder the replacement of polymers used for microplastics fabrication with circular ones. Here, the authors demonstrate that active microencapsulation in a structural protein such as silk fibroin can be achieved by modulating protein protonation and chain relaxation at the point of material assembly. Silk fibroin micelles' size is tuned from several to hundreds of nanometers, enabling the manufacturing-by retrofitting spray drying and spray freeze drying techniques-of microcapsules with tunable morphology and structure, that is, hollow-spongy, hollow-smooth, hollow crumpled matrices, and hollow crumpled multi-domain. Microcapsules degradation kinetics and sustained release of soluble and insoluble payloads typically used in cosmetic and agriculture applications are controlled by modulating fibroin's beta-sheet content from 20% to near 40%. Ultraviolet-visible studies indicate that burst release of a commonly used herbicide (i.e., saflufenacil) significantly decreases from 25% to 0.8% via silk fibroin microencapsulation. As a proof-of-concept for agrochemicals applications, a 6-day greenhouse trial demonstrates that saflufenacil delivered on corn plants via silk microcapsules reduces crop injury when compared to the non-encapsulated version.

Encapsulated Microstructures of Beneficial Functional Lipids and Their Applications in Foods and Biomedicines

Beneficial functional lipids are essential nutrients for the growth and development of humans and animals, which nevertheless possess poor chemical stability because of heat/light-sensitivity. Various encapsulation technologies have been developed to protect these nutrients against adverse factors. Different microstructures are exhibited through different encapsulation methods, which influence the encapsulation efficiency and release behavior at the same time. This review summarizes the effects of preparation methods and process parameters on the microstructures of capsules at first. The mechanisms of the different microstructures on encapsulation efficiency and controlled release behavior of core materials are analyzed. Next, a comprehensive overview on the beneficial functional lipids capsules in the latest food and biomedicine applications are provided as well as the matching relationship between the microstructures of the capsules and applications are discussed. Finally, the remaining challenges and future possible directions that have potential interest are outlined. The purpose of this review is to convey the construction of beneficial functional lipids capsules and the function mechanism, a critical analysis on its current status and challenges, and opinions on its future development. This review is believed to promote communication among the food, pharmacy, agronomy, engineering, and nutrition industries.

Novel nanoparticle-modified multifunctional microcapsules with self-healing and antibacterial activities for dental applications

OBJECTIVE

Although microcapsules (MCs) have been used for dental resins to achieve self-healing capabilities, the fragile organic shell and single healing event functions during the service period limit their use. Herein, a novel nanoparticle-modified MC with a nano-antibacterial inorganic filler (NIF) containing a quaternary ammonium salt was synthesized to address these issues.

METHODS

MCs with 0 %-30 % NIFs were prepared via an in situ polymerization method and characterized their morphology, chemical composition, thermal stability, roughness, mechanical properties, and antibacterial effect. Subsequently, M-10 MCs were mixed into the resin matrix at a mass fraction of 7.5 %. The self-healing capability and cytotoxicity were evaluated.

RESULTS

The introduction of nanomaterials enhances the shell of the MCs and endows them with an antibacterial effect. With the addition of NIFs, the roughness, modulus, and hardness values of MCs all increased (p < 0.05). The presence of M-10 MCs reduced the CFU by 2-3 orders of magnitude compared to the control group. The dental resin containing 7.5 % M-10 MCs obtained almost 69 % self-healing efficiency, without significantly compromising cell viability (p < 0.05).

SIGNIFICANCE

Self-healing MCs with NIFs were prepared for the first time with strong antibacterial properties, a substantial self-healing capability, and low toxicity. This multifunctional MC is a promising candidate for use in dental resins to extend the service life and resolve the problem of bulk fracture and secondary caries.

Synthesis and Characterization of a Multifunctional Sustained-Release Organic-Inorganic Hybrid Microcapsule with Self-Healing and Flame-Retardancy Properties

As their service life increases, cement-based materials inevitably undergo microcracking and local damage. In response to this problem, this study used phacoemulsification-solvent volatilization to prepare a multifunctional sustained-release microcapsule (SFRM) with self-healing and flame-retardant characteristics. The synthesis of SFRM is based on the modification of ethyl cellulose with nano-SiO₂ particles and cross-linking with a silane coupling agent to form an organic-inorganic hybrid wall material. The epoxy resin is blended with hexaphenoxy cyclotriphosphazene (HPCTP) to form a composite core emulsion. The surface morphology, particle size distribution, core-shell composition, and thermal stability of SFRM were analyzed via scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), Malvern, Fourier-transform infrared (FT-IR), and TD-DSC-DTG. It is concluded that SFRM was successfully synthesized with superior particle size distribution and thermal stability. When the ratio of SiO₂ solution and EC alcohol solution reached 1:2, the particle size distribution of the microcapsules was 30-190 μm, and the D₅₀ decreased to 70 μm. The core material content, slow-release performance, and flame retardancy of SFRM were measured using a UV-1800 spectrophotometer and Hartmann tubes, and the compressive and repair properties of SFRM were evaluated by uniaxial compression tests. The results demonstrate that SFRM has satisfactory slow-release and flame-retardancy properties, the LC is 67%, and the first-order kinetic model shows the best fit and conforms to the non-Fickian diffusion mechanism. The SFRM repair rate can reach approximately 61%. This is of substantial significance to the field of self-repairing cement-based materials.