Freeze-drying Method Research Articles

Physicochemical Characterization, Storage Stability Behavior, and Intestinal Bioaccessibility of Clove Extract Encapsulated Using Varying Combinations of Gum Arabic and Maltodextrin

Clove (Syzygium aromaticum, L.) is a rich source of polyphenols and antioxidants, but its intense flavor, poor solubility, and instability may limit its widespread and efficient use in industrial applications. In a series of laboratory-scale experiments, gum Arabic (GA) and maltodextrin (MD) were used as coating agents in various proportions (ranging from 0MD:100GA to 100MD:0GA) for encapsulation of clove extract using a freeze-drying method. The encapsulates were assessed for the physicochemical properties, storage stability behavior, and intestinal bioaccessibility of phenolics using an in vitro gastrointestinal digestion test. The freeze-dried encapsulates were characterized as having low water activity (<0.3, which is a critical threshold to ensure chemical and microbiological stability), high water solubility (>90%), solid (product) recovery (mean 93.1 ± 1.77%), and encapsulation efficiency (91.4−94.9%). Hygroscopicity increased as the GA:MD proportion increased in the encapsulation formulations. Encapsulation was effective in protecting bioactive components of clove extract during storage at room (up to 40 days) or high temperature (60 °C for 7 days) and minimized the loss of antioxidant activity during storage, as compared to the clove extract in a non-encapsulated form. All encapsulation formulations were characterized by a negative zeta potential (from −22.1 to −29.7 mV) and a polydispersity index ranging from 0.47 to 0.68, classifying the formulations as having a mid-range polydisperse particle size distribution. The FTIR analysis demonstrated that the freeze-drying encapsulation process resulted in no evident chemical interaction between coating and core materials. Intestinal bioaccessibility of total phenolics after the in vitro-simulated gastrointestinal digestion was greater in the encapsulated clove extract compared to the non-encapsulated clove extract. In conclusion, the encapsulation process was effective in protecting the bioactivity of the polyphenol-rich clove extract during storage and improved the phenolic bioaccessibility, potentially supporting the application of the encapsulated clove extract for use in functional food development.

Fabrication of Three‐Dimensional Net‐Structured Polyvinyl Alcohol Nanofibers Using Spray‐Freeze‐Drying Technique

ABSTRACTPolyvinyl alcohol (PVA) nanofibers have potential importance in industrial applications. In this study, three‐dimensional (3D) net‐structured PVA nanofibers are successfully fabricated using the spray‐freeze‐drying (SFD) technique for the first time. At first, different concentrations of PVA solutions from 0.001 to 5 wt% are applied to prepare PVA nanofibers using liquid nitrogen at −196°C by the SFD method. These nanofibers are characterized by scanning electron microscopy for morphological analysis, photo ruler software for diameter measurement, thermogravimetric analysis and differential scanning calorimetry for thermal stability and crystallinity, as well as nitrogen adsorption isotherms and pore size distribution curves for specific surface area and porous surface quality. Prepared SFD nanofibers with finer nano diameters, fewer beads, more regular 3D net‐structures and without any massive blocks are obtained from 0.05 to 1 wt%. These are compared with the nanofibers prepared by the freeze‐drying (FD) technique. The SFD method shows better results than the FD method in respect to fiber morphology, finer nanoscale diameter, crystallinity, specific surface area, and surface porous property. The best results are obtained from the nanofibers fabricated by the SFD method at 0.1 wt% concentration. Finally, the findings of this work open the opportunities for potential industrial applications and further development of PVA nanofibers.

Gradient Porous and Carbon Black-Integrated Cellulose Acetate Aerogel for Scalable Radiative Cooling.

Passive temperature controls like passive daytime radiative cooling (PDRC)-heating (PDRH), and thermal insulation are essential to meet the growing demand for energy-efficient thermal solutions. When combined with advanced functions like electromagnetic interferenceshielding, these technologies can significantly enhance scalability. However, existing approaches using single thin films or uniform porous materials face inherent limitations in optimizing versatile functions, while lightweight, insulating aerogels can extend their multifunctionality by manipulating pores and fillers. Herein, carbon black (CB)-containing cellulose acetate (CA)aerogels (CB/CA aerogel) featuring gradient pores and bilayer structures are devised to implement switchable PDRC-PDRHand broadband spectral emissivity from infrared to microwave, along with high thermal insulation and elasticity. Using stirring and freeze-drying methods, the CA aerogels show low thermal conductivity (≈0.034 W mK-1) and demonstrate broad-spectrum functionality, with over 95.7% solar reflectivity and 93% long-wavelength infrared (LWIR) emittance, achieving a 12.25°C temperature reduction in outdoor conditions. Furthermore, the CB/CA aerogels enhance LWIR emittance to 98.7% and provide broadband spectral emissivity with 39.4% microwave absorption. This study offers a viable solution to simultaneously control radiative cooling and microwave absorption across a broad spectrum in porous media.

Optimizing the micro/mesoporous structure of hierarchical graphene aerogel for CO2 capture by controlling the oxygen functional groups of graphene oxide

BackgroundGraphene aerogels as solid porous adsorbents are great candidates for CO2 adsorption based on their tunable hierarchical pore structure and oxygenated groups on graphene oxide can control the self-assembly and pore structure of graphene aerogels. MethodsModified Hummer's method was used to synthesize graphene oxides by using various levels of H2SO4, KMnO4, and H2O2 and 3D graphene aerogels were synthesized via the hydrothermal and freeze-drying method. FTIR, RAMAN, XRD, FE-SEM, and BET analysis were used for characterizations. Significance findingsThe effect of graphite oxidation conditions on the hierarchical porous structure of graphene aerogel for CO2 adsorption was investigated. The graphene aerogel with the high meso and micro surface areas and the highest Sm/ST value (micro surface area/total micro and meso surface area) of 33% and also, the adequate macropores was achieved using high dosage of H2SO4 in the graphene oxidation process led to the highest CO2 adsorption capacity of 1.72 mmol/g. increasing the H2O2 dosages increased the macropores in the aerogel structure and improved the value of Sm/ST leading to an increase in the CO2 adsorption capacity. The high content of KMnO4 led to low Sm/ST value and fewer macropores and decreased the CO2 adsorption capacity (1.04 mmol/g).

Development of reed-based cellulose aerogel: a sustainable solution for crude oil spill clean-up

This study focused on fabricating a cellulose aerogel for oil spill clean-up, using common reed ( Phragmites australis ) as the cellulose source. The process involved isolating cellulose from reed via traditional Kraft pulping, considering the effects of key factors on the isolated cellulose content. After a two-stage HP bleaching sequence, the highest cellulose content achieved was 27.2%, with 80% ISO brightness and 1% ash content under mild Kraft pulping conditions of 30% sulfidity, 20% active alkali (AA), sustained cooking at 165°C for 3 h, and a liquor-to-reed ratio of 8 : 1. Subsequently, reed-based cellulose aerogel was fabricated via a freeze-drying method using an eco-friendly NaOH/poly(ethylene glycol) aqueous solvent system, which was then modified with methyltrimethoxysilane. The resulting aerogel exhibited remarkable characteristics, including a low density of 0.04 g cm −3 , high porosity of 96%, high hydrophobicity with a water contact angle (WAC) of 141°, and a superior crude oil adsorption capacity of 35 g g −1 . Comprehensive characterizations of the fabricated materials, including scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis/differential scanning calorimetry, and WAC measurements, were evaluated. This interdisciplinary study explores the commercial promise of reed-based cellulose aerogel as a sustainable solution for oil spill clean-up efforts.

Synthesis of Hydrogel from a Combination of Cellulose Gracilaria verrucosa and Carboxymethyl Sago Starch using Freeze Dry and Oven oven-drying methods as a Commercial Textile Dye Adsorbent

This research aims to develop a hydrogel adsorbent capable of absorbing dyes from textile industry waste. The hydrogel is synthesized using natural materials, specifically cellulose extracted from Gracilaria verrucosa and...

Bi2O3/Bi quasi-nanospheres in-situ embedded in N-doped porous carbon and reinforced via Bi-O-C bonding towards improved lithium storage performance

To mitigate the volume swelling and poor conductivity issues faced by Bi2O3 during Li storage, this work prepares an efficient Bi2O3-based composite through a simple freeze-drying and subsequent carbonization method, which improves the electrochemical performance of Bi2O3. The findings confirm that in this composite (Bi2O3/Bi@PC) the Bi2O3 (containing small amounts of Bi) quasi-nanospheres are embedded within an N-doped porous carbon matrix (PC) and formation of Bi-O-C chemical bonding between Bi2O3/Bi and carbon matrix. The electrochemical characterization results demonstrate that PC physical embedding and Bi-O-C chemical bonding dual combination endows Bi2O3/Bi@PC with enhanced conductivity, improved Li+ diffusion coefficient and reinforced structural stability during cycle. As a result, Bi2O3/Bi@PC exhibits outstanding electrochemical performance, with 451.4 and 309.3 mAh g-1 after 400 and 600 cycles at 200 and 1000mAg-1, respectively. This study may provide essential guidance for future preparing advanced Bi-based anodes for lithium-ion batteries through a simple and efficient strategy.

Formulation of recombinant Lactococcus lactis as an oral vaccine candidate for COVID-19

Background: Lactococcus lactis is a promising oral vaccine carrier. However, to improve the stability of the bacteria, the freeze-drying method and formulation need to be optimised. Objective: To develop a formulation of oral recombinant food-grade Lactococcus lactis as a candidate oral vaccine for coronavirus disease 2019 (COVID-19). Method: To preserve bacteria during storage, a combination of skim milk, trehalose, and sucrose concentrations was adjusted. The impacts of the freeze-drying procedure were investigated using a bacterial viability test, and bacterial morphology was assessed using scanning electron microscopy. Bacteria produced from the freeze-drying technique were combined with excipients to create granules, tablets, and capsules. After one month of storage, the bacterial viability of each product was assessed after one-month storage in 4°C and 25°C, and physicochemical testing was conducted on each product. Results: The cryoprotectant formula containing 8% of skim milk and 7.5% of sucrose protected the bacteria the most from the freeze-drying process. The tablets and capsules complied with current specifications, including disintegration test, tablet hardness, capsule weight uniformity, and bacteria viability. Conclusion: Among the products, tablets stored for one month at 4°C had the best bacterial viability. This study demonstrated the potential to develop and administer an easy-to-use oral COVID-19 vaccine candidate using L. lactis.

Biomimetic Honeycomb-like Ti3C2Tx MXene/Bacterial Cellulose Aerogel-Based Flexible Pressure Sensor for the Human-Computer Interface.

The pursuit of efficient and accurate human-computer interface design urgently requires high-performance sensors with pressure sensitivity, a wide detection range, and excellent cycling stability. Herein, a biomimetic honeycomb-like Ti3C2Tx MXene/bacterial cellulose (BC) aerogel with a negative Poisson's ratio (ν = -0.14) synthesized from the bidirectional freeze-drying method is used as the active material for a flexible pressure sensor, which exhibits high sensitivity (20.14 kPa-1), fast response time (100 ms), excellent mechanical durability (5000 cycles), and a low detection limit (responding to a grain of rice weighing about 0.022 g). Moreover, when assembled into the sandwich-structured bending sensor with the aerogel layer at just 0.8 mm in thickness, the aerogel-based device has a wide angular detection range (2.7-156.3°), high sensitivity (0.47 deg-1), and good robustness, proving outstanding electromechanical performance. Significantly, a smart glove consisting of five bending sensors fixed to the proximal knuckles and a flexible circuit board as the signal processing unit was designed for the identification of the shape, demonstrating its promising applications in the field of human-computer interaction.

Dry Bondable Porous Silk Fibroin Films for Embedding Micropatterned Electronics in Hierarchical Silk Nacre.

Future structural materials is not only be lightweight, strong, and tough, but also capable of integrating functions like sensing, adaptation, self-healing, deformation, and recovery as needed. Although bio-inspired materials are well developed, directly integrating microelectronic patterns into nacre-mimetic structures remains challenging, limiting the widespread application of electronic biomimetic materials. Here, an in situ freeze-drying method is reported for the successful preparation of porous silk fibroin materials that can achieve dry bonding. The in situ freeze-drying method preserves the structural integrity of the lyophilized membrane while reducing procedural steps, achieving control over pore gradient not feasible with traditional freeze-drying techniques. By leveraging their smooth surfaces and capacity to support heat transfer patterns, layer-by-layer assembly at a macroscopic scale is achieved. The material's excellent mechanical properties, controllable graded structure, and adjustable degradation behavior enable the construction of electronically functionalized hierarchical structures. Additionally, the dry-state, layer-by-layer bonding method for porous polymer films provides advantages in precision control, mechanical stability, functional versatility, hierarchical structuring, and scalability. It represents an innovative approach, offering multi-functional and customizable bulk materials, especially suited for biomedical applications. This work offers an effective pathway for developing high-performance and multifunctional biomimetic devices with controllable hierarchical structures.

An Amorphous Solid Dispersion of Baicalin and its Oral Therapeutic Effect on Ulcerative Colitis.

Ulcerative colitis (UC) treatment currently faces multiple challenges including adverse effects, prolonged therapy durations, and high costs. Baicalin (BA) has demonstrated anti-inflammatory benefits for inflammatory bowel disease, and the objective of this scholarly work is to address the challenges associated with the poor aqueous solubility and diminished oral bioavailability of the compound in question, thereby offering an innovative therapeutic approach for the management of ulcerative colitis. We developed a baicalin-arginine complex (BA-Arg) by screening for suitable basic compounds and utilizing a freeze-drying method, resulting in an amorphous solid dispersion of BA. Our findings revealed that BA·Arg significantly enhances the intestinal absorption and transmembrane transport of BA without inducing toxicity in Caco-2 cells. Pharmacokinetic studies in healthy Wistar rats demonstrated significantly higher plasma concentrations of BA compared to free BA. In a mouse model induced by 3.5% dextran sodium sulfate, BA·Arg treatment markedly alleviated colitis symptoms as evidenced by reduced inflammatory cell infiltration, decreased lymphocyte aggregation in the colon, and better preservation of intestinal mucosa. This improved the overall anti-colitis efficacy of BA. Overall, our study presents a simple, eco-friendly formulation process that enhances BA solubility without the need for organic solvents, offering a practical and sustainable solution for developing BA-based therapies for UC.

High-Efficiency Broad-Spectrum Antibacterial Activity of Chitosan/Zinc Ion/Polyoxometalate Composite Films for Water Treatment.

The development of multifunctional films with rapidly killing microorganisms and adsorbing residual antibiotics in wastewater remains a challenging endeavor. In this work, the chitosan/zinc ion/polyoxometalate (CS/Zn2+/POM) multifunctional films were prepared by the freeze-drying method using chitosan, ZnO, and POM. Notably, the CS/Zn2+/POM films exhibited excellent bactericidal properties against Gram-positive/negative bacterial strains including Staphylococcus aureus (S. aureus, 99.80%), Escherichia coli (E. coli, 99.82%), and drug-resistant E. coli bacterial strains (kanamycin-resistant E. coli, 87.76% and ampicillin-resistant E. coli, 99.71%). This may be due to the chelation of Zn2+ with CS disrupting the cell membrane and bringing POM into direct contact with bacteria, leading to bacterial death. In addition, the CS/Zn2+/POM films showed good adsorption performance to a tetracycline (TC) solution (adsorption rate 75.2%). Further studies showed that the main process of tetracycline removal by CS/Zn2+/POM films was controlled by a physical adsorption. This POM-based film material has an important potential for the synthesis of broad-spectrum antimicrobial materials for the removal of residual antibiotics from water pollutants such as tetracycline.

Effects of partial precipitation and freeze-drying on morphology and physicochemical properties of rice starch hydrolysates

Agricultural bio-catalysis is of immense scientific interest due to its increasing importance in the efforts for more sustainable agriculture while optimizing environmental impacts. In our studies, native rice starch was hydrolyzed with various alpha-amylase concentrations (0, 0.1, 0.2, and 0.3% w/w of starch) at 50°C for 20 min; then purified by partial precipitation (PP) with organic solvents, or freeze-drying (FD) without further purification. The rice starch hydrolysates (RSH) produced by different methods (PP or FD) were determined for dextrose equivalent (DE), morphology, and some physicochemical properties including bulk density, moisture content, hygroscopicity, and water solubility. The results showed that at the same alpha-amylase treatment conditions, the RSH obtained by the PP method had lower DE values and production yields than those of RSH obtained by FD method. The FD-RSH had higher DE values, lower bulk densities and moisture contents, higher hygroscopicity and water solubility. In morphology, the PP-RSH (DE 10.2) had a larger particle size and more condensed microstructure compared to the FD-RSH of almost similar DE 13.5. These findings showed that the PP method resulted in lower-DE RSH with different morphological and physicochemical properties compared to those obtained by the FD method.

3D Biofabrication of Microporous Hydrogels for Tissue Engineering.

Microporous hydrogels have been utilized in an unprecedented manner in the last few decades, combining materials science, biology, and medicine. Their microporous structure makes them suitable for wide applications, especially as cell carriers in tissue engineering and regenerative medicine. Microporous hydrogel scaffolds provide spatial and platform support for cell growth and proliferation, which can promote cell growth, migration, and differentiation, influencing tissue repair and regeneration. This review gives an overview of recent developments in the fabrication techniques and applications of microporous hydrogels. The fabrication of microporous hydrogels can be classified into two distinct categories: fabrication of non-injectable microporous hydrogels including freeze-drying microporous method, two-phase sacrificial strategy, 3D biofabrication technology, etc., and fabrication of injectable microporous hydrogels mainly including microgel assembly. Then, the biomedical applications of microporous hydrogels in cell carriers for tissue engineering, including but not limited to bone regeneration, nerve regeneration, vascular regeneration, and muscle regeneration are emphasized. Additionally, the ongoing and foreseeable applications and current limitations of microporous hydrogels in biomedical engineering are illustrated. Through stimulating innovative ideas, the present review paves new avenues for expanding the application of microporous hydrogels in tissue engineering.

Screening and inclusion of luteolin for β-cyclodextrin: molecular simulations and experiments

In this study, we first established a guest small molecule screening mechanism by molecular simulation and then screened lignans from ten polyphenolic compounds to identify the most suitable guest molecule for encapsulation with β-cyclodextrin (β-CD). Subsequently, the subject–guest interactions and encapsulation mechanisms of lignans with β-CD, 2-hydroxypropyl-cyclodextrin, and 2,6-dimethyl-cyclodextrin (DM-β-CD) were investigated using a combination of molecular simulation and experimental methods, respectively. Molecular simulations were performed to calculate the microstructural parameters, including solubility parameters, binding energies, and mean square displacements. The simulation results demonstrated that DM-β-CD exhibited the strongest interaction with luteolin and formed the most stable inclusion complex. The inclusion complexes of luteolin with the three cyclodextrins were prepared by the freeze-drying method, and the formation of the inclusion complexes was demonstrated using infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and ultraviolet-visible spectroscopy. Phase solubility studies confirmed the formation of 1:1 stoichiometric inclusion complexes of lignans with cyclodextrins. Furthermore, 2,2-diphenyl-1-pyridine hydrazine free radical scavenging experiments demonstrated that the inclusion complexes exhibited enhanced antioxidant capacity. In light of these findings, it can be concluded that among the three cyclodextrins, DM-β-CD was optimally encapsulated with luteolin.

Ultralight and robust polyimide aerogels with tunable porous structures based on cation-π interactions for superior thermal insulation

Polyimide (PI) aerogels, renowned for their ultra-low density and exceptional porosity, exhibit substantial potential for thermal insulation applications. However, conventional freeze-drying method often produces irregular and large pore structures, which compromise the mechanical properties of PI aerogels and limit their practical applications. In this work, the enhanced PI-Cu aerogels by cation-π interactions are fabricated through the introduction of Cu ions and benzimidazole. The findings reveal that cation-π interactions facilitate the transformation of PI aerogels from two-dimensional layered structure to three-dimensional honeycomb structure characterized by smaller and more uniform pores, significantly reducing shrinkage and leading to ultra-light properties. Remarkably, a significant improvement of mechanical performance is also achieved after introducing cation-π interactions, even at a decreased density (0.046 g/cm3). Specifically, for samples with 3.5 wt% solid content, the yield strength and modulus of PI-Cu aerogels increase to 0.71 MPa and 13.58 MPa, respectively, representing improvements of 344 % and 520 % over pristine PI aerogels, which are superior to those of many other previously reported PI aerogels/foams with similar or even higher densities. Additionally, the toughness is significantly elevated from 13.5 MPa to 48.8 MPa. More importantly, after introducing cation-π interactions, the thermal insulation of PI-Cu aerogels are also improved with thermal conductivity decreasing from 0.04214 to 0.03997 W/m·K in axial direction and from 0.0399 to 0.03688 W/m·K in radial direction at 25°C. Interestingly, the thermal conductivity show only a slight increase under 180°C less than 0.05741 W/m·K in axial direction and 0.04923 W/m·K in radial direction owning to their exceptional thermal stability (Tg = 404 °C, T5%=524 °C). These exceptional properties position PI-Cu aerogels as promising candidates for diverse functional applications in the field of energy conservation.

Evaluation of sodium alginate sponge infused bromelain spray and Helichrysum italicum nanoemulsion to accelerate wound healing.

This research introduces a pioneering porous sponge composed of sodium alginate/gellan gum polymers manufactured via the freeze-drying method. Bromelain was encapsulated in H. italicum nanoemulsion and sprayed using a spray device containing a glass gun with a 0.2μm nozzle. Physicochemical properties, including swelling capacity (1570.48±54.2), porosity (88.860±5.7), biodegradability (98.21±8), shape memory, FTIR, and SEM analyses were performed. Blood absorption (1465±82%), anti-inflammatory, and antibacterial activity against various pathogens (35mm S. aureus, 23mm E. coli, 21mm P. aeruginosa) also were investigated. SA/GG/BR/NEHro sponge showed excellent anti-inflammatory (89.34±4.2) and demonstrated effective antibacterial properties, which can help safeguard the wound against bacterial infection. FTIR analysis correctly confirms the presence of bromelain and oil nanoemulsion and SEM micrograph analysis showed high porosity of sponges containing H. italicum oil nanoemulsion. SA/GG/BR/NEHro exhibited remarkable compressive flexibility, mechanical stability, and shape memory properties. The results also show that bromelain helped reduce inflammation, promote tissue repair, and accelerate wound closure. In vitro and in vivo wound healing studies revealed that the sponges exhibited excellent homeostasis. Notably, the SA/GG/BR/NEHro sponge achieved complete closure of full-thickness wounds (100%), underscoring its exceptional performance in wound repair and regeneration.

In vitro study of dimethyl glutamate incorporated chitosan/microfibrillated cellulose based matrix in addition of H and Zr on osteoblast cells.

Tissue engineering techniques can be utilized to repair or regenerate damaged tissue by promoting the proliferation and differentiation of cells in bone regeneration. A critical component of this process is the scaffold employed, which should ideally support consistent tissue development during bone regeneration. The aim of this study was to evaluate the morphological, physicochemical, and biological characteristics of various scaffolds: S1 (C/MFC), S2 (C/H/MFC), S3 (C/MFC/Zr), S4 (C/MFC/PCL), S5 (C/H/MFC/PCL), S6 (C/PCL/MFC/Zr), and S7 (C/H/MFC/Zr), which are intended for application in bone regeneration. The scaffolds containing microfibrillated cellulose, chitosan, polycaprolactone, zirconium, and hydroxyapatite were fabricated by the freeze-drying method. Conventional methods, including scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis, were used to evaluate morphological and physicochemical properties of composite scaffolds. The fabricated scaffolds (S1-S7) had spongy properties that all functional groups were present in the sponge. Biological properties for cell survival were evaluated by the MTT assay, ALP, and ARS activities, respectively. In physicochemical studies, scaffolds showed tunable water absorption, swelling studies, degradation, sustained drug release, and mechanical properties. In biological studies, the cell proliferation and attachment were shown to significantly increase in scaffolds on MG63 cells. After 7 days of cell culture, ALP and ARS activity indicated the enhancement of extracellular calcium deposition of the MG63 cells on the treated scaffolds. In summary, the scaffolds S7 (C/H/MFC/Zr) treated with dimethyl glutamate revealed favorable effects on bone tissues, implying a potential towards the treatment of bone defects and drug delivery.

Construction of Silk Fibroin 3D Microfiber Scaffolds and Their Applications in Anti-Osteoporosis Drug Prediction.

Silk microfiber scaffolds have garnered increasing interest due to their outstanding properties, with degumming being the process used to extract the sericin from the cocoon. In the present study, an attempt to tune the biodegradation period of silk through degumming with various sodium borohydride (NaBH4) concentrations and degumming times was studied. We considered the process, the number of baths used, and the salt concentration. Herein, we report a novel method of expanding microfibers from two-dimensional (2D) to three-dimensional (3D) using a modified gas-foaming technique. Porous three-dimensional (3D) silk fibroin (SF) scaffolds were fabricated by the SF fibers, which were extracted by the NaBH4 degumming method and NaBH4 gas-foaming approach. This study showed that higher salt concentrations, reaching 1.5% in a double bath, effectively removed sericin from silk fibroin, resulting in clean, smooth 3D scaffolds. These scaffolds were then fabricated using a freeze-drying method. The scaffolds were then submerged in solutions containing semen cuscutae (SC) and their surfaces were coated with various percentages of total flavonoids. The scaffolds had no toxicity to the cells in vitro. This work provides a new route for achieving a TFSC-loaded scaffold; it is proved that the coated silk fibroin fiber scaffold has excellent compatibility. Compared with non-drug-loaded silk scaffolds, drug-loaded silk scaffolds promote cell growth.

Nanoporous microparticles of cellulose nanofibrils: The effect of fluid bed atmospheric spray freeze drying

Cellulose nanofibers are abundant, low-cost, biodegradable and non-toxic materials that are a technological alternative for products in pharmaceutical field. The aim of this study was to investigate the effect of fluid bed atmospheric spray freeze drying on cellulose nanofibers characteristics, and compare to conventional spray and freeze drying methods. The atmospheric spray freeze dried nanofibers had moisture content of 2.3 %, mean size 4.0 μm, circularity of 0.86 and angle of repose of 27.3°. Also, solid state evaluation of atmospheric spray freeze dried cellulose nanofibers and other samples showed very similar chemical and thermal characteristics, but a relative crystallinity of 45.3 %, similar to spray dried powders. Furthermore, the most important feature of atmospheric-spray-freeze-dried cellulose nanofibers is their morphology, since unlike the other methods those resulted in highly nanoporous structures. The atmospheric-spray-freeze-drying of cellulose nanofibers may become a new and attractive alternative for the preparation of microsponges for pharmaceutical applications.