Thermo-sensitive hydroxybutyl chitosan/diatom biosilica hydrogel with immune microenvironment regulatory for chronic wound healing.

This study proposes a chronic wound therapeutic strategy based on extracellular matrix (ECM) biomimetics and immune regulation. The hydroxybutyl chitosan/diatom biosilica hydrogel (H/D) which can regulate the immune microenvironment, is prepared from hydroxybutyl chitosan (HBC) as matrix to construct the bionic ECM and diatom biosilica (DB) as structural active unit. The hierarchical porous structure of DB provides strong anchoring interface effect to enhance the mechanical strength of hydrogel, while maintaining its favorable temperature phase transition behavior, improving the material's fit to the wound and convenience of clinical use. Silicates released from DB in H/D accelerate the transition of wounds from inflammation to proliferation and remodeling. In cellular and diabetic rat models, H/D reduces inflammation (induces conversion of M1-type macrophages to M2-type), induces angiogenesis (1.96-fold of control), promotes fibroblast proliferation (180.36 % of control), collagen deposition, keratinocyte migration (47.34 % more than control), and re-epithelialization. This study validates a possible biological mechanism for H/D bioactive hydrogel-mediated regulation of the immune microenvironment and provides a simple synergistic dressing strategy.

Zinc-mineralized diatom biosilica/hydroxybutyl chitosan composite hydrogel for diabetic chronic wound healing.

For sustained and stable improvement of the diabetic wound microenvironment, a temperature-sensitive composite hydrogel (ZnDBs/HBC) composed of inorganic zinc mineralized diatom biosilica (ZnDBs) and hydroxybutyl chitosan (HBC) was developed. The interfacial anchoring effect between ZnDBs and HBC enhanced the mechanical strength of the hydrogel. The mechanical strength of the composite hydrogel containing 3 wt% ZnDBs was increased by nearly 2.3times. The hydrogel can be used as a carrier for sustained release of Zn2+ for at least 72 h. In diabetic rats models, ZnDBs/HBC composite hydrogel could accelerate the inflammatory process by regulating the expression of pro-inflammatory factor IL-6 and anti-inflammatory factor IL-10, and also promote tissue cell proliferation and collagen deposition, thereby restoring the normal healing process and accelerating wound healing. The wound contraction rate of the composite hydrogel group was more than 2 times that of the control group. Therefore, ZnDBs/HBC composite hydrogel has the potential to be used as a therapeutic dressing for diabetic chronic wounds.

Diatom-Inspired Bionic Hydrophilic Polysaccharide Adhesive for Rapid Sealing Hemostasis.

Diatoms are typical marine biofouling organisms that secrete extracellular polymers (EPS) to achieve strong underwater adhesion. Here, we report a diatom-inspired bionic hydrophilic polysaccharide adhesive composed of diatom biosilica (DB) and bletilla striata polysaccharide (BSP) for rapid sealing hemostasis. The hierarchical porous structure of DB with rich surface silanol groups provides a strong anchored interface effect for BSP, which can significantly enhance cross-linking density and interaction strength of the hydrophilic macromolecular network. BSP/DB adhesive offers 6 times greater mechanical strength and viscosity over BSP under different temperature conditions. The aggregation effect of DBs interface for BSP avoided the washout of BSP/DB adhesive during application in a wet environment before cross-linking occurs. This strengthened the adhesion ability of BSP/DB adhesive to biological tissue that brought out complete sealing hemostasis without blood loss in a rat liver injury model. The dry BSP/DB prepared by lyophilization inherited excellent clotting ability of BSP/DB adhesive, which could realize rapidly the cruor of anticoagulant whole blood within 1 min. The results of animal studies confirmed that dry BSP/DB exhibited superior hemostatic performance over silicate-based inorganic Quikclot, in terms of hemostatic rate, blood loss, dosage, and multiscroll wound closure.

The hierarchical porous structures of diatom biosilica-based hemostat: From selective adsorption to rapid hemostasis.

Here, we developed a Ca2+ modified diatom biosilica-based hemostat (DBp-Ca2+) with a full scale hierarchical porous structure (pore sizes range from micrometers to nanometers). The unique porous size in stepped arrangement of DBp-Ca2+give it selective adsorption capacity during coagulation process, resulted in rapid hemorrhage control. Based on in vitro and in vivo studies, it was confirmed that the primary micropores of DBp-Ca2+gave it high porosity to hold water (water absorption: 78.46 ± 1.12 %) and protein (protein absorption: 83.7 ± 1.33 mg/g). Its secondary mesopores to macropores could reduce of water diffusion length to accelerate blood exchange (complete within 300 ms). The tertiary stacking pores of DBp-Ca2+ could absorb platelets and erythrocytes to reduce more than 50 % of thrombosis time, and provided enough contact between Ca active site and coagulation factors for triggering clotting cascade reaction. This work not only developed a novel DBs based hemostat with efficient hemorrhage control, but also provided new insights to study procoagulant mechanism of inorganic hemostat with hierarchical porous structure from selective adsorption to rapid hemostasis.

PEG-mediated hybrid hemostatic gauze with in-situ growth and tightly-bound mesoporous silicon.

Pre-hospital control of bleeding is critical to save lives, however the development of hemostatic agents with efficient and safe performance is still a challenge. In this study, a hybrid hemostatic gauze (MG-PEG) with in-situ growth and tightly bound mesoporous silicon (MSN) was prepared by template method for hemorrhage control. This material integrated meso-porosity, blood coagulation and stability into flexible gauze fiber. The PEG in MG-PEG was not only used as template for the in-suit MSN growth, but also acted as joint connection between the gauze fibers and MSN. The MSN particles were firmly bound to the surface of gauze fibers with extremely low leakage after 3 min of sonication and displayed a comparable coagulant activity to untreated sample. The results of animal experiments confirmed that MG-PEG possessed superior hemostatic performance over silicates-based inorganic hemostasis-Combat Gauze, in terms of higher coagulant activity (in vivo clotting time <200 s), minimized loss of active components (liquids OD was only 3 % of CG), well biocompatibility (hemolysis ratio < 5 %, no cytotoxicity) and wider indications range for practical application.

Reversible Regulation of the Reactive Oxygen Species Level Using a Semiconductor Heterojunction.

Here, we proposed a novel solution for reversible regulation of the reactive oxygen species (ROS) level using a semiconductor heterojunction. Two metal-based ROS scavengers containing n-type CeO2 nanoparticles and n-type Cu-doped diatom biosilica (Cu-DBs) were integrated by a hydrothermal method to form a typical n-n semiconductor heterojunction (Ce/Cu-DBs). Unlike the control of the ROS level by a single ROS scavenger or ROS-generating agent, Ce/Cu-DBs could quickly eliminate ROS by cascade catalytic reaction, which readily switched to ROS generation through a near-infrared (NIR)-triggered photocatalytic effect. This NIR mediated ROS regulation system provided a noninvasive strategy for reversible control of the ROS level in vitro and in vivo. The Ce/Cu-DBs could relieve cellular oxidative stress by clearing local excessive ROS while inhibiting bacterial growth by increasing ROS levels under NIR radiation. Benefiting from the reversible regulatory effect of Ce/Cu-DBs, programmable healing of infected wounds was realized via on-demand anti-infection and inflammation reduction. This work provided a general method with highly spatiotemporal resolution to a remote and sustainable control ROS level, which had great potential for the biomedical field and regulation of chemical reactions.

Diatomite hemostatic particles with hierarchical porous structure for rapid and effective hemostasis.

The development of fast, safe and effective hemostatic materials is crucial for pre-hospital first aid. In this study, diatomite hemostatic granules (Dhp) were developed by rotating granulation method using silica sol as binder. During rotating granulation process, the Pre-Dhp were prepared by rolling snowball effect, in which nano-silica in silica sol uniformly distributed on the surface of diatomite and polymerized through hydrogen bond to produce strong adhesion. After high-temperature calcination, the hydrogen bond transformed to silica oxygen bond and the three-dimensional gel network formed by silica sol was destroyed to exposed the pores of diatomite. Dhp retained the porous structure of diatomite with hierarchical porous structure (from nano to micro scale). Dhp could quickly adsorb the tangible components in the blood, exhibited rapid hemostatic ability (clotting time was shortened by 43 % than that of control group), and good biocompatibility (hemolysis rate < 7 %, no cytotoxicity). Dhp residue was not found in the wound of rat tail amputation model, indicating that the adhesion of silica sol and high-temperature curing treatment enhanced the stability of Dhp and reduced the hidden danger of micro thrombosis caused by residual substances entering blood vessels. Our study proved that Dhp prepared by silica sol bonding and rotary granulation was excellent hemostatic material with non-toxic side effects and rapid coagulation promotion.

Enhanced mechanical properties of hydroxybutyl chitosan hydrogel through anchoring interface effects of diatom biosilica.

The temperature-sensitive hydrogel (H/D) composed of hydroxybutyl chitosan (HBC) and diatom biosilica (DB) was prepared by physically mixing HBC solution with DB at low temperature. The rheological measurements confirmed that the incorporation of DB to hydroxybutyl chitosan could significantly enhance the mechanical strength of the hydrogels without disrupting its reversible phase transition behavior. The hierarchical porous structure of DB and its rich negatively charged surface provided penetration anchor points for HBC molecular chains, which significantly enhanced the mechanical properties of H/D. The gelation temperature, gelation time and mechanical strength could be easily regulated by change of the ratio of DB in composite hydrogel. The maximum storage modulus of HBC hydrogel was increased to 17 times after adding DB. H/D exhibited favorable blood compatibility (hemolysis rate < 5 %) and no cytotoxicity to L929 cells which are promising for the applications as tissue regeneration materials and wound dressing in biomedical fields.

Thrombin immobilized polydopamine-diatom biosilica for effective hemorrhage control.

In this study, an efficient composite hemostatic material (DA-diatom-T) was prepared, using a polydopamine layer as a linker to immobilize thrombin on the surface of diatom biosilica. DA-diatom-T retained the porous structure of the diatom with high water absorption capacity, which can absorb 31 times its own weight of water. The thrombin activity of DA-diatom-T was as high as 5.81 U mg-1 that could be maintained at 67% after 30 days at room temperature. DA-diatom-T exhibited non-toxicity to mouse fibroblast cell lines, favorable hemocompatibility and fast procoagulant ability. DA-diatom-T could promote the initiation of the coagulation process and increase platelet activity and blood clot strength to form a physical barrier at the wound. In an in vivo study, DA-diatom-T could significantly reduce the clotting time and reduce the bleeding volume. The above results showed that DA-diatom-T had potential as a new hemostatic material.

A composite sponge based on alkylated chitosan and diatom-biosilica for rapid hemostasis.

Rapid control of bleeding is of great significance in military trauma and traffic accidents. In this study, alkylated chitosan (AC) and diatom biosilica (DB) were combined to develop a safe and effective hemostatic composite sponge (AC-DB sponge) for hemorrhage control. Due to the procoagulant chemical structure of AC-DB sponge, it exhibited rapid hemostatic ability in vitro (clotting time was shortened by 78% than that of control group), with favorable biocompatibility (hemolysis ratio < 5%, no cytotoxicity). The strong interface effect between AC-DB sponge and blood induced the erythrocyte and platelets activation, deformation and aggregation, intrinsic coagulation pathway activation, resulting in significant coagulation acceleration. AC-DB sponge had excellent performance in in vivo assessments with shortest clotting time (106.2 s) and minimal blood loss (328.5 mg). All above results proved that AC-DB sponge had great potential to be a safe and rapid hemostatic material.

Hypoxia-modulatory nanomaterials to relieve tumor hypoxic microenvironment and enhance immunotherapy: Where do we stand?

The past several years have witnessed the blooming of emerging immunotherapy, as well as their therapeutic potential in remodeling the immune system. Nevertheless, with the development of biological mechanisms in oncology, it has been demonstrated that hypoxic tumor microenvironment (TME) seriously impairs the therapeutic outcomes of immunotherapy. Hypoxia, caused by Warburg effect and insufficient oxygen delivery, has been considered as a primary construction element of TME and drawn tremendous attention in cancer therapy. Multiple hypoxia-modulatory theranostic agents have been facing many obstacles and challenges while offering initial therapeutic effect. Inspired by versatile nanomaterials, great efforts have been devoted to design hypoxia-based nanoplatforms to preserve drug activity, reduce systemic toxicity, provide adequate oxygenation, and eventually ameliorate hypoxic-tumor management. Besides these, recently, some curative and innovative hypoxia-related nanoplatforms have been applied in synergistic immunotherapy, especially in combination with immune checkpoint blockade (ICB), immunomodulatory therapeutics, cancer vaccine therapy and immunogenic cell death (ICD) effect. Herein, the paramount impact of hypoxia on tumor immune escape was initially described and discussed, followed by a comprehensive overview on the design tactics of multimodal nanoplatforms based on hypoxia-enabled theranostic agents. A variety of nanocarriers for relieving tumor hypoxic microenvironment were also summarized. On this basis, we presented the latest progress in the use of hypoxia-modulatory nanomaterials for synergistic immunotherapy and highlighted current challenges and plausible promises in this area in the near future. STATEMENT OF SIGNIFICANCE: Cancer immunotherapy, emerging as a novel treatment to eradicate malignant tumors, has achieved a measure of success in clinical popularity and transition. However, over the last decades, hypoxia-induced tumor immune escape has attracted enormous attention in cancer treatment. Limitations of free targeting agents have paved the path for the development of multiple nanomaterials with the hope of boosting immunotherapy. In this review, the innovative design tactics and multifunctional nanocarriers for hypoxia alleviation are summarized, and the smart nanomaterial-assisted hypoxia-modulatory therapeutics for synergistic immunotherapy and versatile biomedical applications are especially highlighted. In addition, the challenges and prospects of clinical transformation are further discussed.

Multilayer calcium alginate beads containing Diatom Biosilica and Bacillus subtilis as microecologics for sewage treatment.

Organic matter pollution and heavy metal pollution have become one of the main problems in water recycling, and the strategy to simultaneously remove soluble organic matter and metal ions is crucial for sewage treatment. In this study, multilayer calcium Alginate beads (n-Alg-DBs-Bas) containing Diatom Biosilica (DBs) and Bacillus subtilis (Bas) were designed as microecologics for sewage treatment. The introduction of DBs in beads and the multilayer structure could promote Bas growth, prolong the stability of the beads, and enhance the adsorption of beads, further improve the sewage treatment efficiency. The organic matter degradation of 3 layered Alg-DBs-Bas reached to 68.23 ± 0.95 % of COD and 58.88 ± 0.84 % of NH4+-N, and the metal ion adsorption was up to 119.31 mg/g for Fe3+, 110.81 mg/g for Zn2+ and 141.34 mg/g for Cu2+. The prepared multilayer calcium alginate beads combined organic matter degradation and metal ions absorption, which is significant for environmental applications.

Chitosan/Diatom-Biosilica Aerogel with Controlled Porous Structure for Rapid Hemostasis.

Uncontrolled hemorrhage is the main reason of possible preventable death after accidental injury. It is necessary to develop a hemostatic agent with rapid hemostatic performance and good biocompatibility. In this study, a chitosan/diatom-biosilica-based aerogel is developed using dopamine as cross-linker by simple alkaline precipitation and tert-butyl alcohol replacement. The chitosan/diatom-biosilica aerogel exhibits favorable biocompatibility and multiscale hierarchical porous structure (from nanometer to micrometer), which can be controlled by the concentration of tert-butyl alcohol. The displacement of tert-butyl alcohol can keep the porosity of diatom-biosilica in aerogel and give it large surface with efficient water absorption ratio. 30% tert-butyl alcohol replacement of aerogel possesses the largest surface area (74.441 m2 g-1 ), water absorption capacity (316.83 ± 2.04%), and excellent hemostatic performance in vitro blood coagulation (≈70 s). Furthermore, this aerogel exhibits the shortest clotting time and lowest blood loss in rat hemorrhage model. The strong interface effect between aerogel and blood is able to promote erythrocytes aggregation, platelets adhesion, and activation, as well as, activate the intrinsic coagulation pathway to accelerate blood coagulation. All the above results demonstrate that chitosan/diatom-biosilica aerogel has great potential to be a safe and rapid hemostatic material.

Hydroxybutyl chitosan/diatom-biosilica composite sponge for hemorrhage control.

Effective bleeding control is critical first step in current civilian and military trauma treatment, however commercially available hemostatic materials are difficult to achieve expected effects. In this study, a composite sponge (H-D) based on hydroxybutyl chitosan (HBC) and diatom-biosilica (DB) was designed for hemorrhage control. H-D exhibited hierarchical porous structure, favorable biocompatibility (hemolysis ratio < 5 %, no cytotoxicity), along with high and fast fluid absorbability (11-16 times than that of weight), given effective hemostasis effect (clotting time shortened by 70 % than that of control). In vitro coagulation tests demonstrated that H-D could provide strong interface effect to induce erythrocyte absorption and aggregation, as well as activating the intrinsic coagulation pathway and thus accelerated blood coagulation. These results proved that H-D composite sponge has great potential for hemorrhage control.

pH-sensitive amphiphilic chitosan-quercetin conjugate for intracellular delivery of doxorubicin enhancement.

A novel pH-responsive nanomicelle (QT-CA-CS) based on Chitosan, Quercetin and Citraconic anhydride was reported in this study. The QT-CA-CS could self-assemble into nanomicelles for encapsulating anticancer drug doxorubicin (DOX) by ultrasound. The novel nanomicelles had P-gp inhibition and pH responsiveness, which was capable of inhibiting drug efflux and responding to an endo/lysosomal acidic environment. The drug loaded nanomicelles had high encapsulation rate (more than 80%), small particle size (133.52 ± 4.13 nm) and positive zeta potential (+13.5 mV). The release rate of doxorubicin and quercetin in pH 4.5 was faster than that in pH 7.4. QT-CA-CS-DOX nanomicelles could promote cellular uptake of doxorubicin by drug resistance cell line (MCF-7/ADR), which was 8.62 folds higher than that of free doxorubicin. Most importantly, QT-CA-CS-DOX nanomicelles could escape from lysosomes and rapidly release doxorubicin and quercetin in the cytoplasm, which had an enhanced inhibitory effect on tumor cells, especially for MCF-7/ADR. The above results proved that the high potential of QT-CA-CS-DOX nanomicelles for multidrug resistance related tumor therapy.

Gastric environment-stable oral nanocarriers for in situ colorectal cancer therapy.

Colorectal cancer (CRC) is a prevalent and fatal cancer. Oral administration provided the potential for in situ treatment of the colorectal cancer. However, drugs couldn't be well-absorbed mainly due to its degradation in the gastric area and poor intestinal permeability. In this study, we synthesized deoxycholic acid and hydroxybutyl decorated chitosan nanoparticles (DAHBC NPs) as oral curcumin (CUR) delivery system for colorectal cancer treatment. DAHBC with lower critical solution temperature (LCST) below 37 °C (27-33 °C) was obtained. DAHBC NPs were correspondingly stable in simulated gastric conditions (pH 1.2, 37 °C), due to the offset of size change between pH-responsive expansion and thermo-responsive shrinkage. In simulated intestinal tract (pH 7.0-7.4, 37 °C), DAHBC NPs exhibited burst release of CUR owing to the onefold effect of thermo-responsive shrinkage. DAHBC27 NPs showed the minimum CUR leakage (~10%) in simulated gastric conditions, because a furthest temperature-sensitive shrinkage caused by the lowest LCST offset the expansion in acid environment. DAHBC27 NPs induced ~10-fold increased (P < 0.05) CUR absorption by paracellular transport pathway, compared to the free CUR. Thus, DAHBC NPs stabilized in the gastric environment may be a promising oral drugs delivery system for effective in situ colorectal cancer therapy.

Multifunctional quercetin conjugated chitosan nano-micelles with P-gp inhibition and permeation enhancement of anticancer drug.

In this study, quercetin-chitosan conjugate (QT-CS) was synthesized for oral delivery of doxorubicin (DOX) to improve its oral bioavailability by increasing its water solubility, opening tight junction and bypassing the P-glycoprotein (P-gp). The prepared QT-CS self-assembled into micelles which could encapsulate DOX with high encapsulation rate, small particle size (136.9 nm) and strong zeta potential (+16.2 mV). QT-CS-DOX micelles displayed sustained-release profile in gastrointestinal simulation fluid (pH 1.2/pH 7.4). QT-CS micelles could promote cellular uptake of doxorubicin, which was 2.2 folds higher than that of free doxorubicin. The trans epithelial electrical resistance (TEER) value of Caco-2 monolayer cells was significantly reduced (about 57%) by drug loaded QT-CS micelles, leading to a high apparent permeability coefficient (Papp) of doxorubicin, which was 10.17 folds higher than that of free doxorubicin. Above results indicate that QT-CS micelles are promising vehicles for the oral delivery of insoluble anticancer drugs.

Multifunctional chitosan/dopamine/diatom-biosilica composite beads for rapid blood coagulation.

Uncontrollable bleeding is the main cause of death in wars and accidents. The development of emergency material for rapid hemostatic can effectively reduce bleeding-related death. The commercial hemostatic materials available in the market are difficult to meet requirements of rapid hemostasis, good biocompatibility, low cost and ease of use. In this study, we developed chitosan/dopamine/diatom-biosilica composite beads (CDDs) for rapid hemostasis with good biocompatibility. CDDs were prepared by combining chitosan with diatom-biosilica (DB) using dopamine as bio-glue. The porous internal structure of CDDs led to rapid and large amount of water absorption, which contributed to the rapid hemostasis (83 s, 22% of the control group). The hemolytic rate of CDDs was less than 5% and cell viability was above 80%, confirming its good biocompatibility. All the above results indicated that CDDs had potential to develop into safe and non-toxic hemostatic material.

Biosynthetic calcium-doped biosilica with multiple hemostatic properties for hemorrhage control.

In this study, we reported calcium-doped biosilica (Ca-biosilica) with multiple hemostatic properties derived from Coscinodiscus sp. frustule. The incorporation of calcium into the diatom frustule was achieved by a simple biosynthetic route through feeding the diatoms with calcium chloride, which was confirmed by calcein staining and EDXS. Ca-Biosilica exhibited an efficient water absorption ratio (36.36 ± 1.44 times its own weight of liquid), superior compatibility (hemolysis ratio <5%, no cytotoxicity against MEFs) and excellent hemostatic effect (203.67 ± 15.63 s at 5 mg mL-1; 145.01 ± 20.41 s at 10 mg mL-1). The intrinsic blood coagulation pathway was clearly strengthened by the unique interface of Ca-biosilica, which was rich in silanol groups and calcium, leading to fast hemorrhage control in rat-tail amputation model. The clotting time of Ca-biosilica was 88.34 ± 28.54 s, which was similar to that of Quickclot® zeolite, whereas only one-third blood loss by weight (0.21 ± 0.16 g) was found in Ca-biosilica-treated group compared with that of the Quickclot® zeolite group (0.63 ± 0.09 g). The results prove that Ca-biosilica is promising as a quick hemostatic agent due to its effectiveness, excellent biocompatibility and simple and environmentally friendly preparation process.

Construction of multilayer alginate hydrogel beads for oral delivery of probiotics cells.

Multilayer alginate hydrogel beads (MAHBs), which were prepared by emulsion method, had been fabricated via the ionic crosslinking between calcium ion (Ca2+) and carboxylic group of alginate and utilized as encapsulating material for oral delivery of a model probiotic bacteria Bifidobacterium breve. Optical and fluorescence microscopy obviously showed the microorganism cells were encapsulated in the core beads. The viability of B. breve cells encapsulated in MAHBs was significantly enhanced compared with ordinary free cultured ones, the top CFU per mL were (3.70±0.20)×107 and (2.61±0.22)×107 respectively. Meanwhile, B. breve cells encapsulated in MAHBs could still keep viability even after 12h' culture in the broth with pH value similar to gastric juice, while the free cultured cells had no activity in such culture condition. To test applicability of MAHBs for the delivery of microorganisms, a Gram-positive strain, Staphylococcus aureus, as well as a Gram-negative strain, Escherichia coli, were also employed and encapsulated in MAHBs. Similar to B. breve cells, the viability of encapsulated S. aureus cells and E. coli cells in extreme pH value environment were significantly promoted. In addition, a high α-amylase yielding efficiency Bacillus subtilis strain was found and encapsulated in MAHBs. Compared with control groups, MAHBs encapsulated B. subtilis cells produced more α-amylase after 240h' culture, while the release of this enzyme was sustained rather than the burst release like free cultured group, which means this system would not reduce metabolite yield while having long term sustained-release effect. In summary, MAHBs are favorable biological carrier, which has the potential of being applied to oral delivery of probiotics.