CaCO3/Tetraethylenepentamine-Graphene Hollow Microspheres as Biocompatible Bone Drug Carriers for Controlled Release

Quercetin directed transformation of calcium carbonate into porous calcite and their application as delivery system for future foods

The hierarchically porous property of CaCO3 has attracted considerable attention in the field of active delivery ingredients due to its high adsorption capacity. Here, a facile and high-efficient approach to control the calcification processes of CaCO3 ending with calcite microparticles with superior porosity and stability is reported and evaluated. In this work, a series of quercetin promoted CaCO3 microparticles, using soy protein isolate (SPI) as entrapment agent, was synthesized, characterized, and their digestive behavior and antibacterial activity were evaluated. Results obtained indicated that quercetin showed good ability to direct the calcification pathway of amorphous calcium carbonate (ACC) with the formation of flower- and petal-like structures. The quercetin-loaded CaCO3 microparticles (QCM) had a macro-meso-micropore structure, which was identified to be the calcite form. The macro-meso-micropore structure provided QCM with the largest surface area of 78.984 m2g-1. The loading ratio of SPI to QCM was up to 200.94 μg per mg of QCM. The protein and quercetin composite microparticles (PQM) were produced by simply dissolving the CaCO3 core, and the obtained PQM was used for the delivery of quercetin and protein. Thermogravimetric analysis showed PQM presented with good thermal stability without the CaCO3 core. Furthermore, minor discrepancy was noted in protein conformational structures after removing the CaCO3 core. In vitro digestion revealed that approximately 80% of the loaded quercetin was released from PQM during intestinal digestion, and the released quercetin exhibited efficient transportation across the Caco-2 cell monolayer. More importantly, the PQM digesta retained enhanced antibacterial activities to inhibit growth of Escherichia coli and Staphylococcus aureus. Porous calcites show a high potential as a delivery system for food applications.

Titanium Carbide MXene Quantum Dots-Modified Hydroxyapatite Hollow Microspheres as pH/Near-Infrared Dual-Response Drug Carriers

Titanium carbide MXene quantum dots (MQDs) possess intrinsic regulatory properties and selective toxicity to cancer cells. Here, MDQs were selected for the modification of hydroxyapatite (HA) microspheres, and MXene quantum dots-modified hydroxyapatite (MQDs-HA) hollow microspheres with controllable shapes and sizes were prepared as bone drug carriers. The results show that the prepared MQDs-HA hollow microspheres had a large BET surface area (231.2 m2/g), good fluorescence, and low toxicity. In addition, MQDs-HA showed a mild storage-release behavior and good responsiveness of pH and near-infrared (NIR). Thus, the MQDs-HA hollow microspheres have broad application prospects in the field of drug delivery and photothermal therapy.

Regenerative marine waste towards CaCO3 nanoformulation for Alzheimer's therapy

Alzheimer's disorder (AD) is associated with behavioural and cognitive destruction with due respect to the neurological degeneration. Conventional therapeutic approach for treatment of AD using neuroprotective drugs suffered certain limitations such as poor solubility, insufficient bioavailability, adverse side effects at higher dose and ineffective permeability on blood brain barrier (BBB). Development of nanomaterial based drug delivery system helped to overcome these barriers. Hence the present work focused on encapsulating neuroprotective drug citronellyl acetate within CaCO₃ nanoparticles to develop neuroprotective CaCO₃ nanoformulation (CA@CaCO₃ NFs). CaCO₃ was derived from marine conch shell waste, while the neuroprotective drug citronellyl acetate was scrutinized by in-silico high throughput screening. In-vitro findings revealed that CA@CaCO₃ nanoformulation exhibited enhanced free radical scavenging activity of 92% (IC₅₀ value - 29.27 ± 2.6 μg/ml), AChE inhibition of 95% (IC₅₀ value - 25.6292 ± 1.5 μg/ml) at its maximum dose (100 μg/ml). CA@CaCO₃ NFs attenuated the aggregation of β-amyloid peptide (Aβ) and also disaggregated the preformed mature plaques the major risk factor for AD. Overall, the present study reveals that CaCO₃ nanoformulations exhibits potent neuroprotective potential when compared to the CaCO₃ nanoparticles alone and citronellyl acetate alone due to the sustained drug release and synergistic effect of CaCO₃ nanoparticles and citronellyl acetate depicting the fact that CaCO₃ can act as promising drug delivery system for treatment of neurodegenerative and CNS related disorders.

NiS Nanosheets Decorated on Hollow Carbon Spheres from Liquefied Wood for Supercapacitors

Carbon-based supercapacitors with high performance have a wide foreground among various energy storage devices. In this work, wood-based hollow carbon spheres (WHCS) were prepared from liquefied wood through the processes of emulsification, curing, carbonization, and activation. Then, the hydrodeposition method was used to introduce nickel sulfide (NiS) to the surface of the microspheres, obtaining NiS/WHCS as the supercapacitor electrode. The results show that NiS/WHCS microspheres exhibited a core-shell structure and flower-like morphology with a specific surface (307.55 m² g^-1) and a large total pore volume (0.14 cm³ g^-1). Also, the capacitance could be up to 1533.6 F g^-1 at a current density of 1 A g^-1. In addition, after 1000 charge/discharge cycles, the specific capacitance remained at 72.8% at the initial current density of 5 A g^-1. Hence, NiS/WHCS with excellent durability and high specific capacitance is a potential candidate for electrode materials.

Calcium carbonate: controlled synthesis, surface functionalization, and nanostructured materials

Calcium carbonate (CaCO₃) is an important inorganic mineral in biological and geological systems. Traditionally, it is widely used in plastics, papermaking, ink, building materials, textiles, cosmetics, and food. Over the last decade, there has been rapid development in the controlled synthesis and surface modification of CaCO₃, the stabilization of amorphous CaCO₃ (ACC), and CaCO₃-based nanostructured materials. In this review, the controlled synthesis of CaCO₃ is first examined, including Ca²⁺-CO₃^2- systems, solid-liquid-gas carbonation, water-in-oil reverse emulsions, and biomineralization. Advancing insights into the nucleation and crystallization of CaCO₃ have led to the development of efficient routes towards the controlled synthesis of CaCO₃ with specific sizes, morphologies, and polymorphs. Recently-developed surface modification methods of CaCO₃ include organic and inorganic modifications, as well as intensified surface reactions. The resultant CaCO₃ can then be further engineered via template-induced biomineralization and layer-by-layer assembly into porous, hollow, or core-shell organic-inorganic nanocomposites. The introduction of CaCO₃ into nanostructured materials has led to a significant improvement in the mechanical, optical, magnetic, and catalytic properties of such materials, with the resultant CaCO₃-based nanostructured materials showing great potential for use in biomaterials and biomedicine, environmental remediation, and energy production and storage. The influences that the preparation conditions and additives have on ACC preparation and stabilization are also discussed. Studies indicate that ACC can be used to construct environmentally-friendly hybrid films, supramolecular hydrogels, and drug vehicles. Finally, the existing challenges and future directions of the controlled synthesis and functionalization of CaCO₃ and its expanding applications are highlighted.

Mechanical Properties of Single-Crystal Calcite and Their Temperature and Strain-Rate Effects

Calcite is the most stable crystalline phase of calcium carbonate. It is applied or found in composite products, the food industry, biomineralization, archaeology, and geology, and its mechanical properties have attracted more and more attention. In this paper, the mechanical behaviors of single-crystal calcite under uniaxial tension in different directions were simulated with the molecular dynamics method. The obtained elastic moduli are in good agreement with the experimental results. It has been found from further research that single-crystal calcite has typical quasi-brittle failure characteristics, and its elastic modulus, fracture strength, and fracture strain are all strongly anisotropic. The tensile failure is caused by dislocation emission, void formation, and phase transition along the [010] and [421] directions, but by continuous dislocation glide and multiplication along the [421¯] direction. The fracture strength, fracture strain, and elastic modulus are all sensitive to temperature, but only elastic modulus is not sensitive to strain rate. The effects of temperature and logarithmic strain rate on fracture strength are in good agreement with the predictions of fracture dynamics.

Fabrication of Porous Phosphate/Carbonate Composites: Smart Fertilizer with Bimodal Controlled-Release Kinetics and Glyphosate Adsorption Ability

A simple method to prepare phosphate/carbonate composites for use as porous sponge-like phosphate fertilizers (ps-PO₄Fs) is presented. The composites ps-PO₄Fs were prepared by ion-exchange implantation of phosphate onto the surface of vaterite-phase calcium carbonate (CaCO₃) microparticles. The ps-PO₄Fs obtained under the optimized conditions were found to contain a nanoscale porous network of calcium phosphate covering the CaCO₃ support. In addition, ps-PO₄Fs exhibited two distinct phosphate release modes having different kinetics: a fast-release step over the initial 24 h period following a parabolic diffusion model, indicating controlled diffusion from external surfaces/edges, and a second slow-release step over the course of a month following the Ritger-Peppas model, indicating the release and diffusion of phosphate adsorbed at specific sites. The ps-PO₄Fs also adsorbed glyphosate well because of their porous structure and large surface area. However, glyphosate adsorption prevented phosphate release at concentrations greater than 10 mg L^-1. The ps-PO₄Fs were tested for their effects on plant growth and showed effects similar to commercial fertilizers. In summary, these smart, eco-friendly, and multifunctional fertilizers having two-stage phosphate release could enable the application of lower amounts of fertilizer and remove excess glyphosate from the environment.

Antimicrobial Peptides-Loaded Hydroxyapatite Microsphere With Different Hierarchical Structures for Enhanced Drug Loading, Sustained Release and Antibacterial Activity

Antimicrobial peptides (AMPs) have great potential for clinical treatment of bacterial infection due to the broad-spectrum and highly effective antibacterial activity. However, the easy degradation and inactivation in vivo has been a major obstacle for their application and an effective delivery system is demanding. The surface physicochemical properties of the carrier, including surface potential, surface polarity, pore structure and morphology, have exerted great effects on the adsorption and release behavior of AMPs. This study investigated the influence of micro/nano carriers with different hierarchical structures on the loading, release and biological behavior of AMPs. Three types of AMPs-loaded hydroxyapatite microspheres (HA/AMPs MSs) with different hierarchical structures (needle-like, rod-like, and flake-like) were developed, which was investigated by the surface morphology, chemical composition and surface potential in detail. The different hierarchical structures of hydroxyapatite microspheres (HA MSs) had noticeable impact on the loading and release behavior of AMPs, and the flake-like HA MSs with hierarchical structure showed the highest loading efficiency and long-lasting release over 9 days. Meanwhile, the stability of AMPs released from HA MSs was effectively maintained. Moreover, the antibacterial test indicated that the flake-like HA/AMPs MSs showed more sustained antibacterial properties among three composites. In view of the excellent biocompatibility and osteogenic property, high loading efficiency and the long-term release properties of HA MSs with hierarchical structure, the HA/AMPs MSs have a great potential in bone tissue engineering.

Magnetic mesoporous embolic microspheres in transcatheter arterial chemoembolization for liver cancer

Transcatheter arterial chemoembolization (TACE) is the main treatment for liver cancer. Although many embolic agents have been exploited in TACE, embolic agents combining embolization, drug loading, and imaging properties have not yet been constructed. Herein, we report a new magnetic mesoporous embolic microsphere that can simultaneously be loaded with doxorubicin (Dox), block vessels, and be observed by magnetic resonance imaging (MRI). The microspheres were prepared by decorating magnetic polystyrene/Fe₃O₄ particles with mesoporous organosilica microparticles (denoted as PS/Fe₃O₄@MONs). The PS/Fe₃O₄@MONs were uniformly spherical and large (50 µm), with a high specific surface area, uniform mesopores, and a Dox loading capacity of 460.8 µg mg^-1. Dox-loaded PS/Fe₃O₄@MONs (PS/Fe₃O₄@MON@Dox) effectively inhibited liver cancer cell growth. A VX2 rabbit liver tumor model was constructed to study the efficacy of TACE with PS/Fe₃O₄@MON@Dox. In vivo, PS/Fe₃O₄@MON@Dox could be smoothly delivered through an arterial catheter to achieve chemoembolization. Moreover, PS/Fe₃O₄@MON@Dox and residual tumor parenchyma could be distinguished on MRI, which is of great significance for evaluating the efficacy of TACE. Histopathology showed that PS/Fe₃O₄@MON@Dox could be deposited in the tumor vessels, completely blocking the blood supply. Overall, PS/Fe₃O₄@MON@Dox showed good drug loading, embolization and imaging performance as well as potential for use in TACE. STATEMENT OF SIGNIFICANCE: Transcatheter arterial chemoembolization (TACE) is the main treatment for liver cancer. Although many embolic agents have been exploited in TACE, embolic agents combining embolization, drug-loading, and imaging properties have not yet been constructed. In this work, we prepared magnetic mesoporous microspheres as a new embolic agent that can simultaneously load doxorubicin (Dox), block blood vessels and enable magnetic resonance imaging. Overall, this new embolic microsphere-mediated TACE strategy for liver cancer showed good therapeutic effects, and the PS/Fe₃O₄@MON@Dox embolic microspheres provide a new avenue for improving the efficacy of TACE for liver cancer and postoperative evaluation.

Urchin-like Hydroxyapatite/Graphene Hollow Microspheres as pH-Responsive Bone Drug Carriers

Hydroxyapatite (HA) is the main inorganic component of human bones and teeth. It has good biocompatibility and bioactivity, which promotes its good application prospects in the field of bone drug carriers. In this study, tetraethylenepentamine-graphene (rGO-TEPA)/CaCO₃:HA composite microspheres were prepared via microwave hydrothermal synthesis using rGO-TEPA/CaCO₃ solid microspheres as intermediates. Furthermore, the incompletely transformed CaCO₃ was removed by soaking in a citric acid buffer to obtain rGO-TEPA/HA hollow composite microspheres. The two types of as-prepared composite microspheres exhibited sea urchin-like structures, large BET surface areas, and good dispersibility. Mouse preosteoblast cells (MC3T3-E1) were used for in vitro cytotoxicity experiments. The in vitro cell viability test showed that the two composite drug carriers exhibited noncytotoxicity. Moreover, the doxorubicin (DOX) loading and releasing investigations revealed that the two types of prepared carriers had mild storage-release behaviors and good pH responsiveness. Hence, these rGO-TEPA/HA hollow microspheres have promising applications as bone drug carriers.

Synthesis and characterization of porous CaCO3 microspheres templated by yeast cells and the application as pH value-sensitive anticancer drug carrier

Using yeast as organic template and PDDA/PSS with opposite charge as polyelectrolyte, CaCO₃ was deposited on yeast cells by Layer-by-Layer self-assembly method, and then porous calcium carbonate hybrid microspheres (CaCO₃-HMPs) were prepared by calcination. The CaCO₃-HMPs were characterized by FT-IR, XRD, SEM and TG. It was found that the prepared CaCO₃-HMPs were nearly spherical, with visible pores on the surface, small particle size uniformity (d = 3 μ m) and good dispersion. Doxorubicin hydrochloride (DOX) was used as the model drug to study drug loading and release properties of CaCO₃-HMPs. Then, the drug loading, DOX release under different pH conditions, and the degradation of CaCO₃-HMPs under different pH conditions were investigated. The drug release test results showed that the DOX-loaded microspheres released more drugs (99 %) at pH = 4.8 than pH = 7. It indicated that the CaCO₃-HMPs were pH sensitive. The cytotoxicity of DOX-loaded microspheres was also studied. It was found that CaCO₃-HMPs had good biocompatibility. In addition, compared with DOX group, cytotoxicity test results showed that the DOX-loaded microspheres had the same efficacy but sustained drug release for up to 120 h. Therefore, the CaCO₃-HMP microspheres have good application prospects as anticancer drug carriers.

Black phosphorus-based 2D materials for bone therapy

Since their discovery, Black Phosphorus (BP)-based nanomaterials have received extensive attentions in the fields of electromechanics, optics and biomedicine, due to their remarkable properties and excellent biocompatibility. The most essential feature of BP is that it is composed of a single phosphorus element, which has a high degree of homology with the inorganic components of natural bone, therefore it has a full advantage in the treatment of bone defects. This review will first introduce the source, physicochemical properties, and degradation products of BP, then introduce the remodeling process of bone, and comprehensively summarize the progress of BP-based materials for bone therapy in the form of hydrogels, polymer membranes, microspheres, and three-dimensional (3D) printed scaffolds. Finally, we discuss the challenges and prospects of BP-based implant materials in bone immune regulation and outlook the future clinical application.

Applications of Graphene and Its Derivatives in Bone Repair: Advantages for Promoting Bone Formation and Providing Real-Time Detection, Challenges and Future Prospects

During continuous innovation in the preparation, characterization and application of various bone repair materials for several decades, nanomaterials have exhibited many unique advantages. As a kind of representative two-dimensional nanomaterials, graphene and its derivatives (GDs) such as graphene oxide and reduced graphene oxide have shown promising potential for the application in bone repair based on their excellent mechanical properties, electrical conductivity, large specific surface area (SSA) and atomic structure stability. Herein, we reviewed the updated application of them in bone repair in order to present, as comprehensively, as possible, their specific advantages, challenges and current solutions. Firstly, how their advantages have been utilized in bone repair materials with improved bone formation ability was discussed. Especially, the effects of further functionalization or modification were emphasized. Then, the signaling pathways involved in GDs-induced osteogenic differentiation of stem cells and immunomodulatory mechanism of GDs-induced bone regeneration were discussed. On the other hand, their applications as contrast agents in the field of bone repair were summarized. In addition, we also reviewed the progress and related principles of the effects of GDs parameters on cytotoxicity and residues. At last, the future research was prospected.

Synthesis of Polymer Assembled Mesoporous CaCO3 Nanoparticles for Molecular Targeting and pH-Responsive Controlled Drug Release

CaCO3 nanoparticles are very suitable as intelligent carriers because of their ideal biocompatibility and biodegradability, especially their sensitivity to pH. In this paper, we use mesoporous CaCO3 nanoparticles as intelligent carrier, sodium alginate, and chitosan as alternating assembly materials, folic acid as target molecules, and exploit layer-by-layer assembly technology to achieve sensitive molecular targeting and pH response drug release. Mesoporous CaCO3 hybrid nanoparticles have high drug loading on doxorubicin. The effects of different pH values on drug release in vitro were studied by regulating simulated body fluids with different pH values. The cytotoxicity, targeting effect, and drug release of human cervical cancer cell line (HeLa) were studied by cell vitality and imaging experiments. All the evidence suggests that the smart mesoporous CaCO3 nanoparticles may be a potential clinical application platform for cancer therapy.

Injectable Silk-Vaterite Composite Hydrogels with Tunable Sustained Drug Release Capacity

Improving the efficiency of chemotherapy remains a key challenge in drug delivery. Many drug carriers have been designed to achieve multifunctional factors as part of their performance, including controlled release, dispersibility in aqueous environments, and targeting to cancer sites. However, it is difficult to optimize multiple properties simultaneously for a single carrier system. Here, synergistic carriers composed of vaterite microspheres and silk nanofiber hydrogels were developed to improve the dispersibility of vaterite spheres and the control of drug delivery without compromising the injectability or sensitivity to pH. The vaterite microspheres were dispersed homogeneously and remained stable in the silk nanofiber hydrogels. Doxorubicin (DOX) was effectively loaded on the vaterite spheres and silk nanofibers, forming synergistic silk-vaterite hydrogel delivery systems. The sustained delivery of DOX was tuned and controlled by vaterite stability and the DOX content loaded on the spheres and nanofibers. The cytotoxicity was regulated via the controlled delivery of DOX, suggesting the possibility of optimizing chemotherapeutic strategies. These silk-vaterite delivery hydrogels suggest a useful strategy for designing novel delivery systems for improved delivery and therapeutic benefits.

Tumor-pH-Sensitive PLLA-Based Microsphere with Acid Cleavable Acetal Bonds on the Backbone for Efficient Localized Chemotherapy

Nanoparticle- and microsphere-based drug delivery systems (DDSs) have attracted wide attention in cancer therapy; those DDSs that are responsive to tumor environment can selectively identify tumor and normal tissues and therefore have shown enhanced anticancer efficacy and alleviated systemic toxicity. Here, tumor-pH-sensitive polymeric microspheres, which are prepared by multiblock poly(l-lactide) with pH-sensitive acetal bonds in the backbone, are employed to efficiently load water-soluble anticancer drug doxorubicin hydrochloride (DOX·HCl, drug loading content: ∼10%). The pH-sensitive DOX-loaded hollow microspheres were in the size range 2-10 μm and exhibited acid-accelerated degradation of polymer matrix and drug release, and thereby efficient in vitro cancer cell inhibition. The microspheres were further intratumorally injected into breast-tumor-bearing mice, and the in vivo anticancer experiment showed that pH-sensitive DOX-loaded microsphere showed better antitumor efficiency and prolonged life-span than its counterpart that does not have pH-responsive property. Moreover, negligible organ toxicity, especially cardiotoxicity that generally exists in DOX-involved chemotherapy where DOX is administrated by intravenous injection, was observed for DOX-loaded microspheres. Hence, tumor-pH-sensitive polymeric microspheres have appeared to be a simple and efficient platform for delivering hydrophilic anticancer drug with excellent anticancer efficacy and low systemic toxicity.

Fabrication of PAA-PETPTA Janus Microspheres with Respiratory Function for Controlled Release of Guests with Different Sizes

Poly(acrylic acid)-poly(ethoxylated trimethylolpropane triacrylate) (PAA-PETPTA) Janus microspheres with "respiratory" function for controlled release were prepared by polymerization of acrylic acid-ethoxylated trimethylolpropane triacrylate (AA-ETPTA) Janus microdroplets in a continuous oil phase in a simple capillary-based microfluidic device with the assistance of UV radiation. The flow rate ratios of AA and ETPTA phases and surfactant content in the continuous oil phase have a significant effect on the structure of the Janus microspheres. PAA part in the Janus microspheres has respiratory function for loading and release due to the different stimuli responses to different pHs. The hollow structure of PETPTA part with different sizes of opening serves as the host materials for PAA and could control release rate further due to the different opening sizes. The obtained PAA-PETPTA Janus microspheres showed high rhodamine B (RhB) loading of 860 mg g^-1 and different controlled-release behavior in water with different pHs. The release rate increases with the increase of pH and the contact area of PAA part with water. The maximum controlled-release time for RhB was about 3 h in water with pH of 5. In addition, the Janus microspheres also showed controlled-release behavior for larger size guests, e.g., 150 nm polystyrene beads, which indicated a wide range of application. The loading and release behaviors for guests, for instance, for RhB, have almost no change even after six times of reuse, which indicated a high stability.

Advances on graphene-based nanomaterials for biomedical applications

Graphene-based nanomaterials, such as graphene oxide and reduced graphene oxide, have been attracting increasing attention in the field of biology and biomedicine over the past few years. Incorporation of these novel materials with drug, gene, photosensitizer and other cargos to construct novel delivery systems has witnessed rapid advance on the basis of their large surface area, distinct surface properties, excellent biocompatibility and pH sensitivity. Moreover, the inherent photothermal effect of these appealing materials enables them with the ability of killing targeting cells via a physical mechanism. Recently, more attentions have been attached to tissue engineering, including bone, neural, cardiac, cartilage, musculoskeletal, and skin/adipose tissue engineering, due to the outstanding mechanical strength, stiffness, electrical conductivity, various two-dimensional (2D) and three-dimensional (3D) morphologies of graphene-based nanomaterials. Herein, emerging applications of these nanomaterials in bio-imaging, drug/gene delivery, phototherapy, multimodality therapy and tissue engineering were comprehensively reviewed. Inevitably, the burgeon of this kind of novel materials leads to the endeavor to consider their safety so that this issue has been deeply discussed and summarized in our review. We hope that this review offers an overall understanding of these nanomaterials for later in-depth investigations.

Protein-mediated mineralization of edaravone into injectable, pH-sensitive microspheres used for potential minimally invasive treatment of osteomyelitis

Osteomyelitis, an infection within bone, is difficult to treat.