2D Nanoclay for Biomedical Applications: Regenerative Medicine, Therapeutic Delivery, and Additive Manufacturing

The Effect of pH on the Viscoelastic Response of Alginate-Montmorillonite Nanocomposite Hydrogels

Ionically cross-linked alginate hydrogels are used in a wide range of applications, such as drug delivery, tissue engineering, and food packaging. A shortcoming of these gels is that they lose their strength and degrade at low pH values. To develop gels able to preserve their integrity in a wide range of pH values, Ca-alginate-montmorillonite nanocomposite gels are prepared, and their chemical structure, morphology, and mechanical response are analyzed. As the uniformity of nanocomposite gels is strongly affected by concentrations of MMT and CaCl2, it is revealed that homogeneous gels can be prepared with 4 wt.% MMT and 0.5 M CaCl2 at the highest. The viscoelastic behavior of nanocomposite gels in aqueous solutions with pH = 7 and pH = 2 is investigated by means of small-amplitude compressive oscillatory tests. It is shown that Ca-alginate-MMT nanocomposite gels preserve their integrity while being swollen at pH = 2. The experimental data are fitted by a model with only two material parameters, which shows that the elastic moduli increase linearly with a concentration of MMT at all pH values under investigation due to formation of physical bonds between alginate chains and MMT platelets. The presence of these bonds is confirmed by ATR-FTIR spectroscopy. The morphology of nanocomposite gels is studied by means of wide-angle X-ray diffraction, which reveals that intercalation of polymer chains between clay platelets increases the interlayer gallery spacing.

Current State and Perspectives of Exfoliated Zeolites

Zeolites are highly efficient industrial catalysts and sorbents with microporous framework structures. Approximately 10% of the frameworks, but eventually all in the long run, have produced both 3D crystals and 2D layers. The latter can be intercalated and expanded like all 2D materials but proved difficult to exfoliate directly into suspensions of monolayers in solution as precursors for unique synthetic opportunities. Successful exfoliations have been reported recently and are overviewed in this perspective article. The discussion highlights 3 primary challenges in this field, namely finding suitable 2D zeolite preparations that exfoliate directly in high yield, proving uniform layer thickness in solution and identifying applications to exploit the unique synthetic capabilities and properties of exfoliated zeolite monolayers. Four zeolites have been confirmed to exfoliate directly into monolayers: 3 with known structures-MWW, MFI, and RWR and one unknown, bifer with a unit cell close to ferrierite. The exfoliation into monolayers is confirmed by the combination of 5-6 characterization techniques including AFM, in situ and in-plane XRD, and microscopies. The promising areas of development are oriented films and membranes, intimately mixed zeolite phases, and hierarchical nanoscale composites with other active species like nanoparticles and clusters that are unfeasible by solid state processes.

Octacalcium phosphate, a promising bone substitute material: a narrative review

Biomaterials have been used to supplement and restore function and structure by replacing or restoring parts of damaged tissues and organs. In ancient times, the medical use of biomaterials was limited owing to infection during surgery and poor surgical techniques. However, in modern times, the medical applications of biomaterials are diversifying owing to great developments in material science and medical technology. In this paper, we introduce biomaterials, focusing on calcium phosphate ceramics, including octacalcium phosphate, which has recently attracted attention as a bone graft material.

The Art of Building Living Tissues: Exploring the Frontiers of Biofabrication with 3D Bioprinting

The scope of three-dimensional printing is expanding rapidly, with innovative approaches resulting in the evolution of state-of-the-art 3D bioprinting (3DbioP) techniques for solving issues in bioengineering and biopharmaceutical research. The methods and tools in 3DbioP emphasize the extrusion process, bioink formulation, and stability of the bioprinted scaffold. Thus, 3DbioP technology augments 3DP in the biological world by providing technical support to regenerative therapy, drug delivery, bioengineering of prosthetics, and drug kinetics research. Besides the above, drug delivery and dosage control have been achieved using 3D bioprinted microcarriers and capsules. Developing a stable, biocompatible, and versatile bioink is a primary requisite in biofabrication. The 3DbioP research is breaking the technical barriers at a breakneck speed. Numerous techniques and biomaterial advancements have helped to overcome current 3DbioP issues related to printability, stability, and bioink formulation. Therefore, this Review aims to provide an insight into the technical challenges of bioprinting, novel biomaterials for bioink formulation, and recently developed 3D bioprinting methods driving future applications in biofabrication research.

Montmorillonite-Sodium Alginate Oral Colon-Targeting Microcapsule Design for WGX-50 Encapsulation and Controlled Release in Gastro-Intestinal Tract

The montmorillonite-sodium alginate (MMT-SA) colon-targeting microcapsules have been designed as a WGX-50 encapsulation and controlled release vehicle used in oral administration. The MMT-SA microcapsule was formed from a cross-linking reaction, and the stable micropore in the microcapsule changed with a different MMT-SA mixed mass ratio. The MMT-SA microcapsule has a reinforced micropore structure and an enhanced swell-dissolution in SIF and SCF with alkaline environment, which is attributed to the incorporated MMT. The MMT-SA microcapsule exhibited a high WGX-50 encapsulation rate up to 98.81 ± 0.31% and an obvious WGX-50 controlled release in the simulated digestive fluid in vitro. The WGX-50 loaded with MMT-SA microcapsule showed a weak minimizing drug loss in SGF (Simulated Gastric Fluid) with an acidic environment, while it showed a strong maximizing drug release in SIF (Simulated Intestinal Fluid) and SCF (Simulated Colonic Fluid) with an alkaline environment. These features make the MMT-SA microcapsule a nominated vehicle for colon disease treatment used in oral administration.

Nanoclay-Doped Electrospun Nanofibers for Tissue Engineering: Investigation on the Structural Modifications in Physiological Environment

Background

Clay minerals are nanomaterials that have recently been recognized as enabling excipients that can promote cell adhesion, proliferation, and differentiation. When nanoclays are loaded in a 3D polymeric nanostructure, the cell-substrate interaction is enhanced, and other bioactive properties are optimized.

Purpose

In this study, hectorite (HEC)- and montmorillonite (MMT)-doped polymeric scaffolds were explored for the treatment of deep and chronic skin lesions.

Methods

Scaffolds were manufactured by means of electrospinning and then crosslinked by heating. Physicochemical analyses were correlated with in vitro biopharmaceutical characterization to predict the in vivo fate of the clay-doped scaffolds.

Results and Discussion

The addition of MMT or HEC to the polymeric scaffold framework modifies the surface arrangement and, consequently, the potential of the scaffolds to interact with biological proteins. The presence of nanoclays alters the nanofiber morphology and size, and MMT doping increases wettability and protein adhesion. This has an impact on fibroblast behavior in a shorter time since scaffold stiffness facilitates cell adhesion and cell proliferation.

Conclusion

MMT proved to perform better than HEC, and this could be related to its higher hydrophilicity and protein adhesion.

Tracking cellular uptake, intracellular trafficking and fate of nanoclay particles in human bone marrow stromal cells

Clay nanoparticles, in particular synthetic smectites, have generated interest in the field of tissue engineering and regenerative medicine due to their utility as cross-linkers for polymers in biomaterial design and as protein release modifiers for growth factor delivery. In addition, recent studies have suggested a direct influence on the osteogenic differentiation of responsive stem and progenitor cell populations. Relatively little is known however about the mechanisms underlying nanoclay bioactivity and in particular the cellular processes involved in nanoclay-stem cell interactions. In this study we employed confocal microscopy, inductively coupled plasma mass spectrometry and transmission electron microscopy to track the interactions between clay nanoparticles and human bone marrow stromal cells (hBMSCs). In particular we studied nanoparticle cellular uptake mechanisms and uptake kinetics, intracellular trafficking pathways and the fate of endocytosed nanoclay. We found that nanoclay particles present on the cell surface as μm-sized aggregates, enter hBMSCs through clathrin-mediated endocytosis, and their uptake kinetics follow a linear increase with time during the first week of nanoclay addition. The endocytosed particles were observed within the endosomal/lysosomal compartments and we found evidence for both intracellular degradation of nanoclay and exocytosis as well as an increase in autophagosomal activity. Inhibitor studies indicated that endocytosis was required for nanoclay upregulation of alkaline phosphatase activity but a similar dependency was not observed for autophagy. This study into the nature of nanoclay-stem cell interactions, in particular the intracellular processing of nanosilicate, may provide insights into the mechanisms underlying nanoclay bioactivity and inform the successful utilisation of clay nanoparticles in biomaterial design.

Size-dependent viscoelasticity in hybrid colloidal gels based on spherical soft nanoparticles and two-dimensional nanosilicates of varying size

HYPOTHESIS

Hetero-aggregation of oppositely charged colloidal particles with controlled architectural and interactional asymmetry allows modifying gel nanostructure and properties. We hypothesize the relative size ratio between cationic nanospheres and varied-size anionic two-dimensional nanoclays will influence the gel formation mechanisms and resulting rheological performance.

EXPERIMENTS

Hybrid colloidal gels formed via hetero-aggregation of cationic gelatin nanospheres (∼400 nm diameter) and five types of nanoclays with similar 1 nm thickness but different lateral sizes ranging from ∼ 30 nm to ∼ 3000 nm. Structure-property relationships were elucidated using a suite of techniques. Microscopy and scattering probed gel nanostructure and particle configuration. Rheology quantified linear and non-linear viscoelastic properties and yielding behavior. Birefringence and polarized imaging assessed size-dependent nanoclay alignment during shear flow.

FINDINGS

Nanoclay size ratio relative to nanospheres affected the gelation process, network structure, elasticity, yielding, and shear response. Gels with comparably sized components showed maximum elasticity, while yield stress depended on nanoclay rotational mobility. Shear-induced nanoclay alignment was quantified by birefringence, which is more pronounced for larger nanoclay. Varying nanoclay size and interactions with nanospheres controlled dispersion, aggregation, and nematic ordering. These findings indicate that architectural and interactional asymmetry enables more control over gel properties through controlled assembly of anisotropic building blocks.

Progress and future prospects of hemostatic materials based on nanostructured clay minerals

The occurrence of uncontrolled hemorrhage is a significant threat to human life and health. Although hemostatic materials have made remarkable advances in the biomaterials field, it remains a challenge to develop safe and effective hemostatic materials for global medical use. Natural clay minerals (CMs) have long been used as traditional inorganic hemostatic agents due to their good hemostatic capability, biocompatibility and easy availability. With the advancement of science, technology and ideology, CM-based hemostatic materials have undergone continuous innovations by integrating new inspirations with conventional concepts. This review systematically summarizes the hemostatic mechanisms of different natural CMs based on their nanostructures. Moreover, it also comprehensively reviews the latest research progress for CM-based hemostatic hybrid and nanocomposite materials, and discusses the challenges and developments in this field.

Nanoengineered injectable hydrogels derived from layered double hydroxides and alginate for sustained release of protein therapeutics in tissue engineering applications

Chronic Kidney Disease (CKD) which involves gradual loss of kidney function is characterized by low levels of a glycoprotein called Erythropoietin (EPO) that leads to red blood cell  deficiency and anemia. Recombinant human EPO (rhEPO) injections that are administered intravenously or subcutaneously is the current gold standard for treating CKD. The rhEPO injections have very short half-lives and thus demands frequent administration with a risk of high endogenous EPO levels leading to severe side effects that could prove fatal. To this effect, this work provides a novel approach of using lamellar inorganic solids with a brucite-like structure for controlling the release of protein therapeutics such as rhEPO in injectable hydrogels. The nanoengineered injectable system was formulated by incorporating two-dimensional layered double hydroxide (LDH) clay materials with a high surface area into alginate hydrogels for sustained delivery. The inclusion of LDH in the hydrogel network not only improved the mechanical properties of the hydrogels (5-30 times that of alginate hydrogel) but also exhibited a high binding affinity to proteins without altering their bioactivity and conformation. Furthermore, the nanoengineered injectable hydrogels (INHs) demonstrated quick gelation, injectability, and excellent adhesion properties on human skin. The in vitro release test of EPO from conventional alginate hydrogels (Alg-Gel) showed 86% EPO release within 108 h while INHs showed greater control over the initial burst and released only 24% of EPO in the same incubation time. INH-based ink was successfully used for 3D printing, resulting in scaffolds with good shape fidelity and stability in cell culture media. Controlled release of EPO from INHs facilitated superior angiogenic potential in ovo (chick chorioallantoic membrane) compared to Alg-Gel. When subcutaneously implanted in albino mice, the INHs formed a stable gel in vivo without inducing any adverse effects. The results suggest that the proposed INHs in this study can be utilized as a minimally invasive injectable platform or as 3D printed patches for the delivery of protein therapeutics to facilitate tissue regeneration.

pH-sensitive biosystem based on laponite RD/chitosan/polyvinyl alcohol hydrogels for controlled delivery of curcumin to breast cancer cells

In this study, a pH-responsive hydrogels based on laponite rapid dispersion (Lap®)/chitosan (CS)/polyvinyl alcohol (PVA) designed and was used for controlled delivery of the anticancer drug curcumin (CUR). First, it was accomplished by dissolving CUR in Lap® dispersion under the influence of the pH of the environment. Then, in the presence of Lap®CUR cross-linking was incorporated between CS and PVA polymers. The structural features of Lap®CUR/CS@PVA hydrogels are characterized using FT-IR, XRD, SEM/EDS, TEM, TGA, Zeta potential, and XPS. The in vitro drug release profiles confirmed a pH-responsive controlled release of CUR in acidic pH for all hydrogels. During 12 h, the cumulative release of CUR from Lap®CUR/0.1CS@PVA hydrogel was 27.9% and 12.3%, at pH 5.5 and 7.4, respectively. While during three days the release rate reached 48.5% and 18.5%. The CUR release kinetic from hydrogels also suggests that the kinetic data well fitted to the Korsmeyer-Peppas, diffusion-controlled and Fickian diffusion. Furthermore, in vitro cytotoxicity and DAPI staining study clearly illustrated that Lap®CUR/0.1CS@PVA hydrogel had lower cytotoxicity than CUR against MDA-MB 231 cancer cells, which confirmed the controlled release of drug through hydrogels. Meanwhile, in vitro hemolysis, antioxidant and antibacterial tests revealed that the prepared hydrogels have good blood compatibility, excellent antioxidant properties, and antibacterial activity. Based on the obtained results, the designed hydrogels could be potentially applied as pH-controlled drug delivery systems for cancer therapy.

Osteoimmunity-regulating nanosilicate-reinforced hydrogels for enhancing osseointegration

Following the introduction of osteo-immunomodulation as a new and important strategy to enhance material osseointegration, achieving an appropriate immune response after biomaterial implantation has become a significant challenge for efficient bone repair. In this study, a nanosilicate-reinforced sodium alginate (SA) hydrogel was fabricated by introducing montmorillonite (MMT) nanoparticles. Meanwhile, an immunogenically bioactive agent, harmine (HM), was loaded and released to induce macrophage differentiation into the M2 type. The fabricated SA/MMT/HM (SMH) hydrogel exhibited improved mechanical stiffness and stability, which also efficiently promoted macrophage anti-inflammatory M2 phenotype polarization and enhanced the secretion of pro-tissue healing cytokines for inducing a favorable immunomodulatory microenvironment for the osteogenic differentiation of bone marrow stromal cells (BMSCs). Furthermore, a rat air-pouch model and a critical-size bone defect model were used and the results showed that the SMH hydrogel increased the proportion of M2 macrophages and markedly reduced local inflammation, while enhancing desirable new bone formation. Transcriptomic analysis revealed that the SMH hydrogel accelerated the M1-to-M2 transition of macrophages by inhibiting relevant inflammatory signaling pathways and activating the PI3K-AKT1 signaling pathway. Taken together, this high-intensity immunomodulatory hydrogel may be a promising biomaterial for bone regeneration and provide a valuable base and positive enlightenment for massive bone defect repair.

An injectable bioactive dressing based on platelet-rich plasma and nanoclay: Sustained release of deferoxamine to accelerate chronic wound healing

Delayed diabetic wound healing has placed an enormous burden on society. The key factors limiting wound healing include unresolved inflammation and impaired angiogenesis. Platelet-rich plasma (PRP) gel, a popular biomaterial in the field of regeneration, has limited applications due to its non-injectable properties and rapid release and degradation of growth factors. Here, we prepared an injectable hydrogel (DPLG) based on PRP and laponite by a simple one-step mixing method. Taking advantages of the non-covalent interactions, DPLG could overcome the limitations of PRP gels, which is injectable to fill irregular injures and could serve as a local drug reservoir to achieve the sustained release of growth factors in PRP and deferoxamine (an angiogenesis promoter). DPLG has an excellent ability in accelerating wound healing by promoting macrophage polarization and angiogenesis in a full-thickness skin defect model in type I diabetic rats and normal rats. Taken together, this study may provide the ingenious and simple bioactive wound dressing with a superior ability to promote wound healing.

3D bioprinting of complex tissue scaffolds with in situ homogeneously mixed alginate-chitosan-kaolin bioink using advanced portable biopen

Control of in situ 3D bioprinting of hydrogel without toxic crosslinker is ideal for tissue regeneration by reinforcing and homogeneously distributing biocompatible reinforcing agent during fabrication of large area and complex tissue engineering scaffolds. In this study, homogeneous mixing, and simultaneous 3D bioprinting of a multicomponent bioink based on alginate (AL)-chitosan (CH), and kaolin was obtained by an advanced pen-type extruder to ensure structural and biological homogeneity during the large area tissue reconstruction. The static, dynamic and cyclic mechanical properties as well as in situ self-standing printability significantly improved with the kaolin concentration for AL-CH bioink-printed samples due to polymer-kaolin nanoclay hydrogen bonding and cross-linking with less amount of calcium ions. The Biowork pen ensures better mixing effectiveness for the kaolin-dispersed AL-CH hydrogels (evident from computational fluid dynamics study, aluminosilicate nanoclay mapping and 3D printing of complex multilayered structures) than the conventional mixing process. Two different cell lines (osteoblast and fibroblast) introduced during large area multilayered 3D bioprinting have confirmed the suitability of such multicomponent bioinks for in vitro even tissue regeneration. The effect of kaolin to promote uniform growth and proliferation of the cells throughout the bioprinted gel matrix is more significant for this advanced pen-type extruder processed samples.

Sumecton reinforced gelatin-based scaffolds for cell-free bone regeneration

Bone tissue engineering has risen to tackle the challenges of the current clinical need concerning bone fractures that is already considered a healthcare system problem. Scaffold systems for the repair of this tissue have yielded different combinations including biomaterials with nanotechnology or biological agents. Herein, three-dimensional porous hydrogels were engineered based on gelatin as a natural biomaterial and reinforced with synthetic saponite nanoclays. Scaffolds were biocompatible and shown to enhance the inherent properties of pristine ones, in particular, proved to withstand pressures similar to load-bearing tissues. Studies with murine mesenchymal stem cells found that scaffolds had the potential to proliferate and promote cell differentiation. In vivo experiments were conducted to gain insight about the ability of these cell-free scaffolds to regenerate bone, as well as to determine the role that these nanoparticles in the scaffold could play as a drug delivery system. SDF-1 loaded scaffolds showed the highest percentage of bone formation, which was corroborated by osteogenic markers and new blood vessels. Albeit a first attempt in the field of synthetic nanosilicates, these results suggest that the designed constructs may serve as delivery platforms for biomimetic agents to mend bony defects, circumventing high doses of therapeutics and cell-loading systems.

Hybrid cross-linked sodium carboxymethyl starch/polyacrylamide flexible sensing hydrogels with adhesion, antimicrobial properties and multiple responses

Ionic hydrogels used as ideal and flexible strain sensor materials should have excellent mechanical, adhesive and antimicrobial properties. However, it is challenging to achieve these multifunctional requirements simultaneously. Herein, we designed and prepared a multifunctional ionic hydrogel with a multi-length tentacle bentonite backbone to initiate the free radical polymerization of acrylic acid bentonite (AABT) and acrylamide (AAm). The interactions of covalent cross-linking, hydrogen bonding cross-linking, charge interactions and physical entanglement between hybrid polyacrylamide-AABT (PAAm-AABT), sodium carboxymethyl starch (SCMS) and PAAm form an multi-in-one hybrid supramolecular network hydrogel (CABZ). This CABZ ion-conductive hydrogel is capable of detecting weak deformation with a detection limit of 1 % strain, high tensile properties of 995 %, excellent strength of 254.5 kPa, fast response (≈0.21 s), high sensitivity of 0.86 and high conductivity of 0.37 S/m. In addition, this CABZ ion-conductive hydrogel has impressive adhesion properties with shear adhesion strength up to 50.78 kPa and broad-spectrum antibacterial properties achieved by AABT-loaded ZnO nanoparticles. Through special AABT hybrid cross-linking, the CABZ ion-conductive hydrogel achieves stable mechanical properties, highly sensitive signal response and antimicrobial properties, which will make it a good choice for flexible wearable sensor materials.

Nanoclay Drug-Delivery System Loading Potassium Iodide Promotes Endocytosis and Targeted Therapy in Anaplastic Thyroid Cancer

The rapid proliferative biological behavior of primary foci of anaplastic thyroid cancer (ATC) makes it a lethal tumor. According to the specific iodine uptake capacity of thyroid cells and enhanced endocytosis of ATC cells, we designed a kind of nanoclay drug-loading system and showed a promising treatment strategy for ATC. Introducing potassium iodide (KI) improves the homoaggregation of clay nanoparticles and then affects the distribution of nanoparticles in vivo, which makes KI@DOX-KaolinMeOH enriched almost exclusively in thyroid tissue. Simultaneously, the improvement of dispersibility of KI@DOX-KaolinMeOH changes the target uptake of ATC cells by improving the endocytosis and nanoparticle-induced autophagy, which regulate the production of autolysosomes and autophagy-enhanced chemotherapy, eventually contributing to a tumor inhibition rate of more than 90% in the primary foci of ATC. Therefore, this facile strategy to improve the homoaggregation of nanoclay by introducing KI has the potential to become an advanced drug delivery vehicle in ATC treatment.

Recent Advances in Kaolinite Nanoclay as Drug Carrier for Bioapplications: A Review

Advanced functional two-dimensional (2D) nanomaterials offer unique advantages in drug delivery systems for disease treatment. Kaolinite (Kaol), a nanoclay mineral, is a natural 2D nanomaterial because of its layered silicate structure with nanoscale layer spacing. Recently, Kaol nanoclay is used as a carrier for controlled drug release and improved drug dissolution owing to its advantageous properties such as surface charge, strong biocompatibility, and naturally layered structure, making it an essential development direction for nanoclay-based drug carriers. This review outlines the main physicochemical characteristics of Kaol and the modification methods used for its application in biomedicine. The safety and biocompatibility of Kaol are addressed, and details of the application of Kaol as a drug delivery nanomaterial in antibacterial, anti-inflammatory, and anticancer treatment are discussed. Furthermore, the challenges and prospects of Kaol-based drug delivery nanomaterials in biomedicine are discussed. This review recommends directions for the further development of Kaol nanocarriers by improving their physicochemical properties and expanding the bioapplication range of Kaol.

Laponite stabilized endogenous antibacterial hydrogel as wet-tissue adhesive

Clinical adhesives for suture-less wound closure remain the problem of poor biocompatibility, weak adhesive strength, and no endogenous antibacterial ability. Here, we designed a novel antibacterial hydrogel (CP-Lap hydrogel) consisting of chitosan and ε-polylysine after being modified with gallic acid (pyrogallol structure). The hydrogel was crosslinked by glutaraldehyde and Laponite via Schiff base and dynamic Laponite-pyrogallol interaction, free from heavy metal and oxidants. Given its dual crosslinking feature, the CP-Lap hydrogel exhibited adequate mechanical strength (150-240 kPa) and demonstrated swelling and degradation resistance. For a typical lap shear test with pigskin, the apparent adhesion strength of the CP-Lap hydrogel could be enhanced to ∼30 kPa benefiting from the O2 blocking effect provided by nanoconfinement space between Laponite. In addition, the hydrogel showed effective antibacterial properties and excellent biocompatibility. The results indicated that this hydrogel has great potential for wound-closing bioadhesives to avoid chronic infections and further harm.

Layered Clay Minerals in Cancer Therapy: Recent Progress and Prospects

Cancer is one of the deadliest diseases, and current treatment regimens suffer from limited efficacy, nonspecific toxicity, and chemoresistance. With the advantages of good biocompatibility, large specific surface area, excellent cation exchange capacity, and easy availability, clay minerals have been receiving ever-increasing interests in cancer treatment. They can act as carriers to reduce the toxic side effects of chemotherapeutic drugs, and some of their own properties can kill cancer cells, etc. Compared with other morphologies clays, layered clay minerals (LCM) have attracted more and more attention due to adjustable interlayer spacing, easier ion exchange, and stronger adsorption capacity. In this review, the structure, classification, physicochemical properties, and functionalization methods of LCM are summarized. The state-of-the-art progress of LCM in antitumor therapy is systematically described, with emphasis on the application of montmorillonite, kaolinite, and vermiculite. Furthermore, the property-function relationships of LCM are comprehensively illustrated to reveal the design principles of clay-based antitumor systems. Finally, foreseeable challenges and outlook in this field are discussed.

Engineered biomaterials in stem cell-based regenerative medicine

Stem cell-based regenerative therapies, which harness the self-renewal and differentiation properties of stem cells, have been in the spotlight due to their widespread applications in treating degenerative, aging, and other, generally intractable diseases. Therapeutically effective hematopoietic stem cells, mesenchymal stem cells, embryonic stem cells, and induced pluripotent stem cells have been used in numerous basic and translational studies with exciting results. However, pre-/post-transplantation issues of poor cell survival and retention, uncontrolled differentiation, and insufficient numbers of cells engrafted into host tissues are the major challenges in stem cell-based regenerative therapies. Engineered biomaterials have adjustable biochemical and biophysical properties that significantly affect cell behaviors, such as cell engraftment, survival, migration, and differentiation outcomes, thereby enhancing the engraftment of implanted stem cells and guiding tissue regeneration. Therefore, the combination of stem cell biology with bioengineered materials is a promising strategy to improve the therapeutic outcomes of stem cell-based regenerative therapy. In this review, we summarize the advances in the modulation of behaviors of stem cells via engineered biomaterials. We then present different approaches to harnessing bioengineered materials to enhance the transplantation of stem cells. Finally, we will provide future directions in regenerative therapy using stem cells.

Gelatin methacryloyl and Laponite bioink for 3D bioprinted organotypic tumor modeling

Three-dimensional (3D)in vitrotumor models that can capture the pathophysiology of human tumors are essential for cancer biology and drug development. However, simulating the tumor microenvironment is still challenging because it consists of a heterogeneous mixture of various cellular components and biological factors. In this regard, current extracellular matrix (ECM)-mimicking hydrogels used in tumor tissue engineering lack physical interactions that can keep biological factors released by encapsulated cells within the hydrogel and improve paracrine interactions. Here, we developed a nanoengineered ion-covalent cross-linkable bioink to construct 3D bioprinted organotypic tumor models. The bioink was designed to implement the tumor ECM by creating an interpenetrating network composed of gelatin methacryloyl (GelMA), a light cross-linkable polymer, and synthetic nanosilicate (Laponite) that exhibits a unique ionic charge to improve retention of biological factors released by the encapsulated cells and assist in paracrine signals. The physical properties related to printability were evaluated to analyze the effect of Laponite hydrogel on bioink. Low GelMA (5%) with high Laponite (2.5%-3.5%) composite hydrogels and high GelMA (10%) with low Laponite (1.0%-2.0%) composite hydrogels showed acceptable mechanical properties for 3D printing. However, a low GelMA composite hydrogel with a high Laponite content could not provide acceptable cell viability. Fluorescent cell labeling studies showed that as the proportion of Laponite increased, the cells became more aggregated to form larger 3D tumor structures. Reverse transcription-polymerase chain reaction (RT-qPCR) and western blot experiments showed that an increase in the Laponite ratio induces upregulation of growth factor and tissue remodeling-related genes and proteins in tumor cells. In contrast, cell cycle and proliferation-related genes were downregulated. On the other hand, concerning fibroblasts, the increase in the Laponite ratio indicated an overall upregulation of the mesenchymal phenotype-related genes and proteins. Our study may provide a rationale for using Laponite-based hydrogels in 3D cancer modeling.

Nanosilicate-functionalized nanofibrous membrane facilitated periodontal regeneration potential by harnessing periodontal ligament cell-mediated osteogenesis and immunomodulation

Although various new biomaterials have enriched the methods for periodontal regeneration, their efficacy is still controversial, and the regeneration of damaged support tissue in the periodontium remains challenging. Laponite (LAP) nanosilicate is a layered two-dimensional nanoscale, ultrathin nanomaterial with a unique structure and brilliant biocompatibility and bioactivity. This study aimed to investigate the effects of nanosilicate-incorporated PCL (PCL/LAP) nanofibrous membranes on periodontal ligament cells (PDLCs) in vitro and periodontal regeneration in vivo. A PCL/LAP nanofibrous membrane was fabricated by an electrospinning method. The characterization of PCL/LAP nanofibrous membrane were determined by scanning electron microscopy (SEM), energy dispersive spectrum of X-ray (EDS), inductively coupled plasma mass spectrometry (ICP-MS) and tensile test. The proliferation and osteogenic differentiation of PDLCs on the PCL/LAP nanofibrous membrane were evaluated. A PDLCs and macrophage coculture system was used to explore the immunomodulatory effects of the PCL/LAP nanofibrous membrane. PCL/LAP nanofibrous membrane was implanted into rat calvarial and periodontal defects, and the regenerative potential was evaluated by microcomputed topography (micro-CT) and histological analysis. The PCL/LAP nanofibrous membrane showed good biocompatibility and bioactivity. It enhanced the proliferation and osteogenic differentiation of PDLCs. The PCL/LAP nanofibrous membrane also stimulated anti-inflammatory and pro-remodeling N2 neutrophil formation, regulated inflammatory responses and induced M2 macrophage polarization by orchestrating the immunomodulatory effects of PDLCs. The PCL/LAP nanofibrous membrane promoted rat calvarial defect repair and periodontal regeneration in vivo. LAP nanosilicate-incorporated PCL membrane is capable of mediating osteogenesis and immunomodulation of PDLCs in vitro and accelerating periodontal regeneration in vivo. It could be a promising biomaterial for periodontal regeneration therapy.

Laponite-Based Nanocomposite Hydrogels for Drug Delivery Applications

Hydrogels are widely used for therapeutic delivery applications due to their biocompatibility, biodegradability, and ability to control release kinetics by tuning swelling and mechanical properties. However, their clinical utility is hampered by unfavorable pharmacokinetic properties, including high initial burst release and difficulty in achieving prolonged release, especially for small molecules (<500 Da). The incorporation of nanomaterials within hydrogels has emerged as viable option as a method to trap therapeutics within the hydrogel and sustain release kinetics. Specifically, two-dimensional nanosilicate particles offer a plethora of beneficial characteristics, including dually charged surfaces, degradability, and enhanced mechanical properties within hydrogels. The nanosilicate-hydrogel composite system offers benefits not obtainable by just one component, highlighting the need for detail characterization of these nanocomposite hydrogels. This review focuses on Laponite, a disc-shaped nanosilicate with diameter of 30 nm and thickness of 1 nm. The benefits of using Laponite within hydrogels are explored, as well as examples of Laponite-hydrogel composites currently being investigated for their ability to prolong the release of small molecules and macromolecules such as proteins. Future work will further characterize the interplay between nanosilicates, hydrogel polymer, and encapsulated therapeutics, and how each of these components affect release kinetics and mechanical properties.

Application of Silk-Fibroin-Based Hydrogels in Tissue Engineering

Silk fibroin (SF) is an excellent protein-based biomaterial produced by the degumming and purification of silk from cocoons of the Bombyx mori through alkali or enzymatic treatments. SF exhibits excellent biological properties, such as mechanical properties, biocompatibility, biodegradability, bioabsorbability, low immunogenicity, and tunability, making it a versatile material widely applied in biological fields, particularly in tissue engineering. In tissue engineering, SF is often fabricated into hydrogel form, with the advantages of added materials. SF hydrogels have mostly been studied for their use in tissue regeneration by enhancing cell activity at the tissue defect site or counteracting tissue-damage-related factors. This review focuses on SF hydrogels, firstly summarizing the fabrication and properties of SF and SF hydrogels and then detailing the regenerative effects of SF hydrogels as scaffolds in cartilage, bone, skin, cornea, teeth, and eardrum in recent years.

Chemical Transformations of 2D Kaolinic Clay Mineral Surfaces from Sulfuric Acid Exposure

A combined experimental and computational approach is used to investigate the chemical transformations of kaolinite and metakaolin surfaces when exposed to sulfuric acid. These clay minerals are hydrated ternary metal oxides and are shown to be susceptible to degradation by loss of Al as the water-soluble salt Al₂(SO₄)₃, due to interactions between H₂SO₄ and aluminum cations. This degradation process results in a silica-rich interfacial layer on the surfaces of the aluminosilicates, most prominently observed in metakaolin exposed to pH environments of less than 4. Our observations are supported by XPS, ATR-FTIR, and XRD experiments. Concurrently, DFT methodologies are used to probe the interactions between the clay mineral surfaces and H₂SO₄ as well as other sulfur-containing adsorbates. An analysis performed using a DFT + thermodynamics model shows that the surface transformation processes that lead to the loss of Al and SO₄ from metakaolin are favorable at pH below 4; however, such transformations are not favorable for kaolinite, a result that agrees with our experimental efforts. The data obtained from both experimental techniques and computational studies support that the dehydrated surface of metakaolin interacts more strongly with sulfuric acid and provide atomistic insight into the acid-induced transformations of these mineral surfaces.

Injectable Biomimetic Hydrogel Guided Functional Bone Regeneration by Adapting Material Degradation to Tissue Healing

The treatment of irregular bone defects remains a clinical challenge since the current biomaterials (e.g., calcium phosphate bone cement (CPC)) mainly act as inert substitutes, which are incapable of transforming into a regenerated host bone (termed functional bone regeneration). Ideally, the implant degradation rate should adapt to that of bone regeneration, therefore providing sufficient physicochemical support and giving space for bone growth. This study aims to develop an injectable biomaterial with bone regeneration‐adapted degradability, to reconstruct a biomimetic bone‐like structure that can timely transform into new bone, facilitating functional bone regeneration. To achieve this goal, a hybrid (LP‐CPC@gelatin, LC) hydrogel is synthesized via one‐step incorporation of laponite (LP) and CPC into gelatin hydrogel, and the LC gel degradation rate is controlled by adjusting the LP/CPC ratio to match the bone regeneration rate. Such an LC hydrogel shows good osteoinduction, osteoconduction, and angiogenesis effects, with complete implant‐to‐new bone transformation capacity. This 2D nanoclay‐based bionic hydrogel can induce ectopic bone regeneration and promote ligament graft osseointegration in vivo by inducing functional bone regeneration. Therefore, this study provides an advanced strategy for functional bone regeneration and an injectable biomimetic biomaterial for functional skeletal muscle repair in a minimally invasive therapy.

Natural and Synthetic Clay Minerals in the Pharmaceutical and Biomedical Fields

Clay minerals are historically among the most used materials with a wide variety of applications. In pharmaceutical and biomedical fields, their healing properties have always been known and used in pelotherapy and therefore attractive for their potential. In recent decades, the research has therefore focused on the systematic investigation of these properties. This review aims to describe the most relevant and recent uses of clays in the pharmaceutical and biomedical field, especially for drug delivery and tissue engineering purposes. Clay minerals, which are biocompatible and non-toxic materials, can act as carriers for active ingredients while controlling their release and increasing their bioavailability. Moreover, the combination of clays and polymers is useful as it can improve the mechanical and thermal properties of polymers, as well as induce cell adhesion and proliferation. Different types of clays, both of natural (such as montmorillonite and halloysite) and synthetic origin (layered double hydroxides and zeolites), were considered in order to compare them and to assess their advantages and different uses.

Facile synthesis of layered double hydroxide nanosheets assembled porous structures for efficient drug delivery

As one of the important types of two-dimensional materials, layered double hydroxides (LDHs) have been widely used in the biomedical field as carriers for drug delivery. In this case, we propose a facile synthetic method for preparing LDH-based self-assembly structures via a metal ions-mediated zeolitic imidazolate framework-8 (ZIF-8) transformation process. The as-made hierarchical porous ZIF-8@LDHs core-shell structures and porous cages of LDHs (PC-LDHs) in drug delivery systems are used to study the loading and release of small molecular weight drugs such as doxorubicin hydrochloride (DOX) and 5-fluorouracil (5-FU). The intrinsic properties and assembly structures of both carriers are investigated in depth for their impact on slow drug release. Finally, PC-LDHs outperform ZIF-8@LDHs core-shell structures in terms of drug delivery performance under various conditions, indicating that LDH nanosheets would play a decisive role in the drug delivery process. In the drug release system, scattered LDH nanosheets with smaller sizes than their assemblies are gradually produced, allowing nanodrugs to enter cancer tissues more easily across biological barriers. This study provides the preliminary preparation for an LDH-based nanomedicine platform in the field of cancer therapy.

Halloysite nanoclay reinforced hydroxyapatite porous scaffold for hard tissue regeneration

Hydroxyapatite (HAP), a natural constituent of bone tissue is commonly used for the clinical treatment of bone defects due to its similar structure with bone and excellent biocompatibility. However, the processing exertion, poor osteoinductive capability and poor mechanical strength of HAP needs further addressing for its immense implementation in tissue engineering. Different approaches have been reported to escalate the mechanical hardness and osteogenic potential of HAP. In the present work, halloysite nanoclay (HNC) and sericin protein were used for better mechanical and osteogenic properties, respectively. Halloysite nanoclay (HNC, 1.0-4.0%) was used to reinforce hydroxyapatite (HAP) and the mechanical strength of nanocomposite scaffolds were evaluated. After surface modification of nanocomposite scaffolds with 1.0% silk sericin protein; physical properties like microstructure, porosity, swelling ratio and degradation rate were evaluated. Cell morphology, cytocompatibility and alkaline phosphatase (ALP) activity were assessed using MG 63 osteoblast cell lines. HAP reinforced with 4% HNC (HAP@4) showed a significant increase (199 MPa) in young modulus as compared to pure HAP. HAP reinforced with 2% HNC (HAP@2) and 4% HNC (HAP@4) showed a significant decrease in porosity as well as degradation rate than pure HAP but no significant difference was observed in swelling ratio. The scanning electron microscope (SEM) images of the scaffolds showed porous architecture. Remarkably, the incorporation of HNC in HAP enhanced the cytocompatibility as well as ALP activity in comparison to pure HAP. Overall, these results suggested that halloysite nanoclay reinforced HAP scaffold could be an auspicious alternative for bone tissue regeneration.

Minimally invasive bone augmentation through subperiosteal injectable hydroxylapatite/laponite/alginate nanocomposite hydrogels

Bone augmentation has an enormous demand in oral clinical treatment. Although there are various options available for clinical management to address it, these approaches could increase patient suffering due to surgical trauma and even cause psychological trauma to the patients. Moreover, presently, there is still a lack of well-considered microinvasive bone augmentation systems to deal with this challenge. Herein, we newly developed a subperiosteal injectable and osteogenesis-promoting hydroxylapatite/laponite/alginate nanocomposite hydrogels to address the insufficient microinvasive bone augmentation strategies. The physical performances (like swelling profiles, degradation behaviors, mechanical properties, and surface morphologies) of the gels were determined, and can be slightly tuned through altering concentrations of laponite. The cytocompatibility test results show outstanding biocompatibility of the hydrogels. Furthermore, the in vitro testing for bone-inducing activity and in vivo determination of bone-augmentation in the rat cranial subperiosteum exhibit that the hydrogels significantly promoted rat periosteum-derived mesenchymal stromal cells (P-MSCs) osteogenic differentiation in vitro and bone augmentation in vivo. Therefore, the research reveals that the nanocomposite hydrogels possessing subperiosteal microinvasive injectability, osteogenesis-enhancing capability, and clinical applicability have extremely great potential application in subperiosteal microinvasive bone augmentation.

Application of Nanomaterials in Stem Cell-Based Therapeutics for Cardiac Repair and Regeneration

Cardiovascular disease is a leading cause of disability and death worldwide. Although the survival rate of patients with heart diseases can be improved with contemporary pharmacological treatments and surgical procedures, none of these therapies provide a significant improvement in cardiac repair and regeneration. Stem cell-based therapies are a promising approach for functional recovery of damaged myocardium. However, the available stem cells are difficult to differentiate into cardiomyocytes, which result in the extremely low transplantation efficiency. Nanomaterials are widely used to regulate the myocardial differentiation of stem cells, and play a very important role in cardiac tissue engineering. This study discusses the current status and limitations of stem cells and cell-derived exosomes/micro RNAs based cardiac therapy, describes the cardiac repair mechanism of nanomaterials, summarizes the recent advances in nanomaterials used in cardiac repair and regeneration, and evaluates the advantages and disadvantages of the relevant nanomaterials. Besides discussing the potential clinical applications of nanomaterials in cardiac therapy, the perspectives and challenges of nanomaterials used in stem cell-based cardiac repair and regeneration are also considered. Finally, new research directions in this field are proposed, and future research trends are highlighted.

Thermo-Responsive Nanocomposite Bioink with Growth-Factor Holding and its Application to Bone Regeneration

Three-dimensional (3D) bioprinting, which is being increasingly used in tissue engineering, requires bioinks with tunable mechanical properties, biological activities, and mechanical strength for in vivo implantation. Herein, a growth-factor-holding poly(organophosphazene)-based thermo-responsive nanocomposite (TNC) bioink system is developed. The mechanical properties of the TNC bioink are easily controlled within a moderate temperature range (5-37 °C). During printing, the mechanical properties of the TNC bioink, which determine the 3D printing resolution, can be tuned by varying the temperature (15-30 °C). After printing, TNC bioink scaffolds exhibit maximum stiffness at 37 °C. Additionally, because of its shear-thinning and self-healing properties, TNC bioinks can be extruded smoothly, demonstrating good printing outcomes. TNC bioink loaded with bone morphogenetic protein-2 (BMP-2) and transforming growth factor-beta1 (TGF-β1), key growth factors for osteogenesis, is used to print a scaffold that can stimulate biological activity. A biological scaffold printed using TNC bioink loaded with both growth factors and implanted on a rat calvarial defect model reveals significantly improved bone regenerative effects. The TNC bioink system is a promising next-generation bioink platform because its mechanical properties can be tuned easily for high-resolution 3D bioprinting with long-term stability and its growth-factor holding capability has strong clinical applicability.

Progress in self-healing hydrogels and their applications in bone tissue engineering

Bone tissue engineering (BTE) is constantly seeking novel treatments to address bone injuries in all their varieties. It is necessary to find new ways to create structures that perfectly emulate the native tissue. Self-healing hydrogels have been a breakthrough in this regard, as they are able to reconstitute their links after they have been partially broken. Among the most outstanding biomaterials when it comes to developing these hydrogels for BTE, those polymers of natural origin (e.g., gelatin, alginate) stand out, although synthetics such as PEG or nanomaterials like laponite are also key for this purpose. Self-healing hydrogels have proven to be efficient in healing bone, but have also played a key role as delivery-platforms for drugs or other biological agents. Moreover, some researchers have identified novel uses for these gels as bone fixators or implant coatings. Here, we review the progress of self-healing hydrogels, which hold great promise in the field of tissue engineering.

A novel application of hectorite nanoclay for preparation of colorectal cancer spheroids with malignant potential

Three-dimensional (3D) cell culture, which provides an in vivo-like environment in vitro unlike the conventional two-dimensional (2D) cell culture, has attracted much attention from researchers. Although various 3D cell culture methods have been developed, information on a method using inorganic nanoclay is scant. Here, we report that hectorite, an inorganic layered silicate, can be used as an auxiliary material for 3D cell culture. Human colon cancer cell lines cultured in a medium containing 0.01% synthetic hectorite spontaneously formed 3D spheroids in an adherent plate. Morphologically, these spheroids were more dispersed in all directions than control spheroids generated in an ultralow adherent plate. Microarray analysis showed that FGF19, TGM2, and SERPINA3, whose expression is reportedly increased in colon cancer tissues and is related to tumorigenesis or metastasis, were upregulated in HT-29 spheroids formed using synthetic hectorite compared with those in control spheroids. Gene ontology analysis revealed upregulation of genes associated with morphogenesis, cytoskeleton, extracellular matrix, cellular uptake and secretion, signaling pathways, and gene expression regulation. Moreover, fluorescence-labeled hectorite particles were localized in the cytoplasm of individual cells in spheroids. These results suggest that the synthetic hectorite modified the physiological state of and gene expression within the cells, triggering spheroid formation with malignant characteristics. Our findings highlight a novel application of synthetic hectorite for 3D cell culture.

Mussel-Inspired Adhesive Hydrogels Based on Laponite-Confined Dopamine Polymerization as a Transdermal Patch

Transdermal patch for local drug delivery has attained huge attention as an attractive alternative to existing drug delivery techniques as it is painless and user-friendly. However, most adhesive hydrogels either do not have adequate adhesion with the skin or cause discomfort while being removed from the skin surface due to excessive adhesion. To address this challenge, we developed an adhesive hydrogel based on laponite-confined dopamine polymerization as a transdermal patch. Laponite RDS nanoclay was used to control the hydrogel's viscous behavior and dopamine polymerization. The laponite polymerized polydopamine (l-PDA) was incorporated into poly(vinyl alcohol) (PVA) to make the PVA-l-PDA hydrogel. The laponite-confined polymerization improved the hydrogels' water contact angle and adhesion strength. The adhesion strength of the PVA-l-PDA hydrogel was adequate to adhere to the evaluated goat skin, glass, and polypropylene surfaces. Notably, the PVA-l-PDA hydrogel was easy to peel off from the skin. Further, we evaluated the drug release profile in goat skin using lidocaine as a model drug. We observed the controlled release of lidocaine from the PVA-l-PDA hydrogel compared to the PVA-PDA hydrogel. In addition, the nanoclay-confined adhesive hydrogel did not show any cytotoxic effect in fibroblasts. Altogether, PVA-l-PDA hydrogels offer appropriate adhesive strength, toughness, and biocompatibility. Thus, the PVA-l-PDA hydrogel has the potential to be an efficient transdermal patch.

Development of Hybrid Materials Based on Chitosan, Poly(Ethylene Glycol) and Laponite® RD: Effect of Clay Concentration

In the context of increasing interest in biomaterials with applicability in cosmetics and medicine, this research aims to obtain and characterize some hybrid materials based on chitosan (CS) (antibacterial, biocompatible, and biodegradable), poly(ethylene glycol) (PEG) (non-toxic and prevents the adsorption of protein and cell) and Laponite^® RD (Lap) (bioactive). The rheological properties of the starting dispersions were investigated and discussed related to the interactions developed between components. All samples exhibited gel-like properties, and the storage modulus of CS/PEG dispersion increased from 6.6 Pa to 657.7 Pa by adding 2.5% Lap. Structural and morphological characterization of the films, prepared by solution casting method, was performed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and polarized light microscopy (POM). These analyses proved the incorporation of Lap into CS/PEG films and revealed the morphological changes of the films by the addition of clay. Thereby, at the highest Lap concentration (43.8%), the "house of cards" structure formed by Lap platelets, which incorporate chitosan chains, as evidenced by SEM and POM. Two stages of degradation between 200 °C and 410 °C were evidenced for the films with Lap concentration higher than 38.5%, explained by the existence of a clay-rich phase (given by the clay network) and chitosan-rich one (due to the intercalation of chitosan in the clay network). CS/PEG film with 43.8% Lap showed the highest swelling degree of 240.7%. The analysis of the obtained results led to the conclusion that the addition of clay to the CS/PEG films increases their stability in water and gives them greater thermal stability.

3D Printed Hierarchical Porous Poly(ε-caprolactone) Scaffolds from Pickering High Internal Phase Emulsion Templating

In the realm of biomaterials, particularly bone tissue engineering, there has been a great increase in interest in scaffolds with hierarchical porosity and customizable multifunctionality. Recently, the three-dimensional (3D) printing of biopolymer-based inks (solutions or emulsions) has gained high popularity for fabricating tissue engineering scaffolds, which optimally satisfies the desired properties and performances. Herein, therefore, we explore the fabrication of 3D printed hierarchical porous scaffolds of poly(ε-caprolactone) (PCL) using the water-in-oil (w/o) Pickering PCL high internal phase emulsions (HIPEs) as the ink in 3D printer. The Pickering PCL HIPEs stabilized using hydrophobically modified nanoclay comprised of aqueous poly(vinyl alcohol) (PVA) as the dispersed phase. Rheological measurements suggested the shear thinning behavior of Pickering HIPEs having a dispersed droplet diameter of 3-25 μm. The pore morphology resembling the natural extracellular matrix and the mechanical properties of scaffolds were customized by tuning the emulsion composition and 3D printing parameters. In vitro biomineralization and drug release studies proved the scaffolds' potential in developing the apatite-rich bioactive interphase and controlled drug delivery, respectively. During in vitro osteoblast (MG63) growth experiments for up to 7 days, good adhesion and proliferation on PCL scaffolds confirmed their cytocompatibility, assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) analysis. This study suggests that the assembly of HIPE templates and 3D printing is a promising approach to creating hierarchical porous scaffolds potentially suitable for bone tissue engineering and can be stretched to other biopolymers as well.

A Review of 3D Polymeric Scaffolds for Bone Tissue Engineering: Principles, Fabrication Techniques, Immunomodulatory Roles, and Challenges

Over the last few years, biopolymers have attracted great interest in tissue engineering and regenerative medicine due to the great diversity of their chemical, mechanical, and physical properties for the fabrication of 3D scaffolds. This review is devoted to recent advances in synthetic and natural polymeric 3D scaffolds for bone tissue engineering (BTE) and regenerative therapies. The review comprehensively discusses the implications of biological macromolecules, structure, and composition of polymeric scaffolds used in BTE. Various approaches to fabricating 3D BTE scaffolds are discussed, including solvent casting and particle leaching, freeze-drying, thermally induced phase separation, gas foaming, electrospinning, and sol-gel techniques. Rapid prototyping technologies such as stereolithography, fused deposition modeling, selective laser sintering, and 3D bioprinting are also covered. The immunomodulatory roles of polymeric scaffolds utilized for BTE applications are discussed. In addition, the features and challenges of 3D polymer scaffolds fabricated using advanced additive manufacturing technologies (rapid prototyping) are addressed and compared to conventional subtractive manufacturing techniques. Finally, the challenges of applying scaffold-based BTE treatments in practice are discussed in-depth.

Nanoclays-containing bio-based packaging materials: properties, applications, safety, and regulatory issues

Food packaging is an important concept for consumer satisfaction and the increased shelf life of food products. The introduction of novel food packaging materials has become an emerging trend in recent years, which could be mainly due to environmental pollution caused by plastic packaging and to reduce food waste. Recently, numerous studies have been carried out on nanoclays or nanolayered silicate to be used in packaging material development as reinforcing filler composites. Different types of nanoclays have been used as food packaging materials, while montmorillonite (MMT), halloysite, bentonite (BT), Cloisite, and organically modified nanoclays have become of great interest. The incorporation of nanoclays into the packaging matrix improves the mechanical and barrier properties and at the same time prolongs the biodegradation of the packaging material. The purpose of this article is to examine the development of nanoclay-based food packaging materials. The review article highlights the current state of research on bio-based polymers with nanoclay for food packaging. In addition, the report analyses the mechanical, barrier, and antibacterial characteristics of nanoclay-based food packaging materials. Finally, it discusses the migration of nanoclays, toxicity levels, and the legislation associated with the application of nanoclays.

Graphical abstract

A sustained-release PDGF-BB nanocomposite hydrogel for DM-associated bone regeneration

Regeneration of bone tissue in the environment of diabetes mellitus (DM) remains one of the clinical challenges, with malfunction of stem cells in a high-glucose microenvironment being the primary obstacle. We designed an injectable sustained-release PDGF-BB nanocomposite hydrogel. PDGF-BB, a star molecule for treating various complications of DM, was used for the first time for DM-associated bone regeneration, and we showed that it restored stem cell proliferation and migration and facilitated osteogenesis inhibition under high glucose stimulation by activating ERK and AKT pathways. To address the requirements for continuous PDGF-BB release in GelMA while also increasing mechanical strength, nanoclay LAPONITE® was added, which may still exhibit pro-osteogenic activity in diabetic environments by releasing bioactive ions (Si⁴⁺, Mg²⁺, and Li⁺). This injectable hydrogel heals calvarial lesions successfully in diabetic rats and has the potential to be used as a direct and effective tool for treating diabetic patients.

Hierarchy of hybrid materials. Part-II: The place of organics-on-inorganics in it, their composition and applications

Hybrid materials or hybrids incorporating organic and inorganic constituents are emerging as a very potent and promising class of materials due to the diverse but complementary nature of their properties. This complementarity leads to a perfect synergy of properties of the desired materials and products as well as to an extensive range of their application areas. Recently, we have overviewed and classified hybrid materials describing inorganics-in-organics in Part-I (Saveleva, et al., Front. Chem., 2019, 7, 179). Here, we extend that work in Part-II describing organics-on-inorganics, i.e., inorganic materials modified by organic moieties, their structure and functionalities. Inorganic constituents comprise of colloids/nanoparticles and flat surfaces/matrices comprise of metallic (noble metal, metal oxide, metal-organic framework, magnetic nanoparticles, alloy) and non-metallic (minerals, clays, carbons, and ceramics) materials; while organic additives can include molecules (polymers, fluorescence dyes, surfactants), biomolecules (proteins, carbohydtrates, antibodies and nucleic acids) and even higher-level organisms such as cells, bacteria, and microorganisms. Similarly to what was described in Part-I, we look at similar and dissimilar properties of organic-inorganic materials summarizing those bringing complementarity and composition. A broad range of applications of these hybrid materials is also presented whose development is spurred by engaging different scientific research communities.

Functionally modified halloysite nanotubes for personalized bioapplications

Halloysite nanotubes (HNTs) are naturally aluminosilicate clay minerals that have the benefits of large surface areas, high mechanical properties, easy functionalization, and high biocompatibility, HNTs have been developed as multifunctional nanoplatforms for various bioapplications. Although some reviews have summarized the properties and bioapplications of HNTs, it remains unclear how to functionalize the modifications of HNTs for their personalized bioapplications. In this review, based on the physicochemical properties of HNTs, we summarized the methods of functionalized modifications (surface modification and structure modification) on HNTs. Also, we highlighted their personalized bioapplications (anti-bacterial, anti-inflammatory, wound healing, cancer theranostics, bone regenerative, and biosensing) by stressing on the main roles of HNTs. Finally, we provide perspectives on the future of functionalized modifications of HNTs for docking specific biological applications.

Self-Therapeutic Nanomaterials: Applications in Biology and Medicine

Over past decades, nanotechnology has contributed to the biomedical field in areas including detection, diagnosis, and drug delivery via opto-electronic properties or enhancement of biological effects. Though generally considered inert delivery vehicles, a plethora of past and present evidence demonstrates that nanomaterials also exude unique intrinsic biological activity based on composition, shape, and surface functionalization. These intrinsic biological activities, termed self-therapeutic properties, take several forms, including mediation of cell-cell interactions, modulation of interactions between biomolecules, catalytic amplification of biochemical reactions, and alteration of biological signal transduction events. Moreover, study of biomolecule-nanomaterial interactions offers a promising avenue for uncovering the molecular mechanisms of biology and the evolution of disease. In this review, we observe the historical development, synthesis, and characterization of self-therapeutic nanomaterials. Next, we discuss nanomaterial interactions with biological systems, starting with administration and concluding with elimination. Finally, we apply this materials perspective to advances in intrinsic nanotherapies across the biomedical field, from cancer therapy to treatment of microbial infections and tissue regeneration. We conclude with a description of self-therapeutic nanomaterials in clinical trials and share our perspective on the direction of the field in upcoming years.

Nanomaterial-Based Antimicrobial Coating for Biomedical Implants: New Age Solution for Biofilm-Associated Infections

Recently, the upsurge in hospital-acquired diseases has put global health at risk. Biomedical implants being the primary source of contamination, the development of biomedical implants with antimicrobial coatings has attracted the attention of a large group of researchers from around the globe. Bacteria develops biofilms on the surface of implants, making it challenging to eradicate them with the standard approach of administering antibiotics. A further issue of current concern is the fast resurgence of resistance to conventional antibiotics. As nanotechnology continues to advance, various types of nanomaterials have been created, including 2D nanoparticles and metal and metal oxide nanoparticles with antimicrobial properties. Researchers from all over the world are using these materials as a coating agent for biomedical implants to create an antimicrobial environment. This comprehensive and contemporary review summarizes various metals, metal oxide nanoparticles, 2D nanomaterials, and their composites that have been used or may be used in the future as an antimicrobial coating agent for biomedical implants, as well as their succinct mode of action to combat biofilm-associated infection and diseases.