Laponite nanodisks as an efficient platform for Doxorubicin delivery to cancer cells

Bioprinting a Synthetic Smectic Clay for Orthopedic Applications

Bioprinting technology has emerged as an important approach to bone and cartilage tissue engineering applications, because it allows the printing of scaffolds loaded with various components, such as cells, growth factors, or drugs. In this context, the bone has a very complex architecture containing highly vascularized and calcified tissues, while cartilage is avascular and has low cellularity and few nutrients. Owing to this complexity, the repair and regeneration of these tissues are highly challenging. Identification of the appropriate biomaterial and fabrication technologies can provide sustainable solutions to this challenge. Here, nanosized Laponite^® (Laponite is a trademark of the company BYK Additives Ltd.) has shown to be a promising material due to its unique properties such as excellent biocompatibility, facile gel formation, shear-thinning property (reversible physical crosslinking), high specific surface area, degrade into nontoxic products, and with osteoinductive properties. Even though Laponite and Laponite-based composite for 3D bioprinting application are considered as soft gels, they may therefore not be thought exhibiting sufficient mechanical strength for orthopedic applications. However, through the merging with suitable composite and, also by incorporation of crosslinking step, desired mechanical strength for orthopedic application can be obtained. In this review, recent advances and future perspective of bioprinting Laponite and Laponite composites for orthopedic applications are highlighted.

Biocompatibility and biodegradability of 2D materials: graphene and beyond

The potential risks associated with two-dimensional (2D) nanomaterials may cause serious concerns about their real applications and impact in biological systems. In addition, the demonstration of biodegradability of these flat nanomaterials is essential in living organisms. Here, we summarise the state-of-the-art in the field of biocompatibility and biodegradability of graphene-related materials (such as 2D materials like MoS2, BN or WS2). The impact of chemical functionalisation on the potential control of the biodegradability profile of these structures is also discussed.

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

Clay nanomaterials are an emerging class of 2D biomaterials of interest due to their atomically thin layered structure, charged characteristics, and well-defined composition. Synthetic nanoclays are plate-like polyions composed of simple or complex salts of silicic acids with a heterogeneous charge distribution and patchy interactions. Due to their biocompatible characteristics, unique shape, high surface-to-volume ratio, and charge, nanoclays are investigated for various biomedical applications. Here, a critical overview of the physical, chemical, and physiological interactions of nanoclay with biological moieties, including cells, proteins, and polymers, is provided. The state-of-the-art biomedical applications of 2D nanoclay in regenerative medicine, therapeutic delivery, and additive manufacturing are reviewed. In addition, recent developments that are shaping this emerging field are discussed and promising new research directions for 2D nanoclay-based biomaterials are identified.

Interaction of Laponite with Membrane Components-Consequences for Bacterial Aggregation and Infection Confinement

The antimicrobial effects of Laponite nanoparticles with or without loading of the antimicrobial peptide LL-37 was investigated along with their membrane interactions. The study combines data from ellipsometry, circular dichroism, fluorescence spectroscopy, particle size/ζ potential measurements, and confocal microscopy. As a result of the net negative charge of Laponite, loading of net positively charged LL-37 increases with increasing pH. The peptide was found to bind primarily to the outer surface of the Laponite nanoparticles in a predominantly helical conformation, leading to charge reversal. Despite their net positive charge, peptide-loaded Laponite nanoparticles did not kill Gram-negative Escherichia coli bacteria or disrupt anionic model liposomes. They did however cause bacteria flocculation, originating from the interaction of Laponite and bacterial lipopolysaccharide (LPS). Free LL-37, in contrast, is potently antimicrobial through membrane disruption but does not induce bacterial aggregation in the concentration range investigated. Through LL-37 loading of Laponite nanoparticles, the combined effects of bacterial flocculation and membrane lysis are observed. However, bacteria aggregation seems to be limited to Gram-negative bacteria as Laponite did not cause flocculation of Gram-positive Bacillus subtilis bacteria nor did it bind to lipoteichoic acid from bacterial envelopes. Taken together, the present investigation reports several novel phenomena by demonstrating that nanoparticle charge does not invariably control membrane destabilization and by identifying the ability of anionic Laponite nanoparticles to effectively flocculate Gram-negative bacteria through LPS binding. As demonstrated in cell experiments, such aggregation results in diminished LPS-induced cell activation, thus outlining a promising approach for confinement of infection and inflammation caused by such pathogens.

Degradability and Clearance of Inorganic Nanoparticles for Biomedical Applications

Inorganic nanoparticles with tunable and diverse properties hold tremendous potential in the field of nanomedicine, while having non-negligible toxicity concerns in healthy tissues/organs that have resulted in their restricted clinical translation to date. In the past decade, the emergence of biodegradable or clearable inorganic nanoparticles has made it possible to completely solve this long-standing conundrum. A comprehensive understanding of the design of these inorganic nanoparticles with their metabolic performance in the body is of crucial importance to advance clinical trials and expand their biological applications in disease diagnosis. Here, a diverse variety of biodegradable or clearable inorganic nanoparticles regarding considerations of the size, morphology, surface chemistry, and doping strategy are highlighted. Their pharmacokinetics, pathways of metabolism in the body, and time required for excretion are discussed. Some inorganic materials intrinsically responsive to various conditions in the tumor microenvironment are also introduced. Finally, an overview of the encountered challenges is provided along with an outlook for applying these inorganic nanoparticles toward future clinical translations.

Sustained and Prolonged Delivery of Protein Therapeutics from Two-Dimensional Nanosilicates

We present a nanoengineered system for sustained and prolonged delivery of protein therapeutics, which has the potential to impact current orthopedic regeneration strategies. Specifically, we introduce two-dimensional nanosilicates with a high surface area and charged characteristics for delivery of active proteins for more than 30 days. The nanosilicates show high binding efficacy without altering the protein conformation and bioactivity. The released proteins are able to maintain high activity as demonstrated by enhanced differentiation of human mesenchymal stem cells at 10-fold lower concentration compared to the exogenous control. Utilizing the nanosilicates as a delivery vehicle could minimize the negative side effects observed because of the use of supraphysiological dosages of protein therapeutics for orthopedic regeneration strategies.

Poly(amidoamine) Dendrimer-Coordinated Copper(II) Complexes as a Theranostic Nanoplatform for the Radiotherapy-Enhanced Magnetic Resonance Imaging and Chemotherapy of Tumors and Tumor Metastasis

The development of a powerful nanoplatform to realize the simultaneous therapy and diagnosis of cancer using a similar element for theranostics remains a critical challenge. Herein, we report such a theranostic nanoplatform based on pyridine (Pyr)-functionalized generation 5 (G5) poly(amidoamine) dendrimers complexed with copper(II) (Cu(II)) for radiotherapy-enhanced T₁-weighted magnetic resonance (MR) imaging and the synergistic radio-chemotherapy of both tumors and tumor metastasis. In this study, amine-terminated G5 dendrimers were covalently linked with 2-pyridinecarboxylic acid, acetylated to neutralize their remaining terminal amines, and complexed with Cu(II) through both the internal tertiary amines and the surface Pyr groups to form the G5.NHAc-Pyr/Cu(II) complexes. We show that the complexes are able to inhibit the proliferation of different cancer cell lines with half-maximal inhibitory concentrations ranging from 4 to 10 μM and induce significant cancer cell apoptosis. Due to the presence of Cu(II), the G5.NHAc-Pyr/Cu(II) complexes display an r₁ relaxivity of 0.7024 mM^-1 s^-1, enabling effective in vivo MR imaging of tumor xenografts and lung metastatic nodules. Further, under radiotherapy (RT) conditions, the tumor MR imaging sensitivity can be significantly enhanced, and the G5.NHAc-Pyr/Cu(II) complexes enable the enhanced chemotherapy of both a xenografted tumor model and a blood-vessel metastasis model. With the demonstrated theranostic potential of the dendrimer-Cu(II) nanocomplexes without additional agents or elements for RT-enhanced MR imaging and chemotherapy of tumor and tumor metastasis, this novel Cu(II)-based nanohybrids may hold great promise for the theranostics of different cancer types and metastases.

One-pot synthesis of polypyrrole nanoparticles with tunable photothermal conversion and drug loading capacity

With an excellent near-infrared (NIR) light-responsive property, polypyrrole (PPy) nanoparticle has emerged as a promising NIR photothermal transducing agent for tumor photothermal therapy (PTT). Herein, we reported the PVP mediated one-pot synthesis of colloidal stable and biocompatible PPy nanoparticles (PPy-PVP NPs) for combined tumor photothermal-chemotherapy. The influence of molecular weight and PVP concentration on the spectroscopic characteristic, photothermal feature, drug loading performance, and antitumor efficiency of the resultant PPy-PVP NPs was systematically studied. By choosing PVP with a molecular weight of 360 kDa (concentration of 5 mg/mL) as the template and surface modifier during the synthesis, PPy-PVP NPs with optimal spectroscopic characteristic, photothermal feature, drug loading performance, and antitumor efficiency were synthesized. Findings in this study are anticipated to provide an in-depth understanding of the important character of surface engineering in the rational design and biomedical applications of PPy NPs.

The structure-property relationship in LAPONITE® materials: from Wigner glasses to strong self-healing hydrogels formed by non-covalent interactions

Rheology, small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS) analysis, zeta potential measurement, scanning electron microscopy (SEM), and micro-FTIR and absorbance spectroscopy were used to enlighten the controversial literature about LAPONITE® materials. Our data suggest that pristine LAPONITE® in water does not form hydrogels induced by the so-called "house of cards" assembly, but rather forms Wigner glasses governed by repulsive forces. Ionic interactions between anisotropic LAPONITE® nanodiscs, sodium polyacrylate and inorganic salts afforded hydrogels that were transparent, self-standing, moldable, strong, and biocompatible with shear-thinning and self-healing behavior. An extensive study on the role of salts in the gelification process dictates a trend that relates the valence of cations with the viscoelastic properties of the bulk material (G' values follow the trend, monovalent < divalent < trivalent). These hydrogels present G' values up to 5.1 × 104 Pa, which are considered high values for non-covalent hydrogels. Hydrogels crosslinked with sodium phosphate salts are biocompatible, and might be valid candidates for injectable drug delivery systems due to their shear-thinning behavior with rapid self-healing after injection.

Hyaluronic Acid-Decorated Laponite® Nanocomposites for Targeted Anticancer Drug Delivery

In this study, hyaluronic acid (HA), a natural polysaccharide that can specifically bind to CD44 receptors, was conjugated onto laponite® (LAP) nanodisks for the encapsulation and specific delivery of the anti-cancer drug doxorubicin (DOX) to CD44-overexpressed cancer cells. The prepared LM-HA could encapsulate DOX efficiently and release drug in a continuous manner with pH-responsiveness. In vitro cell viability assay proved that LM-HA had good biocompatibility, and drug-loaded LM-HA/DOX exhibited targeted anti-tumor effects against HeLa cells with CD44 receptors overexpressed. In addition, the flow cytometric detection and confocal laser scanning microscope results confirmed that LM-HA/DOX could be specifically internalized by HeLa cells via CD44-mediated endocytosis. Therefore, the HA-modified LAP nanodisks with high drug loading efficiency, pH-sensitive drug release properties and CD44 targetability might be an efficient nanoplatform for cancer chemotherapy.

3D-Printed Hydrogel Composites for Predictive Temporal (4D) Cellular Organizations and Patterned Biogenic Mineralization

Materials chemistries for hydrogel scaffolds that are capable of programming temporal (4D) attributes of cellular decision-making in supported 3D microcultures are described. The scaffolds are fabricated using direct-ink writing (DIW)-a 3D-printing technique using extrusion to pattern scaffolds at biologically relevant diameters (≤ 100 µm). Herein, DIW is exploited to variously incorporate a rheological nanoclay, Laponite XLG (LAP), into 2-hydroxyethyl methacrylate (HEMA)-based hydrogels-printing the LAP-HEMA (LH) composites as functional modifiers within otherwise unmodified 2D and 3D HEMA microstructures. The nanoclay-modified domains, when tested as thin films, require no activating (e.g., protein) treatments to promote robust growth compliances that direct the spatial attachment of fibroblast (3T3) and preosteoblast (E1) cells, fostering for the latter a capacity to direct long-term osteodifferentiation. Cell-to-gel interfacial morphologies and cellular motility are analyzed with spatial light interference microscopy (SLIM). Through combination of HEMA and LH gels, high-resolution DIW of a nanocomposite ink (UniH) that translates organizationally dynamic attributes seen with 2D gels into dentition-mimetic 3D scaffolds is demonstrated. These analyses confirm that the underlying materials chemistry and geometry of hydrogel nanocomposites are capable of directing cellular attachment and temporal development within 3D microcultures-a useful material system for the 4D patterning of hydrogel scaffolds.

Design of dual drug-loaded dendrimer/carbon dot nanohybrids for fluorescence imaging and enhanced chemotherapy of cancer cells

Dual drug-loaded dendrimer/CD nanohybrids can be developed for fluorescence imaging and enhanced chemotherapy of cancer cells.

Atomic-Scale Mechanism of Unidirectional Oxide Growth

A fundamental knowledge of the unidirectional growth mechanisms is required for precise control on size, shape, and thereby functionalities of nanostructures. The oxidation of many metals results in oxide nanowire growth with a bicrystal grain boundary along the axial direction. Using transmission electron microscopy that spatially and temporally resolves CuO nanowire growth during the oxidation of copper, here we provide direct evidence of the correlation between unidirectional crystal growth and bicrystal grain boundary diffusion. Based on atomic scale observations of the upward growth at the nanowire tip, oscillatory downward growth of atomic layers on the nanowire sidewall and the parabolic kinetics of lengthening, bicrystal grain boundary diffusion is the mechanism by which Cu ions are delivered from the nanowire root to the tip. Together with density-functional theory calculations, we further show that the asymmetry in the corner-crossing barriers promotes the unidirectional oxide growth by hindering the transport of Cu ions from the nanowire tip to the sidewall facets. We expect the broader applicability of these results in manipulating the growth of nanostructured oxides by controlling the bicrystal grain boundary structure that favors anisotropic diffusion for unidirectional, one-dimensional crystal growth for nanowires or isotropic diffusion for two-dimensional platelet growth.

A polydopamine-coated LAPONITE®-stabilized iron oxide nanoplatform for targeted multimodal imaging-guided photothermal cancer therapy

A novel targeted theranostic nanoplatform (LAP–Fe₃O₄@PDA–PEG–PBA) is constructed for magnetic resonance and photoacoustic imaging-guided photothermal therapy of cancer cells overexpressing sialic acid.

Stacking of doxorubicin on folic acid-targeted multiwalled carbon nanotubes for in vivo chemotherapy of tumors

In this work, we developed a novel active targeting and pH-responsive system for delivering the drug doxorubicin (DOX) to tumor sites using folic acid (FA)-modified multiwalled carbon nanotubes (MWCNTs). Acid-treated MWCNTs with carboxyl groups were first covalently conjugated with polyethyleneimine (PEI). Subsequent sequential modification with FA (via a polyethylene glycol spacer), fluorescein isothiocyanate (FI), and acetic anhydride/triethylamine resulted in multifunctional FA-bound MWCNT (MWCNT-PEI.Ac-FI-PEG-FA) nanomaterials that possessed exceptional colloidal stability and good biocompatibility in a given concentration range. The FA-bound MWCNTs were characterized using various techniques and exhibited a high drug loading and an encapsulation efficiency as high as 70.4%. DOX/MWCNT-PEI.Ac-FI-PEG-FA nanocomplexes (DOX/MWCNT NCs) exhibited pH-responsive release in acidic environments. Importantly, the DOX/MWCNT NCs targeted tumor cells overexpressing FA receptors (FARs) and effectively inhibited their growth. In vivo anticancer experiments demonstrated that DOX/MWCNT NCs not only enhanced the suppression of tumor growth but also decreased the side effects of free DOX. The developed FA-modified MWCNTs with an unconventionally high DOX loading boosted in vivo anti-tumor efficacy, and the lower systemic toxicity may be utilized for tumor therapy upon clinical translation.

Layered Silicates as a Possible Drug Carrier

The potential of layered silicates as drug carrier is overviewed. Due to their large surface area and expandable interlayer space to accommodate drug molecules, layered silicates have a potential as carrier of various molecules. In addition to the electrostatic interactions between negatively charged layered silicates and positively charged drug molecules, the organic modification of the surface of layered silicates has been applied to accommodate a variety of drug molecules not only cationic ones. The in vitro release experiment of the accommodated drug molecules has been reported under the acidic conditions. In order to discuss the future direction of layered silicates as drug carrier, materials' variation of layered silicates and their modification, and the reported stimuli-responsive hybrids based on layered silicates were introduced.

Laponite®: A key nanoplatform for biomedical applications?

Laponite® is a synthetic smectite clay that already has many important technological applications, which go beyond the conventional uses of clays in pharmaceutics and cosmetics. In biomedical applications, particularly in nanomedicine, this material holds great potential. Laponite® is a 2-dimensional (2D) nanomaterial composed of disk-shaped nanoscale crystals that have a high aspect ratio. These disks can strongly interact with many types of chemical entities (from small molecules or ions, to natural or synthetic polymers, to different inorganic nanoparticles) and are also easily functionalized and readily degraded in the physiological environment giving rise to non-toxic and even bioactive products. This review will highlight the potential of Laponite® as a nanomaterial in the fields of drug delivery, bioimaging, tissue engineering and regenerative medicine. New concepts, as well as novel innovative materials that stand out from the usual ones due to the unique properties of Laponite®, will also be presented and discussed.

Montmorillonite and Laponite Clay Materials for the Solidification of Lipid-Based Formulations for the Basic Drug Blonanserin: In Vitro and in Vivo Investigations

Solid-state lipid-based formulations offer great potential for the improved oral delivery of poorly water-soluble drugs. This study investigates the use of the high-surface-area clay materials, montmorillonite and laponite, as solid carriers for lipid-based formulations. The unique cation-exchange properties of clay platelets were exploited to preload the ionizable hydrophobic compound, blonanserin, prior to encapsulating a drug-loaded lipid solution. Thus, solid-state lipid-based formulations with dual-loading capabilities were developed and studied. These formulations were compared with simple clay-based lipid formulations, where blonanserin was loaded in the lipid phase only. The drug release behavior of all clay-based formulations was assessed during in vitro dissolution studies under simulated gastric conditions and in vitro fasting intestinal lipolysis studies. Montmorillonite- and laponite-based lipid formulations significantly reduced blonanserin solubilization relative to a control lipid solution and silica-lipid hybrid particles, owing to incomplete drug release from the clay cation-exchange sites. This phenomenon was replicated during in vivo pharmacokinetic studies, whereby the bioavailability of simple clay-based lipid formulations was decreased relative to controls. Importantly, the solid-state dual-loaded montmorillonite-based lipid formulation provided an optimal pharmacokinetic performance, achieving the same degree of bioavailability enhancement as the control lipid solution. These findings indicate the potential of solid-state dual-loaded clay-based lipid formulations for increasing drug loading levels and enhancing the oral absorption of poorly soluble weak base compounds.

Effect of ionic strength on shear-thinning nanoclay-polymer composite hydrogels

Nanoclay-polymer shear-thinning composites are designed for a broad range of biomedical applications, including tissue engineering, drug delivery, and additive biomanufacturing. Despite the advances in clay-polymer injectable nanocomposites, colloidal properties of layered silicates are not fully considered in evaluating the in vitro performance of shear-thinning biomaterials (STBs). Here, as a model system, we investigate the effect of ions on the rheological properties and injectability of nanoclay-gelatin hydrogels to understand their behavior when prepared in physiological media. In particular, we study the effect of sodium chloride (NaCl) and calcium chloride (CaCl2), common salts in phosphate buffered saline (PBS) and cell culture media (e.g., Dulbecco's Modified Eagle's Medium, DMEM), on the structural organization of nanoclay (LAPONITE® XLG-XR, a hydrous lithium magnesium sodium silicate)-polymer composites, responsible for the shear-thinning properties and injectability of STBs. We show that the formation of nanoclay-polymer aggregates due to the ion-induced shrinkage of the diffuse double layer and eventually the liquid-solid phase separation decrease the resistance of STB against elastic deformation, decreasing the yield stress. Accordingly, the stress corresponding to the onset of structural breakdown (yield zone) is regulated by the ion type and concentration. These results are independent of the STB composition and can directly be translated into the physiological conditions. The exfoliated nanoclay undergoes visually undetectable aggregation upon mixing with gelatin in physiological media, resulting in heterogeneous hydrogels that phase separate under stress. This work provides fundamental insights into nanoclay-polymer interactions in physiological environments, paving the way for designing clay-based injectable biomaterials.

Loading of Indocyanine Green within Polydopamine-Coated Laponite Nanodisks for Targeted Cancer Photothermal and Photodynamic Therapy

The combination of photothermal therapy (PTT) and photodynamic therapy (PDT) in cancer treatment has attracted much attention in recent years. However, developing highly efficient and targeted therapeutic nanoagents for amplifying PTT and PDT treatments remains challenging. In this work, we developed a novel photothermal and photodynamic therapeutic nanoplatform for treatment of cancer cells overexpressing integrin αvβ₃ through the coating of polydopamine (PDA) on indocyanine green (ICG)-loaded laponite (LAP) and then further conjugating polyethylene glycol-arginine-glycine-aspartic acid (PEG-RGD) as targeted agents on the surface. The ICG/LAP⁻PDA⁻PEG⁻RGD (ILPR) nanoparticles (NPs) formed could load ICG with a high encapsulation efficiency of 94.1%, improve the photostability of loaded ICG dramatically via the protection of PDA and LAP, and display excellent colloidal stability and biocompatibility due to the PEGylation. Under near-infrared (NIR) laser irradiation, the ILPR NPs could exert enhanced photothermal conversion reproducibly and generate reactive oxygen species (ROS) efficiently. More importantly, in vitro experiments proved that ILPR NPs could specifically target cancer cells overexpressing integrin αvβ₃, enhance cellular uptake due to RGD-mediated targeting, and exert improved photothermal and photodynamic killing efficiency against targeted cells under NIR laser irradiation. Therefore, ILPR may be used as effective therapeutic nanoagents with enhanced photothermal conversion performance and ROS generating ability for targeted PTT and PDT treatment of cancer cells with integrin αvβ₃ overexpressed.

Tough Composite Hydrogels with High Loading and Local Release of Biological Drugs

Hydrogels are under active development for controlled drug delivery, but their clinical translation is limited by low drug loading capacity, deficiencies in mechanical toughness and storage stability, and poor control over the drug release that often results in burst release and short release duration. This work reports a design of composite clay hydrogels, which simultaneously achieve a spectrum of mechanical, storage, and drug loading/releasing properties to address the critical needs from translational perspectives. The clay nanoparticles provide large surface areas to adsorb biological drugs, and assemble into microparticles that are physically trapped within and toughen hydrogel networks. The composite hydrogels demonstrate feasibility of storage, and extended release of large quantities of an insulin-like growth factor-1 mimetic protein (8 mg mL-1 ) over four weeks. The release rate is primarily governed by ionic exchange and can be upregulated by low pH, which is typical for injured tissues. A rodent model of Achilles tendon injury is used to demonstrate that the composite hydrogels allow for highly extended and localized release of biological drugs in vivo, while demonstrating biodegradation and biocompatibility. These attributes make the composite hydrogel a promising system for drug delivery and regenerative medicine.

2D Ultrathin MXene-Based Drug-Delivery Nanoplatform for Synergistic Photothermal Ablation and Chemotherapy of Cancer

Two-dimensional (2D) MXenes, as a new 2D functional material nanosystem, have been extensively explored for broad applications. However, their specific performance and applications in theranostic nanomedicine have still rarely been explored. This work reports on the drug-delivery performance and synergistic therapeutic efficiency of Ti₃ C₂ MXenes for highly efficient tumor eradication. These Ti₃ C₂ MXenes not only possess high drug-loading capability of as high as 211.8%, but also exhibit both pH-responsive and near infrared laser-triggered on-demand drug release. Especially, based on the high photothermal-conversion capability of Ti₃ C₂ MXenes, they have been further explored for efficient tumor eradication by synergistic photothermal ablation and chemotherapy, which has been systematically demonstrated both in vitro and in vivo. These Ti₃ C₂ MXenes have also been demonstrated as the desirable contrast agents for photoacoustic imaging, showing the potential for diagnostic-imaging guidance and monitoring during therapy. The high in vivo histocompatibility of Ti₃ C₂ and their easy excretion out of the body have been evaluated and demonstrated, showing the potential high biosafety for further clinical translation. This work paves a new way for broadening biomedical applications of MXenes in nanomedicine where they can exert the high performance and functionality for synergistic therapy, especially on combating cancer.

Mesoporous inorganic nanoscale particles for drug adsorption and controlled release

The review provides an overview of the mesoporous inorganic particles employed as drug delivery systems for controlled and sustained release of drugs. We have classified promising nanomaterials for drug delivery on the basis of their natural or synthetic origin. Nanoclays are available in different morphologies (nanotubes, nanoplates and nanofibers) and they are typically available at low cost from natural resources. The surface chemistry of nanoclays is versatile for targeted modifications to control loading and release properties. Synthetic nanomaterials (imogolite, laponite and mesoporous silica) present the advantages of well-established purity and availability with size features that are finely controlled. Both nanoclays and inorganic synthetic nanoparticles can be functionalized forming organic/inorganic architectures with stimuli-responsive features.

Injectable nanocomposite cryogels for versatile protein drug delivery

Sustained, localized protein delivery can enhance the safety and activity of protein drugs in diverse disease settings. While hydrogel systems are widely studied as vehicles for protein delivery, they often suffer from rapid release of encapsulated cargo, leading to a narrow duration of therapy, and protein cargo can be denatured by incompatibility with the hydrogel crosslinking chemistry. In this work, we describe injectable nanocomposite hydrogels that are capable of sustained, bioactive, release of a variety of encapsulated proteins. Injectable and porous cryogels were formed by bio-orthogonal crosslinking of alginate using tetrazine-norbornene coupling. To provide sustained release from these hydrogels, protein cargo was pre-adsorbed to charged Laponite nanoparticles that were incorporated within the walls of the cryogels. The presence of Laponite particles substantially hindered the release of a number of proteins that otherwise showed burst release from these hydrogels. By modifying the Laponite content within the hydrogels, the kinetics of protein release could be precisely tuned. This versatile strategy to control protein release simplifies the design of hydrogel drug delivery systems.

STATEMENT OF SIGNIFICANCE

Here we present an injectable nanocomposite hydrogel for simple and versatile controlled release of therapeutic proteins. Protein release from hydrogels often requires first entrapping the protein in particles and embedding these particles within the hydrogel to allow controlled protein release. This pre-encapsulation process can be cumbersome, can damage the protein's activity, and must be optimized for each protein of interest. The strategy presented in this work simply premixes the protein with charged nanoparticles that bind strongly with the protein. These protein-laden particles are then placed within a hydrogel and slowly release the protein into the surrounding environment. Using this method, tunable release from an injectable hydrogel can be achieved for a variety of proteins. This strategy greatly simplifies the design of hydrogel systems for therapeutic protein release applications.

Fabrication of a hyaluronic acid conjugated metal organic framework for targeted drug delivery and magnetic resonance imaging

DOX-doped MOF nanoparticles were prepared via a one-pot reaction and successively anchored with Fe³⁺ and HA for simultaneous targeted drug delivery and MR imaging.

LAPONITE® nanoplatform functionalized with histidine modified oligomeric hyaluronic acid as an effective vehicle for the anticancer drug methotrexate

The synthetic clay material, LAPONITE® (LAP), having a nanodisk structure together with a negatively charged surface, has been used for effective drug encapsulation by virtue of its interlayer space.

Ordering of lipid membranes altered by boron nitride nanosheets

Boron nitride nanosheets are novel promising nanomaterials with a lower cytotoxicity than graphene making them a better candidate for biomedical applications.

Drug-mediation formation of nanohybrids for sequential therapeutic delivery in cancer cells

In order to overcome the multidrug resistance (MDR) of tumor cells, it is very important to develop nanocarriers which can effectively load drugs while releasing them in a sequential way. Herein, nanohybrids with such properties have been fabricated by a first loading of one anticancer drug onto a silicate nanodisk (Laponite (LP), 25 nm in diameter and 0.92 nm in thickness) and a subsequent assembly with a pH sensitive poly(N-vinylpyrrolidone) (PVP) as a protective layer, followed by a loading of with another anticancer drug. The resulting nanohybrids (LDPM) present a high drug encapsulation efficiency and long-term colloidal stability. However, if the two drugs are loaded onto LP before PVP decoration, the formed particles tend to form microsized aggregates with poor colloidal stability. In vitro release study indicates that LDPM can deliver the anticancer drugs in a sequential way, which can be further accelerated under acidic microenvironments mimicking both solid tumor and endo-lysosomal compartments, exerting synergistic anticancer cytotoxicity. The drug-mediated formation of nanocarriers may enlighten a design of novel nanoplatform for co-delivery of therapeutic agents, beyond anticancer drugs, in a combinative way for drug delivery applications.

Efficient induction of comprehensive immune responses to control pathogenic E. coli by clay nano-adjuvant with the moderate size and surface charge

In recent decades, diseases caused by pathogenic Escherichia coli (E. coli), enterohaemorrhagic E. coli (EHEC) O26 have been increasingly reported worldwide, which are as severe as those caused by EHEC strain O157:H7 and require effective intervention strategies. Herein, we report the application of clay nanoparticles, i.e. hectorites as effective nano-adjuvants for vaccination against EHEC O26 colonization. We show that medium size HEC (hectorite, around 73~77 nm diameter) is able to induce efficient humoral and cellular immune responses against EHEC antigen - intimin β (IB), which are significantly higher than those triggered by commercially used adjuvants - QuilA and Alum. We also demonstrate that mice immunized with IB adjuvanted with HEC nanoparticles elicit sufficient secretion of mucosal IgA, capable of providing effective protection against EHEC O26 binding to ruminant and human cells. In addition, we demonstrate for the first time that hectorites are able to initiate maturation of RAW 264.7 macrophages, inducing expression of co-stimulatory cytokines at a low nanoparticle concentration (10 μg/mL). Together these data strongly suggest that hectorite with optimized size is a highly efficient vaccine nano-adjuvant.

An RGD-modified hollow silica@Au core/shell nanoplatform for tumor combination therapy

The combination of chemotherapy and photothermal therapy (PTT) in multifunctional nanoplatforms to improve cancer therapeutic efficacy is of great significance while it still remains to be a challenging task. Herein, we report Au nanostar (NS)-coated hollow mesoporous silica nanocapsules (HMSs) with surface modified by arginine-glycine-aspartic acid (RGD) peptide as a drug delivery system to encapsulate doxorubicin (DOX) for targeted chemotherapy and PTT of tumors. Au NSs-coated HMSs core/shell nanocapsules (HMSs@Au NSs) synthesized previously were conjugated with RGD peptide via a spacer of polyethylene glycol (PEG). We show that the prepared HMSs@Au-PEG-RGD NSs are non-cytotxic in the given concentration range, and have a DOX encapsulation efficiency of 98.6±0.7%. The designed HMSs@Au-PEG-RGD NSs/DOX system can release DOX in a pH/NIR laser dual-responsive manner. Importantly, the formed HMSs@Au-PEG-RGD NSs/DOX nanoplatform can specifically target cancer cells overexpressing α_vβ₃ intergrin and exert combination chemotherapy and PTT efficacy to the cells in vitro and a xenografted tumor model in vivo. Our results suggest that the designed HMSs@Au-PEG-RGD NSs/DOX nanoplatform may be used for combination chemotherapy and PTT of tumors.

STATEMENT OF SIGNIFICANCE

We demonstrate a convenient approach to preparing a novel RGD-targeted drug delivery system of HMSs@Au-PEG-RGD NSs/DOX that possesses pH/NIR laser dual-responsive drug delivery performance for combinational chemotherapy and PTT of tumors. The developed Au NS-coated HMS capsules have both merits of HMS capsules that can be used for high payload drug loading and Au NSs that have NIR laser-induced photothermal conversion efficiency (70.8%) and can be used for PTT of tumors.

pH-responsive self-healing injectable hydrogel based on N-carboxyethyl chitosan for hepatocellular carcinoma therapy

Injectable hydrogels with pH-responsiveness and self-healing ability have great potential for anti-cancer drug delivery. Herein, we developed a series of polysaccharide-based self-healing hydrogels with pH-sensitivity as drug delivery vehicles for hepatocellular carcinoma therapy. The hydrogels were prepared by using N-carboxyethyl chitosan (CEC) synthesized via Michael reaction in aqueous solution and dibenzaldehyde-terminated poly(ethylene glycol) (PEGDA). Doxorubicin (Dox), as a model of water-soluble small molecule anti-cancer drug was encapsulated into the hydrogel in situ. Self-healing behavior of the hydrogels was investigated at microscopic and macroscopic levels, and the hydrogels showed rapid self-healing performance without any external stimulus owing to the dynamic covalent Schiff-base linkage between amine groups from CEC and benzaldehyde groups from PEGDA. The chemical structures, rheological property, in vitro gel degradation, morphology, gelation time and in vitro Dox release behavior from the hydrogels were characterized. Injectability was verified by in vitro injection and in vivo subcutaneous injection in a rat. pH-responsive behavior was verified by in vitro Dox release from hydrogels in PBS solutions with different pH values. Furthermore, the activity of Dox released from hydrogel matrix was evaluated by employing human hepatocellular liver carcinoma (HepG2). Cytotoxicity test of the hydrogels using L929 cells confirmed their good cytocompatibility. Together, these pH-responsive self-healing injectable hydrogels are excellent candidates as drug delivery vehicles for liver cancer treatment. STATEMENT OF SIGNIFICANCE: pH-responsive drug delivery system could release drug efficiently in targeted acid environment and minimalize the amount of drug release in normal physiological environment. pH-sensitive injectable hydrogels as smart anti-cancer drug delivery carriers show great potential application for cancer therapy. The hydrogels with self-healing property could prolong their lifetime during implantation and provide the advantage of minimally invasive surgery and high drug-loading ratio. This work reported the design of a series of pH-responsive self-healing injectable hydrogels based on N-carboxyethyl chitosan synthesized in aqueous solution and dibenzaldehyde-terminated poly(ethylene glycol) via a green approach, and demonstrated their potential as intelligent delivery vehicle of doxorubicin for hepatocellular carcinoma therapy via the pH-responsive nature of dynamic Schiff base.

PEG-PE/clay composite carriers for doxorubicin: Effect of composite structure on release, cell interaction and cytotoxicity

A novel drug delivery system for doxorubicin (DOX), based on organic-inorganic composites was developed. DOX was incorporated in micelles (M-DOX) of polyethylene glycol-phosphatidylethanolamine (PEG-PE) which in turn were adsorbed by the clay, montmorillonite (MMT). The nano-structures of the PEG-PE/MMT composites of LOW and HIGH polymer loadings were characterized by XRD, TGA, FTIR, size (DLS) and zeta measurements. These measurements suggest that for the LOW composite a single layer of polymer intercalates in the clay platelets and the polymer only partially covers the external surface, while for the HIGH composite two layers of polymer intercalate and a bilayer may form on the external surface. These nanostructures have a direct effect on formulation stability and on the rate of DOX release. The release rate was reversely correlated with the degree of DOX interaction with the clay and followed the sequence: M-DOX>HIGH formulation>LOW formulation>DOX/MMT. Despite the slower release from the HIGH formulation, its cytotoxicity effect on sensitive cells was as high as the "free" DOX. Surprisingly, the LOW formulation, with the slowest release, demonstrated the highest cytotoxicity in the case of Adriamycin (ADR) resistant cells. Confocal microscopy images and association tests provided an insight into the contribution of formulation-cell interactions vs. the contribution of DOX release rate. Internalization of the formulations was suggested as a mechanism that increases DOX efficiency, particularly in the ADR resistant cell line. The employment of organic-inorganic hybrid materials as drug delivery systems, has not reached its full potential, however, its functionality as an efficient tunable release system was demonstrated.

STATEMENT OF SIGNIFICANCE

DOX PEG-PE/clay formulations were design as an efficient drug delivery system. The main aim was to develop PEG-PE/clay formulations of different structures based on various PEG-PE/clay ratios in order to achieve tunable release rates, to control the external surface characteristics and formulation stability. The formulations showed significantly higher toxicity in comparison to "free" DOX, explained by formulation internalization. For each cell line tested, sensitive and ADR resistant, a different formulation structure was found most efficient. The potential of PEG-PE/clay-DOX formulations to improve DOX administration efficacy was demonstrated and should be further explored and implemented for other cancer drugs and cells.

PEG coated and doxorubicin loaded multimodal Gadolinium oxide nanoparticles for simultaneous drug delivery and imaging applications

We report water-in-oil microemulsion mediated synthesis of PEG¹ coated Gd₂O₃ NPs² loaded with fluorescent anti-cancer drug dox³ for synchronous drug delivery, optical and MR⁴ imaging applications. These PEG covered Gd₂O₃ NPs loaded with dox (Gd-PEG-dox NPs) were found to possess spherical morphology with 13nm size as measured from TEM and the hydrodynamic diameter comes out to be 37nm as determined from DLS. Fluorescence spectra and fluorescence microscopy images confirmed optical activity of the NPs. The paramagnetic nature of NPs was affirmed by NMR line broadening effect on the spectrum of surrounding water protons. Therefore, these particles can be efficiently used as CA⁵ in MR imaging. In vitro analysis showed significant cellular uptake of particles by A-549 cells. A pH dependent drug release pattern was observed for the NPs. Cell viability assay performed on A-549, PANC-1 and U-87 cancerous cell lines revealed that Gd-PEG-dox NPs are cytotoxic. On the basis of these observations, it can be concluded that these multi-modal paramagnetic NPs promise potential cancer therapy along with optical and MR imaging applications.

LAPONITE®-stabilized iron oxide nanoparticles for in vivo MR imaging of tumors

We report the synthesis, characterization and utilization of LAPONITE®-stabilized magnetic iron oxide nanoparticles (LAP-Fe3O4 NPs) as a high performance contrast agent for in vivo magnetic resonance (MR) detection of tumors. In this study, Fe3O4 NPs were synthesized by a facile controlled coprecipitation route in LAP solution, and the formed LAP-Fe3O4 NPs have great colloidal stability and about 2-fold increase of T2 relaxivity than Fe3O4 NPs (from 247.6 mM(-1) s(-1) to 475.9 mM(-1) s(-1)). Moreover, cytotoxicity assay and cell morphology observation demonstrate that LAP-Fe3O4 NPs display good biocompatibility in the given Fe concentration range, and in vivo biodistribution results prove that NPs can be metabolized and cleared out of the body. Most importantly, LAP-Fe3O4 NPs can not only be used as a contrast agent for MR imaging of cancer cells in vitro due to the effective uptake by tumor cells, but also significantly enhance the contrast of a xenografted tumor model. Therefore, the developed LAP-based Fe3O4 NPs with good colloidal stability and exceptionally high transverse relaxivity may have tremendous potential in MR imaging applications.

Gadolinium-Loaded Poly(N-vinylcaprolactam) Nanogels: Synthesis, Characterization, and Application for Enhanced Tumor MR Imaging

We report the synthesis of poly(N-vinylcaprolactam) nanogels (PVCL NGs) loaded with gadolinium (Gd) for tumor MR imaging applications. The PVCL NGs were synthesized via precipitation polymerization using the monomer N-vinylcaprolactam (VCL), the comonomer acrylic acid (AAc), and the degradable cross-linker 3,9-divinyl-2,4,8,10-tetraoxaspiro-[5,5]-undecane (VOU) in aqueous solution, followed by covalently binding with 2,2',2″-(10-(4-((2-aminoethyl)amino)-1-carboxy-4-oxobutyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (NH₂-DOTA-GA)/Gd complexes. We show that the formed Gd-loaded PVCL NGs (PVCL-Gd NGs) having a size of 180.67 ± 11.04 nm are water dispersible, colloidally stable, uniform in size distribution, and noncytotoxic in a range of the studied concentrations. The PVCL-Gd NGs also display a r₁ relaxivity (6.38-7.10 mM^-1 s^-1), which is much higher than the clinically used Gd chelates. These properties afforded the use of the PVCL-Gd NGs as an effective positive contrast agent for enhanced MR imaging of cancer cells in vitro as well as a subcutaneous tumor model in vivo. Our study suggests that the developed PVCL-Gd NGs could be applied as a promising contrast agent for T₁-weighted MR imaging of diverse biosystems.

Nanoreinforced Hydrogels for Tissue Engineering: Biomaterials that are Compatible with Load-Bearing and Electroactive Tissues

Given their highly porous nature and excellent water retention, hydrogel-based biomaterials can mimic critical properties of the native cellular environment. However, their potential to emulate the electromechanical milieu of native tissues or conform well with the curved topology of human organs needs to be further explored to address a broad range of physiological demands of the body. In this regard, the incorporation of nanomaterials within hydrogels has shown great promise, as a simple one-step approach, to generate multifunctional scaffolds with previously unattainable biological, mechanical, and electrical properties. Here, recent advances in the fabrication and application of nanocomposite hydrogels in tissue engineering applications are described, with specific attention toward skeletal and electroactive tissues, such as cardiac, nerve, bone, cartilage, and skeletal muscle. Additionally, some potential uses of nanoreinforced hydrogels within the emerging disciplines of cyborganics, bionics, and soft biorobotics are highlighted.

LAPONITE-Polyethylenimine Based Theranostic Nanoplatform for Tumor-Targeting CT Imaging and Chemotherapy

In this study, laponite (LAP) nanodisks and polyethylenimine (PEI) were used to build a hybrid theranostic nanoplatform for targeted computed tomography (CT) imaging and chemotherapy of cancer cells overexpressing CD44 receptors. First, amphiphilic copolymer poly(lactic acid)-poly(ethylene glycol) (PLA-PEG-COOH) were assembled on the surface of LAP nanodisks via hydrophobic interaction, and then PEI were conjugated by the formation of amide groups via1-ethyl-3-(3-(dimethylamino)propyl) carbodiimide (EDC) coupling chemistry. The developed LAP-PLA-PEG-PEI nanoparticles were used as templates for the embedding of gold nanoparticles (Au NPs), followed by modification with hyaluronic acid (HA) as a targeting ligand for cancer cells overexpressing CD44 receptors. Finally, anticancer drug doxorubicin (DOX) was loaded. The formed LAP-PLA-PEG-PEI-(Au⁰)₅₀-HA/DOX nanocomplexes display good stability, a high drug loading efficiency as 91.0 ± 1.8%, and sustained drug release profile with a pH-sensitive manner. In vitro cell viability assay, flow cytometric analysis, and laser scanning confocal microscopy observation demonstrate that the formed nanocomplexes can specifically deliver and inhibit cancer cells overexpressing CD44 receptors. In vivo experiments illustrate that LAP-PLA-PEG-PEI-(Au⁰)₅₀-HA/DOX nanocomplexes can not only significantly inhibit the growth of tumors and decrease the side-effect of DOX, but also be used as a targeted contrast agent for CT imaging of tumors. Therefore, the developed LAP-PLA-PEG-PEI-(Au⁰)₅₀-HA/DOX nanocomplexes can be used as a promising theranostic platform for targeted imaging and chemotherapy of CD44-overexpressed tumors.

LAPONITE®-pilocarpine hybrid material: experimental and theoretical evaluation of pilocarpine conformation

DFT calculations were applied to evaluate conformational changes of protonated pilocarpine after immobilization into LAPONITE®.

Laponite as carrier for controlled in vitro delivery of dexamethasone in vitreous humor models

Laponite clay is able to retain dexamethasone by simple physisorption, presumably accomplished by hydrogen bonding formation and/or complexation with sodium counterions, as shown by solid state NMR. The physisorption can be somehow modulated by changing the solvent in the adsorption process. This simple system is able to deliver dexamethasone in a controlled manner to solutions used as models for vitreous humor. The proven biocompatibility of laponite as well as its transparency in the gel state, together with the simplicity of the preparation method, makes this system suitable for future in vivo tests of ophthalmic treatment.