Bio-Layered Double Hydroxides Nanohybrids for Theranostics Applications

Advances of Layered Double Hydroxide-Based Materials for Tumor Imaging and Therapy

Layered double hydroxides (LDH) are a class of functional anionic clays that typically consist of orthorhombic arrays of metal hydroxides with anions sandwiched between the layers. Due to their unique properties, including high chemical stability, good biocompatibility, controlled drug loading, and enhanced drug bioavailability, LDHs have many potential applications in the medical field. Especially in the fields of bioimaging and tumor therapy. This paper reviews the research progress of LDHs and their nanocomposites in the field of tumor imaging and therapy. First, the structure and advantages of LDH are discussed. Then, several commonly used methods for the preparation of LDH are presented, including co-precipitation, hydrothermal and ion exchange methods. Subsequently, recent advances in layered hydroxides and their nanocomposites for cancer imaging and therapy are highlighted. Finally, based on current research, we summaries the prospects and challenges of layered hydroxides and nanocomposites for cancer diagnosis and therapy.

Engineering the Morphostructural Properties and Drug Loading Degree of Organic-Inorganic Fluorouracil-MgAl LDH Nanohybrids by Rational Control of Hydrothermal Treatment

Layered double hydroxides (LDHs) or hydrotalcite-like compounds have attracted great attention for the delivery of anticancer drugs due to their 2D structure, exhibiting a high surface-to-volume ratio and a high chemical versatility. The drug is protected between the layers from which it is slowly released, thus increasing the therapeutic effect and minimizing the side effects associated to nonspecific targeting. This work aimed to design LDHs with Mg and Al (molar ratio of 2/1) in brucite-like layers, which retained fluorouracil (5-FU; 5-FU/Al = 1, molar ratio) in the interlayer gallery as the layers grow during the co-precipitation step of the synthesis. To rationally control the physicochemical properties, particularly the size of the crystallites, the aging step following the co-precipitation was performed under carefully controlled conditions by changing the time and temperature (i.e., 25 °C for 16 h, 100 °C for 16 h, and 120 °C for 24 h). The results revealed the achievement of the control of the size of the crystals, which are gathered in three different agglomeration systems, from tight to loose, as well as the loading degree of the drug in the final organic-inorganic hybrid nanomaterials. The role played by the factors and parameters affecting the drug-controlled release was highlighted by assessing the release behavior of 5-FU by changing the pH, solid mass/volume ratio, and ionic strength. The results showed a pH-dependent behavior but not necessarily in a direct proportionality. After a certain limit, the mass of the solid diminishes the rate of release, whereas the ionic strength is essential for the payload discharge.

Biofunctional Layered Double Hydroxide Nanohybrids for Cancer Therapy

Layered double hydroxides (LDHs) with two-dimensional nanostructure are inorganic materials that have attractive advantages such as biocompatibility, facile preparation, and high drug loading capacity for therapeutic bioapplications. Since the intercalation chemistry of DNA molecules into the LDH materials were reported, various LDH nanohybrids have been developed for biomedical drug delivery system. For these reasons, LDHs hybridized with numerous therapeutic agents have a significant role in cancer imaging and therapy with targeting functions. In this review, we summarized the recent advances in the preparation of LDH nanohybrids for cancer therapeutic strategies including gene therapy, chemotherapy, immunotherapy, and combination therapy.

Advanced drug delivery applications of layered double hydroxide

Layered double hydroxides (LDHs), also known as anionic clays or hydrotalcite-like compounds, are a class of nanomaterials that attained great attention as a carrier for drug delivery applications. The lamellar structure of this compound exhibits a high surface-to-volume ratio which enables the intercalation of therapeutic agents and releases them at the target site, thereby reducing the adverse effect. Moreover, the intercalated drug can be released in a sustained manner, and hence the frequency of drug administration can be decreased. The co-precipitation, ion exchange, manual grinding, and sol-gel methods are the most employed for their synthesis. The unique properties like the ease of synthesis, low cost, high biocompatibility, and low toxicity render them suitable for biomedical applications. This review presents the advances in the structure, properties, method of preparation, types, functionalization, and drug delivery applications of LDH. Also, this review provides various new conceptual insights that can form the basis for new research questions related to the drug delivery applications of LDH.

Monolayer Nanosheets with an Extremely High Drug Loading toward Controlled Delivery and Cancer Theranostics

2D nanomaterials have attracted considerable research interest in drug delivery systems, owing to their intriguing quantum size and surface effect. Herein, Gd³⁺ -doped monolayered-double-hydroxide (MLDH) nanosheets are prepared via a facile bottom-up synthesis method, with a precisely controlled composition and uniform morphology. MLDH nanosheets as drug carrier are demonstrated in coloading of doxorubicin and indocyanine green (DOX&ICG), with an ultrahigh drug loading content (LC) of 797.36% and an encapsulation efficiency (EE) of 99.67%. This is, as far as it is known, the highest LC level at nearly 100% of EE among previously reported 2D drug delivery systems so far. Interestingly, the as-prepared DOX&ICG/MLDH composite material shows both pH-controlled and near-infrared-irradiation-induced DOX release, which holds a promise in stimulated drug release. An in vivo dual-mode imaging, including near-infrared fluorescence and magnetic resonance imaging, enables a noninvasive visualization of distribution profiles at the tumor site. In addition, in vitro and in vivo therapeutic evaluations demonstrate an excellent trimode synergetic anticancer activity and superior biocompatibility of DOX&ICG/MLDH. Therefore, MLDH nanosheets provide new perspectives in the design of multifunctional nanomedicine, which shows promising applications in controlled drug delivery and cancer theranostics.

A layered drug nanovehicle toward targeted cancer imaging and therapy

A layered drug nanovehicle with superior anticancer performance was fabricated via the co-intercalation of doxorubicin (DOX) and folic acid (FA) into the gallery of layered double hydroxides (LDHs), which can be potentially applied in medical imaging/therapy.