Emerging role of nanoclays in cancer research, diagnosis, and therapy

Cancer remains one of the deadliest diseases, and its effective diagnosis and treatment remains challenging; therefore, progress in earlier detection and improved therapeutics are urgently required. Conventional chemotherapy has only limited efficacy, suffers from non-specific toxicity and the induction of chemoresistance. Prospective templates for these are natural materials such as nanosized clay mineral structures of different shapes (platy, tubule, spherical, and fibrous) with tunable physicochemical, morphological, and structural properties. Their submicron size, individual morphology, high specific surface area, enhanced adsorption ability, cation exchange capacity, and multilayered organization of 0.7-1 nm thick single sheets have attracted considerable interest as multifunctional biocompatible nanocarriers with versatile applications in cancer research, diagnosis, and therapy. The most common nanoclay minerals studied for oncology are kaolinite, halloysite, montmorillonite, laponite, bentonite, sepiolite, palygorskite, and allophane. These multilayered minerals can act as nanocarriers (with a typical drug load of 1-10 wt%) for improved dispersibility, stabilization, sustained controlled release, and the efficient transport of a wide range of anticancer drugs to the tumor site. Nanoclays having both positive and negative surfaces possess the potential to transport proteins and DNA/RNA. Nanoclays can serve as a platform for phototherapeutic agents. Several surface engineering strategies have been devised to develop clays with biofunctionality that could benefit cancer clinical practice. This review explores the potential of nanoclays as unique crystalline materials with applications in cancer research, diagnosis, and therapy. (C) 2021 Elsevier B.V. All rights reserved.