pH/redox/thermo-stimulative nanogels with enhanced thermosensitivity via incorporation of cationic and anionic components for anticancer drug delivery

Strategic Design of Intelligent-Responsive Nanogel Carriers for Cancer Therapy

Owing to the distinctive constituents of tumor tissue from those healthy organs, nanomedicine strategies show significant potentials in smart drug delivery. Nowadays, stimuli-responsive nanogels are playing increasingly important roles in the application of cancer therapy because of their sensitivity to various internal or external physicochemical stimuli, which exhibit site-specific and markedly enhanced drug release. Besides, nanogels are promising as drug carriers because of their porous structures, good biocompatibility, large surface area, and excellent capability with drugs. Taking advantage of multiresponsiveness, recent years have witnessed the rapid evolution of stimulus-responsive nanogels from monoresponsive to multiresponsive systems; however, there lacks a comprehensive review summarizing these reports. In this Review, we discuss the properties, synthesis, and characterization of nanogels. Moreover, tumor microenvironment and corresponding designing strategies for stimuli-response nanogels, both exogenous (temperature, magnetic field, light) and endogenous (pH, biomolecular, redox, ROS, pressure, hypoxia) are summarized on the basis of the recent advances in multistimuli-responsive nanogel systems. Nanogel and two-dimensional material composites show excellent performance in the field of constructing multistimulus-responsive nanoparticles and precise intelligent drug release integrated system for multimodal cancer diagnosis and therapy. Finally, potential progresses and suggestions are provided for the further design of hybrid nanogels based on emerging two-dimensional materials.

Theranostic applications of stimulus-responsive systems based on carbon dots

Over recent years, many different nanoparticle-based drug delivery systems (NDDSs) have been developed. Recently the development of stimulus-responsive NDDSs has come into sharper focus. Carbon dots (CDs) possess outstanding features such as useful optical properties, good biocompatibility, and the ability for easy surface modification. Appropriate surface modification can allow these NDDSs to respond to various chemical or physical stimuli that are characteristic of their target cells or tissue (frequently malignant cells or tumors). The present review covers recent developments of CDs in NDDSs with a particular focus on internal stimulus response capability that allows simultaneous imaging and therapeutic delivery (theranostics). Relevant stimuli associated with tumor cells and tumors include pH levels, redox potential, and different enzymatic activities can be used to activate the CDs at the desired sites.

Hybridization of graphene oxide into nanogels to acquire higher photothermal effects for therapeutic delivery

Although the special architecture of two-dimensional (2D) nanomaterials endows them with unique properties, their poor colloidal stability remains a main bottleneck to fully exploit their applications in the biomedical field. Herein, this study aims to develop a simple and effective approach to in situ incorporate 2D graphene oxide (GO) nanoplatelets into a thermosensitive matrix to acquire hybrid nanogels with good stability and photothermal effect. In order to improve its stability, GO firstly underwent silanization to its surface with double bonds, followed by intercalation with N-isopropylacrylamide (NIPAM) in the presence of a disulfide-containing crosslinker via an emulsion method. Radical polymerization was then initiated to accelerate direct GO exfoliation in PNIPAM nanogels by forming covalent bonds between them. The well-dispersed GO nanopletlets in the nanogels not only displayed an enhanced photothermal effect, but also improved the encapsulation efficiency of an anticancer drug. The hybrid nanogels accelerate drug release under conditions mimicking the acidic/reducible solid tumor and intracellular microenvironments, most importantly, it can be further enhanced via remote photothermal treatment. The multifunctional nanogels potentiate their synergistic anticancer bioactivity as an ideal nanoplatform for cancer treatment.

Preparation of thermo/redox/pH-stimulative poly(N-isopropylacrylamide-co-N,N'-dimethylaminoethyl methacrylate) nanogels and their DOX release behaviors

Stimuli-sensitive drug delivery systems show beneficial features of both medical and pharmaceutical fields. In this article, polymeric nanogel P (N-isopropylacrylamide-N,N '-dimethylaminoethyl methacrylate [NIPAM-DMAEMA]) (PND) with pH/redox/thermo-responsivenesses was synthesized by the in situ polymerization of NIPAM and DMAEMA for the controlled release of doxorubicin hydrochloride (DOX) and N,N '-bis(acryloyl)cystamine (BAC) and N,N '-methylenebisacrylamide (MBA) act as the crosslinkers, respectively. The structure, size, and zeta potential of PND-BAC and PND-MBA were further characterized. Moreover, after loading DOX, the encapsulation efficiency and the in vitro release behavior of PND-BAC/DOX and PND-MBA/DOX nanogels were discussed in detail. Compared to PND-MBA NGs, PND-BAC nanogels have redox degradability due to the presence of the crosslinker BAC. After loading DOX, the PND-BAC/DOX nanogel showed a higher encapsulation efficiency (81.6 ± 1.2)% and thermo- and pH-responsiveness as well as redox-responsive in vitro release. These properties together with excellent environmentally sensitive properties make PND-BAC as an attractive candidate for application in drug nanocarriers for the targeted drug delivery of model payloads. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1195-1203, 2019.

Smart co-delivery of 6-mercaptopurine and methotrexate using disulphide-based PEGylated-nanogels for effective treatment of breast cancer

Smart co-delivery of 6-mercaptopurine and methotrexate using disulphide-based PEGylated-nanogels.

Redox-responsive nano-carriers as tumor-targeted drug delivery systems

With ever increasing scientific knowledge and awareness, research is underway around the globe to design new types of stimuli (external/internal) responsive nano-carriers for biotechnological applications at large and biomedical/pharmaceutical in particular. Based on literature evidence, stimuli-responsive carriers have been classified into four major categories, i.e. (1) physical, (2) chemical, (3) biological, and (4) dual (combination of any of the first three classes). Among various types, redox-responsive nano-carriers are of supreme interests and discussed here in this review. The difference in redox potential in tumor and normal tissue is considered as a potential target for tumor targeting leading to the development of redox-responsive drug delivery systems (DDS). In this regard, a high concentration of glutathione in tumor/intracellular environment has extensively been exploited. Disulfide bonds were found as a promising tool for designing redox-responsive which tend to cleave in a reductive environment forming sulfhydryl groups. Many nano-carriers have been explored widely to control tumor growth. These systems were used against the tumor xenograft animal model and showed improved tumor targeting with tumor growth inhibition. Herein, an effort has been made to summarize various aspects from design to development of numerous types of redox-responsive DDS including liposomes, micelles, nanoparticles, nanogel and prodrug based nanomedicines. An emphasis is also given on various types of nano-carriers with special reference to the tumor-targeted drug delivery applications. Also, dual responsive nano-carriers (in addition to redox-responsive) have also been briefly discussed. Towards the end of the chapter, the information is also given on their future perspectives.