Red-emitting polyaniline-based nanoparticle probe for pH-sensitive fluorescence imaging

Fluorescent probes based on semiconducting polymer nanoparticles (NPs) such as polyaniline (PANI) usually require external fluorophore doping to provide fluorescence function. Direct use of PANI-based NPs for bioimaging applications has been limited by PANI's weak blue fluorescence and aggregation-induced quenching in physiological medium. In this report, we developed a facile solid-state synthesis method to produce fluorescent polyaniline nanoparticles (FPNs) that are not only water-soluble but also exhibit high intensity and pH-sensitive red fluorescence. The FPNs showed high photoluminescence quantum yield (PLQY) of 19.3 % at physiological pH, which makes FPNs ideal for application as fluorescent nanoprobes in bioimaging. Moreover, we performed an in-depth study of photoluminescence dependence on pH and the phenomena of exciton-polaron quenching at low pH was highlighted. We also found that the ratio of emission intensity at 600 nm and 650 nm increased from 0.04 to 1.65 as pH was raised from 2.6 to 11.8, which could find its application in ratiometric pH sensing. FPNs exhibited excellent biocompatibility with >85 % cell viability for fibroblasts NIH/3 T3 and prostate cancer 22RV1 cells even at concentrations as high as 1000 μg/mL. In addition, fluorescence microscopy demonstrated concentration-dependent red fluorescence in the cytoplasm owing to the cellular uptake of FPNs in prostate cancer cells.

Carbon Dots in Biomedicine: A Review

Despite the rapid development of science and technology, the effective treatment of cancer still threatens human life and health. However, the success of cancer treatment is closely related to early diagnosis, identification, and effective treatment. In recent years, with the strengthening of the development and research of nanomaterials for cancer diagnosis and treatment, researchers have found that carbon dots (CDs) have the advantages of wide absorption, excellent biocompatibility, diverse imaging characteristics, and photostability and are widely used in various fields, such as sensing, imaging, and drug/gene transportation. Recently, researchers also discovered that CDs could be used as an effective photosensitizer to generate active oxygen or convert light energy into heat under the stimulation of the external lasers, making them have the effects of photothermal and photodynamic therapy for cancer. In this review, we first outline the single-modal and multimodal imaging analysis of CDs in cancer cells. After introducing diversified imaging functions, we focused on the design and the latest research progress of CDs in phototherapy and introduced in detail the strategies of CDs in phototherapy treatment and the challenges faced by clinical applications. We hope that this overview can provide important insights for researchers and accelerate the pace of research on CDs in imaging-guided phototherapy treatment.

Hyaluronic Acid-Functionalized Hollow Mesoporous Silica Nanoparticles as pH-Sensitive Nanocarriers for Cancer Chemo-Photodynamic Therapy

Hollow mesoporous silica nanoparticles (HMSNs) served as nanocarriers for transporting doxorubicin hydrochloride (DOX) and indocyanine green (ICG) and were incorporated into a pH-sensitive targeted drug delivery system (DDS). Boronate ester bonds were employed to link HMSNs and dopamine-modified hyaluronic acid (DA-HA), which acted as both the "gatekeeper" and targeting agents (HMSNs-B-HA). Well-dispersed HMSNs-B-HA with a diameter of about 170 nm was successfully constructed. The conclusion was drawn from the in vitro drug release experiment that ICG and DOX (ID) co-loaded nanoparticles (ID@HMSNs-B-HA) with high drug loading efficiency could sustain drug release under acidic conditions. More importantly, in vitro cell experiments perfectly showed that ID@HMSNs-B-HA could well inhibit murine mammary carcinoma (4T1) cells via chemotherapy combined with photodynamic therapy and accurately target 4 T1 cells. In summary, all test results sufficiently demonstrated that the prepared ID@HMSNs-B-HA was a promising nano-DDS for cancer photodynamic combined with chemotherapy.

Emerging photothermal-derived multimodal synergistic therapy in combating bacterial infections

Due to the emerging bacterial resistance and the protection of tenacious biofilms, it is hard for the single antibacterial modality to achieve satisfactory therapeutic effects nowadays. In recent years, photothermal therapy (PTT)-derived multimodal synergistic treatments have received wide attention and exhibited cooperatively enhanced bactericidal activity. PTT features spatiotemporally controllable generation of hyperthermia that could eradicate bacteria without inducing resistance. The synergy of it with other treatments, such as chemotherapy, photo-dynamic/catalytic therapy (PDT/PCT), immunotherapy, and sonodynamic therapy (SDT), could lower the introduced laser density in PTT and avoid undesired overheating injury of normal tissues. Simultaneously, by heat-induced improvement of the bacterial membrane permeability, PTT is conducive for accelerated intracellular permeation of chemotherapeutic drugs as well as reactive oxygen species (ROS) generated by photosensitizers/sonosensitizers, and could promote infiltration of immune cells. Thereby, it could solve the currently existing sterilization deficiencies of other combined therapeutic modes, for example, bacterial resistance for chemotherapy, low drug permeability for PDT/PCT/SDT, adverse immunoreactions for immunotherapy, etc. Admittedly, PTT-derived synergistic treatments are becoming essential in fighting bacterial infection, especially those caused by antibiotic-resistant strains. This review firstly presents the classical and newly reported photothermal agents (PTAs) in brief. Profoundly, through the introduction of delicately designed nanocomposite platforms, we systematically discuss the versatile photothermal-derived multimodal synergistic therapy with the purpose of sterilization application. At the end, challenges to PTT-derived combinational therapy are presented and promising synergistic bactericidal prospects are anticipated.

Recent advances in the modification of carbon-based quantum dots for biomedical applications

Carbon-based quantum dots (CDs) are mainly divided into two sub-groups; carbon quantum dots (CQDs) and graphene quantum dots (GQDs), which exhibit outstanding photoluminescence (PL) properties, low toxicity, superior biocompatibility and facile functionalization. Regarding these features, they have been promising candidates for biomedical science and engineering applications. In this work, we reviewed the efforts made to modify these zero-dimensional nano-materials to obtain the best properties for bio-imaging, drug and gene delivery, cancer therapy, and bio-sensor applications. Five main surface modification techniques with outstanding results are investigated, including doping, surface functionalization, polymer capping, nano-composite and core-shell structures, and the drawbacks and challenges in each of these methods are discussed.

Recent Advances of Polyaniline-Based Biomaterials for Phototherapeutic Treatments of Tumors and Bacterial Infections

Conventional treatments fail to completely eradicate tumor or bacterial infections due to their inherent shortcomings. In recent years, photothermal therapy (PTT) has emerged as an attractive treatment modality that relies on the absorption of photothermal agents (PTAs) at a specific wavelength, thereby transforming the excitation light energy into heat. The advantages of PTT are its high efficacy, specificity, and minimal damage to normal tissues. To this end, various inorganic nanomaterials such as gold nanostructures, carbon nanostructures, and transition metal dichalcogenides have been extensively explored for PTT applications. Subsequently, the focus has shifted to the development of polymeric PTAs, owing to their unique properties such as biodegradability, biocompatibility, non-immunogenicity, and low toxicity when compared to inorganic PTAs. Among various organic PTAs, polyaniline (PANI) is one of the best-known and earliest-reported organic PTAs. Hence, in this review, we cover the recent advances and progress of PANI-based biomaterials for PTT application in tumors and bacterial infections. The future prospects in this exciting area are also addressed.

The Progress and Prospect of Zeolitic Imidazolate Frameworks in Cancer Therapy, Antibacterial Activity, and Biomineralization

The progressive development of zeolitic imidazolate frameworks (ZIFs), as a subfamily of metal-organic frameworks (MOFs), and their unique features, including tunable pore size, large surface area, high thermal stability, and biodegradability/biocompatibility, have made them attractive in the field of biomedicine, especially for drug delivery and biomineralization applications. The high porosity of ZIFs gives them the opportunity for encapsulating a high amount of therapeutic drugs, proteins, imaging cargos, or a combination of them to construct advanced multifunctional drug delivery systems (DDSs) with combined therapeutic and imaging capabilities. This review summarizes recent strategies on the design and fabrication of ZIF-based nansystems and their exploration in the biomedical field. First, recent developments for the adjustment of particle size, functionality, and morphology of ZIFs are discussed, which are important for achieving optimized therapeutic/theranostic nanosystems. Second, recent trends on the application of ZIF nanocarriers for the loading of diverse cargos, including anticancer medicines, antibiotic drugs, enzymes, proteins, photosensitizers, as well as imaging and photothermal agents, are investigated in order to understand how multifunctional DDSs can be designed based on the ZIF nanoparticles to treat different diseases, such as cancer and infection. Finally, prospects on the future research direction and applications of ZIF-based nanomedicines are discussed.

Progress in Conductive Polyaniline-Based Nanocomposites for Biomedical Applications: A Review

Inherently conducting polymers (ICPs) are a specific category of synthetic polymers with distinctive electro-optic properties, which involve conjugated chains with alternating single and double bonds. Polyaniline (PANI), as one of the most well-known ICPs, has outstanding potential applications in biomedicine because of its high electrical conductivity and biocompatibility caused by its hydrophilic nature, low-toxicity, good environmental stability, and nanostructured morphology. Some of the limitations in the use of PANI, such as its low processability and degradability, can be overcome by the preparation of its blends and nanocomposites with various (bio)polymers and nanomaterials, respectively. This review describes the state-of-the-art of biological activities and applications of conductive PANI-based nanocomposites in the biomedical fields, such as antimicrobial therapy, drug delivery, biosensors, nerve regeneration, and tissue engineering. The latest progresses in the biomedical applications of PANI-based nanocomposites are reviewed to provide a background for future research.

Horizons of nanotechnology applications in female specific cancers

Female-specific cancers are the most common cancers in women worldwide. Early detection methods remain unavailable for most of these cancers, signifying that most of them are diagnosed at later stages. Furthermore, current treatment options for most female-specific cancers are surgery, radiation and chemotherapy. Although important milestones in molecularly targeted approaches have been achieved lately, current therapeutic strategies for female-specific cancers remain limited, ineffective and plagued by the emergence of chemoresistance, which aggravates prognosis. Recently, the application of nanotechnology to the medical field has allowed the development of novel nano-based approaches for the management and treatment of cancers, including female-specific cancers. These approaches promise to improve patient survival rates by reducing side effects, enabling selective delivery of drugs to tumor tissues and enhancing the uptake of therapeutic compounds, thus increasing anti-tumor activity. In this review, we focus on the application of nano-based technologies to the design of novel and innovative diagnostic and therapeutic strategies in the context of female-specific cancers, highlighting their potential uses and limitations.

Multifunctional System Polyaniline-Decorated ZIF-8 Nanoparticles as a New Chemo-Photothermal Platform for Cancer Therapy

Polyaniline-decorated ZIF-8 nanoparticles (nPANI@nZIF-8) were easily synthesized and employed as a multifunctional system for the delivery of the antitumor drug 5-fluorouracil (5-FU). Because of the storage ability of the network ZIF-8, 68% of the total amount of the 5-FU drug was released at pH 5.2. The system exhibits absorption in the near-infrared (NIR) region and can be used in the photothermal therapy owing to the presence of nPANI, which has a strong NIR uptake. This absorption causes local hyperthermia by aiding in the diffusion of the drug molecules contained by the polymer into nPANI@nZIF-8/5-FU achieving a greater release of the 5-FU drug, about 80% activated by an NIR laser (λ = 980 nm). This hyperthermia reached about 70 °C (200 μL, 1 mg mL-1 nPANI@nZIF-8), which was directly proportional to the concentration of the material. Therefore, our work can aid in the construction of new chemo-photothermal platforms that may be employed in cancer therapy.

Dual-Responsive Carbon Dot for pH/Redox-Triggered Fluorescence Imaging with Controllable Photothermal Ablation Therapy of Cancer

Herein we describe fluorescence resonance energy transfer (FRET) for a pH/redox-activatable fluorescent carbon dot (FNP) to realize "off-on" switched imaging-guided controllable photothermal therapy (PTT). The FNP is a carbonized self-crosslinked polymer that allows IR825 loading (FNP[IR825]) via hydrophobic interactions for cancer therapy. Fluorescence bioimaging was achieved by the internalization of FNP(IR825) into tumor cells, wherein glutathione (GSH) disulfide bonds are reduced, and benzoic imine groups are cleaved under acidic conditions. The release of IR825 from the FNP core in this system may be used to efficiently control PTT-mediated cancer therapy via its photothermal conversion after near-infrared (NIR) irradiation. In vitro and in vivo cellular uptake studies revealed efficient uptake of FNP(IR825) by tumor cells to treat the disease site. In this way we demonstrated in mice that our smart nanocarrier can effectively kill tumor cells under exposure to a NIR laser, and that the particles are biocompatible with various organs. This platform responds sensitively to the exogenous environment inside the cancer cells and may selectively induce the release of PTT-mediated cytotoxicity. Furthermore, this platform may be useful for monitoring the elimination of cancer cells through the fluorescence on/off switch, which can be used for various applications in the field of cancer cell therapy and diagnosis.

Combined Adsorption and Covalent Linking of Paclitaxel on Functionalized Nano-Graphene Oxide for Inhibiting Cancer Cells

Developing targeted delivery nanosystems for delivering chemotherapeutic anticancer drugs specifically to cancerous tissues with improvement in the specificity of drugs for different cancer cells can result in high therapeutic efficacy and low toxicity in healthy tissues. Herein, we proposed the synthesis of a multifunctional nanodelivery system, folic acid (FA) decorating nanographene oxide (nGO) functionalized with poly(ethylene glycol) (PEG), called pGO-FA, with good biocompatibility and good delivering performance of a hydrophobic water-insoluble anticancer drug of paclitaxel (PTX). 4-br-PEG-NH2, FA, and PTX were attached to PEG-functionalized nGO (pGO) through a combined chemical and physical force to form a nanosized complex, pGO-FA-PTX, defined as the nanodrug system. WST-8 assay in vitro illustrated that pGO-FA-PTX inhibited A2780 cells in a concentration-dependent manner. Cell viability was kept high to 60% when treated with 200 nM of free PTX. However, pGO-FA-PTX with the same dose of PTX (cell viability less than 30%) had double the cytotoxicity effect compared to free PTX. Furthermore, fluorescence observation demonstrated that pGO-FA-PTX exhibited an improved efficiency in killing A2780 cells due to the special affinity between FA and FA receptor, which has high expression in cancer cells. The strategy and method used in this study could be effective in improving both the bioavailability of PTX and therapy efficiency.

Progress in internal/external stimuli responsive fluorescent carbon nanoparticles for theranostic and sensing applications

In the past decade, fluorescent carbon nanoparticles (FNPs) prepared from natural resources and biomaterials have been attractive due to their various properties, such as unique optical properties, great biocompatibility, water dispersion, and facile surface functionalization. Depending on the properties of the carbon sources and the subsequent carbonization processes, internal/external stimuli responsive carbon nanoparticles have been generated that are useful for theranostic and sensing applications. In this review, we highlight the recent developments in the use of FNPs in nanomedicine in great detail, particularly for FNPs responding to internal stimuli, including redox, pH, and enzymes, and external stimuli, including temperature, light, and magnetic fields, for drug delivery and sensing applications. Furthermore, we hope to provide insight that could stimulate further research aiming for unparalleled useful applications. As a result, there are many possibilities that can be explored from this smart material.