Stimuli responsive drug delivery systems based on nano-graphene for cancer therapy

Rejuvenated Photodynamic Therapy for Bacterial Infections

The emergence of multidrug resistant bacterial strains has hastened the exploration of advanced microbicides and antibacterial techniques. Photodynamic antibacterial therapy (PDAT), an old-fashioned technique, has been rejuvenated to combat "superbugs" and biofilm-associated infections owing to its excellent characteristics of noninvasiveness and broad antibacterial spectrum. More importantly, bacteria are less likely to produce drug resistance to PDAT because it does not require specific targeting interaction between photosensitizers (PSs) and bacteria. This review mainly focuses on recent developments and future prospects of PDAT. The mechanisms of PDAT against bacteria and biofilms are briefly introduced. In addition to classical macrocyclic PSs, several innovative PSs, including non-self-quenching PSs, conjugated polymer-based PSs, and nano-PSs, are summarized in detail. Numerous multifunctional PDAT systems such as in situ light-activated PDAT, stimuli-responsive PDAT, oxygen self-enriching enhanced PDAT, and PDAT-based multimodal therapy are highlighted to overcome the inherent defects of PDAT in vivo (e.g., limited penetration depth of light and hypoxic environment of infectious sites).

Mitochondria-Targeted and Resveratrol-Loaded Dual-Function Titanium Disulfide Nanosheets for Photothermal-Triggered Tumor Chemotherapy

A subcellular organelle-targeted delivery of anti-cancer drugs is a promising strategy to maximize the anti-cancer effects and minimize the adverse effects. Herein, we prepared a mitochondria-targeted drug delivery nanoplatform based on IR780 iodide (IR780) and titanium disulfide (TiS2) nanosheets. Due to the large specific surface area of TiS2 nanosheets, the nanoplatform could highly load anti-cancer drug resveratrol (RV). The as-prepared nanocomposite (IR780-TiS2/RV) was used for an efficacious photothermal-triggered tumor chemotherapy. IR780-TiS2/RV showed satisfactory stability and biocompatibility, and the loading ratio of RV and IR780 was about 112% and 56%, respectively. Upon the near-infrared (NIR) irradiation, the heat generated by IR780-TiS2/RV could trigger the RV release. Due to the conjugation with the mitochondria-specific IR780, IR780-TiS2/RV could target and accumulate in mitochondria and release RV when triggered by NIR to decrease the mitochondrial membrane potential, rapidly induce the upregulation of key intrinsic apoptotic factors such as cytochrome c, and initiate the caspase cascade, thereby achieving the chemotherapeutic effect. The IR780-TiS2/RV nanocomposite was demonstrated to have a high anti-tumor efficacy in vitro and in vivo as well as no remarkable tissue toxicity. We believe our study demonstrates that the NIR-triggered IR780-TiS2/RV nanoplatform could be a promising chemotherapeutic agent in clinical practice.

Effect of polydiacetylene-based nanosomes on cell viability and endocytosis

Polydiacetylene-based nanoparticles have been developed as nanocarriers for various bio-applications. However, how nanocarriers enter the cell environment and affect cell viability has not yet been considerably explored. In this study, polydiacetylene-based nanoliposomes (nanosomes) were electrostatically complexed with rhodamine fluorophores. Based on real-time cell imaging and cell viability assessment, the most highly polymerized nanosomes were found to be less toxic to cells. Moreover, it was revealed that the rhodamine/polydiacetylene nanosome complex dissociates at cell environment, the polydiacetylene nanosome penetrates into cells, as suggested by the fluorescence observed in confocal microscopy images.

Co-delivery of DOX and PDTC by pH-sensitive nanoparticles to overcome multidrug resistance in breast cancer

Chemotherapeutic drugs have a series of limitations in the conventional clinical treatments, mainly including serious adverse effects and multidrug resistance (MDR). Herein, we developed a pH-sensitive polymeric nanoparticle with using poly(ortho ester urethanes) copolymers for co-delivering doxorubicin (DOX) and pyrrolidinedithiocarbamate (PDTC) to settle these problems. Dual-drug-loaded nanoparticles were nano-sized (˜220 nm) with the spherical morphology and excellent physiological stability. Both drugs both could be quickly released in the mild acidic conditions due to the cleavage of ortho ester bonds. Monolayer cultured cells (2D) and multicellular spheroids (3D) experiments proved that PDTC could reverse multidrug resistance (MDR), improve intracellular drugs accumulation and enhance tumor penetration by down-regulating the expression of P-gp, then resulting in higher DOX-induced cytotoxicity and apoptosis in MCF-7 and MCF-7/ADR cells. Besides, in vivo experiments further demonstrated that co-encapsulated nanoparticles had higher DOX accumulation and superiorer tumor growth inhibition (TGI 82.9%) than free drugs or single-drug-loaded nanoparticles on MCF-7/ADR bearing-mice. Accordingly, the pH-sensitive co-delivery systems possess a promising potential to overcome MDR in cancer therapy.

Stimuli-responsive polyvinylpyrrolidone-NIPPAm-lysine graphene oxide nano-hybrid as an anticancer drug delivery on MCF7 cell line

Despite the advances in the development of chemotherapeutic agents, resistance to chemotherapy and adverse side effects are still big challenges against successful cancer treatment. To overcome these problems, one strategy is the application of nanomaterials and drug delivery systems to efficiently deliver the anticancer agents to tumour tissues with minimum toxic effects on healthy organs. In this study a graphene oxide nanohybrid (GO/NHs) was designed and fabricated for the delivery of chemotherapeutic agent fluorouracil (FU) to the breast cancer MCF7 cells. After preparation and characterization of GO/NHs, several biological analysis including haemolysis assay, cytotoxicity assay, cellular uptake, apoptosis assay, and protein expression were performed. The cytotoxic effects of FU, FU loaded GO/NHs (FU-GO/NHs), and blank GO/NHs was determined by MTT assay. The results of MTT assay showed no significant cytotoxicity for blank nano-hybrid on MCF7 cells. Furthermore, FU-GO/NHs were more cytotoxic than free FU. The uptake analysis results showed that developed nanocarrier could completely be internalized into the cells in the first hour. Besides, apoptotic effects and nuclear morphology changes of cells was evaluated by DAPI staining under fluorescent microscopy. Protein expression levels of p53, PARP, cleaved PARP, Bcl-2, and Bax were determined by western blot analysis. Western blot results showed higher levels of p53 and cleaved PARP after treatment with FU-GO/NHs, however, no substantial effect was observed for Bax and Bcl-2 protein concentrations.

Cascade-amplification of therapeutic efficacy: An emerging opportunity in cancer treatment

Increasing research evidence reveals that cancer is complex disease involving many biological factors, processes and systems, which may severely limit the actual efficacy of conventional monotonic anticancer approaches. To overcome these obstacles in cancer treatment, a new strategy has been proposed by combining multiple synergistic therapeutic modalities accessing different but inherently related targets and acting sequentially. A major benefit of this strategy is that the multi-target mechanism could result in a cascade-amplification effect leading to enhanced anticancer activity. In this review, we provide a critical discussion on the application of cascade-amplification strategy in the treatment of various cancer indications, focusing on the rational combination of therapeutic agents and their mechanisms of action. A concise yet comprehensive analysis on the potential therapeutic benefit of this strategy was also included. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Histidine-Rich Cell-Penetrating Peptide for Cancer Drug Delivery and Its Uptake Mechanism

In this work, we report a drug delivery system based on the pH-responsive self-assembly and -disassembly behaviors of peptides. Here, a systematically designed histidine-rich lipidated peptide (NP1) is presented to encapsulate and deliver an anticancer drug ellipticine (EPT) into two model cells: non-small-cell lung carcinoma and Chinese hamster ovary cells. The mechanism of pH-responsive peptide self-assembly and -disassembly involved in the drug encapsulation and release process are extensively investigated. We found that NP1 could self-assemble as a spherical nanocomplex (diameter = 34.43 nm) in a neutral pH environment with EPT encapsulated and positively charged arginine amino acids aligned outward and EPT is released in an acidic environment due to the pH-triggered disassembly. Furthermore, the EPT-encapsulating peptide could achieve a mass loading ability of 18% (mass of loaded-EPT/mass of NP1) with optimization. More importantly, it is revealed that the positively charged arginine on the periphery of the NP1 peptides could greatly facilitate their direct translocation through the negatively charged plasma membrane via electrostatic interaction, instead of via endocytosis, which provides a more efficient uptake pathway.

Graphene-Based Smart Platforms for Combined Cancer Therapy

The extensive research of graphene and its derivatives in biomedical applications during the past few years has witnessed its significance in the field of nanomedicine. Starting from simple drug delivery systems, the application of graphene and its derivatives has been extended to a versatile platform of multiple therapeutic modalities, including photothermal therapy, photodynamic therapy, magnetic hyperthermia therapy, and sonodynamic therapy. In addition to monotherapy, graphene-based materials are widely applied in combined therapies for enhanced anticancer activity and reduced side effects. In particular, graphene-based materials are often designed and fabricated as "smart" platforms for stimuli-responsive nanocarriers, whose therapeutic effects can be activated by the tumor microenvironment, such as acidic pH and elevated glutathione (termed as "endogenous stimuli"), or light, magnetic, or ultrasonic stimuli (termed as "exogenous stimuli"). Herein, the recent advances of smart graphene platforms for combined therapy applications are presented, starting with the principle for the design of graphene-based smart platforms in combined therapy applications. Next, recent advances of combined therapies contributed by graphene-based materials, including chemotherapy-based, photothermal-therapy-based, and ultrasound-therapy-based synergistic therapy, are outlined. In addition, current challenges and future prospects regarding this promising field are discussed.

Nanotechnology in the diagnosis and treatment of lung cancer

Lung cancer is an umbrella term for a subset of heterogeneous diseases that are collectively responsible for the most cancer-related deaths worldwide. Despite the tremendous progress made in understanding lung tumour biology, advances in early diagnosis, multimodal therapy and deciphering molecular mechanisms of drug resistance, overall curative outcomes remain low, especially in metastatic disease. Nanotechnology, in particular nanoparticles (NPs), continue to progressively impact the way by which tumours are diagnosed and treated. The unique physicochemical properties of materials at the nanoscale grant access to a diverse molecular toolkit that can be manipulated for use in respiratory oncology. This realisation has resulted in several clinically approved NP formulations and many more in clinical trials. However, NPs are not a panacea and have yet to be utilised to maximal effect in lung cancer, and medicine in a wider context. This review serves to: describe the complexity of lung cancer, the current diagnostic and therapeutic environment, and highlight the recent advancements of nanotechnology based approaches in diagnosis and treatment of respiratory malignancies. Finally, a brief outlook on the future directions of nanomedicine is provided; presently the full potential of the field is yet to be realised. By gleaning lessons and integrating advancements from neighbouring disciplines, nanomedicine can be elevated to a position where the current barriers that stymie full clinical impact are lifted.

Biocompatible Heat-Shock Protein Inhibitor-Delivered Flowerlike Short-Wave Infrared Nanoprobe for Mild Temperature-Driven Highly Efficient Tumor Ablation

Multifunctional nanomaterials for dual-mode imaging guided cancer therapy are highly desirable in clinical applications. Herein, a flowerlike NiS₂-coated NaLuF₄:Nd (Lu:Nd@NiS₂) nanoparticle was synthesized as a novel therapeutic agent for short-wave infrared light imaging and magnetic resonance imaging to guide photothermal therapy (PTT). The material was then loaded with phenolic epigallocatechin 3-gallate (EGCG), which is a natural heat-shock protein 90 (HSP90) inhibitor. Upon near infrared irradiation, EGCG was released from the Lu:Nd@NiS₂-EGCG, which bound HSP90 and reduced cell tolerance to heat, resulting in a better therapeutic effect at the same elevated temperature. Therefore, with minimal side effects and remarkable antitumor efficacy in vivo, Lu:Nd@NiS₂-EGCG appeared to be a promising photothermal agent for enhanced PTT.

A Logic-Gated Modular Nanovesicle Enables Programmable Drug Release for On-Demand Chemotherapy

It remains a major challenge to achieve precise on-demand drug release. Here, we developed a modular nanomedicine integrated with logic-gated system enabling programmable drug release for on-demand chemotherapy.

Methods: We employed two different logical AND gates consisting of four interrelated moieties to construct the nanovesicles, denoted as v-A-CED₂, containing oxidation-responsive nanovesicles (v), radical generators (A), and Edman linker conjugated prodrugs (CED₂). The first AND logic gate is connected in parallel by mild hyperthermia (I) and acidic pH (II), which executes NIR laser triggered prodrug-to-drug transformation through Edman degradation. Meanwhile, the mild hyperthermia effect triggers alkyl radical generation (III) which contributes to internal oxidation and degradation of nanovesicles (IV). The second AND logic gate is therefore formed by the combination of I-IV to achieve programmable drug release by a single stimulus input NIR laser. The biodistribution of the nanovesicles was monitored by positron emission tomography (PET), photoacoustic, and fluorescence imaging.

Results: The developed modular nanovesicles exhibited high tumor accumulation and effective anticancer effects both in vitro and in vivo.

Conclusions: This study provides a novel paradigm of logic-gated programmable drug release system by a modular nanovesicle, which may shed light on innovation of anticancer agents and strategies.

NIR-Light- and pH-Responsive Graphene Oxide Hybrid Cyclodextrin-Based Supramolecular Hydrogels

Here, a novel triple-responsive graphene oxide hybrid supramolecular hydrogel based on the electrostatic self-assembly between graphene oxide and a quaternized polymer and the host-guest inclusion between α-cyclodextrins and poly(ethylene glycol) monomethyl ether (mPEG) was constructed. The quaternized polymer was synthesized by quaternization between pH-sensitive poly( N, N-dimethylaminoethyl methacrylate) and bromine end-capped poly(ethylene glycol) monomethyl ether. The supramolecular hydrogels prepared from the host-guest inclusion of poly(ethylene glycol) monomethyl ether and α-cyclodextrins would turn into a mobile sol phase when the temperature was increased above a certain temperature (Tgel-sol). Graphene oxide sheets not only acted as a core material to provide additional cross-linking but also absorbed NIR light and converted NIR light into heat to trigger the gel-sol transition. The constructed graphene oxide hybrid cyclodextrin-based supramolecular hydrogels could respond to NIR light, temperature, and pH, which could be beneficial for controlled release of cargoes and would hold great promise in the field of delivery systems.

Surface-Adaptive and Initiator-Loaded Graphene as a Light-Induced Generator with Free Radicals for Drug-Resistant Bacteria Eradication

Since generating toxic reactive oxygen species is largely dependent on oxygen, bacteria-infected wounds' hypoxia significantly inhibits photodynamic therapy's antibacterial efficiency. Therefore, a novel therapeutic method for eradicating multidrug-resistant bacteria is developed based on the light-activated alkyl free-radical generation (that is oxygen independent). According to the polydopamine-coated carboxyl graphene (PDA@CG), an initiator-loaded and pH-sensitive heat-producible hybrid of bactericides was synthesized. According to fluorescence/thermal imaging, under the low pH of the bacterial infection sites, this platform turned positively charged, which allows their accumulation in local infection site. The plasmonic heating effects of PDA@CG can make the initiator decomposed to generate alkyl radical (R^•) under the followed near-infrared light irradiation. As a result, oxidative stress can be elevated, DNA damages in bacteria can be caused, and finally even multidrug-resistance death can be caused under different oxygen tensions. Moreover, our bactericidal could promote wound healing in vivo and negligible toxicity in vivo and in vitro and eliminate abscess. Accordingly, this study proves that combination of oxygen-independent free-radical-based therapy along with a stimulus-responsiveness moiety not only can be used as an effective treatment of multidrug-resistant bacteria infection, but also creates a use of a variety of free radicals for treatment of multidrug-resistant bacteria infection wounds.

Graphene Quantum Dots-Mediated Theranostic Penetrative Delivery of Drug and Photolytics in Deep Tumors by Targeted Biomimetic Nanosponges

Dual-targeted delivery of drugs and energy by nanohybrids can potentially alleviate side effects and improve the unique features required for precision medicine. To realize this aim, however, the hybrids which are often rapidly removed from circulation and the piled up tumors periphery near the blood vessels must address the difficulties in low blood half-lives and tumor penetration. In this study, a sponge-inspired carbon composites-supported red blood cell (RBC) membrane that doubles as a stealth agent and photolytic carrier that transports tumor-penetrative agents (graphene quantum dots and docetaxel (GQD-D)) and heat with irradiation was developed. The RBC-membrane enveloped nanosponge (RBC@NS) integrated to a targeted protein that accumulates in tumor spheroids via high lateral bilayer fluidity exhibits an 8-fold increase in accumulation compared to the NS. Penetrative delivery of GQDs to tumor sites is actuated by near-infrared irradiation through a one-atom-thick structure, facilitating penetration and drug delivery deep into the tumor tissue. The synergy of chemotherapy and photolytic effects was delivered by the theranostic GQDs deep into tumors, which effectively damaged and inhibited the tumor in 21 days when treated with a single irradiation. This targeted RBC@GQD-D/NS with the capabilities of enhanced tumor targeting, NIR-induced drug penetration into tumors, and thermal ablation for photolytic therapy promotes tumor suppression and exhibits potential for other biomedical applications.

Recent advances of stimuli-responsive systems based on transition metal dichalcogenides for smart cancer therapy

A comprehensive overview of the development of stimuli-responsive TMDC-based nanoplatforms for “smart” cancer therapy is presented to demonstrate a more intelligent and better controllable therapeutic strategy.

Physically-triggered nanosystems based on two-dimensional materials for cancer theranostics

There is an increasing demand to develop effective methods for treating malignant diseases to improve healthcare in our society. Stimuli-responsive nanosystems, which can respond to internal or external stimuli are promising in cancer therapy and diagnosis due to their functionality and versatility. As a newly emerging class of nanomaterials, two-dimensional (2D) nanomaterials have attracted huge interest in many different fields including biomedicine due to their unique physical and chemical properties. In the past decade, stimuli-responsive nanosystems based on 2D nanomaterials have been widely studied, showing promising applications in cancer therapy and diagnosis, including phototherapies, magnetic therapy, drug and gene delivery, and non-invasive imaging. Here, we will focus our attention on the state-of-the-art of physically-triggered nanosystems based on graphene and two-dimensional nanomaterials for cancer therapy and diagnosis. The physical triggers include light, temperature, magnetic and electric fields.

Poly(glycidyl methacrylate)-coated magnetic graphene oxide as a highly efficient nanocarrier: preparation, characterization, and targeted DOX delivery

Herein, we report the preparation of novel magnetic graphene oxide grafted with brush polymer via SI-RAFT polymerization and its application as a nanocarrier for magnetic and pH-triggered delivery of DOX anticancer drug.

Flower-like gold nanoparticles for enhanced photothermal anticancer therapy by the delivery of pooled siRNA to inhibit heat shock stress response

Surface modified gold nanoflowers were employed as synergistic therapeutics for photothermal ablation and gene silencing.

Photo-triggered polymer nanomedicines: From molecular mechanisms to therapeutic applications

The use of nanotechnology to improve treatment efficacy and reduce side effects is central to nanomedicine. In this context, stimuli-responsive drug delivery systems (DDS) such as chemical/physical gels or nanoparticles such as polymersomes, micelles or nanogels are particularly promising and are the focus of this review. Several stimuli have been considered but light as an exogenous trigger presents many advantages that are pertinent for clinical applications such as high spatial and temporal control and low cost. Underlying mechanisms required for the release of therapeutic agents in vitro and in vivo range from the molecular scale, namely photoisomerization, hydrophobicity photoswitching, photocleavage or heat generation via nanoheaters, through to the macromolecular scale. As well as these approaches, DDS destabilization, DDS permeation pore unblocking and formation are discussed.

Stimuli-responsive graphene-incorporated multifunctional chitosan for drug delivery applications: a review

INTRODUCTION

Recently, the use of chitosan (CS) in the drug delivery has reached an acceptable maturity. Graphene-based drug delivery is also increasing rapidly due to its unique physical, mechanical, chemical, and electrical properties. Therefore, the combination of CS and graphene can provide a promising carrier for the loading and controlled release of therapeutic agents.

AREAS COVERED

In this review, we will outline the advantages of this new drug delivery system (DDS) in association with CS and graphene alone and will list the various forms of these carriers, which have been studied in recent years as DDSs. Finally, we will discuss the application of this hybrid composite in other fields.

EXPERT OPINION

The introducing the GO amends the mechanical characteristics of CS, which is a major problem in the use of CS-based carriers in drug delivery due to burst release in a CS-based controlled release system through the poor mechanical strength of CS. Many related research on this area are still not fully unstated and occasionally they seem inconsistent in spite of the intent to be complementary. Therefore, a sensitive review may be needed to understand the role of graphene in CS/graphene carriers for future drug delivery applications.

Detachable Polyzwitterion-Coated Ternary Nanoparticles Based on Peptide Dendritic Carbon Dots for Efficient Drug Delivery in Cancer Therapy

In this work, we presented ternary nanoparticles [poly(carboxybetaine methacrylate) (pCBMA)(peptide dendrimer-modified carbon dots (CD-D)/doxorubicin (DOX))] based on peptide dendritic carbon dots (CDs) to realize tumor-specific drug delivery and highly efficient cancer therapy. The versatile nanoparticles could achieve "stealth" delivery in blood due to the antifouling zwitterion coating. Meanwhile, charge changes of the zwitterions could be moderated during their transportation toward/inside tumor cells, where subtle environmental pH variations acted as potent stimuli to actualize desired functions. In particular, the detachment of the zwitterionic "coat" at the tumor site resulted in the exposure of abundant peripheral guanidine groups on peptide dendritic carbon dots (CD-D/DOX) owing to the extracellular pH environment (pH 6.8)-induced charge conversion. Consequently, the positively charged CD-D/DOX (+7.02 mV) interacted with the negatively charged cancer cell membrane to enhance cellular uptake. After endocytosis, tumor intracellular microenvironments (acidic conditions and high glutathione (GSH) levels) could lead to effective disintegration of the CD-D/DOX entities due to acid-induced protonation of guanidine groups and glutathione-induced cleavage of peptide dendritic components on CDs, and then effective endosomal escape and fast doxorubicin hydrochloride (DOX·HCl) release (73.2% accumulative release within 4 h) were achieved successively. This strategy enabled a 9.19-fold drug release rate at tumor sites in comparison with the one in the physiological environment. Moreover, the excellent fluorescence properties of CDs endowed the pCBMA(CD-D/DOX) with fluorescence bioimaging function. In view of the above-mentioned advantages, pCBMA(CD-D/DOX) exhibited outstanding antitumor activities both in vitro and in vivo, demonstrating much higher antitumor efficacy and less side effects than the free DOX·HCl.

Codelivery of Hydrophobic and Hydrophilic Drugs by Graphene-Decorated Magnetic Dendrimers

In this study, a nanocarrier was prepared for the codelivery of a hydrophilic drug (doxorubicin) and a hydrophobic drug (curcumin) to cancer cells. In this nanocarrier, the edges of graphene oxide sheets were decorated with a magnetic-functionalized polyamidoamine dendrimer with hydrazone groups at the end of the polymer. The edge functionalization of graphene sheets not only improved the solubility and dispersibility of graphene sheets but also imparted the magnetic properties to the nanocarrier. The resulting nanocarrier was loaded with doxorubicin through the covalent linkage and curcumin through π-π stacking. The nanocarrier showed a pH-sensitive release for both drugs, and the drug release behavior was also improved by the coimmobilization of both drugs. The cytotoxicity assay of nanocarrier showed low toxicity toward MCF-7 cell compared to unmodified graphene oxide, which was attributed to the presence of a magnetic dendrimer. Besides, the drug-loaded nanocarrier was highly toxic for cells even more than for free drugs. The cellular uptake images revealed higher drug internalization for coloaded nanocarrier than for the nanocarrier loaded with one drug alone. All of the results showed that the codelivery of curcumin and doxorubicin in the presence of the nanocarrier was more effective in chemotherapy than the nanocarrier loaded with one drug.

Enhancing Antitumor Efficacy by Simultaneous ATP-Responsive Chemodrug Release and Cancer Cell Sensitization Based on a Smart Nanoagent

The exploitation of smart nanoagents based drug delivery systems (DDSs) has proven to be a promising strategy for fighting cancers. Hitherto, such nanoagents still face challenges associated with their complicated synthesis, insufficient drug release in tumors, and low cancer cell chemosensitivity. Here, the engineering of an adenosine triphosphate (ATP)-activatable nanoagent is demonstrated based on self-assembled quantum dots-phenolic nanoclusters to circumvent such challenges. The smart nanoagent constructed through a one-step assembly not only has high drug loading and low cytotoxicity to normal cells, but also enables ATP-activated disassembly and controlled drug delivery in cancer cells. Particularly, the nanoagent can induce cell ATP depletion and increase cell chemosensitivity for significantly enhanced cancer chemotherapy. Systematic in vitro and in vivo studies further reveal the capabilities of the nanoagent for intracellular ATP imaging, high tumor accumulation, and eventual body clearance. As a result, the presented multifunctional smart nanoagent shows enhanced antitumor efficacy by simultaneous ATP-responsive chemodrug release and cancer cell sensitization. These findings offer new insights toward the design of smart nanoagents for improved cancer therapeutics.

Advances and Future Perspectives in 4D Bioprinting

Three-dimensionally printed constructs are static and do not recapitulate the dynamic nature of tissues. Four-dimensional (4D) bioprinting has emerged to include conformational changes in printed structures in a predetermined fashion using stimuli-responsive biomaterials and/or cells. The ability to make such dynamic constructs would enable an individual to fabricate tissue structures that can undergo morphological changes. Furthermore, other fields (bioactuation, biorobotics, and biosensing) will benefit from developments in 4D bioprinting. Here, the authors discuss stimuli-responsive biomaterials as potential bioinks for 4D bioprinting. Natural cell forces can also be incorporated into 4D bioprinted structures. The authors introduce mathematical modeling to predict the transition and final state of 4D printed constructs. Different potential applications of 4D bioprinting are also described. Finally, the authors highlight future perspectives for this emerging technology in biomedicine.

Redox/pH dual-controlled release of chlorhexidine and silver ions from biodegradable mesoporous silica nanoparticles against oral biofilms

BACKGROUND

Oral plaque biofilms pose a threat to periodontal health and are challenging to eradicate. There is a growing belief that a combination of silver nanoparticles and chlorhexidine (CHX) is a promising strategy against oral biofilms.

PURPOSE

To overcome the side effects of this strategy and to exert maximum efficiency, we fabricated biodegradable disulfide-bridged mesoporous silica nanoparticles (MSNs) to co-deliver silver nanoparticles and CHX for biofilm inhibition.

MATERIALS AND METHODS

CHX-loaded, silver-decorated mesoporous silica nanoparticles (Ag-MSNs@CHX) were fabricated after CHX loading, and the pH- and glutathione-responsive release profiles of CHX and silver ions along with their mechanism of degradation were systematically investigated. Then, the efficacy of Ag-MSNs@CHX against Streptococcus mutans and its biofilm was comprehensively assessed by determining the minimum inhibitory concentration, minimum bactericidal concentration, minimal biofilm inhibitory concentration, and the inhibitory effect on S. mutans biofilm formation. In addition, the biosafety of nanocarriers was evaluated by oral epithelial cells and a mouse model.

RESULTS

The obtained Ag-MSNs@CHX possessed redox/pH-responsive release properties of CHX and silver ions, which may be attributed to the redox-triggered matrix degradation mechanism of exposure to biofilm-mimetic microenvironments. Ag-MSNs@CHX displayed dose-dependent antibacterial activity against planktonic and clone formation of S. mutans. Importantly, Ag-MSNs@CHX had an increased and long-term ability to restrict the growth of S. mutans biofilms compared to free CHX. Moreover, Ag-MSNs@CHX showed less cytotoxicity to oral epithelial cells, whereas orally administered Ag-MSNs exhibited no obvious toxic effects in mice.

CONCLUSION

Our findings constitute a highly effective and safe strategy against biofilms that has a good potential as an oral biofilm therapy.

Clinical Applications of Carbon Nanomaterials in Diagnostics and Therapy

Nanomaterials have the potential to improve how patients are clinically treated and diagnosed. While there are a number of nanomaterials that can be used toward improved drug delivery and imaging, how these nanomaterials confer an advantage over other nanomaterials, as well as current clinical approaches is often application or disease specific. How the unique properties of carbon nanomaterials, such as nanodiamonds, carbon nanotubes, carbon nanofibers, graphene, and graphene oxides, make them promising nanomaterials for a wide range of clinical applications are discussed herein, including treating chemoresistant cancer, enhancing magnetic resonance imaging, and improving tissue regeneration and stem cell banking, among others. Additionally, the strategies for further improving drug delivery and imaging by carbon nanomaterials are reviewed, such as inducing endothelial leakiness as well as applying artificial intelligence toward designing optimal nanoparticle-based drug combination delivery. While the clinical application of carbon nanomaterials is still an emerging field of research, there is substantial preclinical evidence of the translational potential of carbon nanomaterials. Early clinically trial studies are highlighted, further supporting the use of carbon nanomaterials in clinical applications for both drug delivery and imaging.

HP-β-CD Functionalized Fe3O4/CNPs-Based Theranostic Nanoplatform for pH/NIR Responsive Drug Release and MR/NIRFL Imaging-Guided Synergetic Chemo/Photothermal Therapy of Tumor

The combination of chemotherapy and photothermal therapy has aroused great interest due to its better antitumor effect than either single therapy alone. Herein, we report on the development of hydroxypropyl-β-cyclodextrin functionalized Fe₃O₄/carbon nanoparticles (HFCNPs) for pH/near-infrared (NIR) responsive drug release, magnetic resonance/NIR fluorescence (MR/NIRFL) imaging-guided combined chemo/photothermal therapy. The high doxorubicin (DOX) loading capacity (61.2%) and controlled drug release by NIR irradiation and weak acid microenvironment render HFCNPs a good vector for DOX delivery and controlled release. Moreover, the MR/NIRFL dual-modal imaging was used to define the tumor location, size, and boundary and to track the tumor accumulation of HFCNPs and their biodistribution. The efficient accumulation and prolonged retention time of the nanoparticles in tumor are beneficial to tumor therapy. Taking advantage of the NIR laser-induced heating and hence promoted drug permeation, remarkable tumor inhibition was realized by synergetic chemo/photothermal therapy. In conclusion, the current work offers a promising approach to the development of smart and efficient multimodal cancer-targeted nanotheranostics.

Stimuli-Responsive Therapeutic Metallodrugs

The success of platinum-based anticancer agents has motivated the exploration of novel metal-based drugs for several decades, whereas problems such as drug-resistance and systemic toxicity hampered their clinical applications and efficacy. Stimuli-responsiveness of some metal complexes offers a good opportunity for designing site-specific prodrugs to maximize the therapeutic efficacy and minimize the side effect of metallodrugs. This review presents a comprehensive and up-to-date overview on the therapeutic stimuli-responsive metallodrugs that have appeared in the past two decades, where stimuli such as redox, pH, enzyme, light, temperature, and so forth were involved. The compounds are classified into three major categories based on the nature of stimuli, that is, endo-stimuli-responsive metallodrugs, exo-stimuli-responsive metallodrugs, and dual-stimuli-responsive metallodrugs. Representative examples of each type are discussed in terms of structure, response mechanism, and potential medical applications. In the end, future opportunities and challenges in this field are tentatively proposed. With diverse metal complexes being introduced, the foci of this review are pointed to platinum and ruthenium complexes.

Ultrasonicated graphene oxide enhances bone and skin wound regeneration

In the present study, we investigated the applications of ultrasonicated graphene oxide (UGO) for bone regeneration and skin wound healing. Ultrasonication of a GO suspension increased the dispersion and stability (by increasing the zeta potential) of the GO suspension. UGO has fewer oxygen-containing groups but still displays excellent water dispersion. The UGO supension showed high biocompatibility for human fetal osteoblast (hFOB cells), human endothelial cells (EA.hy 926 cells), and mouse embryonic fibroblasts. Importantly, UGO could support cell attachment and proliferation, in addition to promoting the osteogenesis of seeded cells and the promotion of new bone formation. In addition, a 1% UGO supension enhanced cell migration in an in vitro skin scratch assay and promoted wound closure in an in vivo rat excisional skin defect model. These results showed that UGO offers a good environment for cells involved in bone and skin healing, suggesting its potential application in tissue regeneration.

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.

Simultaneous drug delivery and cellular imaging using graphene oxide

Graphene oxide (GO), a derivative of graphene, and its related nanomaterials have attracted much attention in recent years due to the excellent biocompatibility and large surface area of GO with abundant oxygen functional groups, which further enable it to serve as a nano-bio interface. Herein, we demonstrate the induction of blue fluorescence in GO suspensions via a mild thermal annealing procedure. Additionally, this procedure preserves the oxygen functional groups on the graphene plane which enables the conjugation of cancer drugs without obvious cytotoxicity. Consequently, we demonstrate the capability of GO to simultaneously play the dual-role of a: (i) cellular imaging agent and (ii) drug delivery agent in CT26 cancer cells without the need for additional fluorescent protein labeling. Our method offers a simple, controllable strategy to tune and enhance the fluorescence property of GO, which shows potential for biomedical applications and fundamental studies.