Versatile fluorescence resonance energy transfer-based mesoporous silica nanoparticles for real-time monitoring of drug release

Fusogenic Lipid Nanovesicle for Biomacromolecular Delivery

Although biomacromolecules are promising cytosolic drugs which have attracted tremendous attention, the major obstacles were the cellular membrane hindering the entrance and the endosome entrapment inducing biomacromolecule degradation. How to avoid those limitations to realize directly cytosolic delivery was still a challenge. Here, we prepared oligoarginine modified lipid to assemble a nanovesicle for biomacromolecules delivery, including mRNA (mRNA) and proteins which could be directly delivered into the cytoplasm of dendritic cells through subendocytosis-mediated membrane fusion. We named this membrane fusion lipid nanovesicle as MF-LNV. The mRNA loaded MF-LNV as nanovaccines showed efficient antigen expression to elicit robust immuno responses for cancer therapy. What's more, the antigen protein loaded MF-LNV as nanovaccines elicits much stronger CD8+ T cell specific responses than lipid nanoparticles through normal uptake pathways. This MF-LNV represented a refreshing strategy for intracellular delivery of the biomacromolecule.

Water-dispersable photoreactors based on core-shell mesoporous silica particles

Robust solid-core silica particles with submicrometer size and anthracene-containing mesoporous shell were obtained and studied as model water-dispersable photoreactors. An anthracene derivative containing a triethoxysilyl group was synthesized and co-condensed with tetraethoxysilane in various ratios to form a photoactive mesoporous shell with a thickness up to approximately 80 nm on previously prepared solid silica particles. Mesopores of as-synthesized particles, without a commonly applied removal of the micellar templates, offered a confined space for solubilization of hydrophobic molecules. Efficient excitation energy transfer from anthracene chromophores to both hydrophobic (perylene) and hydrophilic (fluoresceine) encapsulated acceptors was observed in an aqueous dispersion of the particles. Photosensitized oxidation of encapsulated perylene was shown to proceed efficiently in such systems serving as water-dispersable photoreactors. Importantly, the designed core-shell systems were found to be stable for a long time (at least 24 months) and robust enough, thanks to the presence of solid cores, to be handled by centrifugation in aqueous dispersions. All these features make them promising candidates for reusable systems for the photosensitized degradation of water pollutants, especially hydrophobic pollutants.

FRET-Modulated Fluorescence Lifetime-Traceable Nanocarriers for Multidrug Release Monitoring and Synergistic Therapy

In situ monitoring multidrug release in complex cellular microenvironments is significant, and currently, it is still a great challenge. In this work, a smart nanocarrier with the capability of codelivery of small molecules and gene materials as well as with Förster resonance energy transfer (FRET)-modulated fluorescence lifetime is fabricated by integrating gold nanoparticles (the acceptor) into dual-mesoporous silica loaded with multiple drugs (the donor). Once internalized into tumor cells, in weakly acidic environments, the conformation switch of the polymer grafted on nanocarriers causes its shedding from the mesopores, triggering the release of drugs. Simultaneously, based on the strong overlap between the emission spectrum of donors and the absorption spectrum of the acceptors, any slight fluctuation of the dissociation of the drugs from nanocarriers can result in a change in the FRET-modulated lifetime signal due to the extraordinarily sensitive FRET signal to the separation distance between donors and acceptors. All these implied the potential applications of this nanoplatform in various biomedical fields that require the codelivery and real-time monitoring of multidrug-based synergistic therapy.

Visible Light-Guided Gene Delivery with Nonviral Supramolecular Block Copolymer Vectors

To achieve efficient gene delivery in vitro or in vivo, nonviral vectors should have excellent biostability across cellular and tissue barriers and also smart stimuli responsiveness toward controlled release of therapeutic genes into the cell nucleus. However, it remains a key challenge to effectively combine the biostability of covalent polymers with the stimuli responsiveness of noncovalent polymers into one nonviral vehicle. In this work, we report the construction of a kind of cationic supramolecular block copolymers (SBCs) through noncovalent polymerization of β-cyclodextrin/azobenzene-terminated pentaethylenehexamine (DMA-Azo-PEHA-β-CD) in aqueous media using β-CD-monosubstituted poly(ethylene glycol) (PEG-β-CD) as a supramolecular initiator. The resultant SBC exhibits superior biostability, biocompatibility, and light/pH dual-responsive characteristics, and it also demonstrates efficient plasmid DNA condensation capacity and the ability to rapidly release plasmid DNA into cells driven by visible light (450 nm). Eventually, this SBC-based delivery system demonstrates visible light-induced enhancement of gene delivery in both COS-7 and HeLa cells. We anticipate that this work provides a facile and robust strategy to enhance gene delivery in vitro or in vivo via visible light-guided manipulation of genes, further achieving safe, highly efficient, targeting gene therapy for cancer.

Metal-Free Far-Red Light-Driven Photolysis via Triplet Fusion to Enhance Checkpoint Blockade Immunotherapy

Metal-free long-wavelength light-driven prodrug photoactivation is highly desirable for applications such as neuromodulation, drug delivery, and cancer therapy. Herein, via triplet fusion, we report on the far-red light-driven photo-release of an anti-cancer drug by coupling the boron-dipyrromethene (BODIPY)-based photosensitizer with a photocleavable perylene-based anti-cancer drug. Notably, this metal-free triplet fusion photolysis (TFP) strategy can be further advanced by incorporating an additional functional dopant, i.e. an immunotherapy medicine inhibiting the indoleamine 2,3-dioxygenase (IDO), with the far-red responsive triplet fusion pair in an air-stable nanoparticle. With this IDO inhibitor-assisted TFP system we observed efficient inhibition of primary and distant tumors in a mouse model at record-low excitation power, compared to other photo-assisted immunotherapy approaches. This metal-free TFP strategy will spur advancement in photonics and biophotonics fields.

A novel epoxy coating with nanocatalytic anticorrosion performance achieved by single-atom Fe-N-C catalyst

In view of the critical importance of oxygen to corrosion evolution, to starve corrosion via depleting oxygen in coatings is a promising strategy. In this work, a novel nanocatalytic anticorrosion concept is proposed to design new coating with outstanding corrosion resistance. Different from the passive barrier of traditional coatings and self-repair after corrosion of current stimuli-feedback coatings, such coating could spontaneously eliminate internal diffused oxygen and greatly suppress the corrosion process. As a proof of concept, single-atom Fe-N-C electrocatalyst with isolated FeN₄ active sites is synthesized by a simple confined carbonization method, exhibiting excellent oxygen reduction performance (E_1/2 = 0.902 V). In composite coating, the evenly dispersed Fe-N-C compensates for the coating defects and serves as oxygen scavengers, which could actively adsorb and consume ambient oxygen, thereby preventing oxygen penetration to the metal substrate surface, eliminating the oxygen contribution to corrosion and significantly boosting the anticorrosion performance of epoxy coating. This in-situ mediation for oxygen in coating prevents metal substrate from receiving new supply of oxygen, while imparting active anticorrosion property to the coating.

Glycopolymer Decorated pH-Dependent Ratiometric Fluorescent Probe Based on Förster Resonance Energy Transfer for the Detection of Cancer Cells

Development of fluorescent imaging probes is an important topic of research for the early diagnosis of cancer. Based on the difference between the cellular environment of tumor cells and normal cells, several "smart" fluorescent probes have been developed. In this work, a glycopolymer functionalized Förster resonance energy transfer (FRET) based fluorescent sensor is developed, which can monitor the pH change in cellular system. One-pot sequential reversible addition-fragmentation chain transfer (RAFT)polymerization technique is employed to synthesize fluorescent active triblock glycopolymer that can undergo FRET change on the variation of pH. A FRET pair, fluorescein o-acrylate (FA) and 7-amino-4-methylcoumarin (AMC) is linked via a pH-responsive polymer poly [2-(diisopropylamino)ethyl methacrylate] (PDPAEMA), which can undergo reversible swelling/deswelling under acidic/neutral condition. The presence of glycopolymer segment provides stability, water solubility, and specificity toward cancer cells. The cellular FRET experiments on cancer cells (MDA MB 231) and normal cells (3T3 fibroblast cells) demonstrate that the material is capable of distinguishing cells as a function of pH change.

Smart Drug-Delivery System of Upconversion Nanoparticles Coated with Mesoporous Silica for Controlled Release

Drug-delivery vehicles have garnered immense interest in recent years due to unparalleled progress made in material science and nanomedicine. However, the development of stimuli-responsive devices with controllable drug-release systems (DRSs) is still in its nascent stage. In this paper, we designed a two-way controlled drug-release system that can be promoted and prolonged, using the external stimulation of near-infrared light (NIR) and protein coating. A hierarchical nanostructure was fabricated using upconversion nanoparticles (UCNPs)-mesoporous silica as the core-shell structure with protein lysozyme coating. The mesoporous silica shell provides abundant pores for the loading of drug molecules and a specific type of photosensitive molecules. The morphology and the physical properties of the nanostructures were thoroughly characterized. The results exhibited the uniform core-shell nanostructures of ~four UCNPs encapsulated in one mesoporous silica nanoparticle. The core-shell nanoparticles were in the spherical shape with an average size of 200 nm, average surface area of 446.54 m²/g, and pore size of 4.6 nm. Using doxorubicin (DOX), a chemotherapy agent as the drug model, we demonstrated that a novel DRS with capacity of smart modulation to promote or inhibit the drug release under NIR light and protein coating, respectively. Further, we demonstrated the therapeutic effect of the designed DRSs using breast cancer cells. The reported novel controlled DRS with dual functionality could have a promising potential for chemotherapy treatment of solid cancers.

Fluorescence Resonance Energy Transfer Measurements in Polymer Science: A Review

Fluorescence resonance energy transfer (FRET) is a non-invasive characterization method for studying molecular structures and dynamics, providing high spatial resolution at nanometer scale. Over the past decades, FRET-based measurements are developed and widely implemented in synthetic polymer systems for understanding and detecting a variety of nanoscale phenomena, enabling significant advances in polymer science. In this review, the basic principles of fluorescence and FRET are briefly discussed. Several representative research areas are highlighted, where FRET spectroscopy and imaging can be employed to reveal polymer morphology and kinetics. These examples include understanding polymer micelle formation and stability, detecting guest molecule release from polymer host, characterizing supramolecular assembly, imaging composite interfaces, and determining polymer chain conformations and their diffusion kinetics. Finally, a perspective on the opportunities of FRET-based measurements is provided for further allowing their greater contributions in this exciting area.

Intracellular Self-Immolative Polyprodrug with Near-Infrared Light Guided Accumulation and in Vivo Visualization of Drug Release

The selective accumulation and real-time monitoring of drug release at tumor site are the key bottlenecks to the clinical translation of polyprodrug. Herein, an intracellular self-immolative polyprodrug (PMTO) is exploited, which not only shows the enhanced cellular internalization and selective accumulation in tumor site under the mild hyperthermia triggered by laser irradiation, but also possesses the self-monitoring drug release ability in vivo. The polyprodrug amphiphiles are synthesized by sequential esterification reaction, and hydrophilic poly(ethylene glycol) serves as blocking agent. On account of the mild hyperthermia produced by PMTO under the laser irradiation at tumor site, the cell membranous permeability increases, resulting in the enhanced cellular internalization and drug accumulation in tumor. After internalized by cells, the self-immolative PMTO nanoparticles can release free mitoxantrone (MTO) in intracellular reductive environment, and ratiometric photoacoustic imaging based on distinct signals between MTO and PMTO is presented to trace the drug release in vivo. Finally, this self-monitoring polyprodrug presents significant tumor suppression efficacy, which exhibits great potential for guiding the clinical medication in cancer treatment.

Multifunctional Cellular Targeting, Molecular Delivery, and Imaging by Integrated Mesoporous-Silica with Optical Nanocrescent Antenna: MONA

Multifunctional nanoprobes have attracted significant attention in a wide range of disciplines such as nanomedicine, precision medicine, and cancer diagnosis and treatment. However, integrating multifunctional ability in a nanoscale structure to precisely target, image, and deliver with cellular spatial/temporal resolution is still challenging in cellulo applications. This is because the development of such high-precision resolution needs to be carried out without labeling, photobleaching, and structurally segregating live cells. In this study, we present an integrated nanostructure of a mesoporous-silica nanosphere with an optical nanocrescent antenna (MONA) for multifunctional cellular targeting, drug delivery, and molecular imaging with spatiotemporal resolution. MONA comprises a systematically constructed Au nanocrescent (AuNC) antenna as a nanosensor and optical switch on a mesoporous-silica nanosphere as a cargo to molecular delivery. MONA made of antiepithelial cell adhesion molecules (anti-EpCAM)-conjugated AuNC facilitates the specific targeting of breast cancer cells, resulting in a highly focused photothermal gradient that functions as a molecular emitter. This light-driven molecular, doxorubicin (DOX) delivery function allows rapid apoptosis of breast cancer cells. Since MONA permits the tracking of quantum biological electron-transfer processes, in addition to its role as an on-demand optical switch, it enables the monitoring of the dynamic behavior of cellular cytochrome c pivoting cell apoptosis in response to the DOX delivery. Owing to the integrated functions of molecular actuation and direct sensing at the precisely targeted spot afforded by MONA, we anticipate that this multifunctional optical nanoantenna structure will have an impact in the fields of nanomedicine, cancer theranostics, and basic life sciences.

Amino Acid Nanofibers Improve Glycemia and Confer Cognitive Therapeutic Efficacy to Bound Insulin

Diabetes poses a high risk for debilitating complications in neural tissues, regulating glucose uptake through insulin-dependent and predominantly insulin-independent pathways. Supramolecular nanostructures provide a flexible strategy for combinatorial regulation of glycemia. Here, we compare the effects of free insulin to insulin bound to positively charged nanofibers comprised of self-assembling amino acid compounds (AACs) with an antioxidant-modified side chain moiety (AAC2) in both in vitro and in vivo models of type 1 diabetes. Free AAC2, free human insulin (hINS) and AAC2-bound-human insulin (AAC2-hINS) were tested in streptozotocin (STZ)-induced mouse model of type 1 diabetes. AAC2-hINS acted as a complex and exhibited different properties compared to free AAC2 or hINS. Mice treated with the AAC2-hINS complex were devoid of hypoglycemic episodes, had improved levels of insulin in circulation and in the brain, and increased expression of neurotransmitter taurine transporter, Slc6a6. Consequently, treatment with AAC2-hINS markedly advanced both physical and cognitive performance in mice with STZ-induced and genetic type 1 diabetes compared to treatments with free AAC2 or hINS. This study demonstrates that the flexible nanofiber AAC2 can serve as a therapeutic platform for the combinatorial treatment of diabetes and its complications.

Advanced nanomedicine approaches applied for treatment of skin carcinoma

Skin-cancer is the commonest malignancy affecting huge proportion of the population, reaching heights in terms of morbidity. The treatment strategies are presently focusing on surgery, radiation and chemotherapy, which eventually cause destruction to unaffected cells. To overcome this limitation, wide range of nanoscaled materials have been recognized as potential carriers for delivering selective response to cancerous cells and neoplasms. Nanotechnological approach has been tremendously exploited in several areas, owing to their functional nanometric dimensions. The alarming incidence of skin cancer engenders burdensome effects worldwide, which is further awakening innovational medicinal approaches, accompanying target specific drug delivery tools for coveted benefits to provide reduced toxicity and tackle proliferative episodes of skin cancer. The developed nanosystems for anti-cancer agents include liposomes, ethosomes, nanofibers, solid lipid nanoparticles and metallic nanoparticles, which exhibit pronounced outcomes for skin carcinoma. In this review, skin cancer with its sub-types is explained in nutshell, followed by compendium of specific nanotechnological tools presented, in addition to therapeutic applications of drug-loaded nano systems for skin cancer.

The facile formation of hierarchical mesoporous silica nanocarriers for tumor-selective multimodal theranostics

The combination of therapeutic and diagnostic functions in a single platform has aroused great interest due to the more optimal synergistic effects that can be obtained as compared to any single theranostic approach alone. However, current nanotheranostics are normally formed via complicated construction steps involving the pre-synthesis of each component and further conjugation via chemical bonds, which may cause low integration efficiency and limit production and applications. Herein, a tumor-targeting and tumor-responsive all-in-one nanoplatform based on mesoporous silica nanocarriers (MSNs) was fabricated via a facile approach utilizing efficient and nondestructive physical interactions for long-wavelength fluorescence imaging-guided synergistic chemo-catalytic-photothermal tumor therapy. The MSNs were endowed with these multimodal theranostics via a simple hydrothermal method after coordinating with Fe2+ and glutathione (GSH) to introduce ferroferric oxide and carbon dots in situ. The former acts as a photothermal agent and catalytic agent to generate local heat under 808 nm irradiation and also when toxic hydroxyl radicals (˙OH) are in contact with abundant hydrogen peroxide in cancer cells, while the latter participates in fluorescence imaging. After loading with paclitaxel (PTX), polyester and folic-acid-conjugated cyclodextrin were employed to serve as an esterase-sensitive gatekeeper controlling PTX release from the MSN pores and as a tumor-targeting agent for accurate therapy, respectively. As expected, the nanoplatform was efficiently taken up by tumor cells over healthy cells, and then, synergetic chemo-catalytic-photothermal therapy was performed, resulting in 5-fold greater apoptosis of tumor cells as compared to healthy cells under 808 nm irradiation. Moreover, in vivo data from tumor-bearing mouse models showed that tumors were significantly inhibited, and the survival rates of these mice increased to greater than 80% after 5 weeks of treatment with our nanoplatform. These therapeutic processes could be directly tracked via fluorescence imaging enabled by carbon dots and, therefore, our nanoplatform provides a promising theranostics approach for tumor treatment.

Layered terbium hydroxides for simultaneous drug delivery and imaging

Layered rare-earth hydroxides have begun to gather increasing attention as potential theranostic platforms owing to their extensive intercalation chemistry combined with magnetic and fluorescent properties. In this work, the potential of layered terbium hydroxide (LTbH) as a platform for simultaneous drug delivery and fluorescence imaging was evaluated. LTbH-Cl ([Tb2(OH)5]Cl·yH2O) was loaded with three nonsteroidal anti-inflammatory drugs (diclofenac, ibuprofen, and naproxen) via ion-exchange. Drug release studies in phosphate buffered saline (pH = 7.4) revealed all three formulations release their drug cargo rapidly over the course of approximately 5 hours. In addition, solid state fluorescence studies indicated that fluorescence intensity is strongly dependent on the identity of the guest anion. It was postulated that this feature may be used to track the extent of drug release from the formulation, which was subsequently successfully demonstrated for the ibuprofen loaded LTbH. Overall, LTbH exhibits good biocompatibility, high drug loading, and a strong, guest-dependent fluorescence signal, all of which are desirable qualities for theranostic applications.

Degradation of Drug Delivery Nanocarriers and Payload Release: A Review of Physical Methods for Tracing Nanocarrier Biological Fate

Nanoformulations offer multiple advantages over conventional drug delivery, enhancing solubility, biocompatibility, and bioavailability of drugs. Nanocarriers can be engineered with targeting ligands for reaching specific tissue or cells, thus reducing the side effects of payloads. Following systemic delivery, nanocarriers must deliver encapsulated drugs, usually through nanocarrier degradation. A premature degradation, or the loss of the nanocarrier coating, may prevent the drug's delivery to the targeted tissue. Despite their importance, stability and degradation of nanocarriers in biological environments are largely not studied in the literature. Here we review techniques for tracing the fate of nanocarriers, focusing on nanocarrier degradation and drug release both intracellularly and in vivo. Intracellularly, we will discuss different fluorescence techniques: confocal laser scanning microscopy, fluorescence correlation spectroscopy, lifetime imaging, flow cytometry, etc. We also consider confocal Raman microscopy as a label-free technique to trace colocalization of nanocarriers and drugs. In vivo we will consider fluorescence and nuclear imaging for tracing nanocarriers. Positron emission tomography and single-photon emission computed tomography are used for a quantitative assessment of nanocarrier and payload biodistribution. Strategies for dual radiolabelling of the nanocarriers and the payload for tracing carrier degradation, as well as the efficacy of the payload delivery in vivo, are also discussed.

Multifunctional nanocomposite eye drops of cyclodextrin complex@layered double hydroxides for relay drug delivery to the posterior segment of the eye

Topical drug delivery system to the posterior segment of the eye is facing many challenges, such as rapid drug elimination, low permeability, and low concentration at the targeted sites. To overcome these challenges, Multifunctional nanocomposite eye drops of dexamethasone-carboxymethyl-β-cyclodextrin@layered double hydroxides-glycylsarcosine (DEX-CM-β-CD@LDH-GS) were developed for relay drug delivery. Herein, our studies demonstrated that DEX-CM-β-CD@LDH-GS could penetrate through human conjunctival epithelial cells with an intact structure and exhibited integrity in the sclera of rabbits' eyes with in vivo fluorescence resonance energy transfer imaging. Consequently, tissue distribution indicated that DEX-CM-β-CD@LDH-GS nanocomposite eye drops could maintain the effective therapeutic concentration of DEX in choroid-retina within 3 h. As a relay drug delivery system, drug-CD@LDH nanocomposites offer an efficient strategy for drug delivery from ocular surface to the posterior segment.

Advances in Multiple Stimuli-Responsive Drug-Delivery Systems for Cancer Therapy

Nanomedicines afford unique advantages in therapeutic intervention against tumors. However, conventional nanomedicines have failed to achieve the desired effect against cancers because of the presence of complicated physiological fluids and the tumor microenvironment. Stimuli-responsive drug-delivery systems have emerged as potential tools for advanced treatment of cancers. Versatile nano-carriers co-triggered by multiple stimuli in different levels of organisms (eg, extracorporeal, tumor tissue, cell, subcellular organelles) have aroused widespread interest because they can overcome sequential physiological and pathological barriers to deliver diverse therapeutic “payloads” to the desired targets. Furthermore, multiple stimuli-responsive drug-delivery systems (MSR-DDSs) offer a good platform for co-delivery of agents and reversing multidrug resistance. This review affords a comprehensive overview on the “landscape” of MSR-DDSs against tumors, highlights the design strategies of MSR-DDSs in recent years, discusses the putative advantage of oncotherapy or the obstacles that so far have hindered the clinical translation of MSR-DDSs.

A mechanistic insight into benefits of aggregation induced emissive luminogens in cancer

Exploration of advanced chemotheranostics that benefit from a combined in vivo strategy of cancer diagnosis and chemotherapy simultaneously is highly valued and will expose novel possibilities in modifying treatment and reduce side effects. In recent years, nanodrug delivery systems that incorporate aggregation-induced emissive luminogens (AIEgens) have been developed to track and monitor anticancer drug release, trace translocation processes and predict chemotherapeutic responses. There are several classes of AIEgen based chemotheranostics such us stimuli-responsive nanoprodrugs, pH-sensitive mesoporous silica nanocarriers, supramolecular polymer systems, drug encapsulated carriers, carrier-free nanodrugs, self-indicating drug delivery nanomachines and AIEgen-prodrug co-assembly. The present review conveys mechanistic insight into the benefits of AIEgens in the theranostic application by illustrating the recent breakthroughs in chemotheranostic nanomedicines that incorporate these unique fluorophores as signal reporters. The perspectives that can be further explored are also highlighted with the hope to instil more research interest in the advancement of AIE active cancer chemotheranostics for imaging and treatment in vivo.HIGHLIGHTSAggregation induced emissive materials (AIEgens) exhibit unique advantages over conventional luminogens for synergistic diagnosis and chemotherapy of cancer in vivo.The combination of AIE and nanotechnology offers an excellent platform to fabricate advanced chemotheranostics for cancer therapy.

Nanoparticles Incorporating a Fluorescence Turn-on Reporter for Real-Time Drug Release Monitoring, a Chemoenhancer and a Stealth Agent: Poseidon's Trident against Cancer?

The rate and extent of drug release under physiological conditions is a key factor influencing the therapeutic activity of a formulation. Real-time detection of drug release by conventional pharmacokinetics approaches is confounded by low sensitivity, particularly in the case of tissue-targeted novel drug delivery systems, where low concentrations of the drug reach systemic circulation. We present a novel fluorescence turn-on platform for real-time monitoring of drug release from nanoparticles based on reversible fluorescence quenching in fluorescein esters. Fluorescein-conjugated carbon nanotubes (CNTs) were esterified with methotrexate in solution and solid phase, followed by supramolecular functionalization with a chemoenhancer (suramin) or/and a stealth agent (dextran sulfate). Suramin was found to increase the cytotoxicity of methotrexate in A549 cells. On the other hand, dextran sulfate exhibited no effect on cytotoxicity or cellular uptake of CNTs by A549 cells, while a decrease in cellular uptake of CNTs and cytotoxicity of methotrexate was observed in macrophages (RAW 264.7 cells). Similar results were also obtained when CNTs were replaced with graphene. Docking studies revealed that the conjugates are not internalized by folate receptors/transporters. Further, docking and molecular dynamics studies revealed the conjugates do not exhibit affinity toward the methotrexate target, dihydrofolate reductase. Molecular dynamics studies also revealed that distinct features of dextran-CNT and suramin-CNT interactions, characterized by π-π interactions between CNTs and dextran/suramin. Our study provides a simple, cost-effective, and scalable method for the synthesis of nanoparticles conferred with the ability to monitor drug release in real-time. This method could also be extended to other drugs and other types of nanoparticles.

Precise magnetic resonance imaging-guided sonodynamic therapy for drug-resistant bacterial deep infection

The precise treatment of drug-resistant deep bacterial infections remains a huge challenge in clinic. Herein, a polymer-peptide-porphyrin conjugate (PPPC), which can be real-time monitored in infectious site, is developed for accurate and deep sonodynamic therapy (SDT) based on "in vivo self-assembly" strategy. The PPPC contains four moieties, i.e., a hyperbranched polymer backbone, a self-assembled peptide linked with an enzyme-cleavable peptide-poly (ethylene glycol) terminal, a bacterial targeting peptide, and a porphyrin sonosensitizer (MnTCPP) segment. Once PPPC nanoparticles reach the infectious area, the protecting PEG layers are removed due to the over-expressed gelatinase, leading to the secondary assembly into large nanoaggregates and resultant enhanced accumulation of sonosensitizer. The nanoaggregates exhibit enhanced interaction with bacterial membrane and decrease the minimum inhibitory concentration (MIC) significantly. Meanwhile, compared with free MnTCPP, the concentration of which can not be accurately quantified, the accumulation amount of MnTCPP in PPPCs at infectious site can be in situ monitored by magnetic resonance imaging (MRI) using T₁ combined with T₂. When the concentration of PPPC-1 reaches MIC, the drug-resistant bacterial infection area is exposed to ultrasound irradiation, causing the precise and efficient elimination of bacteria. Therefore, the MRI-guided SDT system shows extraordinary tissue penetration depth, drug concentration monitoring, morphology-transformation induced accumulation and improved treatment capacity toward drug-resistant bacteria.

Chitosan-Gated Fluorescent Mesoporous Silica Nanocarriers for the Real-Time Monitoring of Drug Release

We have constructed a novel gated nanocarrier for the real-time monitoring of drug release, consisting of three parts: (i) mesoporous silica nanoparticles (MSNs) as the drug carrier, (ii) chitosan as the nanovalve to block and unlock the pores, and (iii) 1,8-naphthalimide fluorophore as a connecting arm and fluorescent signal source. In the absence of glutathione (GSH), the integrity of the system results in the formation of pores in a closed state and the sulfone would block the intramolecular charge transfer (ICT) process, leading to no fluorescence emission. However, the nucleophilic attack of GSH can cause the removal of the chitosan and recovery of ICT property, thus triggering drug release and green fluorescence emission. The results demonstrate that the change of GSH concentration in vivo or vitro would lead to a change in drug release as well as a concurrent change in fluorescence signal, which can expand the application of our gated nanocarrier for monitoring different drug release in real time.

Tumor-Sensitive Biodegradable Nanoparticles of Molecularly Imprinted Polymer-Stabilized Fluorescent Zeolitic Imidazolate Framework-8 for Targeted Imaging and Drug Delivery

Targeting enrichment of nanocarriers at tumor sites and effective drug release are critical in cancer treatment. Accordingly, we used fluorescent zeolitic imidazolate framework-8 nanoparticles loaded with doxorubicin (FZIF-8/DOX) as the core and a molecularly imprinted polymer (MIP) as the shell to synthesize tumor-sensitive biodegradable FZIF-8/DOX-MIP nanoparticles (FZIF-8/DOX-MIPs). The MIP prepared with the epitope of CD59 cell membrane glycoprotein as the template allowed FZIF-8/DOX-MIPs to be enriched to tumor sites by actively targeting recognition of MCF-7 cancer cells (CD59-positive). Moreover, using N,N'-diacrylylcystamine as the cross-linker and dimethylaminoethyl methacrylate as the main monomer, the MIP's framework will be broken under the stimulation of a tumor microenvironment (high-concentration glutathione and weakly acidic), so that the internal FZIF-8/DOX is exposed to a microacidic environment to release DOX through further degradation. More importantly, the ability of FZIF-8/DOX-MIPs in targeted fluorescence imaging and effective drug release has been validated both in vitro and in vivo. Compared to other cells and nanoparticles, FZIF-8/DOX-MIPs were more capable of being phagocytosed by MCF-7 cells and were more lethal to MCF-7 cells. In the comparative experiments carried out on tumor-bearing mice, FZIF-8/DOX-MIPs had the best inhibitory effect on the growth of MCF-7 tumors. Furthermore, the FZIF-8/DOX-MIPs can serve as a diagnostic agent because of the active targeting of MCF-7 cells and the stronger red fluorescence of the embedded carbon quantum dots. Because of the active targeting ability, good biocompatibility, tumor-sensitive biodegradability, and effective drug release performance, FZIF-8/DOX-MIPs can be widely used in tumor imaging and treatment.

Smart wound dressing for infection monitoring and NIR-triggered antibacterial treatment

Hydrogel-based wound dressings can monitor infection via pH-responsive FRET changes and provide on-demand antibacterial treatment via NIR-triggered antibiotic release.

Fluorescent glycoconjugates and their applications

Fluorescent glycoconjugates are discussed for their applications in biology in vitro, in cell assays and in animal models. Advantages and limitations are presented for each design using a fluorescent core conjugated with glycosides, or vice versa.

Quantitative Drug Release Monitoring in Tumors of Living Subjects by Magnetic Particle Imaging Nanocomposite

In vivo drug release monitoring provides accurate and reliable information to guide drug dosing. Image-based strategies for in vivo monitoring are advantageous because they are non-invasive and provide visualization of the spatial distribution of drug, but those imaging modalities in use (e.g., fluorescence imaging (FI) and magnetic resonance imaging (MRI)) remain inadequate because of the low tissue penetration depth (for FI) or difficulty with quantification of release rate and signal convolution with noise sources (for MRI). Magnetic particle imaging (MPI), employing superparamagnetic nanoparticles as the contrast agent and sole signal source, enables large tissue penetration and quantifiable signal intensity. These properties make it ideal for application to in vivo drug release monitoring. In this work, we design a superparamagnetic Fe₃O₄ nanocluster@poly(lactide-co-glycolide acid) core-shell nanocomposite loaded with a chemotherapy drug (doxorubicin) which serves as a dual drug delivery system and MPI quantification tracer. The as-prepared nanocomposite can degrade under a mild acidic microenvironment (pH = 6.5), which induces a sustained release of doxorubicin and gradual decomposition of the Fe₃O₄ nanocluster, causing the MPI signal changes. We showed that nanocomposite-induced MPI signal changes display a linear correlation with the release rate of doxorubicin over time (R² = 0.99). Utilizing this phenomenon, we successfully established quantitative monitoring of the release process in cell culture. We then performed in vivo drug release monitoring in a cancer therapy setting using a murine breast cancer model by injecting the nanocomposite, monitoring the drug release, and assessing the induced tumor cell kill. This study provides an improved solution for in vivo drug release monitoring compared to other available monitoring strategies. This translational strategy using a biocompatible polymer-coated iron oxide nanocomposite will be promising in future clinical use.

Therapeutic gene regulation using pyrrole-imidazole polyamides

Recent innovations in cutting-edge sequencing platforms have allowed the rapid identification of genes associated with communicable, noncommunicable and rare diseases. Exploitation of this collected biological information has facilitated the development of nonviral gene therapy strategies and the design of several proteins capable of editing specific DNA sequences for disease control. Small molecule-based targeted therapeutic approaches have gained increasing attention because of their suggested clinical benefits, ease of control and lower costs. Pyrrole-imidazole polyamides (PIPs) are a major class of DNA minor groove-binding small molecules that can be predesigned to recognize specific DNA sequences. This programmability of PIPs allows the on-demand design of artificial genetic switches and fluorescent probes. In this review, we detail the progress in the development of PIP-based designer ligands and their prospects as advanced DNA-based small-molecule drugs for therapeutic gene modulation.

Dual-Sensitive Graphene Oxide Loaded with Proapoptotic Peptides and Anticancer Drugs for Cancer Synergetic Therapy

A dual-sensitive drug delivery system (DDS) based on graphene oxide (GO) which is simultaneously loaded with proapoptotic peptides and anticancer drugs was rationally designed and fabricated for cancer synergetic therapy. Specifically, a kind of cell apoptosis peptide (KLAKLAK)₂ (KLA) was anchored on the surface of GO via a disulfide bond to obtain GO-SS-KLA. Then, the aromatic anticancer drug doxorubicin (DOX) was loaded on GO through π-π conjugation and hydrogen bonding interactions. Finally, bovine serum albumin (BSA) was used to coat the GO carrier to obtain a biological medium-stable GO-based DDS, DOX@GO-SS-KLA/BSA. The results show that KLA and DOX can be released responding to the reductive and pH stimulus inside the cells, respectively, and achieve a synergetic therapy for cancer. Moreover, the results of stability studies show that DOX@GO-SS-KLA/BSA could be stably dispersed in water for more than 8 days and in 10% fetal bovine serum for at least 6 days. The constructed DOX@GO-SS-KLA/BSA exhibits great potential as a drug carrier for co-delivery of various therapeutic agents.

Application of Förster Resonance Energy Transfer (FRET) technique to elucidate intracellular and In Vivo biofate of nanomedicines

Extensive studies on nanomedicines have been conducted for drug delivery and disease diagnosis (especially for cancer therapy). However, the intracellular and in vivo biofate of nanomedicines, which is significantly associated with their clinical therapeutic effect, is poorly understood at present. This is because of the technical challenges to quantify the disassembly and behaviour of nanomedicines. As a fluorescence- and distance-based approach, the Förster Resonance Energy Transfer (FRET) technique is very successful to study the interaction of nanomedicines with biological systems. In this review, principles on how to select a FRET pair and construct FRET-based nanomedicines have been described first, followed by their application to study structural integrity, biodistribution, disassembly kinetics, and elimination of nanomedicines at intracellular and in vivo levels, especially with drug nanocarriers including polymeric micelles, polymeric nanoparticles, and lipid-based nanoparticles. FRET is a powerful tool to reveal changes and interaction of nanoparticles after delivery, which will be very useful to guide future developments of nanomedicine.

Advances of nanosystems containing cyclodextrins and their applications in pharmaceuticals

For many years, researchers have worked with supramolecular structures involving inclusion complexes with cyclodextrins. These studies have resulted in new commercially available drugs which have been of great benefit. More recently, studies using nanoparticles, including nanosystems containing cyclodextrins, have become a focus of academic research due to the versatility of the systems and their remarkable therapeutic potential. This review focuses on studies published between 2002 and 2018 involving nanosystems containing cyclodextrins. We consider the type of nanosystems, their importance in a health context, the physicochemical techniques used to show the quality of these systems and their potential for the development of novel pharmaceutical formulations. These have been developed in recent studies which have mainly been focusing on basic science with no clinical trials as yet being performed. This is important to note because it means that the studies do not include any toxicity tests. Despite this limitation, the characterization assays performed suggest that these new formulations may have therapeutic potential. However, more research is required to assess the efficacy and safety of these nanosystems.

Amino-BODIPY as the ratiometric fluorescent sensor for monitoring drug release or “power supply” selector for molecular electronics

The glutathione cleavable conjugates of amino-BODIPY dye with model drugs have been tested for monitoring the drug release via ratiometric fluorescence based on two excitation and one emission wavelength. As a self-immolative linker was used for the construction of conjugates, free amino-BODIPY was released with the drug. Different excitation profiles of the dye before and after conjugate cleavage and similar emission wavelengths that enabled monitoring the release of the drug via the OFF–ON effect were successfully tested inside the cancer cells. UV/Vis spectrometry could be used in the quantification of the conjugate/drug in an analyte irrespective of the cleavage grade. As the system functionality was based only on the altered acylamino-BODIPY present in the conjugate to amino-BODIPY released during the cleavage, the method could be applied as a ratiometric fluorescence theranostic system to other non-fluorescent drugs. Moreover, the present conjugates demonstrated their potential application in molecular electronics as a “power supply” selector enabling the application of two power sources for one “bulb” to maintain its light intensity.

Amino-BODIPY as the universal and highly fluorescent OFF–ON and ratiometric sensor for thiol-mediated drug release monitoring.

Stimuli-Responsive Nanotheranostics for Real-Time Monitoring Drug Release by Photoacoustic Imaging

Molecular photoacoustic imaging (PA) is a promising technology to understand tumor pathology and guide precision therapeutics. Despite the capability of activatable PA probes to image tumor-specific biomarkers, limitations in their molecular structure hamper them from effective drug delivery and the drug release monitoring. Herein, we developed a perylene diimide (PDI) based theranostic platform that provides noninvasive PA imaging signals to monitor tumor-specific pH-responsive drug release.

Methods: we first designed and synthesized an acid-responsive amine-substituted PDI derivative. The pH sensitive properties of the PDI was demonstrated by density functional theory (DFT) calculations, UV-vis experiments and PA studies. The theranostic platform (THPDINs) was fabricated by self-assembly of the acid-responsive PDI, a pH irrelevant IR825 dye, and anti-cancer drug doxorubicin (DOX). The PA properties in various pH environment, drug delivery, cytotoxicity, cell uptake, ratiometric PA imaging and anti-tumor efficacy of the THPDINs were investigated in vitro and in vivo by using U87MG glioma cell line and U87MG tumor model.

Results: We found that our designed PDI was sensitive to the tumor specific pH environment, reflected by absorbance shift, PA intensity and aggregation morphology changes in aqueous solution. The as-synthesized pH sensitive PDI acted as a molecular switch in the THPDINs, in which the switch can be triggered in the mild acidic tumor microenvironment to accelerate DOX release. Meanwhile, the DOX release could be monitored by ratiometric PA imaging.

Conclusions: We developed a multifunctional PDI based theranostic platform for noninvasive real-time ratiometric PA imaging of tumor acidic pH and monitoring of drug release in living mice simultaneously. This strategy will shed light on the development of smart activatable theranostic nanoplatforms and will significantly advance the application of PA theranostics in biology and medicine.

Chemodrug-Gated Biodegradable Hollow Mesoporous Organosilica Nanotheranostics for Multimodal Imaging-Guided Low-Temperature Photothermal Therapy/Chemotherapy of Cancer

Noninvasive physical treatment with relatively low intensity stimulation and the development of highly efficient anticancer medical strategy are still desirable for cancer therapy. Herein a versatile, biodegradable, hollow mesoporous organosilica nanocapsule (HMONs) nanoplatform that is capped by the gemcitabine (Gem) molecule through a pH-sensitive acetal covalent bond is designed. The fabricated nanocapsule exhibits desirable small molecule release at the tumor tissues/cell sites and shows a reduced risk for drug accumulation. After loading indocyanine green (ICG), the heat-shock protein 90 (Hsp 90) inhibitor, and 17AAG and modification with polyethylene glycol (NH₂-PEG), the resulting ICG-17AAG@HMONs-Gem-PEG exhibited a precisely controlled release of ICG and 17AAG and low-temperature photothermal therapy (PTT) (∼41 °C) with excellent tumor destruction efficacy. In addition, ICG loading conferred the nanoplatform with near-infrared fluorescence imaging (FL) and photoaccoustic (PA) imaging capability. In short, this work not only presents a smart drug self-controlled nanoplatform with pH-responsive payload release and theranostic performance but also provides an outstanding low-temperature PTT strategy, which is highly valid in the inhibition of cancer cells with minimal damage to the organism. Therefore, this research provides a paradigm that has a chemodrug-gated HMONs-based theranostic nanoplatform with intrinsic biodegradability, multimodal imaging capacity, high low-temperature PTT/chemotherapy efficacy, and reduced systemic toxicity.

Synthesis and Biomedical Applications of Multifunctional Nanoparticles

The accumulated knowledge of nanoparticle (NP) synthesis for the last 30 years has enabled the development of functional NPs for biomedical applications. Especially, NPs with multifunctional capabilities are gaining popularity as the demand for versatile and efficient NP agents increases. Various combinations of functional materials are integrated to form multicomponent NPs with designed size, structure, and multifunctionality. Their use as diagnostic and/or therapeutic tools is demonstrated, suggesting their application potentials in healthcare and medical practice. Here, the recent achievements in the synthesis and biomedical applications of multifunctional NPs are summarized. Starting with a brief overview regarding the advances in NP synthesis and accompanying progress in nanobiotechnology, various components to construct the multifunctional NP agents, which include polymers and mesoporous, magnetic, catalytic, and semiconducting NPs, are discussed together with their overall integration forms, such as NP assembly, hollow/porous structures, or hybrid/doped systems. Following the explanation of the features that multifunctional NP agents can offer, an outlook and a brief comment regarding the future research directions are provided.

Controlled drug release with surface-capped mesoporous silica nanoparticles and its label-free in situ Raman monitoring

Mesoporous silica nanoparticles (MSNs) have drawn attention as efficient nanocarriers for drug delivery systems owing to their unique physiochemical properties. However, systemically controlling the kinetics of drug release from the nanocarriers and in situ monitoring of the drug release are still challenging. Here, we report surface-capped MSNs used for controlled drug release and demonstrate label-free in situ Raman monitoring of released drugs based on the molecule-specific spectral fingerprints. By capping the surface of MSNs with amine moieties, gold nanoparticles, and albumin, we achieved high loading efficiencies (up to 97%) of doxorubicin and precisely controlled drug release stimulated by changing pH value. Moreover, we monitored in real-time drug release profile and visualized cellular distribution of the delivered drug at nanoscale based on its intrinsic Raman peak. Finally, we evaluated drug responses in cancer cells and normal cells to investigate whether capped-dMSNs exhibit selective drug release. Our findings would be beneficial for designing smart drug carriers and directly monitoring the release behavior of drugs in actual cellular environments.

Seeing, Targeting and Delivering with Upconverting Nanoparticles

Efficient control over drug release is critical to increasing drug efficacy and avoiding side effects. An ideal drug delivery system would deliver drugs in the right amount, at the right location and at the right time noninvasively. This can be achieved using light-triggered delivery: light is noninvasive, spatially precise and safe if appropriate wavelengths are chosen. However, the use of light-controlled delivery systems has been limited to areas that are not too deep inside the body because ultraviolet (UV) or visible (Vis) light, the typical wavelengths used for photoreactions, have limited penetration and are toxic to biological tissues. The advent of upconverting nanoparticles (UCNPs) has made it possible to overcome this crucial challenge. UCNPs can convert near-infrared (NIR) radiation, which can penetrate deeper inside the body, to shorter wavelength NIR, Vis and UV radiation. UCNPs have been used as bright, in situ sources of light for on-demand drug release and bioimaging applications. These remote-controlled, NIR-triggered drug delivery systems are especially attractive in applications where a drug is required at a specific location and time such as in anesthetics, postwound healing, cardiothoracic surgery and cancer treatment. In this Perspective, we discuss recent progress and challenges as well as propose potential solutions and future directions, especially with regard to their translation to the clinic.