Hypoxia-specific ultrasensitive detection of tumours and cancer cells in vivo

Hydrogen Polysulfide Biosignal-Responsive Polymersomes as a Nanoplatform for Distinguishing Intracellular Reactive Sulfur Species (RSS)

Reactive sulfur species (RSS) are a family of crucial biosignals for regulating cell processes. Among these, hydrogen polysulfide (H₂ S_n , n ≥ 2) is a hallmark of tumor suppressor activation and regarded as the actual regulator to mediate sulfur-related biology. However, high effective recognition of intracellular H₂ S_n is insurmountable due to its extremely low concentration and the disturbance of RSS analogues. Here an H₂ S_n -responsive macromolecule that can distinguish H₂ S_n from intracellular RSS through polymer degradation in ultrasensitive and highly selective manner is reported. This kind of polymers can further self-assemble into vesicular nanostructure. Upon cell uptake, they can be function as "all-in-one" H₂ S_n -nanoplatforms, in order to fulfill multiple ambitious tasks including monitoring the H₂ S_n biosynthetic pathways, unraveling the puzzles of H₂ S_n -mediated cellular events, and conducting H₂ S_n pathological milieu-specific drug delivery.

Ultralong Phosphorescence of Water-Soluble Organic Nanoparticles for In Vivo Afterglow Imaging

Afterglow or persistent luminescence eliminates the need for light excitation and thus circumvents the issue of autofluorescence, holding promise for molecular imaging. However, current persistent luminescence agents are rare and limited to inorganic nanoparticles. This study reports the design principle, synthesis, and proof-of-concept application of organic semiconducting nanoparticles (OSNs) with ultralong phosphorescence for in vivo afterglow imaging. The design principle leverages the formation of aggregates through a top-down nanoparticle formulation to greatly stabilize the triplet excited states of a phosphorescent molecule. This prolongs the particle luminesce to the timescale that can be detected by the commercial whole-animal imaging system after removal of external light source. Such ultralong phosphorescent of OSNs is inert to oxygen and can be repeatedly activated, permitting imaging of lymph nodes in living mice with a high signal-to-noise ratio. This study not only introduces the first category of water-soluble ultralong phosphorescence organic nanoparticles but also reveals a universal design principle to prolong the lifetime of phosphorescent molecules to the level that can be effective for molecular imaging.

Stimuli-Responsive "Cluster Bomb" for Programmed Tumor Therapy

In this paper, mesoporous silica nanoparticle (MSN) loaded with doxorubicin (DOX) and capped with tumor-homing/-penetrating peptide tLyP-1-modified tungsten disulfide quantum dots (WS₂-HP) was designed and applied as a stimuli-responsive "Cluster Bomb" for high-performance tumor suppression. The peptide tLyP-1 on the surface can both facilitate the homing of DOX@MSN-WS₂-HP to 4T1 tumor and greatly enhance the penetration of WS₂-HP in tumor. The benzoic-imine bonds as the linkers between "bomblets" and "dispenser" are stable under normal physical conditions and quite labile at pH 6.8. After arriving at the mild acidic tumor microenvironment, the nanoplatform can rapidly break into two parts: (1) electropositive DOX@MSN-NH₂ for efficient chemotherapy on surface tumor cells and (2) small-sized WS₂-HP with improved tumor penetrating ability for near-infrared (NIR)-light-triggered photothermal therapy (PTT) among deep-seated tumor cells. Having killed the tumor cells in different depths, DOX@MSN-WS₂-HP exhibited significant antitumor effect, which will find great potential in clinical trials.

Controllable Photodynamic Therapy Implemented by Regulating Singlet Oxygen Efficiency

With singlet oxygen (1O2) as the active agent, photodynamic therapy (PDT) is a promising technique for the treatment of various tumors and cancers. But it is hampered by the poor selectivity of most traditional photosensitizers (PS). In this review, we present a summary of controllable PDT implemented by regulating singlet oxygen efficiency. Herein, various controllable PDT strategies based on different initiating conditions (such as pH, light, H2O2 and so on) have been summarized and introduced. More importantly, the action mechanisms of controllable PDT strategies, such as photoinduced electron transfer (PET), fluorescence resonance energy transfer (FRET), intramolecular charge transfer (ICT) and some physical/chemical means (e.g. captivity and release), are described as a key point in the article. This review provide a general overview of designing novel PS or strategies for effective and controllable PDT.

Context-dependent intravital imaging of therapeutic response using intramolecular FRET biosensors

Intravital microscopy represents a more physiologically relevant method for assessing therapeutic response. However, the movement into an in vivo setting brings with it several additional considerations, the primary being the context in which drug activity is assessed. Microenvironmental factors, such as hypoxia, pH, fibrosis, immune infiltration and stromal interactions have all been shown to have pronounced effects on drug activity in a more complex setting, which is often lost in simpler two- or three-dimensional assays. Here we present a practical guide for the application of intravital microscopy, looking at the available fluorescent reporters and their respective expression systems and analysis considerations. Moving in vivo, we also discuss the microscopy set up and methods available for overlaying microenvironmental context to the experimental readouts. This enables a smooth transition into applying higher fidelity intravital imaging to improve the drug discovery process.

Molecular imaging of the tumor microenvironment

The tumor microenvironment plays a critical role in tumor initiation, progression, metastasis, and resistance to therapy. It is different from normal tissue in the extracellular matrix, vascular and lymphatic networks, as well as physiologic conditions. Molecular imaging of the tumor microenvironment provides a better understanding of its function in cancer biology, and thus allowing for the design of new diagnostics and therapeutics for early cancer diagnosis and treatment. The clinical translation of cancer molecular imaging is often hampered by the high cost of commercialization of targeted imaging agents as well as the limited clinical applications and small market size of some of the agents. Because many different cancer types share similar tumor microenvironment features, the ability to target these biomarkers has the potential to provide clinically translatable molecular imaging technologies for a spectrum of cancers and broad clinical applications. There has been significant progress in targeting the tumor microenvironment for cancer molecular imaging. In this review, we summarize the principles and strategies of recent advances made in molecular imaging of the tumor microenvironment, using various imaging modalities for early detection and diagnosis of cancer.

Imaging the pharmacology of nanomaterials by intravital microscopy: Toward understanding their biological behavior

Therapeutic nanoparticles (NPs) can deliver cytotoxic chemotherapeutics and other drugs more safely and efficiently to patients; furthermore, selective delivery to target tissues can theoretically be accomplished actively through coating NPs with molecular ligands, and passively through exploiting physiological "enhanced permeability and retention" features. However, clinical trial results have been mixed in showing improved efficacy with drug nanoencapsulation, largely due to heterogeneous NP accumulation at target sites across patients. Thus, a clear need exists to better understand why many NP strategies fail in vivo and not result in significantly improved tumor uptake or therapeutic response. Multicolor in vivo confocal fluorescence imaging (intravital microscopy; IVM) enables integrated pharmacokinetic and pharmacodynamic (PK/PD) measurement at the single-cell level, and has helped answer key questions regarding the biological mechanisms of in vivo NP behavior. This review summarizes progress to date and also describes useful technical strategies for successful IVM experimentation.

In Vivo Biosensing: Progress and Perspectives

In vivo biosensors are emerging as powerful tools in biomedical research and diagnostic medicine. Distinct from "labels" or "imaging", in vivo biosensors are designed for continuous and long-term monitoring of target analytes in real biological systems and should be selective, sensitive, reversible and biocompatible. Due to the challenges associated with meeting all of the analytical requirements, we found relatively few reports of research groups demonstrating devices that meet the strict definition in vivo. However, we identified several case studies and a range of emerging materials likely to lead to significant developments in the field.

AIE-active theranostic system: selective staining and killing of cancer cells

Cancer is the leading cause of death worldwide. With the advantages of low cost, high sensitivity and ease of accessibility, fluorescence imaging has been widely used for cancer detection in the scientific field. Aggregation-induced emission luminogens (AIEgens) are a class of synthesized fluorescent probes with high brightness and photostability in the aggregate state. Herein, a new positively-charged AIEgen, abbreviated as TPE-IQ-2O, is designed and characterized. TPE-IQ-2O not only can distinguish cancer cells from normal cells with high contrast with the aid of the difference in mitochondrial membrane potential as well as the quantity of mitochondria, but it also works as a promising photosensitizer to kill cancer cells through generation of reactive oxygen species upon white light irradiation, thus making it a promising AIE theranostic system.

Unveiling a New Aspect of Simple Arylboronic Esters: Long-Lived Room-Temperature Phosphorescence from Heavy-Atom-Free Molecules

Arylboronic esters can be used as versatile reagents in organic synthesis, as represented by Suzuki-Miyaura cross-coupling. Here we report a serendipitous finding that simple arylboronic esters are phosphorescent in the solid state at room temperature with a lifetime on the order of several seconds. The phosphorescence properties of arylboronic esters are remarkable in light of the general notion that phosphorescent organic molecules require heavy atoms and/or carbonyl groups for the efficient generation of a triplet excited state. Theoretical calculations on phenylboronic acid pinacol ester indicated that this molecule undergoes an out-of-plane distortion at the (pinacol)B-C_ipso moiety in the T₁ excited state, which is responsible for its phosphorescence. A compound survey with 19 arylboron compounds suggested that the phosphorescence properties might be determined by solid-state molecular packing rather than by the patterns and numbers of boron substituents on the aryl units. The present finding may update the general notion of phosphorescent organic molecules.

Imaging the Tumor Microenvironment

The tumor microenvironment consists of tumor, stromal, and immune cells, as well as extracellular milieu. Changes in numbers of these cell types and their environments have an impact on cancer growth and metastasis. Non-invasive imaging of aspects of the tumor microenvironment can provide important information on the aggressiveness of the cancer, whether or not it is metastatic, and can also help to determine early response to treatment. This chapter provides an overview on non-invasive in vivo imaging in humans and mouse models of various cell types and physiological parameters that are unique to the tumor microenvironment. Current clinical imaging and research investigation are in the areas of nuclear imaging (positron emission tomography (PET) and single photon emission computed tomography (SPECT)), magnetic resonance imaging (MRI) and optical (near infrared (NIR) fluorescence) imaging. Aspects of the tumor microenvironment that have been imaged by PET, MRI and/or optical imaging are tumor associated inflammation (primarily macrophages and T cells), hypoxia, pH changes, as well as enzymes and integrins that are highly prevalent in tumors, stroma and immune cells. Many imaging agents and strategies are currently available for cancer patients; however, the investigation of novel avenues for targeting aspects of the tumor microenvironment in pre-clinical models of cancer provides the cancer researcher with a means to monitor changes and evaluate novel treatments that can be translated into the clinic.

Leveraging Physiology for Precision Drug Delivery

Physiological characteristics of diseases bring about both challenges and opportunities for targeted drug delivery. Various drug delivery platforms have been devised ranging from macro- to micro- and further into the nanoscopic scale in the past decades. Recently, the favorable physicochemical properties of nanomaterials, including long circulation, robust tissue and cell penetration attract broad interest, leading to extensive studies for therapeutic benefits. Accumulated knowledge about the physiological barriers that affect the in vivo fate of nanomedicine has led to more rational guidelines for tailoring the nanocarriers, such as size, shape, charge, and surface ligands. Meanwhile, progresses in material chemistry and molecular pharmaceutics generate a panel of physiological stimuli-responsive modules that are equipped into the formulations to prepare “smart” drug delivery systems. The capability of harnessing physiological traits of diseased tissues to control the accumulation of or drug release from nanomedicine has further improved the controlled drug release profiles with a precise manner. Successful clinical translation of a few nano-formulations has excited the collaborative efforts from the research community, pharmaceutical industry, and the public towards a promising future of smart drug delivery.

Redox-Activated Light-Up Nanomicelle for Precise Imaging-Guided Cancer Therapy and Real-Time Pharmacokinetic Monitoring

Simultaneous tumor imaging, therapy, and pharmacokinetic monitoring can offer a safe and effective strategy for cancer therapy. This work describes the design of a fluorescence light-up nanomicelle that can afford precise imaging-guided drug delivery and pharmacokinetic monitoring in a real-time fashion for cancer chemotherapy. The nanomicelle, which contains a boron dipyrromethene based fluorescent probe as the hydrophobic core and a redox-triggered detachable poly(ethylene glycol) (PEG) shell, can accumulate at the tumor site via enhanced permeation and retention effect. The PEG detachment induced by tumoral and intracellular glutathione can destabilize the nanomicelle, leading to fluorescence light up and simultaneous drug release. Importantly, the fluorescence intensities generated by the nanomicelles in different organs are well-correlated with released drug concentrations in both temporal and spatial manners, suggesting its precise role for imaging-guided drug delivery and pharmacokinetic monitoring in vivo. The tumor growth can be effectively inhibited by the docetaxel-loaded nanomicelle formulation, and the nanomicelles are monitored to be excreted via hepatobiliary routes. This nanomicelle for precise imaging-guided chemotherapy provides a safe and robust theranostic strategy for the evaluation of cancer nanomedicine.

Redox-Mediated Disassembly to Build Activatable Trimodal Probe for Molecular Imaging of Biothiols

Activatable multimodal probes that show enhancement of multiplex imaging signals upon interaction with their specific molecular target have become powerful tools for rapid and precise imaging of biological processes. Herein, we report a stimuli-responsive disassembly approach to construct a redox-activatable fluorescence/¹⁹F-MRS/¹H-MRI triple-functional probe 1. The small molecule probe 1 itself has a high propensity to self-assemble into nanoparticles with quenched fluorescence, attenuated ¹⁹F-MRS signal, and high ¹H-MRI contrast. Biothiols that are abundant in reducing biological environment were able to cleave the disulfide bond in probe 1 to induce disassembly of the nanoparticles and lead to fluorescence activation (∼70-fold), ¹⁹F-MRS signal amplification (∼30-fold) and significant r₁ relaxivity reduction (∼68% at 0.5 T). Molecular imaging of reducing environment in live cells and in vivo was realized using probe 1. This approach could facilitate the development of other stimuli-responsive trimodal probes for molecular imaging.

Increased Gold Nanoparticle Retention in Brain Tumors by in Situ Enzyme-Induced Aggregation

The treatment of brain tumors remains a challenge due to the limited accumulation of drugs and nanoparticles. Here, we triggered the aggregation of gold nanoparticles (AuNPs) using legumain to enhance the retention of chemotherapeutics in brain tumors. This nanoplatform, AuNPs-A&C, is comprised of Ala-Ala-Asn-Cys-Lys modified AuNPs (AuNPs-AK) and 2-cyano-6-aminobenzothiazole modified AuNPs (AuNPs-CABT). AuNPs-AK could be hydrolyzed to expose the 1,2-thiolamino groups on AuNPs-AK in the presence of legumain, which occurs by a click cycloaddition with the contiguous cyano group on AuNPs-CABT, resulting in formation of AuNPs aggregates. This strategy led to an enhanced retention of the AuNPs in glioma cells both in vitro and in vivo due to the blocking of nanoparticle exocytosis and minimizing nanoparticle backflow to the bloodstream. After conjugation of doxorubicin (DOX) via a pH-sensitive linker to AuNPs-A&C, the efficiency for treating glioma was improved. The median survival time for the DOX-linked AuNPs-A&C increased to 288% in comparison to the saline group. We further show the use of the AuNPs-A&C for optical imaging applications. In conclusion, we provide a strategy to increase nanoparticle tumor accumulation with the potential to improve therapeutic outcome.

Dual-channel NIR activatable theranostic prodrug for in vivo spatiotemporal tracking thiol-triggered chemotherapy

Real-time tracking for where (W), when (W), and how (H) prodrugs are delivered and activated in vivo is a great challenge for prodrug development. Disulfide linkage-based prodrugs as well as their delivery systems have been studied extensively, but the WWH question in spatial and temporal (spatiotemporal) precision remains unanswered. Herein, we present a novel prodrug of camptothecin (CPT) linked to a near-infrared (NIR) cyanine dye via a disulfide linkage (Cy-S-CPT). The cleavage of the disulfide bond in Cy-S-CPT by endogenous glutathione (GSH) can activate the anti-cancer drug CPT and induce a remarkable fluorescence shift from 825 to 650 nm, thereby providing dual fluorescent channels to real-time track the prodrug biodistribution and activation in vivo. Impressively, the dual-channel NIR fluorescence bioimaging exhibits the pervasive drug distribution, i.e., the biodistribution of the intact prodrug was traced at the 825 nm-NIR fluorescence channel, whereas the activated drug was tracked at the 650 nm red fluorescence channel. In this way, we can overcome the blind spot in the metabolism kinetics of prodrugs in a certain organ or tissue. As demonstrated, the prodrug prompts activation in all the organs, particularly in the liver after an intravenous injection, and achieves predominant accumulation and activation in tumors at 24 h post injection. Cy-S-CPT loaded in PEG-PLA nanoparticles display significantly improved therapeutic efficacy and low side effects with respect to the clinical used drug CPT-11. As a consequence, the NIR spatiotemporal bioimaging in vivo with dual fluorescence channels allows the prodrug release profile to be extracted precisely, particularly in visualizing drug-released information from complex biological systems such as mice, thereby providing a unique opportunity to take insight into the relationship between theranosis and pharmacokinetics.

Facile synthesis of a ratiometric oxygen nanosensor for cellular imaging

A new type of cell-penetrating ratiometric fluorescence oxygen sensing nanoparticle was prepared through a facile co-precipitation method. Amphiphilic polymer poly (styrene-co-maleic anhydride) (PSMA) was firstly cooperated with polystyrene (PS) to envelop the highly photostable phosphorescent oxygen indicator, platinum(II)-tetrakis(pentafluorophenyl)porphyrin (PtTFPP, emission at 648nm), and the reference fluorophore, poly(9, 9-dioctylfluorene) (PFO, emission at 440nm ), via hydrophobic interaction in aqueous solution. To improve the sensor biocompatibility, the biomacromolecule poly-l-lysine (PLL) was selected to act as a shell via electrostatic forces. The as-prepared PtTFPP doped core-shell nanoparticles (called PPMA/PLL NPs) exhibited an excellent ratiometric luminescence response to O2 content with high quenching efficiency and full reversibility in the oxygen sensing. More importantly, these oxygen nanosensors passed across the cell membrane after co-incubation without external force. Labeled cells exhibited high brightness in the matching blue and red channels of a digital camera. And most nanosensors were found locating in cytoplasm rather than being trapped in endosomes.

Heteronuclear Ir(III)-Ln(III) Luminescent Complexes: Small-Molecule Probes for Dual Modal Imaging and Oxygen Sensing

Luminescent, mixed metal d-f complexes have the potential to be used for dual (magnetic resonance imaging (MRI) and luminescence) in vivo imaging. Here, we present dinuclear and trinuclear d-f complexes, comprising a rigid framework linking a luminescent Ir center to one (Ir·Ln) or two (Ir·Ln2) lanthanide metal centers (where Ln = Eu(III) and Gd(III), respectively). A range of physical, spectroscopic, and imaging-based properties including relaxivity arising from the Gd(III) units and the occurrence of Ir(III) → Eu(III) photoinduced energy-transfer are presented. The rigidity imposed by the ligand facilitates high relaxivities for the Gd(III) complexes, while the luminescence from the Ir(III) and Eu(III) centers provide luminescence imaging capabilities. Dinuclear (Ir·Ln) complexes performed best in cellular studies, exhibiting good solubility in aqueous solutions, low toxicity after 4 and 18 h, respectively, and punctate lysosomal staining. We also demonstrate the first example of oxygen sensing in fixed cells using the dyad Ir·Gd, via two-photon phosphorescence lifetime imaging (PLIM).

Difluoroboron β-Diketonate Materials with Long-Lived Phosphorescence Enable Lifetime Based Oxygen Imaging with a Portable Cost Effective Camera

Lifetime-based oxygen imaging is useful in many biological applications but instrumentation can be stationary, expensive, and complex. Herein, we present a portable, cost effective, simple alternative with high spatiotemporal resolution that uses a complementary metal oxide silicon (CMOS) camera to measure oxygen sensitive lifetimes on the millisecond scale. We demonstrate its compatibility with difluoroboron β-diketonate poly(lactic acid) (BF₂bdkPLA) polymers which are nontoxic and exhibit long-lived oxygen sensitive phosphorescence. Spatially resolved lifetimes of four BF₂bdkPLA variants are measured using nonlinear least squares (NLS) and rapid lifetime determination (RLD) both of which are shown to be accurate and precise. Real-time imaging in a dynamic environment is demonstrated by determining lifetime pixel-wise. The setup costs less than $5000, easily fits into a backpack, and can operate on battery power alone. This versatility combined with the inherent utility of lifetime measurements make this system a useful tool for a wide variety of oxygen sensing applications. This study serves as an important foundation for the development of dual mode real time lifetime plus ratiometric imaging with bright, long lifetime difluoroboron β-diketonate probes.

Morphology-Tailoring of a Red AIEgen from Microsized Rods to Nanospheres for Tumor-Targeted Bioimaging

Efficient morphology modulation of a red AIEgen from pristine microsized rods to nanospheres is achieved via encapsula ting QM-2 (quinolinemalononitrile-2) into hybrid micelles. This novel reagent shows great potential in tumor-targeted bioimaging because of its monodispersion in aqueous systems, the uniform diameter of ≈30 nm, enhanced fluorescence brightness with a large Stokes shift of 190 nm, and strongly increased biocompatibility and photostability.

Intracellularly Acid-Switchable Multifunctional Micelles for Combinational Photo/Chemotherapy of the Drug-Resistant Tumor

The intrinsic or acquired drug resistance is the main challenge for cancer chemotherapy today. So far, many nanosized drug delivery systems (NDDS) have been exploited to combat cancer drug resistance. However, the therapy efficacy of current NDDS is severely impaired by the limited tumor penetration of the nanoparticles due to the existence of physiological and pathological barriers in the solid tumor. In this study, we report on the design and fabrication of intracellularly acid-switchable multifunctional micelles for combinational photo- and chemotherapy of the drug-resistant tumor. The micelles were composed of a pH-responsive diblock copolymer, a photosensitizer, and a polymeric prodrug of doxorubicin. The micelle displayed silenced fluorescence and photoactivity during the blood circulation and switched to an active state in weakly acid conditions (i.e., pH ≤ 6.2) in the endocytic vesicles to dramatically induce a 7.5-fold increase of the fluorescence signal for fluorescence imaging. Upon near-infrared (NIR) laser irradiation, the micelle induced notable reactive oxygen species generation to trigger cytosol release of the chemotherapeutics and perform photodynamic therapy (PDT). Moreover, the micelle efficiently converted the NIR light to local heat for enhancing tumor penetration of the anticancer drug, tumor specific photothermal therapy, and photoacoustic (PA) imaging. Furthermore, the micelles could generate amplified magnetic resonance (MR) signal in an acidic microenvironment to perform MR imaging. Collectively, this study presents a robust nanoplatform for multimodal imaging and combinational therapy of the drug-resistant tumor, which might provide an insight for developing polymer-based NDDS for cancer therapy.

Development of an Amino Acid-Functionalized Fluorescent Nanocarrier to Deliver a Toxin to Kill Insect Pests

Large-scale cultivation of Bacillus thuringiensis Berliner (Bt) crops has led to the rapid development of drug resistance. Herein, a fluorescent star poly(amino acid) is synthesized with l-isoleucine functionalization for the efficient delivery of either positively or negatively charged exogenous proteins into live cells. Poly(amino acid)s (P1)/Cry1Ab complexes greatly increase the cytotoxicity of the Bt toxin, Cry1Ab, and efficiently kill Bt-resistant pests.

Smart conjugated polymer nanocarrier for healthy weight loss by negative feedback regulation of lipase activity

Healthy weight loss represents a real challenge when obesity is increasing in prevalence. Herein, we report a conjugated polymer nanocarrier for smart deactivation of lipase and thus balancing calorie intake. After oral administration, the nanocarrier is sensitive to lipase in the digestive tract and releases orlistat, which deactivates the enzyme and inhibits fat digestion. It also creates negative feedback to control the release of itself. The nanocarrier smartly regulates activity of the lipase cyclically varied between high and low levels. In spite of high fat diet intervention, obese mice receiving a single dose of the nanocarrier lose weight over eight days, whereas a control group continues the tendency to gain weight. Daily intragastric administration of the nanocarrier leads to lower weight of livers or fat pads, smaller adipocyte size, and lower total cholesterol level than that of the control group. Near-infrared fluorescence of the nanocarrier reveals its biodistribution.

Multifunctional Phosphorescent Conjugated Polymer Dots for Hypoxia Imaging and Photodynamic Therapy of Cancer Cells

Molecular oxygen (O2) plays a key role in many physiological processes, and becomes a toxicant to kill cells when excited to 1O2. Intracellular O2 levels, or the degree of hypoxia, are always viewed as an indicator of cancers. Due to the highly efficient cancer therapy ability and low side effect, photodynamic therapy (PDT) becomes one of the most promising treatments for cancers. Herein, an early-stage diagnosis and therapy system is reported based on the phosphorescent conjugated polymer dots (Pdots) containing Pt(II) porphyrin as an oxygen-responsive phosphorescent group and 1O2 photosensitizer. Intracellular hypoxia detection has been investigated. Results show that cells treated with Pdots display longer lifetimes under hypoxic conditions, and time-resolved luminescence images exhibit a higher signal-to-noise ratio after gating off the short-lived background fluorescence. Quantification of O2 is realized by the ratiometric emission intensity of phosphorescence/fluorescence and the lifetime of phosphorescence. Additionally, the PDT efficiency of Pdots is estimated by flow cytometry, MTT cell viability assay, and in situ imaging of PDT induced cell death. Interestingly, Pdots exhibit a high PDT efficiency and would be promising in clinical applications.

l-Cystine-Crosslinked Polypeptide Nanogel as a Reduction-Responsive Excipient for Prostate Cancer Chemotherapy

Smart polymer nanogel-assisted drug delivery systems have attracted more and more attention in cancer chemotherapy because of their well-defined morphologies and pleiotropic functions in recent years. In this work, an l-cystine-crosslinked reduction-responsive polypeptide nanogel of methoxy poly(ethylene glycol)-poly(l-phenylalanine-co-l-cystine) (mPEG-P(LP-co-LC)) was employed as a smart excipient for RM-1 prostate cancer (PCa) chemotherapy. Doxorubicin (DOX), as a regular chemotherapy drug, was embedded in the nanogel. The loading nanogel marked as NG/DOX was shown to exhibit glutathione (GSH)-induced swelling and GSH-accelerated DOX release. Subsequently, NG/DOX showed efficient cellular uptake and proliferation inhibition. Furthermore, NG/DOX presented enhanced antitumor efficacy and security in an RM-1 PCa-grafted mouse model in vivo, indicating its great potential for clinical treatment.

A Bifunctional Photosensitizer for Enhanced Fractional Photodynamic Therapy: Singlet Oxygen Generation in the Presence and Absence of Light

The photosensitized generation of singlet oxygen within tumor tissues during photodynamic therapy (PDT) is self-limiting, as the already low oxygen concentrations within tumors is further diminished during the process. In certain applications, to minimize photoinduced hypoxia the light is introduced intermittently (fractional PDT) to allow time for the replenishment of cellular oxygen. This condition extends the time required for effective therapy. Herein, we demonstrated that a photosensitizer with an additional 2-pyridone module for trapping singlet oxygen would be useful in fractional PDT. Thus, in the light cycle, the endoperoxide of 2-pyridone is generated along with singlet oxygen. In the dark cycle, the endoperoxide undergoes thermal cycloreversion to produce singlet oxygen, regenerating the 2-pyridone module. As a result, the photodynamic process can continue in the dark as well as in the light cycles. Cell-culture studies validated this working principle in vitro.

Poly(ethylene glycol)-b-poly(lysine) copolymer bearing nitroaromatics for hypoxia-sensitive drug delivery

Hypoxia occurs in a variety of pathological conditions including stroke, rheumatoid arthritis, atherosclerosis, and tumors. In this study, an amphiphilic block copolymer, composed of poly(ethylene glycol) as the hydrophilic block and poly(ε-(4-nitro)benzyloxycarbonyl-L-lysine) as the hydrophobic block, was prepared for hypoxia-sensitive drug delivery. Owing to its amphiphilic nature, the block copolymer formed micelles and encapsulated doxorubicin (DOX) in an aqueous condition. The DOX-loaded micelles exhibited rapid intracellular release of DOX under the hypoxic condition, implying high potential as a drug carrier for cancer therapy.

STATEMENT OF SIGNIFICANCE

Hypoxia occurs in a variety of pathological conditions including stroke, rheumatoid arthritis, atherosclerosis, and tumors. In this study, we developed a novel type of hypoxia-sensitive polymeric micelles (HS-PMs) that can specifically release the drug under the hypoxic conditions. HS-PMs were prepared using poly(ethylene glycol) as the hydrophilic block and poly(ε-(4-nitro)benzyloxycarbonyl-L-lysine) as the hydrophobic block. Owing to its amphiphilic nature, the block copolymer formed micelles and encapsulated doxorubicin (DOX) in an aqueous condition. The DOX-loaded micelles exhibited rapid intracellular release of DOX under the hypoxic condition. Overall, it is evident that the HS-PMs prepared in this study have the potential to effectively deliver hydrophobic drugs into the hypoxic cells involved in various intractable diseases.

Hypoxia-responsive nanocarriers for cancer imaging and therapy: recent approaches and future perspectives

This review focuses on hypoxia-responsive nanocarriers, which can be disintegrated by recognizing the hypoxic microenvironment of cancer cells, and their utilization in cancer imaging and therapy.

Carbon-Dot-Based Nanosensors for the Detection of Intracellular Redox State

Carbon-dot-based nanosensors are prepared through sequentially assembling a polymer/carbon dot multilayer shell on mesoporous silica nanoparticles with different crosslinking densities of disulfide bonds; they can be utilized to evaluate the gluthathione (GSH) concentration. In vitro cell assays demonstrate the feasibility of using such nanosensors in evaluating the intracellular redox state of different cells.

Core-Shell MnSe@Bi2 Se3 Fabricated via a Cation Exchange Method as Novel Nanotheranostics for Multimodal Imaging and Synergistic Thermoradiotherapy

MnSe@Bi2 Se3 core-shell nanostructures with highly integrated imaging and therapy functions are fabricated by a simple cation exchange method. Using those nanoparticles as a theranostic agent, a promise concept is further demonstrated to enhance conventional radiotherapy by: i) using X-ray absorbing agents to locally concentrate radiation energy and ii) employing near-infrared-light-triggered photothermal therapy to overcome hypoxia-associated radioresistance.

Cell Death Conversion under Hypoxic Condition in Tumor Development and Therapy

Hypoxia, which is common during tumor progression, plays important roles in tumor biology. Failure in cell death in response to hypoxia contributes to progression and metastasis of tumors. On the one hand, the metabolic and oxidative stress following hypoxia could lead to cell death by triggering signal cascades, like LKB1/AMPK, PI3K/AKT/mTOR, and altering the levels of effective components, such as the Bcl-2 family, Atg and p62. On the other hand, hypoxia-induced autophagy can serve as a mechanism to turn over nutrients, so as to mitigate the adverse condition and then avoid cell death potentially. Due to the effective role of hypoxia, this review focuses on the crosstalk in cell death under hypoxia in tumor progression. Additionally, the illumination of cell death in hypoxia could shed light on the clinical applications of cell death targeted therapy.

Activatable Ferritin Nanocomplex for Real-Time Monitoring of Caspase-3 Activation during Photodynamic Therapy

One mechanism of photodynamic therapy (PDT) for the ablation of tumors is to induce apoptosis. Visualization of apoptosis during PDT in real-time is of great benefit for predicting and evaluating therapeutic outcomes. Herein, we engineered a highly stable and sensitive caspase-3 ferritin activatable probe (FABP/ZnPc) for simultaneous delivery of a photosensitizer (ZnPc) and real-time visualization of apoptosis during PDT. Upon near-infrared (NIR) light irradiation, ZnPc becomes active and initiates apoptosis, upon which the outer layer of the FABP/ZnPc is degraded by the apoptotic marker, caspase-3, to boost strong fluorescent signals, ultimately allowing real-time imaging of apoptosis. Our results demonstrate the utility of FABP/ZnPc as a tool for PDT and simultaneous imaging of caspase-3 activation in vitro and in vivo. Overall, the ability of FABP/ZnPc to image apoptosis during PDT will not only facilitate optimizing and personalizing the PDT strategy but is also important for understanding the mechanisms of PDT.