Self-Sensing Porphysomes for Fluorescence-Guided Photothermal Therapy

Porphysome Engineered With Specific Protein Binding Sites as a Multimodal Theranostic Nanocarrier for Targeted Protein Delivery

The immobilization of proteins on the surface of carriers is challenging due to the loss of protein structure and function in this process. Here, we report the development of the protein immobilization on the surface of the metallated-porphyrin complex in the porphysome nanocarrier. The conjugated Ni-porphyrin to fatty acid (as a tail) has been synthesized and independently placed at the depth of the bilayer center of Dipalmitoylphosphatidylcholine (DPPC) in which the Ni-porphyrin was at the polar region of the membrane and is thus superficial. This porphysome (DPPC: Ni-porphyrin, 4 : 1 mole ratio) was formed by supramolecular self-assembly with a diameter of 173±7 nm and zeta potential -8.5±3.4 mv, which exhibited no significant toxicity at the experimental concentrations and acceptable cellular uptake on MCF-7 cells. The physicochemical properties and specific protein binding sites of the firefly luciferase as a model protein into the porphysome (1 : 2 mole ratio) show the conjugation efficiency about 80 % and the conformation of protein was completely maintained. Furthermore, bioluminescence assay and SDS-PAGE confirmed the preservation of protein function. The stabilized platform of porphyrin-lipid structure can potentially improve the efficacy of protein functionality for a particular display, shifting porphysomes from a simple carrier to a therapeutic agent.

Photothermal therapy: a novel potential treatment for prostate cancer

Prostate cancer (PCa) is a leading cause of cancer-related death in men, and most PCa patients treated with androgen deprivation therapy will progress to metastatic castration-resistant prostate cancer (mCRPC) due to the lack of efficient treatment. Recently, lots of research indicated that photothermal therapy (PTT) was a promising alternative that provided an accurate and efficient prostate cancer therapy. A photothermic agent (PTA) is a basic component of PPT and is divided into organic and inorganic PTAs. Besides, the combination of PTT and other therapies, such as photodynamic therapy (PDT), immunotherapy (IT), chemotherapy (CT), etc., provides an more efficient strategy for PCa therapy. Here, we introduce basic information about PTT and summarize the PTT treatment strategies for prostate cancer. Based on recent works, we think the combination of PPT and other therapies provides a novel possibility for PCa, especially CRPC clinical treatment.

Self-Disassembling and Oxygen-Generating Porphyrin-Lipoprotein Nanoparticle for Targeted Glioblastoma Resection and Enhanced Photodynamic Therapy

The dismal prognosis for glioblastoma multiform (GBM) patients is primarily attributed to the highly invasive tumor residual that remained after surgical intervention. The development of precise intraoperative imaging and postoperative residual removal techniques will facilitate the gross total elimination of GBM. Here, a self-disassembling porphyrin lipoprotein-coated calcium peroxide nanoparticles (PLCNP) is developed to target GBM via macropinocytosis, allowing for fluorescence-guided surgery of GBM and improving photodynamic treatment (PDT) of GBM residual by alleviating hypoxia. By reducing self-quenching and enhancing lysosome escape efficiency, the incorporation of calcium peroxide (CaO2) cores in PLCNP amplifies the fluorescence intensity of porphyrin-lipid. Furthermore, the CaO2 core has diminished tumor hypoxia and improves the PDT efficacy of PLCNP, enabling low-dose PDT and reversing tumor progression induced by hypoxia aggravation following PDT. Taken together, this self-disassembling and oxygen-generating porphyrin-lipoprotein nanoparticle may serve as a promising all-in-one nanotheranostic platform for guiding precise GBM excision and empowering post-operative PDT, providing a clinically applicable strategy to combat GBM in a safe and effective manner.

Aptamers in cancer therapy: problems and new breakthroughs

Aptamers, a class of oligonucleotides that can bind with molecular targets with high affinity and specificity, have been widely applied in research fields including biosensing, imaging, diagnosing, and therapy of diseases. However, compared with the rapid development in the research fields, the clinical application of aptamers is progressing at a much slower speed, especially in the therapy of cancer. Obstructions including nuclease degradation, renal clearance, a complex selection process, and potential side effects have inhibited the clinical transformation of aptamer-conjugated drugs. To overcome these problems, taking certain measures to improve the biocompatibility and stability of aptamer-conjugated drugs in vivo is necessary. In this review, the obstructions mentioned above are thoroughly discussed and the methods to overcome these problems are introduced in detail. Furthermore, landmark research works and the most recent studies on aptamer-conjugated drugs for cancer therapy are also listed as examples, and the future directions of research for aptamer clinical transformation are discussed.

Porphyrin-lipid nanovesicles (Porphysomes) are effective photosensitizers for photodynamic therapy

Porphysomes (PS) are liposome-like nanoparticles comprising pyropheophorbide-conjugated phospholipids that have demonstrated potential as multimodal theranostic agents for applications that include phototherapies, targeted drug delivery and in vivo fluorescence, photoacoustic, magnetic resonance or positron emission imaging. Previous therapeutic applications focused primarily on photothermal therapy (PTT) and suggested that PSs require target-triggered activation for use as photodynamic therapy (PDT) sensitizers. Here, athymic nude mice bearing subcutaneous A549 human lung tumors were randomized into treatment and control groups: PS-PDT at various doses, PS-only and no treatment negative controls, as well as positive controls using the clinical photosensitizer Photofrin. Animals were followed for 30 days post-treatment. PS-PDT at all doses demonstrated a significant tumor ablative effect, with the greatest effect seen with 10 mg/kg PS at a drug-light interval of 24 h. By comparison, negative controls (PS-only, Photofrin-only, and no treatment) showed uncontrolled tumor growth. PDT with Photofrin at 5 mg/kg and PS at 10 mg/kg demonstrated similar tumor growth suppression and complete tumor response rates (15 vs. 25%, p = 0.52). Hence, porphysome nanoparticles are an effective PDT agent and have the additional advantages of multimodal diagnostic and therapeutic applications arising from their intrinsic structure. Porphysomes may also be the first single all-organic agent capable of concurrent PDT and PTT.

Self-Assembled Porphyrinoids: One-Component Nanostructured Photomedicines

Photodynamic therapy (PDT) is becoming a promising way to treat various kinds of cancers, with few side effects. Porphyrinoids are the most relevant photosensitizers (PS) in PDT, because they present high extinction coefficients, biocompatibility, and excellent photochemical behavior. To maximize therapeutic effects, polymer-PS conjugates, and PS-loaded nanoparticles have been developed, with insights in improving tumor delivery. However, some drawbacks such as non-biodegradability, multistep fabrication, and low reagent loadings limit their clinical application. A novel strategy, noted by some authors as the "one-for-all" approach, is emerging to circumvent the use of additional delivery agents. This approach relies on the self-assembly of amphiphilic PS to fabricate nanostructures with improved transport properties. In this review we focus on different rational designs of porphyrinoid PS to achieve some of the following attributes in nanoassembly: i) selective uptake, through the incorporation of recognizable biological vectors; ii) responsiveness to stimuli; iii) combination of imaging and therapeutic functions; and iv) multimodal therapy, including photothermal or chemotherapy abilities.

Weakly conjugated bacteriochlorin-bacteriochlorin dyad: Synthesis and photophysical properties

Dyads containing two near-infrared absorbing and emitting bacteriochlorins with distinct spectral properties have been prepared and characterized by absorption, emission, and transient-absorption spectroscopies. The dyads exhibit ultrafast ([Formula: see text]3 ps) energy transfer from the bacteriochlorin with the higher-energy S1 state to the bacteriochlorin emitting at the longer wavelength. The dyads exhibit strong fluorescence and relatively long excited state lifetimes ([Formula: see text]4 ns) in both non-polar and polar solvents, which indicates negligible photoinduced electron transfer between the two bacteriochlorins in the dyads. These dyads are thus attractive for the development of light-harvesting arrays and fluorophores for in vivo bioimaging.

Nano versus Molecular: Optical Imaging Approaches to Detect and Monitor Tumor Hypoxia

Hypoxia is a ubiquitous feature of solid tumors, which plays a key role in tumor angiogenesis and resistance development. Conventional hypoxia detection methods lack continuous functional detection and are generally less suitable for dynamic hypoxia measurement. Optical sensors hereby provide a unique opportunity to noninvasively image hypoxia with high spatiotemporal resolution and enable real-time detection. Therefore, these approaches can provide a valuable tool for personalized treatment planning against this hallmark of aggressive cancers. Many small optical molecular probes can enable analyte triggered response and their photophysical properties can also be fine-tuned through structural modification. On the other hand, optical nanoprobes can acquire unique intrinsic optical properties through nanoconfinement as well as enable simultaneous multimodal imaging and drug delivery. Furthermore, nanoprobes provide biological advantages such as improving bioavailability and systemic delivery of the sensor to enhance bioavailability. This review provides a comprehensive overview of the physical, chemical, and biological analytes for cancer hypoxia detection and focuses on discussing the latest nano- and molecular developments in various optical imaging approaches (fluorescence, phosphorescence, and photoacoustic) in vivo. Finally, this review concludes with a perspective toward the potentials of these optical imaging approaches in hypoxia detection and the challenges with molecular and nanotechnology design strategies.

Photo-Based Nanomedicines Using Polymeric Systems in the Field of Cancer Imaging and Therapy

The use of photo-based nanomedicine in imaging and therapy has grown rapidly. The property of light in converting its energy into different forms has been exploited in the fields of optical imaging (OI) and phototherapy (PT) for diagnostic and therapeutic applications. The development of nanotechnology offers numerous advantages to overcome the challenges of OI and PT. Accordingly, in this review, we shed light on common photosensitive agents (PSAs) used in OI and PT; these include fluorescent and bioluminescent PSAs for OI or PT agents for photodynamic therapy (PDT) and photothermal therapy (PTT). We also describe photo-based nanotechnology systems that can be used in photo-based diagnostics and therapies by using various polymeric systems.

Conjugated Photosensitizers for Imaging and PDT in Cancer Research

Early cancer detection and perfect understanding of the disease are imperative toward efficient treatments. It is straightforward that, for choosing a specific cancer treatment methodology, diagnostic agents undertake a critical role. Imaging is an extremely intriguing tool since it assumes a follow up to treatments to survey the accomplishment of the treatment and to recognize any conceivable repeating injuries. It also permits analysis of the disease, as well as to pursue treatment and monitor the possible changes that happen on the tumor. Likewise, it allows screening the adequacy of treatment and visualizing the state of the tumor. Additionally, when the treatment is finished, observing the patient is imperative to evaluate the treatment methodology and adjust the treatment if necessary. The goal of this review is to present an overview of conjugated photosensitizers for imaging and therapy.

Current trends in pyrrole and porphyrin-derived nanoscale materials for biomedical applications

This article is written to provide an up-to-date review of pyrrole-based biomedical materials. Porphyrins and other tetrapyrrolic molecules possess unique magnetic, optical and other photophysical properties that make them useful for bioimaging and therapy. This review touches briefly on some of the synthetic strategies to obtain porphyrin- and tetrapyrrole-based nanoparticles, as well as the variety of applications in which crosslinked, self-assembled, porphyrin-coated and other nanoparticles are utilized. We explore examples of these nanoparticles' applications in photothermal therapy, drug delivery, photodynamic therapy, stimuli response, fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, computed tomography and positron emission tomography. We anticipate that this review will provide a comprehensive summary of pyrrole-derived nanoparticles and provide a guideline for their further development.

Facile Preparation of Phthalocyanine-Based Nanodots for Photoacoustic Imaging and Photothermal Cancer Therapy In Vivo

The development of near-infrared (NIR)-absorbing nanoagents for personalized multifunctional phototheranostics has attracted considerable attention in the past decade. Recently, the organic nanomaterials with good biosafety are considered as promising phototheranostic agents, while their facile synthesis remains challenging. Inspired by the preparation of carbon nanodots, we fabricate the NIR-absorbing phthalocyanine-based nanodots (ZnPc-NDs) using a facile method for multifunctional phototheranostics. The significant aggregation of phthalocyanines in nanodots induces a complete fluorescence quenching, which affords a high photothermal conversion efficiency (η = 45.7%). The ZnPc-NDs disperse very well in water media with an average diameter around 80 nm. Further conjugation of biotin on the surface of ZnPc-NDs affords tumor-targeting phthalocyanine nanodots (ZnPc-BT). The ZnPc-BT are demonstrated with favorable biocompatibility, intense photoacoustic signals, high tumor accumulation, and effective tumor suppression in vivo. This Article provides a new insight for further developing nanomedicines with imaging and therapeutic functions to treat cancers precisely and effectively.

Facile synthesis of hollow mesoporous nickel sulfide nanoparticles for highly efficient combinatorial photothermal-chemotherapy of cancer

Traditional techniques for the synthesis of nickel sulfide (NiS) nanoparticles (NPs) always present drawbacks of morphological irregularity, non-porous structure and poor long-term stability, which are extremely unfavorable for establishing effective therapeutic agents. Here, a category of hollow mesoporous NiS (hm-NiS) NPs with uniform spherical structure and good aqueous dispersity were innovatively developed based on a modified solvothermal reaction technique. Upon the successful synthesis of hm-NiS NPs, dopamine was seeded and in situ polymerized into polydopamine (PDA) on the NP surface, followed by functionalization with thiol-polyethylene glycol (SH-PEG) and encapsulation of the chemotherapeutic drug, doxorubicin (DOX), to form hm-NiS@PDA/PEG/DOX (NiPPD) NPs. The resultant NiPPD NPs exhibited a decent photothermal response and stability, attributed to the optical absorption of the hm-NiS nanocore and PDA layer in the near-infrared (NIR) region. Furthermore, stimulus-responsive drug release was achieved under both acidic pH conditions and NIR laser irradiation, owing to the protonation of -NH₂ groups in the DOX molecules and local thermal shock, respectively. Lastly, a strong combinatorial photothermal-chemotherapeutic effect was demonstrated for tumor suppression with minimal systemic toxicity in vivo. Collectively, this state-of-the-art paradigm may provide useful insights to deepen the application of hm-NiS NPs for disease management and precision medicine.

Extraspecific Manifestation of Nanoheater's Position Effect on Distinctive Cellular Photothermal Responses

Subcellular localization of nanoparticles plays critical roles in precision medicine that can facilitate an in-depth understanding of disease etiology and achieve accurate theranostic regulation via responding to the aiding stimuli. The photothermal effect is an extensively employed strategy that converts light into heat stimulation to induce localized disease ablation. Despite diverse manipulations that have been investigated in photothermal nanotheranostics, influences of nanoheaters' subcellular distribution and their molecular mechanism on cellular heat response remain elusive. Herein, we disclose the biological basis of distinguishable thermal effects at subcellular resolution by localizing photothermal upconversion nanoparticles into specific locations of cell compartments. Upon 808 nm light excitation, the lysosomal cellular uptake initialized by poly(ethylenimine)-modified nanoheaters promoted mitochondria apoptosis through the activation of Bid protein, whereas the cell surface nanoheaters anchored via metabolic glycol biosynthesis triggered necrosis by direct perturbation of the membrane structure. Intriguingly, these two different thermolyses revealed similar levels of heat shock protein expression in live cells. This study stipulates insights underlying the different subcellular positions of nanoparticles for the selective thermal response, which provides valuable perspectives on optimal precision nanomedicine.

Recent advances in self-actuation and self-sensing materials: State of the art and future perspectives

The contradiction between human's strong demand of fossil fuels and their limited reserves becomes increasingly severe. Without external power input, intelligent materials responding sharply and reversibly to various external stimuli are the topic of intense research these years, especially the self-actuation and self-sensing materials. The promising family of these materials will play a significant role in energy-saving, low-cost and environment-friendly intelligent systems in the future. This review summarizes the latest advances in self-actuation and self-sensing materials. The synthetic strategies, morphologies and performance of these materials are introduced, as well as their applications in energy harvest, self-powering sensors, wearable devices, etc. Finally, tentative conclusions and assessments regarding the opportunities and challenges for the future development of these materials are presented.

Recent advances in porphyrin-based nanocomposites for effective targeted imaging and therapy

Porphyrins are organic compounds that continue to attract much theoretical interest, and have been called the "pigments of life". They have a wide role in photodynamic and sonodynamic therapy, along with uses in magnetic resonance, fluorescence and photoacoustic imaging. There is a vast range of porphyrins that have been isolated or designed, but few of them have real clinical applications. Due to the hydrophobic properties of porphyrins, and their tendency to aggregate by stacking of the planar molecules they are difficult to work with in aqueous media. Therefore encapsulating them in nanoparticles (NPs) or attachment to various delivery vehicles have been used to improve delivery characteristics. Porphyrins can be used in a composite designed material with properties that allow specific targeting, immune tolerance, extended tissue lifetime and improved hydrophilicity. Drug delivery, healing and repairing of damaged organs, and cancer theranostics are some of the medical uses of porphyrin-based nanocomposites covered in this review.

The Dark Side: Photosensitizer Prodrugs

Photodynamic therapy (PDT) and photodiagnosis (PD) are essential approaches in the field of biophotonics. Ideally, both modalities require the selective sensitization of the targeted disease in order to avoid undesired phenomena such as the destruction of healthy tissue, skin photosensitization, or mistaken diagnosis. To a large extent, the occurrence of these incidents can be attributed to “background” accumulation in non-target tissue. Therefore, an ideal photoactive compound should be optically silent in the absence of disease, but bright in its presence. Such requirements can be fulfilled using innovative prodrug strategies targeting disease-associated alterations. Here we will summarize the elaboration, characterization, and evaluation of approaches using polymeric photosensitizer prodrugs, nanoparticles, micelles, and porphysomes. Finally, we will discuss the use of 5-aminolevulinc acid and its derivatives that are selectively transformed in neoplastic cells into photoactive protoporphyrin IX.

Porphyrin-Based Nanomedicines for Cancer Treatment

As unique molecules with both therapeutic and diagnostic properties, porphyrin derivatives have been extensively employed for cancer treatment. Porphyrins not only show powerful phototherapeutic effects (photodynamic and photothermal therapies), but also exhibit excellent imaging capacities, such as near-infrared fluorescent imaging (NIRFI), magnetic resonance imaging (MRI), photoacoustic imaging (PAI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT). In order to take advantage of their robust phototherapeutic effects and excellent imaging capacities, porphyrins can be used to create nanomedicines with effective therapeutic and precise diagnostic properties for cancer treatment. In this Review, we summarize porphyrin-based nanomedicines which have been developed recently, including porphyrin-based liposomes, micelles, polymeric nanoparticles, peptide nanoparticles, and small-molecule nanoassemblies, and their applications on cancer therapy and diagnosis. The outlook and limitation of porphyrin-based nanomedicines are also reviewed.

Tailoring Porphyrin Conjugation for Nanoassembly-Driven Phototheranostic Properties

Lipoprotein mimetic nanostructures, which consist of an amphiphilic lipid shell, a hydrophobic core, and an apolipoprotein mimetic peptide, serve as a versatile platform for the design of drug delivery vehicles as well as the investigation of supramolecular assemblies. Porphyrin incorporation into biomimetic lipoproteins allows one to take advantage of the inherent multimodal photophysical properties of porphyrins, yielding various fluorescence, photoacoustic, and photodynamic agents. To facilitate their incorporation into a lipoprotein structure, porphyrins have been conjugated through a variety of strategies. However, the effects of the conjugate structure on the associated nanoparticle's phototherapeutic properties warrants further investigation. Herein, we systematically investigated the effects of two widely utilized porphyrin conjugates, oleylamide and lipid, on biophotonic properties of their resultant porphyrin-lipoprotein nanoparticles in vitro and in vivo. Specifically, we demonstrated that incorporation of the porphyrin moiety as an oleylamide conjugate leads to a highly stable J-aggregate with strong photoacoustic contrast, while incorporation as an ampiphilic lipid moiety into the lipid shell yields an effective fluorescent and photodynamic agent. The current study proposes a rational design strategy for next-generation lipoprotein-based phototheranostic agents, for which nanoassembly-driven biophotonic and therapeutic properties can be tailored through the specific selection of porphyrin conjugate structures.

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.

Applications of Light-Responsive Systems for Cancer Theranostics

Achieving controlled and targeted delivery of chemotherapeutic drugs and other therapeutic agents to tumor sites is challenging. Among many stimulus strategies, light as a mode of action shows various advantages such as high spatiotemporal selectivity, minimal invasiveness and easy operation. Thus, drug delivery systems (DDSs) have been designed with the incorporation of various functionalities responsive to light as an exogenous stimulus. Early development has focused on guiding chemotherapeutic drugs to designated location, followed by the utilization of UV irradiation for controlled drug release. Because of the disadvantages of UV light such as phototoxicity and limited tissue penetration depth, scientists have moved the research focus onto developing nanoparticle systems responsive to light in the visible region (400-700 nm), aiming to reduce the phototoxicity. In order to enhance the tissue penetration depth, near-infrared light triggered DDSs become increasingly important. In addition, light-based advanced systems for fluorescent and photoacoustic imaging, as well as photodynamic and photothermal therapy have also been reported. Herein, we highlight some of recent developments by applying light-responsive systems in cancer theranostics, including light activated drug release, photodynamic and photothermal therapy, and bioimaging techniques such as fluorescent and photoacoustic imaging. Future prospect of light-mediated cancer treatment is discussed at the end of the review. This Spotlights on Applications article aims to provide up-to-date information about the rapidly developing field of light-based cancer theranostics.

Turning double hydrophilic into amphiphilic: IR825-conjugated polymeric nanomicelles for near-infrared fluorescence imaging-guided photothermal cancer therapy

Developing biocompatible and photodegradable photothermal agents (PTAs) holds great promise for potential clinical applications in photothermal cancer therapy. Herein, a new PTA was innovatively constructed by conjugating the hydrophobic near-infrared (NIR) heptamethine cyanine molecule IR825-NH₂ with a double hydrophilic block copolymer methoxypoly(ethylene glycol)_5k-block-poly(l-aspartic acid sodium salt)₁₀ (abbreviated as PEG-PLD) via amine-carboxyl reaction. The as-designed PEG-PLD(IR825) was amphiphilic and could self-assemble into polymeric nanomicelles in aqueous solutions. Benefiting from the chemical conjugation strategy, PEG-PLD(IR825) nanomicelles realized a considerably high drug loading rate (∼21.0%) and substantially avoided the premature release of IR825 during systemic circulation. Confocal imaging revealed that the nanomicelles mainly located at mitochondria and endoplasmic reticulum after cellular internalization. In vitro photothermal therapy demonstrated the excellent cancer killing efficiency of PEG-PLD(IR825) nanomicelles due to their high light-to-heat conversion efficiency upon NIR laser irradiation. In addition, PEG-PLD(IR825) nanomicelles showed polarity-sensitive fluorescence at ∼610 nm (under 552 nm excitation) and 830 nm (under 780 nm excitation), which was especially useful for both in vitro visible fluorescence imaging and in vivo near-infrared fluorescence imaging-guided photothermal therapy (PTT). At the in vivo level, PEG-PLD(IR825) nanomicelles exhibited an excellent tumor-homing ability and a long retention time in tumor tissues as evidenced by the in vivo fluorescence imaging results. The desirable properties of PEG-PLD(IR825) nanomicelles ensured their effective tumor ablation during PTT treatment. More importantly, the PEG-PLD(IR825) nanomicelles underwent degradation after laser irradiation, which ensured their post-treatment biosafety. Therefore, the nanomicelles are promising to serve as an efficient and safe PTA for imaging-guided photothermal cancer therapy.

Förster Resonance Energy Transfer-Based Dual-Modal Theranostic Nanoprobe for In Situ Visualization of Cancer Photothermal Therapy

The visualization of the treatment process in situ could facilitate to accurately monitor cancer photothermal therapy (PTT), and dramatically decrease the risk of thermal damage to normal cells and tissues, which represents a major challenge for cancer precision therapy. Herein, we prepare theranostic nanoprobes (NPs) for Förster resonance energy transfer (FRET)-based dual-modal imaging-guided cancer PTT, and clear visualization of the therapeutic process. The FRET-based theranostic NPs exhibit high FRET efficiency (88.2%), good colloidal stability, and tumor-targeting ability. Tumor tissue and surrounding blood vessels are visualized clearly by FRET-based NIR fluorescence imaging with a high signal-to-background ratio (14.5) and photoacoustic imaging with an excellent resolution at 24 h post injection of NPs. Under the guidance of dual-modal imaging, the NPs-induced photothermal effect selectively destructs cancer cells, simultaneously decreasing the FRET efficiency and leading to fluorescence and photoacoustic signal changes. The sensitive self-feedback process enables the in situ visualization of therapeutic process and precision guidance of in vivo cancer PTT. A high therapeutic efficacy and minimum side effects are achieved in C6 tumor-bearing nude mice, holding great promise for precision therapy and cancer theranostics.

Ultrasmall-in-Nano Approach: Enabling the Translation of Metal Nanomaterials to Clinics

Currently, nanomaterials are of widespread use in daily commercial products. However, the most-promising and potentially impacting application is in the medical field. In particular, nanosized noble metals hold the promise of shifting the current medical paradigms for the detection and therapy of neoplasms thanks to the: (i) localized surface plasmon resonances (LSPRs), (ii) high electron density, and (iii) suitability for straightforward development of all-in-one nanoplatforms. Nonetheless, there is still no clinically approved noble metal nanomaterial for cancer therapy and diagnostics. The clinical translation of noble metal nanoparticles (NPs) is mainly prevented by the issue of persistence in organism after the medical action. Such persistence increases the likelihood of toxicity and the interference with common medical diagnoses. Size reduction to ultrasmall nanoparticles (USNPs) is a suitable approach to promoting metal excretion by the renal pathway. However, most of the functionalities of NPs are lost or severely altered in USNPs, jeopardizing clinical applications. A ground-breaking advance to jointly combine the appealing behaviors of NPs with metal excretion relies on the ultrasmall-in-nano approach for the design of all-in-one degradable nanoplatforms composed of USNPs. Such nanoarchitectures might lead to the delivery of a novel paradigm for nanotechnology, enabling the translation of noble metal nanomaterials to clinics to treat carcinomas in a less-invasive and more-efficient manner. This Review covers the recent progresses related to this exciting approach. The most-significant nanoarchitectures designed with the ultrasmall-in-nano approach are discussed, and perspectives on these nanoarchitectures are provided.

BODIPY-Bacteriochlorin Energy Transfer Arrays: Toward Near-IR Emitters with Broadly Tunable, Multiple Absorption Bands

A series of energy transfer arrays, comprising a near-IR absorbing and emitting bacteriochlorin, and BODIPY derivatives with different absorption bands in the visible region (503-668 nm) have been synthesized. Absorption band of BODIPY was tuned by installation of 0, 1, or 2 styryl substituents [2-(2,4,6-trimethoxyphenyl)ethenyl], which leads to derivatives with absorption maxima at 503, 587, and 668 nm, respectively. Efficient energy transfer (>0.90) is observed for each dyad, which is manifested by nearly exclusive emission from bacteriochlorin moiety upon BODIPY excitation. Fluorescence quantum yield of each dyad in nonpolar solvent (toluene) is comparable with that observed for corresponding bacteriochlorin monomer, and is significantly reduced in solvent of high dielectric constants (DMF), most likely by photoinduced electron transfer. Given the availability of diverse BODIPY derivatives, with absorption between 500-700 nm, BODIPY-bacteriochlorin arrays should allow for construction of near-IR emitting agents with multiple and broadly tunable absorption bands. Solvent-dielectric constant dependence of Φf in dyads gives an opportunity to construct environmentally sensitive fluorophores and probes.

Activatable fluorescence: From small molecule to nanoparticle

Molecular imaging has emerged as an indispensable technology in the development and application of drug delivery systems. Targeted imaging agents report the presence of biomolecules, including therapeutic targets and disease biomarkers, while the biological behaviour of labelled delivery systems can be non-invasively assessed in real time. As an imaging modality, fluorescence offers additional signal specificity and dynamic information due to the inherent responsivity of fluorescence agents to interactions with other optical species and with their environment. Harnessing this responsivity is the basis of activatable fluorescence imaging, where interactions between an engineered fluorescence agent and its biological target induce a fluorogenic response. Small molecule activatable agents are frequently derivatives of common fluorophores designed to chemically react with their target. Macromolecular scale agents are useful for imaging proteins and nucleic acids, although their biological delivery can be difficult. Nanoscale activatable agents combine the responsivity of fluorophores with the unique optical and physical properties of nanomaterials. The molecular imaging application and overall complexity of biological target dictate the most advantageous fluorescence agent size scale and activation strategy.

Robust Colloidal Nanoparticles of Pyrrolopyrrole Cyanine J-Aggregates with Bright Near-Infrared Fluorescence in Aqueous Media: From Spectral Tailoring to Bioimaging Applications

Colloidal nanoparticles (NPs) containing near-infrared-fluorescent J-aggregates (JAGGs) of pyrrolopyrrole cyanines (PPcys) stabilized by amphiphilic block co-polymers were prepared in aqueous medium. JAGG formation can be tuned by means of the chemical structure of PPcys, the concentration of chromophores inside the polymeric NPs, and ultrasonication. The JAGG NPs exhibit a narrow emission band at 773 nm, a fluorescence quantum yield comparable to that of indocyanine green, and significantly enhanced photostability, which is ideal for long-term bioimaging.

Advanced Functional Nanomaterials for Theranostics

Nanoscale materials have been explored extensively as agents for therapeutic and diagnostic (i.e. theranostic) applications. Research efforts have shifted from exploring new materials in vitro to designing materials that function in more relevant animal disease models, thereby increasing potential for clinical translation. Current interests include non-invasive imaging of diseases, biomarkers and targeted delivery of therapeutic drugs. Here, we discuss some general design considerations of advanced theranostic materials and challenges of their use, from both diagnostic and therapeutic perspectives. Common classes of nanoscale biomaterials, including magnetic nanoparticles, quantum dots, upconversion nanoparticles, mesoporous silica nanoparticles, carbon-based nanoparticles and organic dye-based nanoparticles, have demonstrated potential for both diagnosis and therapy. Variations such as size control and surface modifications can modulate biocompatibility and interactions with target tissues. The needs for improved disease detection and enhanced chemotherapeutic treatments, together with realistic considerations for clinically translatable nanomaterials will be key driving factors for theranostic agent research in the near future.

Targeted Nanomaterials for Phototherapy

Phototherapies involve the irradiation of target tissues with light. To further enhance selectivity and potency, numerous molecularly targeted photosensitizers and photoactive nanoparticles have been developed. Active targeting typically involves harnessing the affinity between a ligand and a cell surface receptor for improved accumulation in the targeted tissue. Targeting ligands including peptides, proteins, aptamers and small molecules have been explored for phototherapy. In this review, recent examples of targeted nanomaterials used in phototherapy are summarized.

A Porphyrin-Based Conjugated Polymer for Highly Efficient In Vitro and In Vivo Photothermal Therapy

Conjugated polymers have been increasingly studied for photothermal therapy (PTT) because of their merits including large absorption coefficient, facile tuning of exciton energy dissipation through nonradiative decay, and good therapeutic efficacy. The high photothermal conversion efficiency (PCE) is the key to realize efficient PTT. Herein, a donor-acceptor (D-A) structured porphyrin-containing conjugated polymer (PorCP) is reported for efficient PTT in vitro and in vivo. The D-A structure introduces intramolecular charge transfer along the backbone, resulting in redshifted Q band, broadened absorption, and increased extinction coefficient as compared to the state-of-art porphyrin-based photothermal reagent. Through nanoencapsulation, the dense packing of a large number of PorCP molecules in a single nanoparticle (NP) leads to favorable nonradiative decay, good photostability, and high extinction coefficient of 4.23 × 10⁴ m^-1 cm^-1 at 800 nm based on porphyrin molar concentration and the highest PCE of 63.8% among conjugated polymer NPs. With the aid of coloaded fluorescent conjugated polymer, the cellular uptake and distribution of the PorCP in vitro can be clearly visualized, which also shows effective photothermal tumor ablation in vitro and in vivo. This research indicates a new design route of conjugated polymer-based photothermal therapeutic materials for potential personalized theranostic nanomedicine.

Multifunctional Nanoparticles Self-Assembled from Small Organic Building Blocks for Biomedicine

Supramolecular self-assembly shows significant potential to construct responsive materials. By tailoring the structural parameters of organic building blocks, nanosystems can be fabricated, whose performance in catalysis, energy storage and conversion, and biomedicine has been explored. Since small organic building blocks are structurally simple, easily modified, and reproducible, they are frequently employed in supramolecular self-assembly and materials science. The dynamic and adaptive nature of self-assembled nanoarchitectures affords an enhanced sensitivity to the changes in environmental conditions, favoring their applications in controllable drug release and bioimaging. Here, recent significant research advancements of small-organic-molecule self-assembled nanoarchitectures toward biomedical applications are highlighted. Functionalized assemblies, mainly including vesicles, nanoparticles, and micelles are categorized according to their topological morphologies and functions. These nanoarchitectures with different topologies possess distinguishing advantages in biological applications, well incarnating the structure-property relationship. By presenting some important discoveries, three domains of these nanoarchitectures in biomedical research are covered, including biosensors, bioimaging, and controlled release/therapy. The strategies regarding how to design and characterize organic assemblies to exhibit biomedical applications are also discussed. Up-to-date research developments in the field are provided and research challenges to be overcome in future studies are revealed.

Rethinking translational nanomedicine: insights from the 'bottom-up' design of the Porphysome for guiding the clinical development of imageable nanomaterials

Progress in therapeutics and biotechnologies leveraging new insights in our understanding of cancer biology and progression have had an underwhelming clinical significance thus far. A key challenge arising from the creation of nanomedicines consolidating multiple desirable functionalities into a 'all-in-one' platform is that the layering of functionalities into a single agent introduces novel complexities that significantly impede clinical translation. An alternative design approach seeks to exploit intrinsically multi-functional building block to assemble nanomedicines from the bottom-up, yielding agents with a multiplicity of radiologic, pharmacologic, and therapeutic properties derived from a single constituent. Herein are highlighted recent developments in the formulation, multi-modal imaging, and targeting of an exemplary 'one-for-all' nanomaterial-the Pyropheophorbide Porphysome-treated from a hitherto unexplored clinical design and development perspective.

Integrity of lipid nanocarriers in bloodstream and tumor quantified by near-infrared ratiometric FRET imaging in living mice

Lipid nanocarriers are considered as promising candidates for drug delivery and cancer targeting because of their low toxicity, biodegradability and capacity to encapsulate drugs and/or contrasting agents. However, their biomedical applications are currently limited because of a poor understanding of their integrity in vivo. To address this problem, we report on fluorescent nano-emulsion droplets of 100 nm size encapsulating lipophilic near-infrared cyanine 5.5 and 7.5 dyes with a help of bulky hydrophobic counterion tetraphenylborate. Excellent brightness and efficient Förster Resonance Energy Transfer (FRET) inside lipid NCs enabled for the first time quantitative fluorescence ratiometric imaging of NCs integrity directly in the blood circulation, liver and tumor xenografts of living mice using a whole-animal imaging set-up. This unique methodology revealed that the integrity of our FRET NCs in the blood circulation of healthy mice is preserved at 93% at 6 h of post-administration, while it drops to 66% in the liver (half-life is 8.2 h). Moreover, these NCs show fast and efficient accumulation in tumors, where they enter in nearly intact form (77% integrity at 2 h) before losing their integrity to 40% at 6 h (half-life is 4.4 h). Thus, we propose a simple and robust methodology based on ratiometric FRET imaging in vivo to evaluate quantitatively nanocarrier integrity in small animals. We also demonstrate that nano-emulsion droplets are remarkably stable nano-objects that remain nearly intact in the blood circulation and release their content mainly after entering tumors.