Structure-inherent near-infrared bilayer nanovesicles for use as photoacoustic image-guided chemo-thermotherapy

Review on ultrasound-guided photoacoustic imaging for complementary analyses of biological systems in vivo

Photoacoustic imaging has been developed as a new biomedical molecular imaging modality. Due to its similarity to conventional ultrasound imaging in terms of signal detection and image generation, dual-modal photoacoustic and ultrasound imaging has been applied to visualize physiological and morphological information in biological systems in vivo. By complementing each other, dual-modal photoacoustic and ultrasound imaging showed synergistic advances in photoacoustic imaging with the guidance of ultrasound images. In this review, we introduce our recent progresses in dual-modal photoacoustic and ultrasound imaging systems at various scales of study, from preclinical small animals to clinical humans. A summary of the works reveals various strategies for combining the structural information of ultrasound images with the molecular information of photoacoustic images.

Cellular Nanodiscs Made from Bacterial Outer Membrane as a Platform for Antibacterial Vaccination

Vaccination has become an increasingly attractive strategy for protecting against antibiotic-resistant infections. Nanovaccines based on the outer membrane from Gram-negative bacteria are appealing due to their multiantigenic nature and inherent immunogenicity. Here, we develop cellular nanodiscs made of bacterial outer membrane (OM-NDs), as a platform for antibacterial vaccination. Using Pseudomonas aeruginosa as a model pathogen, the resulting OM-NDs can effectively interact with antigen-presenting cells, exhibiting accelerated uptake and an improved capacity for immune stimulation. With their small size, the OM-NDs are also capable of efficiently transporting to the lymph nodes after in vivo administration. As a result, the nanovaccine is effective at eliciting potent humoral and cellular immune responses against P. aeruginosa. In a murine model of pneumonia, immunization with OM-NDs confers strong protection against subsequent lung infection, resulting in improved survival, reduced bacterial loads, and alleviation of immune overactivation. Overall, this report illustrates the advantages of cellular nanodiscs, which can be readily generalized to other pathogens and may be applied toward other biomedical applications.

Biomedical Photoacoustic Imaging for Molecular Detection and Disease Diagnosis: "Always-On" and "Turn-On" Probes

Photoacoustic (PA) imaging is a nonionizing, noninvasive imaging technique that combines optical and ultrasonic imaging modalities to provide images with excellent contrast, spatial resolution, and penetration depth. Exogenous PA contrast agents are created to increase the sensitivity and specificity of PA imaging and to offer diagnostic information for illnesses. The existing PA contrast agents are categorized into two groups in this review: "always-on" and "turn-on," based on their ability to be triggered by target molecules. The present state of these probes, their merits and limitations, and their future development, is explored.

Listening to drug delivery and responses via photoacoustic imaging

Administrating pharmaceutic agents efficiently to achieve the therapeutic effect is the aim of all drug delivery techniques. Recent drug delivery systems aim to deliver high doses of drugs to disease sites accurately while maximizing therapeutic effects and minimizing potential side effects. Key approaches apply image guidance techniques for the quantification of drug biodistribution and pharmacokinetic parameters during drug delivery. This review highlights recent research on image-guided drug delivery systems based on photoacoustic imaging, which has been attracting attention for its non-invasiveness, non-ionizing radiation, and real-time imaging functions. Photoacoustic imaging based on the photothermal conversion efficiency of agents can be easily combined with various phototherapeutics, making them highly suitable for drug delivery therapy platforms. Here, we summarize and compare the characteristics of various types of photoacoustic imaging systems, focus on contrast-enhanced photoacoustic imaging and controlled release of therapeutics in drug delivery systems for synergistic therapies.

Review on Optical Imaging Techniques for Multispectral Analysis of Nanomaterials

Biomedical imaging is an essential tool for investigating biological responses in vivo. Among the several imaging techniques, optical imaging systems with multispectral analysis of nanoparticles have been widely investigated due to their ability to distinguish the substances in biological tissues in vivo. This review article focus on multispectral optical imaging techniques that can provide molecular functional information. We summarize the basic principle of the spectral unmixing technique that enables the delineation of optical chromophores. Then, we explore the principle, typical system configuration, and biomedical applications of the representative optical imaging techniques, which are fluorescence imaging, two-photon microscopy, and photoacoustic imaging. The results in the recent studies show the great potential of the multispectral analysis techniques for monitoring responses of biological systems in vivo.

New contrast agents for photoacoustic imaging and theranostics: Recent 5-year overview on phthalocyanine/naphthalocyanine-based nanoparticles

The phthalocyanine (Pc) and naphthalocyanine (Nc) nanoagents have drawn much attention as contrast agents for photoacoustic (PA) imaging due to their large extinction coefficients and long absorption wavelengths in the near-infrared region. Many investigations have been conducted to enhance Pc/Ncs' photophysical properties and address their poor solubility in an aqueous solution. Many diverse strategies have been adopted, including centric metal chelation, structure modification, and peripheral substitution. This review highlights recent advances on Pc/Nc-based PA agents and their extended use for multiplexed biomedical imaging, multimodal diagnostic imaging, and image-guided phototherapy.

Targeting the tumor microenvironment with amphiphilic near-infrared cyanine nanoparticles for potentiated photothermal immunotherapy

Despite the potential of photothermal therapy (PTT) for cancer treatments, PTT alone has limitations in treating metastatic tumors and preventing tumor recurrence, highlighting the need to combine PTT with immunotherapy. This study reports tumor microenvironment (TME)-targeting, near-infrared (NIR) dye derivative-based nanomedicine for effective combined PTT-immunotherapy. Amphiphilic NIR dye cyanine derivatives are used not only for constructing the nanoparticle mass, but also for creating a stable complex with CpG adjuvant; a peptide specific to fibronectin extra domain B (APT_EDB) is also introduced as a TME-targeting ligand, yielding the TME-targeting nanomedicine, APT_EDB-cyNP@CpG. APT_EDB-cyNP@CpG shows cancer-targeting ability in EDB-overexpressing CT26 colon tumor-bearing mice. When combined with laser irradiation, it induces immunogenic cell death (ICD) and subsequently leads to significant increase in CD8⁺ T cell population in the tumor, resulting in greater antitumor therapeutic efficacy than does cyNP@CpG lacking the TME-targeting ligand. Moreover, the combination of APT_EDB-cyNP@CpG-based PTT and an immune checkpoint blockade (ICB) antibody leads to remarkable antitumor efficacy against the laser-irradiated primary tumor as well as distant tumor through potentiation of systemic cancer cell-specific T cell immunity. Furthermore, the PTT-immunotherapy combination regimen is highly effective in inhibiting tumor recurrence and metastasis.

Cyanine conjugates in cancer theranostics

Cyanine is a meritorious fluorogenic core for the construction of fluorescent probes and its phototherapeutic potential has been enthusiastically explored as well. Alternatively, the covalent conjugation of cyanine with other potent therapeutic agents not only boosts its therapeutic efficacy but also broadens its therapeutic modality. Herein, we summarize miscellaneous cyanine-therapeutic agent conjugates in cancer theranostics from literature published between 2014 and 2020. The application scenarios of such theranostic cyanine conjugates covered common cancer therapeutic modalities, including chemotherapy, phototherapy and targeted therapy. Besides, cyanine conjugates that serve as nanocarriers for drug delivery are introduced as well. In an additional section, we analyze the potential of these conjugates for clinical translation. Overall, this review is aimed to stimulate research interest in exploring unattempted therapeutic agents and novel conjugation strategies and hopefully, accelerate clinical translation in this field.

Recent Trends in Photoacoustic Imaging Techniques for 2D Nanomaterial-Based Phototherapy

A variety of 2D materials have been developed for therapeutic biomedical studies. Because of their excellent physicochemical properties, 2D materials can be used as carriers for delivering therapeutic agents into a lesion, leading to phototherapy. Various optical imaging techniques have been used for the monitoring of the treatment process. Among these, photoacoustic imaging has unique advantages including relatively deep imaging depth and large field of view with high spatial resolution. In this review article, we summarize the types of photoacoustic imaging systems used for phototherapy monitoring, then we explore contrast-enhanced photoacoustic images using 2D materials. Finally, photoacoustic image-guided phototherapies are discussed. We conclude that 2D material-based phototherapy can be efficiently monitored by photoacoustic imaging techniques.

Folic Acid-Modified Erythrocyte Membrane Loading Dual Drug for Targeted and Chemo-Photothermal Synergistic Cancer Therapy

To overcome the challenges of systemic toxicity and weak tumor selectivity caused by traditional antitumor drugs, numerous nanocarrier systems have been developed in recent decades, and their therapeutic effect has been improved to varying degrees. However, because of the drug resistance effect and metastasis involved in tumor recurrence, a single chemotherapy can no longer satisfy the diversified treatment needs. Recently, the application of chemotherapy in combination with thermotherapy as a synergistic approach has been proven to be more effective, and it provides a new strategy for cancer therapy. In this work, by utilizing the unique properties of erythrocytes, a surface-modified erythrocyte membrane was constructed as a novel nanocarrier system (DOX and ICG-PLGA@RBC nanoparticles, DIRNPs for short) for the simultaneous transportation of chemotherapeutic drugs (doxorubicin, DOX) and photothermal agents (indocyanine green, ICG) to achieve the effects of long-term circulation, active tumor targeting, and triggered drug release. The results indicated that DIRNPs have a nanoscale particle size of 158.4 nm with a narrow size distribution and a negative surface charge of -5.79 mV. No particle aggregation or remarkable drug leakage was observed during the 30 day storage test, and because of the excellent photothermal conversion ability of ICG, the local temperature of DIRNPs could dramatically increase from 33.7 to 49.8 °C in 10 min under near-infrared (NIR) laser irradiation. The in vitro drug dissolution data demonstrated that the DOX release from the DIRNPs was pH-dependent and NIR-triggered. Folic acid modifications of the erythrocyte membrane effectively facilitated the intracellular uptake of DIRNPs by HepG2 cells and, as a result, it significantly inhibited tumor cell growth, promoted reactive oxygen species levels, induced cell apoptosis, and restricted cell recovery and migration. In vivo pharmacokinetics and biodistribution studies indicated that the DIRNPs prolonged the half-life of DOX from 6.03 to 17.6 h and remarkably reduced the DOX level in the heart to avoid drug-related cardiotoxicity. More importantly, the DIRNPs exerted excellent in vivo antitumor efficacy against H22 tumors with superior safety. In conclusion, utilizing the advantageous properties of erythrocytes to construct a tumor-targeted biomimetic nanocarrier for codelivery of chemotherapeutics and photothermal agents to produce synergistic effects is considered an effective method for cancer therapy.

Stimuli-responsive phospholipid-drug conjugates (PDCs)-based nanovesicles for drug delivery and theranostics

Liposomes represent one of the most successful nano-drug delivery systems among enormous nano-carriers. Although great progress has been made in conventional liposomes, the emerging shortcomings still impair the therapeutic index. The proposal of stimuli-responsive phospholipid-drug conjugates (PDCs)-based nanovesicles solves the challenges that conventional liposomes are faced with, showing great potential for cancer diagnosis and therapy. Herein, we intend to overview the current progress and unique advantages of stimuli-responsive PDCs-based nanovesicles. First, the challenges of conventional liposomes and the development of PDCs-based nanovesicles are summarized. Next, the stimuli-responsive elements used in current stimuli-responsive PDCs-based nanovesicles are outlined. Then, the unique superiorities of stimuli-responsive PDCs-based nanovesicles for drug delivery and theranostics are highlighted in detail. Finally, the future opportunities and challenges of stimuli-responsive PDCs-based nanovesicles for clinical translation are put forward.

Parallel-Stacked Flexible Organic Light-Emitting Diodes for Wearable Photodynamic Therapeutics and Color-Tunable Optoelectronics

Deformable organic light-emitting diode (OLED) based optoelectronic devices hold promise for various wearable applications including biomedical systems and displays, but current OLED technologies require high voltage and lack the power needed for wearable photodynamic therapy (PDT) applications and wearable displays. This paper presents a parallel-stacked OLED (PAOLED) with high power, more than 100 mW/cm², at low voltage (<8 V). The current dispersion ratio can be tuned by optimizing the structure of the individual OLEDs stacked to create the PAOLED, allowing control of the PAOLED's wavelength shapes, current efficiency, and power. In this study, a fabricated PAOLED operated reliably for 100 h at a high power of 35 mW/cm². Confirming its potential application to PDT, the measured singlet oxygen generation ratio of the PAOLED was found to be 3.8 times higher than the reference OLED. The high-power PAOLED achieved a 24% reduction in melanoma cancer cell viability after a short (0.5 h) irradiation. In addition, a white light PAOLED with color tuning was realized through OLED color combination, and a high brightness of over 30 000 cd/m² was realized, below 8.5 V. In conclusion, the PAOLED was demonstrated to be suitable for a variety of low-voltage, high-power wearable optoelectronic applications.