PA/US dual-modality imaging to guide VEGFR-2 targeted photothermal therapy using ZnPc-/PFH-loaded polymeric nanoparticles

Noise-insensitive defocused signal and resolution enhancement for optical-resolution photoacoustic microscopy via deep learning

Optical-resolution photoacoustic microscopy suffers from narrow depth of field and a significant deterioration in defocused signal intensity and spatial resolution. Here, a method based on deep learning was proposed to enhance the defocused resolution and signal-to-noise ratio. A virtual optical-resolution photoacoustic microscopy based on k-wave was used to obtain the datasets of deep learning with different noise levels. A fully dense U-Net was trained with randomly distributed sources to improve the quality of photoacoustic images. The results show that the PSNR of defocused signal was enhanced by more than 1.2 times. An over 2.6-fold enhancement in lateral resolution and an over 3.4-fold enhancement in axial resolution of defocused regions were achieved. The large volumetric and high-resolution imaging of blood vessels further verified that the proposed method can effectively overcome the deterioration of the signal and the spatial resolution due to the narrow depth of field of optical-resolution photoacoustic microscopy.

Nanoparticle-Based Photothermal Therapy for Breast Cancer Noninvasive Treatment

Rapid advancements in materials science and nanotechnology, intertwined with oncology, have positioned photothermal therapy (PTT) as a promising noninvasive treatment strategy for cancer. The breast's superficial anatomical location and aesthetic significance render breast cancer a particularly pertinent candidate for the clinical application of PTT following melanoma. This review comprehensively explores the research conducted on the various types of nanoparticles employed in PTT for breast cancer and elaborates on their specific roles and mechanisms of action. The integration of PTT with existing clinical therapies for breast cancer is scrutinized, underscoring its potential for synergistic outcomes. Additionally, the mechanisms underlying PTT and consequential modifications to the tumor microenvironment after treatment are elaborated from a medical perspective. Future research directions are suggested, with an emphasis on the development of integrative platforms that combine multiple therapeutic approaches and the optimization of nanoparticle synthesis for enhanced treatment efficacy. The goal is to push the boundaries of PTT toward a comprehensive, clinically applicable treatment for breast cancer.

Recent Advances for Dynamic-Based Therapy of Atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory disease, which may lead to high morbidity and mortality. Currently, the clinical treatment strategy for AS is administering drugs and performing surgery. However, advanced therapy strategies are urgently required because of the deficient therapeutic effects of current managements. Increased number of energy conversion-based organic or inorganic materials has been used in cancer and other major disease treatments, bringing hope to patients with the development of nanomedicine and materials. These treatment strategies employ specific nanomaterials with specific own physiochemical properties (external stimuli: light or ultrasound) to promote foam cell apoptosis and cholesterol efflux. Based on the pathological characteristics of vulnerable plaques, energy conversion-based nano-therapy has attracted increasing attention in the field of anti-atherosclerosis. Therefore, this review focuses on recent advances in energy conversion-based treatments. In addition to summarizing the therapeutic effects of various techniques, the regulated pathological processes are highlighted. Finally, the challenges and prospects for further development of dynamic treatment for AS are discussed.

Smart Nanoparticle-Based Platforms for Regulating Tumor Microenvironment and Cancer Immunotherapy

Tumor development and metastasis are closely related to the tumor microenvironment (TME). Recently, several studies indicate that modulating TME can enhance cancer immunotherapy. Among various approaches to modulating TME, nanoparticles (NPs) with unique inherent advantages and smart modified characteristics are promising candidates in delivering drugs to cancer cells, amplifying the therapeutic effects, and leading to a cascade of immune responses. In this review, several smart NP-based platforms are briefly introduced, such as responsive NPs, targeting NPs, and the composition of TME, including dendritic cells, macrophages, fibroblasts, endothelial cells, myeloid-derived suppressor cells, and regulatory T cells. Moreover, the recent applications of smart NP-based platforms in regulating TME and cancer immunotherapy are briefly introduced. Last, the advantages and disadvantages of these smart NP-based platforms in potential clinical translation are discussed.

Bessel acoustic-beam acoustic lens for extending the depth of field of detection in optical-resolution photoacoustic microscopy

As an important part of optical-resolution photoacoustic microscopy, the acoustic lens is responsible for efficient collection of photoacoustic signals. The spherical focused acoustic lens is commonly used in photoacoustic microscopy because of its efficient detection of the photoacoustic signal in the focus area. However, the narrow depth of field of the spherical focused acoustic lens limits the expansion of the depth of field of the photoacoustic microscopy. To solve this problem, a Bessel acoustic-beam acoustic lens is proposed. The Bessel acoustic-beam acoustic lens replaces the spherical concave surface with a conical concave surface to generate a Bessel acoustic beam with non-diffraction. Using the simulation model of Bessel acoustic-beam acoustic lens constructed by COMSOL Multiphysics, it is verified theoretically that the Bessel acoustic-beam acoustic lens can improve the depth of field of detection by ∼2 times. The Bessel acoustic-beam acoustic lens can further promote the capability of high-speed and large volumetric imaging of optical-resolution photoacoustic microscopy and will be helpful in the acquisition of physiological and pathological processes.

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.

Virtual optical-resolution photoacoustic microscopy using the k-Wave method

Deep learning has been widely used in image processing, quantitative analysis, and other applications in optical-resolution photoacoustic microscopy (OR-PAM). It requires a large amount of photoacoustic data for training and testing. However, due to the complex structure, high cost, slow imaging speed, and other factors of OR-PAM, it is difficult to obtain enough data required by deep learning, which limits the research of deep learning in OR-PAM to a certain extent. To solve this problem, a virtual OR-PAM based on k-Wave is proposed. The virtual photoacoustic microscopy mainly includes the setting of excitation light source and ultrasonic probe, scanning and signal processing, which can realize the common Gaussian-beam and Bessel-beam OR-PAMs. The system performance (lateral resolution, axial resolution, and depth of field) was tested by imaging a vertically tilted fiber, and the effectiveness and feasibility of the virtual simulation platform were verified by 3D imaging of the virtual vascular network. The ability to the generation of the dataset for deep learning was also verified. The construction of the virtual OR-PAM can promote the research of OR-PAM and the application of deep learning in OR-PAM.

Phthalocyanine-based photoacoustic contrast agents for imaging and theranostics

Phthalocyanine, as an organic dye, has attracted much attention due to its high molar absorption coefficient in the near-infrared region (NIR). It is precisely because of this advantage that phthalocyanine is very beneficial to photoacoustic imaging (PAI). At present, many different strategies have been adopted to design phthalocyanine-based contrast agents with photoacoustic (PA) effect, including increasing water solubility, changing spectral properties, prolonging the circulation time, constructing activatable supramolecular nanoparticles, increasing targeting, etc. Based on this, this minireview highlighted the above ways to enhance the PA effect of phthalocyanine. What's more, the application of phthalocyanine-based PA contrast agents in biomedical imaging and image-guided phototherapy has been discussed. Finally, this minireview also provides the prospects and challenges of phthalocyanine-based PA contrast agents in order to provide some reference for the application of phthalocyanine-based PA contrast agents in biomedical imaging and guiding tumor treatment.

Immune/Hypoxic Tumor Microenvironment Regulation-Enhanced Photodynamic Treatment Realized by pH-Responsive Phase Transition-Targeting Nanobubbles

Due to a special pathological type of triple-negative breast cancer (TNBC) and the lack of expression of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (Her 2), targeted therapies are not effective. The lack of effective treatment drugs and insensitivity to the current single-treatment methods are the biggest problems that we face with the TNBC treatment. Therefore, new strategies to achieve selective treatment and further visual efficacy evaluation will be powerful tools against TNBC. Herein, a novel tumor-targeted nanosized ultrasound contrast nanobubble loaded with chlorin e6 (Ce6), metformin (MET), and perfluorohexane (PFH) and covalently connected to the anti-PD-L1 peptide (^DPPA-1) in the outer shell was fabricated. When accumulated in acidic tumor tissues, poly(ethylene glycol) (PEG) ligands detach, and ^DPPA-1 is exposed for programmed death-ligand 1 (PD-L1) targeting and blocking. The released metformin can relieve hypoxia by inhibiting mitochondrial complex I in the tumor microenvironment (TME) and enhance the therapeutic efficacy of Ce6 while synergizing with ^DPPA-1 by reducing PD-L1 expression. More significantly, photodynamic therapy (PDT) using multifunctional tumor-targeted nanosized ultrasound contrast agents (PD-L1-targeted pH-sensitive chlorin e6 (Ce6) and metformin (MET) drug-loaded phase transitional nanoparticles (Ce6/MET NPs-^DPPA-1)) combined with PD-L1 checkpoint blocking can not only reduce tumor-mediated immunosuppression but also produce strong antitumor immunity. This finding provides a new idea for constructing multifunctional TNBC therapeutic nanoagents.

Ferrite-encapsulated nanoparticles with stable photothermal performance for multimodal imaging-guided atherosclerotic plaque neovascularization therapy

Pathological angiogenesis is a critical contributor to atherosclerotic plaque rupture. However, there are few effective theranostic strategies to stabilize plaques by suppressing neovascularization. In this study, we fabricated a polymeric nanosystem using 3 nm manganese ferrite (MnFe₂O₄) and perfluorohexane (PFH) stabilized by polylactic acid-glycolic acid (PLGA) shells and conjugated to the surface of an anti-vascular endothelial growth factor receptor 2 (VEGFR2) antibody [ramucirumab (Ram)]. The PFH@PLGA/MnFe₂O₄-Ram nanoparticles (NPs) were used as atherosclerotic plaque angiogenesis theranostics for multimodal imaging-guided photothermal therapy (PTT). Three-nanometer MnFe₂O₄ is an excellent magnetic resonance imaging T1 and photoacoustic imaging contrast agent. Upon exposure to near-infrared (NIR) light, MnFe₂O₄ in the NPs could transform NIR light into thermal energy for the photothermal elimination of plaque angiogenesis. Additionally, optical droplet vaporization of PFH in the NPs triggered by the thermal effect to form gas bubbles enhanced ultrasound imaging. Our in vitro experiments revealed that PFH@PLGA/MnFe₂O₄-Ram NPs actively accumulated in rabbit aortic endothelial cells, and NP-mediated PTT promoted endothelial cell apoptosis while inhibiting their proliferation, migration, and tubulogenesis. Notably, the PFH@PLGA/MnFe₂O₄-Ram NPs possessed excellent photostability and biocompatibility. In the rabbit advanced atherosclerotic plaque model, PFH@PLGA/MnFe₂O₄-Ram NP-guided PTT significantly induced apoptosis of neovascular endothelial cells and improved the hypoxia status in the plaque 3 days after treatment. On day 28, PTT significantly reduced the density of neovessels and subsequently stabilized rabbit plaques by inhibiting plaque hemorrhage and macrophage infiltration. Collectively, these results suggest that PFH@PLGA/MnFe₂O₄-Ram NP-guided PTT is a safe and effective theranostic strategy for inhibiting atherosclerotic plaque angiogenesis.

Paying attention to tumor blood vessels: Cancer phototherapy assisted with nano delivery strategies

Cancer phototherapy has attracted increasing attention for its promising effectiveness and relative non-invasiveness. Over the past years, tremendous efforts have been made to develop better phototherapy strategies with various nano delivery systems. This review introduces cancer phototherapy strategies based on tumor blood vessels for improved therapeutic outcomes from the angle of direct tumor destruction and improved delivery process assisted with nano delivery designs. Latest directions and ideas of cancer phototherapy with translation potential are also discussed. Focusing on the double role of tumor vessels not only as an anti-tumor target but also as part of the delivery process, we highlight the crosstalk between photo-induced extensive effects and the complicated drug delivery process. Due to the heterogeneity of tumors, deeper investigations about the interconnection between tumor vessels and cancer phototherapy remain to be carried out. More delicate and intelligent nano delivery systems are expected to help realize the full potential of this therapeutic strategy.

CDCP1-targeted nanoparticles encapsulating phase-shift perfluorohexan for molecular US imaging in vitro

BACKGROUND

Molecular targeted contrast-enhanced ultrasound (CEUS) imaging is a potential imaging strategy to improve the diagnostic accuracy of conventional ultrasound (US) imaging. US contrast agents are usually micrometer-sized and non-target gas bubbles while nano-sized and targeted agents containing phase-shift materials absorb more attractions for their size and the liquid core and excellent molecular imaging effect.

METHODS

PLGA12k-mPEG2k-NH2, DSPE-mPEG2k and perfluorohexan (PFH) were used to construct a new targeted ultrasound contrast agent with CUB domain-containing protein 1 (CDCP1) receptor for the detection and diagnosis of prostate cancer. The potential of tumor-targeted nanoparticles (CDCP1-targeted perfluorohexan-loaded phase-transitional nanoparticles, anti-CDCP1 NPs) as contrast agents for ultrasound (US) imaging was assessed in vitro. Moreover, studies on the cytotoxicity and the targeting ability of anti-CDCP1 NPs assisted by US were carried out.

RESULTS

The results showed that anti-CDCP1 NPs had low cytotoxicity, and with the increasing of polymer concentration in anti-CDCP1 NPs, the CEUS imaging of agent gradually enhanced, and enhanced imaging associated with the length of observing time. Furthermore, it was testified that anti-CDCP1 assisted the agent to target cells expressing CDCP1, which demonstrated the active targeting of anti-CDCP1 NPs in vitro.

CONCLUSION

All in all, the feasibility of using targeted anti-CDCP1 NPs to enhance ultrasound imaging has been demonstrated in vitro, which laid a solid foundation for molecular US imaging in vivo, and anti-CDCP1 NPs might have a great clinical application prospect.

Preparation and in vitro study of stromal cell-derived factor 1-targeted Fe3O4/poly(lactic-co-glycolic acid)/perfluorohexane nanoparticles

Compared with traditional imaging techniques, multimodal imaging obtains more accurate images that may increase disease detection rates. The present study prepared stromal cell-derived factor 1 (SDF-1)-loaded, targeted nanoparticles coated with iron (II,III) oxide and perfluorohexane (PFH) to be used as polymer-shelled contrast agents with multimodal imaging functions, with the aim of improving tongue cancer and lymph node metastasis diagnosis. The multifunctional, targeted, polymeric nanoparticles were prepared using a double emulsion method and chemokine SDF-1 was conjugated to nanoparticles by a sulfide bond. The nanoparticles were spherical, uniform size and well dispersed. The results of the in vitro photoacoustic and ultrasonic imaging experiments demonstrated that the multifunctional nanoparticles displayed excellent multimodal imaging functions, as even small concentrations of nanoparticles presented clear ultrasound and photoacoustic imaging. When the temperature reached the boiling point of PFH (56˚C), a liquid-gas phase change occurred and the microsphere volume and acoustic impedance increased, leading to enhanced ultrasonic development. The nanoparticles were automatically targeted to tongue squamous carcinoma cells in vitro via SDF-1-CXC chemokine receptor 4 interactions. The targeted experiment and flow cytometry results indicated that the nanoparticles underwent strong targeted binding to human tongue squamous cell carcinoma (SCC-15) cells. In summary, the nanoparticles were automatically targeted to SCC-15 cells and displayed promising characteristics for ultrasound and photoacoustic imaging. Higher concentrations of nanoparticles was associated with clearer imaged and greater echo intensity value and photoacoustic value. The present study established a foundation for the development of procedures for primary tongue cancer and lymph node metastasis diagnosis.

Nanotechnology for angiogenesis: opportunities and challenges

Angiogenesis plays a critical role within the human body, from the early stages of life (i.e., embryonic development) to life-threatening diseases (e.g., cancer, heart attack, stroke, wound healing). Many pharmaceutical companies have expended huge efforts on both stimulation and inhibition of angiogenesis. During the last decade, the nanotechnology revolution has made a great impact in medicine, and regulatory approvals are starting to be achieved for nanomedicines to treat a wide range of diseases. Angiogenesis therapies involve the inhibition of angiogenesis in oncology and ophthalmology, and stimulation of angiogenesis in wound healing and tissue engineering. This review aims to summarize nanotechnology-based strategies that have been explored in the broad area of angiogenesis. Lipid-based, carbon-based and polymeric nanoparticles, and a wide range of inorganic and metallic nanoparticles are covered in detail. Theranostic and imaging approaches can be facilitated by nanoparticles. Many preparations have been reported to have a bimodal effect where they stimulate angiogenesis at low dose and inhibit it at higher doses.

Dual-targeted photothermal agents for enhanced cancer therapy

Photothermal therapy, in which light is converted into heat and triggers local hyperthermia to ablate tumors, presents an inherently specific and noninvasive treatment for tumor tissues. In this area, the development of efficient photothermal agents (PTAs) has always been a central topic. Although many efforts have been made on the investigation of novel molecular architectures and photothermal materials over the past decades, PTAs can cause severe damage to normal tissues because of the poor tumor aggregate ability and high irradiation density. Recently, dual-targeted photothermal agents (DTPTAs) provide an attractive strategy to overcome these problems and enhance cancer therapy. DTPTAs are functionalized with two classes of targeting units, including tumor environment targeting sites, tumor targeting sites and organelle targeting sites. In this perspective, typical targeted ligands and representative examples of photothermal therapeutic agents with dual-targeted properties are systematically summarized and recent advances using DTPTAs in tumor therapy are highlighted.

A sequential targeting nanoplatform for anaplastic thyroid carcinoma theranostics

Effective accumulation of nanoparticles (NPs) in tumor regions is one of the major motivations in nanotechnology research and that the establishment of an efficient targeting nanoplatform for the treatment of malignant tumors is urgently needed for theranostic applications. In this study, we engineered multifunctional sequential targeting NPs for achieving synergistic antiangiogenic photothermal therapy (PTT) and multimodal imaging-guided diagnosis for anaplastic thyroid carcinoma (ATC) theranostics. Antibody bevacizumab with an affinity towards vascular endothelial growth factor (VEGF) on the tumor cell surface was conjugated onto the surface of polymer NPs for VEGF targeting and antiangiogenic therapy. Encapsulated IR825 was employed as a photothermal agent (PTA) with a mitochondrial targeting capability, which further cascades NPs into mitochondria to enhance hyperthermic efficiency in the ablation of tumor cells. Importantly, the combination of bevacizumab and IR825 in a single nanosystem achieved desirable accumulations of NPs and that sequential targeted PTT combined with antiangiogenesis significantly promoted the therapeutic efficiency in eradicating tumors by near-infrared (NIR) laser irradiation. Furthermore, these NPs are extraordinary contrast agents for photoacoustic, ultrasound and fluorescence imaging applications, providing multimodal imaging capabilities for therapeutic monitoring and a precise diagnosis. Therefore, this multifunctional nanoplatform provides a promising theranostic strategy for extremely malignant ATC. STATEMENT OF SIGNIFICANCE: Anaplastic thyroid carcinoma (ATC), with extremely aggressive behavior, lacks a satisfactory therapeutic method and a comprehensive early diagnostic strategy. Herein, we successfully synthesized a sequential targeting nanoplatform (IR825@Bev-PLGA-PFP NPs) with theranostic function, which specifically binds to VEGF on the tumor cell surface and further cascades into mitochondria to achieve effective accumulation of NPs in the tumor regions. As a result, it solves the urgent demand for ATC detection and therapy. By breaking the limitation of traditional target, such as low efficacy and frequent recurrence as the results of low accumulation, sequential targeting combined with synergistic antiangiogenic PTT completely eradicates tumors without any residual tissue and side effect. Therefore, this strategy paves a solid way for further investigation in the theranostic progressing of ATC.

Multifunctional phototheranostic nanomedicine for cancer imaging and treatment

Cancer, as one of the most life-threatening diseases, shows a high fatality rate around the world. When improving the therapeutic efficacy of conventional cancer treatments, researchers also conduct extensive studies into alternative therapeutic approaches, which are safe, valid, and economical. Phototherapies, including photodynamic therapy (PDT) and photothermal therapy (PTT), are tumor-ablative and function-reserving oncologic interventions, showing strong potential in clinical cancer treatment. During phototherapies, the non-toxic phototherapeutic agents can be activated upon light irradiation to induce cell death without causing much damage to normal tissues. Besides, with the rapid development of nanotechnology in the past decades, phototheranostic nanomedicine also has attracted tremendous interests aiming to continuously refine their performance. Herein, we reviewed the recent progress of phototheranostic nanomedicine for improved cancer therapy. After a brief introduction of the therapeutic principles and related phototherapeutic agents for PDT and PTT, the existing works on developing of phototheranostic nanomedicine by mainly focusing on their categories and applications, particularly on phototherapy-synergized cancer immunotherapy, are comprehensively reviewed. More importantly, a brief conclusion and future challenges of phototheranostic nanomedicine from our point of view are delivered in the last part of this article.

Single-molecular phosphorus phthalocyanine-based near-infrared-II nanoagent for photothermal antitumor therapy

As one of the noninvasive cancer treatments, photothermal therapy (PTT) has drawn intense attention recently. In this context, an important task is to explore novel and versatile nanoscale photothermal agents (PTAs), especially those with strong NIR-II light absorption, high photothermal conversion efficiency, good photostability and biocompatibility. Phthalocyanines (Pcs), as the second-generation photosensitizers, are a promising class of candidates for PTT due to their strong NIR absorption and high photothermal conversion efficiency. However, the poor water solubility severely limited their application as PTAs in tumor treatment. Herein, we report a molecular phosphorus phthalocyanine (P-Pc)-based nanoagent via incorporation of human serum albumin (HSA) under mild conditions. The obtained nanoscale P-Pc-HSA possesses excellent photothermal conversion efficiency (64.7%) upon 1064 nm light irradiation, furthermore, it can be a highly efficient NIR-II antitumor nanoagent via photothermal treatment (PTT), which is fully evidenced by the in vitro and in vivo experiments.

A molecular phosphorus phthalocyanine (P-Pc)-based nanoagent P-Pc-HSA, which can be a highly efficient NIR-II antitumor agent, is reported.

Nanoscale Covalent Organic Framework for Combinatorial Antitumor Photodynamic and Photothermal Therapy

Despite the excellent photodynamic and photothermal properties of organic molecular photosensitizers (PSs) and photothermal agents (PTAs), such as porphyrin and naphthalocyanine, their poor water solubility severely impedes their biological applications. Covalent organic frameworks (COFs), as an emerging class of organic crystalline porous materials, possess free active end groups (bonding defects) and large inner pores, which make them an ideal type of nanocarriers for loading hydrophobic organic molecular PSs and PTAs by both bonding defect functionalization (BDF) and guest encapsulation approaches to obtain multifunctional nanomedicines for PDT/PTT combination therapy. In this work, we report a nanoscale COF (NCOF) prepared via a facile synthetic approach under ambient conditions. Furthermore, a dual-modal PDT/PTT therapeutic nanoagent, VONc@COF-Por (3), is successfully fabricated by stepwise BDF and guest encapsulation processes. The covalently grafted porphyrinic PS (Por) and the noncovalently loaded naphthalocyanine PTA (VONc) are independently responsible for the PDT and PTT functionalities of the nanoagent. Upon visible (red LED) and NIR (808 nm laser) irradiation, VONc@COF-Por (3) displayed high ¹O₂ generation and photothermal conversion ability (55.9%), consequently providing an excellent combined PDT/PTT therapeutic effect on inhibiting MCF-7 tumor cell proliferation and metastasis, which was well evidenced by in vitro and in vivo experiments. We believe that the results obtained herein can significantly promote the development of NCOF-based multifunctional nanomedicines for biomedical applications.

Gas-Mediated Cancer Bioimaging and Therapy

Gas-involving cancer theranostics have attracted considerable attention in recent years due to their high therapeutic efficacy and biosafety. We have reviewed the recent significant advances in the development of stimuli-responsive gas releasing molecules (GRMs) and gas nanogenerators for cancer bioimaging, targeted and controlled gas therapy, and gas-sensitized synergistic therapy. We have focused on gases with known anticancer effects, such as oxygen (O₂), carbon monoxide (CO), nitric oxide (NO), hydrogen sulfide (H₂S), hydrogen (H₂), sulfur dioxide (SO₂), carbon dioxide (CO₂), and heavy gases that act via the gas-generating process. The GRMs and gas nanogenerators for each gas have been described in terms of the stimulation method, followed by their applications in ultrasound and multimodal imaging, and finally their primary and synergistic actions with other cancer therapeutic modalities. The current challenges and future possibilities of gas therapy and imaging vis-à-vis clinical translation have also been discussed.

Recent Progress in the Development of Poly(lactic-co-glycolic acid)-Based Nanostructures for Cancer Imaging and Therapy

Diverse nanosystems for use in cancer imaging and therapy have been designed and their clinical applications have been assessed. Among a variety of materials available to fabricate nanosystems, poly(lactic-co-glycolic acid) (PLGA) has been widely used due to its biocompatibility and biodegradability. In order to provide tumor-targeting and diagnostic properties, PLGA or PLGA nanoparticles (NPs) can be modified with other functional materials. Hydrophobic or hydrophilic therapeutic cargos can be placed in the internal space or adsorbed onto the surface of PLGA NPs. Protocols for the fabrication of PLGA-based NPs for cancer imaging and therapy are already well established. Moreover, the biocompatibility and biodegradability of PLGA may elevate its feasibility for clinical application in injection formulations. Size-controlled NP’s properties and ligand–receptor interactions may provide passive and active tumor-targeting abilities, respectively, after intravenous administration. Additionally, the introduction of several imaging modalities to PLGA-based NPs can enable drug delivery guided by in vivo imaging. Versatile platform technology of PLGA-based NPs can be applied to the delivery of small chemicals, peptides, proteins, and nucleic acids for use in cancer therapy. This review describes recent findings and insights into the development of tumor-targeted PLGA-based NPs for use of cancer imaging and therapy.

PEGylation of model drug carriers enhances phagocytosis by primary human neutrophils

Targeted drug carriers are attractive for the delivery of therapeutics directly to the site of a disease, reducing systemic side effects and enhancing the efficacy of therapeutic molecules. However, the use of particulate carriers for drug delivery comes with its own set of challenges and barriers. Among these, a great deal of research effort has focused on protecting carriers from clearance by phagocytes via altering carrier surface chemistry, mostly with the use of polyethylene glycol (PEG) chain coatings. However, few papers have explored the effects of PEGylation on uptake by freshly-obtained primary human phagocytes in physiological conditions. In this work, we investigate the effect of PEGylation on particle uptake by primary human neutrophils in vitro and compare these effects to several cell lines and other model phagocytic cells systems. We find that human neutrophils in whole blood preferentially phagocytose PEGylated particles (e.g., ∼40% particle positive neutrophils for PEGylated versus ∼20% for carboxylated polystyrene microspheres) and that this effect is linked to factors present in human plasma. Model phagocytes internalized PEGylated particles less efficiently or equivalently to carboxylated particles in culture medium but preferentially phagocytosed PEGylated particles in the human plasma (e.g., ∼86% versus ∼63% PEGylated versus carboxylated particle positive cells, respectively). These findings have significant implications for the efficacy of PEGylation in designing long-circulating drug carriers, as well as the need for thorough characterization of drug carrier platforms in a wide array of in vitro and in vivo assays.

STATEMENT OF SIGNIFICANCE

The work in this manuscript is highly significant to the field of drug delivery, as it explores in-depth the effects of polyethylene glycol (PEG) coatings, which are frequently used to prevent phagocytic clearance of particulate drug carriers, on the phagocytosis of such carriers by neutrophils, the most abundant leukocyte in blood circulation. Surprisingly, we find that PEGylation enhances uptake by primary human neutrophils, specifically in the presence of human plasma. This result suggests that PEGylation may not confer the benefits in humans once thought, and may help to explain why PEG has not become the "magic bullet" it was once thought to be in the field of particulate drug delivery.

Laser-Activated Bioprobes with High Photothermal Conversion Efficiency for Sensitive Photoacoustic/Ultrasound Imaging and Photothermal Sensing

Laser-activated bioprobes with high photothermal conversion efficiency (IRPDA@PFH NDs) based on biocompatible IR-780 doped polydopamine perfluorocarbon nanodroplets (NDs) were developed. When protected by gelatin microspheres, their near-spherical morphologies can be easily observed with transmission electron microscope. Doping IR-780 (3 w/w % of added dopamine hydrochloride) can significantly enhance near-infrared (NIR) absorption and photothermal conversion efficiency to 57.7%. The enhanced NIR absorption and nonradiative relaxation are preferred to stronger photoacoustic (PA) signals and higher PA imaging definition; ultrasound (US) signals also increase more than 2.5 times because of easier phase change of NDs. These bioprobes had sensitive PA/US imaging capability with highly effective substitute utilizations, in which polydopamine was used either as a PA contrast or a photothermal agent. Perfluorocarbon can be used as an US contrast agent and temperature indicator. More importantly, the gray value increments of US increase with temperature in a general range from 35 to 55 °C. Especially, an approximate linear increasing of gray value in the optimized photothermal therapy (PTT) range from 35 °C to 50 °C could be used for the temperature monitoring and control of PTT. During PTT, the heated regions and the extent of photothermal heating can be visualized by US imaging. These findings indicate their great potential for biosensing and PTT monitoring.