A novel ROS-Related chemiluminescent semiconducting polymer nanoplatform for acute pancreatitis early diagnosis and severity assessment

Acute pancreatitis (AP) is a common and potentially life-threatening inflammatory disease of the pancreas. Reactive oxygen species (ROS) play a key role in the occurrence and development of AP. With increasing ROS levels, the degree of oxidative stress and the severity of AP increase. However, diagnosing AP still has many drawbacks, including difficulties with early diagnosis and undesirable sensitivity and accuracy. Herein, we synthesized a semiconducting polymer nanoplatform (SPN) that can emit ROS-correlated chemiluminescence (CL) signals. The CL intensity increased in solution after optimization of the SPN. The biosafety of the SPN was verified in vitro and in vivo. The mechanism and sensitivity of the SPN for AP early diagnosis and severity assessment were evaluated in three groups of mice using CL intensity, serum marker evaluations and hematoxylin and eosin staining assessments. The synthetic SPN can be sensitively combined with different concentrations of ROS to produce different degrees of high-intensity CL in vitro and in vivo. Notably, the SPN shows an excellent correlation between CL intensity and AP severity. This nanoplatform represents a superior method to assess the severity of AP accurately and sensitively according to ROS related chemiluminescence signals. This research overcomes the shortcomings of AP diagnosis in clinical practice and provides a novel method for the clinical diagnosis of pancreatitis in the future.

Reactive Oxygen Correlated Chemiluminescent Imaging of a Semiconducting Polymer Nanoplatform for Monitoring Chemodynamic Therapy

In chemodynamic therapy (CDT), real-time monitoring of reactive oxygen species (ROS) production is critical to reducing the nonspecific damage during CDT and feasibly evaluating the therapeutic response. However, CDT agents that can emit ROS-related signals are rare. Herein, we synthesize a semiconducting polymer nanoplatform (SPN) that can not only produce highly toxic ROS to kill cancer cells but also emit ROS-correlated chemiluminescent signals. Notably, the efficacy of both chemiluminescence and CDT can be significantly enhanced by hemin doping (∼10-fold enhancement for luminescent intensity). Such ROS-dependent chemiluminescence of SPN allows ROS generation within a tumor to be optically monitored during the CDT process. Importantly, SPN establishes an excellent correlation of chemiluminescence intensities with cancer inhibition rates in vitro and in vivo. Thus, our nanoplatform represents the first intelligent strategy that enables chemiluminescence-imaging-monitored CDT, which holds potential in assessing therapeutic responsivity and predicting treatment outcomes in early stages.

Two-photon semiconducting polymer nanoparticles as a new platform for imaging of intracellular pH variation

Intracellular pH (pHi) plays a crucial role in cell physiological and pathological processes. We herein report an efficient pH-sensitive sensor based on two-photon excitable semiconducting polymer nanoparticles (PFV/PSMA-DA NPs) for pHi sensing. PFV/PSMA NPs were functionalized with redox-active dopamine (DA) and the obtained PFV/PSMA-DA NPs showed sensitive and reversible pH response over the pH range of 5.0-9.0. Owning to the high biocompatibility and pH-responsive DA, PFV/PSMA-DA NPs show low cytotoxicity and the quantification and imaging of intracellular pH changes of HeLa cells were successfully realized. Moreover, the detection of intracellular pH fluctuation induced by redox species such as NAC (N-acetylcysteine) and H₂O₂ was also achieved by both one- and two-photon excitation of the PFV/PSMA-DA NPs probe. This work clearly shows that nanoprobe based on two-photon PFV/PSMA-DA NPs could serve as a promising platform for quantitatively monitoring the intracellular pH fluctuations.

Recent progress on semiconducting polymer nanoparticles for molecular imaging and cancer phototherapy

As a new class of organic optical nanomaterials, semiconducting polymer nanoparticles (SPNs) have the advantages of excellent optical properties, high photostability, facile surface functionalization, and are considered to possess good biocompatibility for biomedical applications. This review surveys recent progress made on the design and synthesis of SPNs for molecular imaging and cancer phototherapy. A variety of novel polymer design, chemical modification and nanoengineering strategies have been developed to precisely tune up optoelectronic properties of SPNs to enable fluorescence, chemiluminescence and photoacoustic (PA) imaging in living animals. With these imaging modalities, SPNs have been demonstrated not only to image tissues such as lymph nodes, vascular structure and tumors, but also to detect disease biomarkers such as reactive oxygen species (ROS) and protein sulfenic acid as well as physiological indexes such as pH and blood glucose concentration. The potentials of SPNs in cancer phototherapy including photodynamic and photothermal therapy are also highlighted with recent examples. Future efforts should further expand the use of SPNs in biomedical research and may even move them beyond pre-clinical studies.

Amphiphilic semiconducting polymer as multifunctional nanocarrier for fluorescence/photoacoustic imaging guided chemo-photothermal therapy

Chemo-photothermal nanotheranostics has the advantage of synergistic therapeutic effect, providing opportunities for optimized cancer therapy. However, current chemo-photothermal nanotheranostic systems generally comprise more than three components, encountering the potential issues of unstable nanostructures and unexpected conflicts in optical and biophysical properties among different components. We herein synthesize an amphiphilic semiconducting polymer (PEG-PCB) and utilize it as a multifunctional nanocarrier to simplify chemo-photothermal nanotheranostics. PEG-PCB has a semiconducting backbone that not only serves as the diagnostic component for near-infrared (NIR) fluorescence and photoacoustic (PA) imaging, but also acts as the therapeutic agent for photothermal therapy. In addition, the hydrophobic backbone of PEG-PCB provides strong hydrophobic and π-π interactions with the aromatic anticancer drug such as doxorubicin for drug encapsulation and delivery. Such a trifunctionality of PEG-PCB eventually results in a greatly simplified nanotheranostic system with only two components but multimodal imaging and therapeutic capacities, permitting effective NIR fluorescence/PA imaging guided chemo-photothermal therapy of cancer in living mice. Our study thus provides a molecular engineering approach to integrate essential properties into one polymer for multimodal nanotheranostics.

Self-quenched semiconducting polymer nanoparticles for amplified in vivo photoacoustic imaging

Development of photoacoustic (PA) imaging agents provides opportunities for advancing PA imaging in fundamental biology and medicine. Despite the promise of semiconducting polymer nanoparticles (SPNs) for PA imaging, the molecular guidelines to enhance their imaging performance are limited. In this study, semiconducting polymers (SPs) with self-quenched fluorescence are synthesized and transformed into SPNs for amplified PA imaging in living mice. The self-quenched process is induced by the incorporation of an electron-deficient structure unit into the backbone of SPs, which in turn promotes the nonradiative decay and enhances the heat generation. Such a simple chemical alteration of SP eventually leads to 1.7-fold PA amplification for the corresponding SPN. By virtue of the targeting capability of cyclic-RGD, the amplified SPN can effectively delineate tumor in living mice and increase the PA intensity of tumor by 4.7-fold after systemic administration. Our study thus provides an effective molecular guideline to amplify the PA brightness of organic imaging agents for in vivo PA imaging.