Incorporation of Porphyrin to π‑Conjugated Backbone for Polymer-Dot-Sensitized Photodynamic Therapy

The photosensitizers used in photodynamic therapy are mainly based on porphyrin derivatives. However, clinical applications encounter several limitations regarding photosensitizers such as their low absorption coefficients, poor water-solubility, and leaching from delivery carriers. Here, we describe covalent incorporation of porphyrin in conjugated polymer backbone for development of efficient polymer-dot photosensitizer. Spectroscopic characterizations revealed that the light-harvesting polymer dominantly transfer the excitation energy to the porphyrin unit, yielding efficient singlet oxygen generation for photodynamic therapy. The polymer dots (Pdots) also possess excellent stability that overcomes the photosensitizer leaching problem as encountered in other nanoparticle carriers. In vitro cytotoxicity and photodynamic efficacy of the Pdots were evaluated in MCF-7 cells by in vitro assay, indicating that the Pdots can efficiently damage cancer cells. In vivo photodynamic therapy by using the Pdots was further investigated with xenograft tumors in Balb/c nude mice, which show that the tumors were significantly inhibited or eradicated in certain cases. The high-yield singlet oxygen generation and excellent stability of porphyrin-incorporated Pdots are promising for photodynamic treatment of malignant tumors

Covalent Patterning and Rapid Visualization of Latent Fingerprints with Photo-Cross-Linkable Semiconductor Polymer Dots

Fingerprint imaging and recognition represent the most important approach in personal identification. Here we designed and synthesized oxetane-functionalized semiconductor polymer dots (Ox-Pdots) for covalent patterning and rapid visualization of latent fingerprints. The high fluorescence brightness, large Stokes shift, and excellent surface properties of the Ox-Pdots lead to fingerprint imaging with high sensitivity and resolution. Fingerprint ridge structures with the first, second, and third levels of details were clearly developed within minutes. The method was facile and robust for visualization of fingerprints on various surfaces including glass, metal, and plastics. Moreover, the oxetane groups in the Ox-Pdots undergo cross-linking reactions induced by a short-time UV irradiation, yielding 3-D intermolecular polymer network. The resulting fingerprint patterns exhibit unparalleled stability against rigorous treatment, as compared to those by traditional Pdots. Our results demonstrate that the Ox-Pdots hold great promise for latent fingerprint imaging and fluorescence anticounterfeiting applications

Size-Dependent Property and Cell Labeling of Semiconducting Polymer Dots

Semiconducting polymer dots (Pdots) represent a new class of fluorescent nanoparticles for biological applications. In this study, we investigated their size-dependent fluorescence and cellular labeling properties. We demonstrate that the polymer conformation in solution phase largely affects the polymer folding and packing during the nanoparticle preparation process, resulting in solution-phase control over the fluorescence properties of semiconducting polymer nanoparticles. The resulting Pdots exhibit apparent size dependent absorption and emission, a characteristic feature of different chain packing behaviors due to the preparation conditions. Single-particle fluorescence imaging was employed to perform a side-by-side comparison on the Pdot brightness, indicating a quadratic dependence of single-particle brightness on particle size. Upon introducing a positively charged dye Nile blue, all the three type of Pdots were quenched very efficiently (<i>K</i>_sv > 1 × 10⁷ M^–1) in an applied quenching process at low dye concentrations, but exhibit apparent difference in quenching efficiency with increasing dye concentration. Furthermore, Pdots of different sizes were used for cell uptake and cellular labeling involving biotin–streptavidin interactions. Fluorescence imaging together with flow cytometry studies clearly showed size dependent labeling brightness. Small-sized Pdots appear to be more effective for immunolabeling of cell surface, whereas medium-sized Pdots exhibit the highest uptake efficiency. This study provides a concrete guidance for selecting appropriate particle size for biological imaging and sensing applications

Ultrabright Polymer-Dot Transducer Enabled Wireless Glucose Monitoring <i>via</i> a Smartphone

Optical methods such as absorptiometry, fluorescence, and surface plasmon resonance have long been explored for sensing glucose. However, these schemes have not had the clinical success of electrochemical methods for point-of-care testing because of the limited performance of optical sensors and the bulky instruments they require. Here, we show that an ultrasensitive optical transducer can be used for wireless glucose monitoring <i>via</i> a smartphone. The optical transducer combines oxygen-sensitive polymer dots (Pdots) with glucose oxidase that sensitively detect glucose when oxygen is consumed in the glucose oxidation reaction. By judicious design of the Pdots with ultralong phosphorescence lifetime, the transducer exhibited a significantly enhanced sensitivity by 1 order of magnitude as compared to the one in a previous study. As a result, the optical images of subcutaneous glucose level obtained with the smartphone camera could be utilized to clearly distinguish between euglycemia and hyperglycemia. We further developed an image processing algorithm and a software application that was installed on a smartphone. Real-time dynamic glucose monitoring in live mice was demonstrated with the smartphone and the implanted Pdot transducer

<i>In Vivo</i> Dynamic Monitoring of Small Molecules with Implantable Polymer-Dot Transducer

Small molecules participate extensively in various life processes. However, specific and sensitive detection of small molecules in a living system is highly challenging. Here, we describe <i>in vivo</i> real-time dynamic monitoring of small molecules by a luminescent polymer-dot oxygen transducer. The optical transducer combined with an oxygen-consuming enzyme can sensitively detect small-molecule substrates as the enzyme-catalyzed reaction depletes its internal oxygen reservoir in the presence of small molecules. We exemplify this detection strategy by using glucose-oxidase-functionalized polymer dots, yielding high selectivity, large dynamic range, and reversible glucose detection in cell and tissue environments. The transducer–enzyme assembly after subcutaneous implantation provides a strong luminescence signal that is transdermally detectable and continuously responsive to blood glucose fluctuations for up to 30 days. In view of a large library of oxygen-consuming enzymes, this strategy is promising for <i>in vivo</i> detection and quantitative determination of a variety of small molecules