Yanlin Lv

Conjugated Polymer-Based Hybrid Nanoparticles with Two-Photon Excitation and Near-Infrared Emission Features for Fluorescence Bioimaging within the Biological Window

Hybrid fluorescent nanoparticles (NPs) capable of fluorescing near-infrared (NIR) light (centered ∼730 nm) upon excitation of 800 nm laser light were constructed. A new type of conjugated polymer with two-photon excited fluorescence (TPEF) feature, P-F8-DPSB, was used as the NIR-light harvesting component and the energy donor while a NIR fluorescent dye, DPA-PR-PDI, was used as the energy acceptor and the NIR-light emitting component for the construction of the fluorescent NPs. The hybrid NPs possess δ value up to 2.3 × 10(6) GM per particle upon excitation of 800 nm pulse laser. The excellent two-photon absorption (TPA) property of the conjugated polymer component, together with its high fluorescence quantum yield (ϕ) up to 45% and the efficient energy transfer from the conjugated polymer to NIR-emitting fluorophore with efficiency up to 90%, imparted the hybrid NPs with TPEF-based NIR-input-NIR-output fluorescence imaging ability with penetration depth up to 1200 μm. The practicability of the hybrid NPs for fluorescence imaging in Hela cells was validated.

Single-fluorophore-based fluorescent probes enable dual-channel detection of Ag+ and Hg2+ with high selectivity and sensitivity

A new type of fluorescent probe capable of detecting Ag(+) and Hg(2+) in two independent channels was developed in the present work. Specifically, in CH3CN-MOPS mixed solvents with CH3CN/MOPS ratio (v/v) of 15/85, this type of probe fluoresced weakly, and the addition of Ag(+) remarkably induced fluorescence enhancement of the probe. In CH3CN-MOPS mixed solvents with the percentage of CH3CN increased up to 65%, the probe was highly fluorescent and addition of Hg(2+) dramatically induced the fluorescence quenching. Thus, using such single-fluorophore-based probe and tuning the polarity of the mixed solvent, Ag(+), and Hg(2+) can be detected in independent channels with high selectivity and sensitivity. As a result, the mutual interference usually encountered in most cases of Ag(+) and Hg(2+) sensing owing to the similar fluorescence response that these two ions induced, can be effectively circumvented by using the probes developed herein.

A BODIPY-Based Fluorescent Probe for Detection of Subnanomolar Phosgene with Rapid Response and High Selectivity

A new type of phosgene probe with a limit of detection down to 0.12 nM, response time of less than 1.5 s, and high selectivity over other similarly reactive toxic chemicals was developed using ethylenediamine as the recognition moiety and 8-substituted BODIPY unit as the fluorescence signaling component. The probe undergoes sequential phosgene-mediated nucleophilic substitution reaction and intramolecular cyclization reaction with high rate, yielding a product with the intramolecular charge transfer (ICT) process from amine to the BODIPY core significantly inhibited. Owing to the emission feature of 8-substituted BODIPY that is highly sensitive to the substituents electronic nature, such inhibition on the ICT process strikingly generates strong fluorescence contrast by a factor of more than 23 300, and therefore creates the superhigh sensitivity of the probe for phosgene. Owing to the high reactivity of ethylenediamine of the probe in nucleophilic substitution reactions, the probe displays a very fast response rate to phosgene.

Beyond a Carrier: Graphene Quantum Dots as a Probe for Programmatically Monitoring Anti-Cancer Drug Delivery, Release, and Response

On the basis of the unique physicochemical properties of graphene quantum dots (GQDs), we developed a novel type of theranostic agent by loading anticancer drug doxorubicin (DOX) to GQDs surface and conjugating Cy5.5 (Cy) dye to GQD though a cathepsin D-responsive (P) peptide. Such type of agents demonstrated superior therapeutic performance both in vitro and in vivo because of the improved tissue penetration and cellular uptake. More importantly, they are capable of functioning as probes for programmed tracking the delivery and release of anticancer drug as well as drug-induced cancer cell apoptosis through GQDs, DOXs, and Cys charateristic fluorescence, respectively.

A flavone-based turn-on fluorescent probe for intracellular cysteine/homocysteine sensing with high selectivity

A new type of flavone-based fluorescent probe (DMAF) capable of cysteine (Cys)/homocysteine (Hcy) sensing with high selectivity over other amino acids was developed. Such type of probe undergoes Cys/Hcy-mediated cyclization reaction with the involvement of its aldehyde group, which suppresses of the photoinduced electron transfer (PET) process of the probe molecule and consequently leads to the enhancement of fluorescence emission upon excitation using visible light. The formation of product of the Cys/Hcy-mediated cyclization reaction was confirmed and the preliminary fluorescence imaging experiments revealed the biocompatibility of the as-prepared probe and validated its practicability for intracellular Cys/Hcy sensing.

Photoswitching Near-Infrared Fluorescence from Polymer Nanoparticles Catapults Signals over the Region of Noises and Interferences for Enhanced Sensitivity

As a very sensitive technique, photoswitchable fluorescence not only gains ultrasensitivity but also imparts many novel and unexpected applications. Applications of near-infrared (NIR) fluorescence have demonstrated low background noises, high tissue-penetrating ability, and an ability to reduce photodamage to live cells. Because of these desired features, NIR-fluorescent dyes have been the premium among fluorescent dyes, and probes with photoswitchable NIR fluorescence are even more desirable for enhanced signal quality in the emerging optical imaging modalities but rarely used because they are extremely challenging to design and construct. Using a spiropyran derivative functioning as both a photoswitch and a fluorophore to launch its periodically modulated red fluorescence excitation energy into a NIR acceptor, we fabricated core-shell polymer nanoparticles exhibiting a photoswitchable fluorescence signal within the biological window (∼700-1000 nm) with a peak maximum of 776 nm. Live cells constantly synthesize new molecules, including fluorescent molecules, and also endocytose exogenous particles, including fluorescent particles. Upon excitation at different wavelengths, these fluorescent species bring about background noises and interferences covering nearly the whole visible region and therefore render many intracellular targets unaddressable. The oscillating NIR fluorescence signal with an on/off ratio of up to 67 that the polymer nanoparticles display is beyond the typical background noises and interferences, thus producing superior sharpness, reliability, and signal-to-noise ratios in cellular imaging. Taking these salient features, we anticipate that these types of nanoparticles will be useful for in vivo imaging of biological tissue and other complex specimens, where two-photon activation and excitation are used in combination with NIR-fluorescence photoswitching.

Cancer Cell Membrane-Biomimetic Nanoprobes with Two-Photon Excitation and Near-Infrared Emission for Intravital Tumor Fluorescence Imaging

Biomimetic fluorescent nanoprobes capable of emitting near-infrared (NIR) fluorescence (λmax ≈ 720 nm) upon excitation of 800 nm light were developed. The key conjugated polymer enabled two-photon absorption and Förster resonance energy transfer (FRET) processes within the nanoprobes, which imparted the nanoprobes with ideal NIR-incoming-NIR-outgoing fluorescence features. The cancer cell membrane (CM) coating endowed these nanoprobes with perfect biocompatibility and highly specific targeting ability to homologous tumors. It was believed that CM encapsulation provided an additional protecting layer for the photoactive components residing in the core of nanoprobes for retaining their intrinsic fluorescing ability in the physiological milieu. The long-term structural integrity, excellent photostability (fluorescence decrease <10% upon 30 min illumination of 800 nm pulse laser), high NIR fluorescence quantum yield (∼20%), and long in vivo circulation time of the target nanoprobes were also confirmed. The ability of these feature-packed nanoprobes for circumventing the challenges of absorption and light scattering caused by cellular structures and tissues was definitely confirmed via in vivo and in vitro experiments. The superior performances of these nanoprobes in terms of fluorescence signaling as well as targeting specificity were verified in intravital fluorescence imaging on tumor-bearing model mice. Specifically, these nanoprobes unequivocally enabled high-resolution visualization of the fine heterogeneous architectures of intravital tumor tissue, which proclaims the great potential of this type of probe for high-contrast fluorescence detection of thick biological samples in practical applications.

A Turn-On Fluorescent Probe for Detection of Sub-ppm Levels of a Sulfur Mustard Simulant with High Selectivity

A new type of fluorescent probe capable of detecting a sulfur mustard (SM) simultant at a concentration of 1.2 μM in solution and 0.5 ppm in the gas phase has been developed. Owing to its molecular structure with a thiocarbonyl component and two piperidyl moieties integrated into the xanthene molecular skeleton, this probe underwent a highly selective nucleophilic reaction with the SM simultant and generated a thiopyronin derivative emitting intensive pink fluorescence. The distinct difference in electronic structure between the probe and thiopyronin derivative generated a marked shift of the absorption band from 445 to 567 nm, which enabled an optimal wavelength propitious for exciting the thiopyronin derivative but adverse to the probe. Such efficient separation of the excitation wavelength and tremendous increase in fluorescence quantum yield, from less than 0.002 to 0.53, upon conversion from the probe to the thiopyronin derivative, jointly led to a distinct contrast in the beaconing fluorescence signal (up to 850-fold) and therefore the unprecedented sensitivity for detecting SM species.

Development of Nile red-functionalized magnetic silica nanoparticles for cobalt ion sensing and entrapping

A new type of hybrid nanoparticles (NPs) with combined magnetic and fluorescent properties in single particle was developed by incorporating magnetic silica NPs with highly fluorescent Nile red dyes. These NPs clearly exhibit Co2+ ion entrapping ability in aqueous milieu and Co2+-induced fluorescence enhancement features with high selectivity owing to the Co2+-triggered inhibition on the photoinduced electron transfer progress in the efficient fluorophore (Nile red derivative). Moreover, these dual-functional NPs display superparamagnetic features and the motion of these fluorescent NPs can be induced by the application of an external magnetic field, enabling a facile separation/removal of toxic Co2+ ion from the aqueous milieu and real-time monitoring via fluorescence measurements.