Synthesis, Crystal Structure, Two-photon Absorption and Biological Imaging Application of a Water Soluble Carbazole Quaternary Ammonium Compound

A novel carbazole quaternary ammonium compound（abbreviated as T_2） had been synthesized and characterized by ~1H NMR, ^（13）C NMR and Mass spectrometry. The single-crystal structure has been determined by X-ray single-crystal diffraction. The electrochemical and two-photon absorption properties of T_2 were systematically studied by cyclic voltammetry and Z-scan determination methods, respectively. The results suggested that T_2 had a good oxidation-reduction and excellent nonlinear optical property. The two-photon absorption（TPA） value has a maximum corresponding to cross section σ = 7963.3 GM（Goeppert-Mayer units） at 700 nm, indicating potential applications in nonlinear optical materials. Furthermore, attributing to the excellent water solubility and low cytotoxicity, the compound was explored on its primary application in biological imaging.

Green process of biomass waste derived fluorescent carbon quantum dots for biological imaging in vitro and in vivo

In the context of the circular economy,the huge amounts of biomass waste should be converted into value-added materials and energy to diminish pollution,atmospheric CO_(2)levels and costly waste disposal.Biological imaging usually uses expensive and toxic chemicals e.g.,organic dyes,semiconductor quantum dots,calling for safer,greener,cheaper fluorescent probes for biological imaging in vitro and in vivo.In these regards,carbon quantum dots(CQDs)-based fluorescent probes using biomass waste as a precursor may have much higher potential.Here we transformed the biomass waste of peach leaves into value-added fluorescent CQDs through a low-cost and green one-step hydrothermal process.The obtained CQDs show excitation-dependent photoluminescence properties with a fluorescence lifetime of 5.96 ns and a quantum yield of 7.71%without any passivation.In addition,the CQDs have a fine size of 1.9 nm with good hydrophilicity and high fluorescent stability over pH 4.0-11.0 range.Fluorescence imaging of in vitro cell cultures and in vivo with zebrafish show that CQDs possess ultra-low toxicity and remarkable performance for biological imaging.Even when CQDs present at a concentration as high as500μg/m L,the organism can still maintain more than 90%activity both in vitro and in vivo,and present bright fluorescence.The cheaper,greener,ultra-low toxicity CQDs developed in this work is a potential candidate for biological imaging in vitro and in vivo.

Polymerizable AEE-active Dye with Optical Activity for Fluorescent Nanoparticles Based on Phenothiazine:Synthesis,Self-assembly and Biological Imaging

In consideration of various advantages such as less harm,higher sensitivity,and deeper imaging depth,etc.,AIE materials with longwave emission are attracting extensive attention in the fields of vascular visualization,organelle imaging,cells tracker,forensic detection,bioprobe and chemosensor,etc.In this work,a novel fluorescent(R)-PVHMA monomer with chirality and aggregation-induced emission enhancement(AEE)characteristics was acquired through enzymatic transesterification reaction basing on phenothiazine,and its[α]D25℃value was about-6.39°with a 3.08 eV bandgap calculated by the quantum calculations.Afterwards,a series of PEG-PVH1 and PEG-PVH2 copolymers with chirality feature were achieved through RAFT polymerization of the obtained(R)-PVHMA and PEGMA with various feed ratios.When the feed molar ratio of(R)-PVHMA increased from 21.5%to 29.6%,its actual molar fractions in the PEG-PVH1 and PEG-PVH2 copolymers accordingly increased from 18.1%to 25.7%.The molecular weight of PEG-PVH1 was about 2.2×10^(4) with a narrow PDI,and their kinetics estimation showed a first-order quasilinear procedure.In aqueous solution,the amphiphilic copolymers PEG-PVH could self-assemble into about 100 nm nanoparticles.In a 90%water solution of H_(2)O and THF mixture,the fluorescence intensity had the maximum value,and the emission wavelength presented at 580 and 630 nm.The investigation of cytotoxicity and cells uptake showed that PEG-PVH FONs performed outstanding biocompatibility and excellent cells absorption effects,which have great potential in bioimaging application.

Recent Advances in Pure-Organic Host-Guest Room-Temperature Phosphorescence Systems Toward Bioimaging

Organic room-temperature phosphorescence(RTP)materials have garnered considerable attention in the fields of biosensing,optoelectronic devices,and anticounterfeiting because of their substantial Stokes shifts,tunable emission wavelengths,and prolonged lifetimes.These materials offer remarkable advantages for biological imaging applications by effectively reducing environmental autofluorescence and enhancing imaging resolution.Recently,host-guest systems have been employed as efficient approaches to fabricate pure-organic RTP materials for bioimaging,providing benefits such as controllable preparation and flexible modulation.Consequently,an increasing number of corresponding studies are being reported;however,a comprehensive systematic review is still lacking.Therefore,we summarize recent advances in the development of pureorganic RTP materials using host-guest systems with regard to bioimaging,including rigid matrices and sensitization.The challenge and potential of RTP for biological imaging are also proposed to promote the biomedical applications of organic RTP materials with excellent optical properties.

High Optical Magnification Three-Dimensional Integral Imaging of Biological Micro-organism

A high optical magnification three-dimensional imaging system is proposed using an optic microscope whose ocular （eyepiece） is retained and the structure of the transmission mode is not destroyed. The elemental image array is captured through the micro lens array. Due to the front diffuse transmission element, each micro lens sees a slightly different spatial perspective of the scene, and a different independent image is formed in each micro lens channel. Each micro lens channel is imaged by a Fourier lens and captured by a CCD. The design translating the stage in x or y provides no parallax. Compared with the conventional integral imaging of micro-objects, the optical magnification of micro-objects in the proposed system can enhanced remarkably. The principle of the enhancement of the image depth is explained in detail and the experimental results are presented.

Zebrafish imaging and two-photon fluorescence imaging using ZnSe quantum dots

This study is to report a ZnSe quantum dot with a large two-photon absorption cross section and good biocompatibility,which can be used in bioimaging.Fluorescence emission at 410 nm is observed in the quantum dot under 760-nm laser excitation.These biocompatible quantum dots exhibit a two-photon cross-section of 9.1×105 GM(1 GM=10-50 cm4·s/photon).Two-photon excited laser scanning microscopic images show that cells co-cultured with ZnSe quantum dots are found in the blue channel at a fluorescence intensity that is 14.5 times that of control cells not cocultured with quantum dots.After incubating zebrafish larvae with ZnSe quantum dots for 24 h,the fluorescence intensity of the yolk sac stimulated by ultraviolet light is 2.9 times that of the control group.The proposed material shows a great potential application in biological imaging.

Handheld diffuse optical breast scanner probe for cross-sectional imaging of breast tissue

Diffuse optical spectroscopy is a relatively new,noninvasive and nonionizing technique for breast cancer diagnosis.In the present study,we have introduced a novel handheld diffuse optical breast scan(DOB-Scan)probe to measure optical properties of the breast in vivo and create functional and compositional images of the tissue.In addition,the probe gives more information about breast tissue's constituents,which helps distinguish a healthy and cancerous tissue.Two symmetrical light sources,each including four different wavelengths,are used to illuminate the breast tissue.A high-resolution linear array detector measures the intensity of the back-scattered photons at different radial destinations from the illumination sources on the surface of the breast tissue,and a unique image reconstruction algorithm is used to create four cross-sectional images for four different wavelengths.Different fromfiber optic-based illumination techniques,the proposed method in this paper integrates multi-wavelength light-emitting diodes to act as pencil beam sources into a scattering medium like breast tissue.This unique design and its compact structure reduce the complexity,size and cost of a potential probe.Although the introduced technique miniaturizes the probe,this study points to the reliability of this technique in the phantom study and clinical breast imaging.We have received ethical approval to test the DOB-Scan probe on patients and we are currently testing the DOB-Scan probe on subjects who are diagnosed with breast cancer.

CLASSIFYING OPTICAL PROPERTIES OF SURFACE-AND BULK-SCATTERING BIOLOGICAL LAYERS WITH POLARIZATION SINGULAR STATES

The results of singular approach usage in the tasks of description and classification of appearance of optical anisotropy of different types of phase-inhomogeneous biological layers(surface-scattering,optically thin and optically thick)have been presented.The characteristic values of the fourth Stokes vector parameter(S_(4)=0-linear polarization-(L-state);S_(4)=±1-circular polarization-(C-state))have been chosen as the main analytical tool descni bing polarization-singular states.The value of S.has been deternined by the value of phase shift betwoen the ort hogonal components of amplitude in the point of biological layer laser image and therefore is azimuthally stable.Hence,statistic moments of the first to the fourth orders characterizing the distribution of the amount of characteristic values S4=0;S_(4)=±1 have been used for definition and di ferentiation of optical properties of diferent types of biological layers-surface scattering,optically thin and optically thick human skin.

Atomically precise gold nanoclusters for healthcare applications

The potential application of gold nanoparticles(GNPs)in biomedicine has been extensively reported.However,there is still too much puzzle about their real face and potential health risks in comparison with the commercial drug molecules.The emergence of atomically precise gold nanoclusters(APGNCs)provides the opportunity to address the puzzle due to their ultrasmall size,defined molecular formula,editable surface engineering,available structures and unique physicochemical properties including excellent biocompatibility,strong luminescence,enzyme-like activity and efficient renal clearance,et al.Recently,these advantages of APGNCs also endow them promising performances in healthcare such as bioimaging,drug delivery,antibacterial and cancer therapy.Especially,their clear composition and structures like the commercial drug molecules facilitate the study of their functions and the structure-activity relationship in healthcare,which is essential for the guided design of APGNC nanomedicine.Therefore,this review will focus the advantages and recent progress of APGNCs in health care and envision their prospects for the future.

A mini-review on rare-earth down-conversion nanoparticles for NIR-II imaging of biological systems

Rare-earth(RE)based luminescent probes exhibit rich optical properties including upconversion and down-conversion luminescence spanning a broad spectral range from 300 to 3,000 nm,and have generated great scientific and practical interest from telecommunication to biological imaging.While upconversion nanoparticles have been investigated for decades,down-conversion luminescence of RE-based probes in the second near-infrared(NIR-II,1,000-1,700 nm)window for in vivo biological imaging with sub-centimeter tissue penetration and micrometer image resolution has come into light only recently.In this review,we present recent progress on RE-based NIR-II probes for in vivo vasculature and molecular imaging with a focus on Er3+-based nanoparticles due to the down-conversion luminescence at the long-wavelength end of the NIR-II window(NIR-IIb,1,500-1,700 nm).Imaging in NIR-IIb is superior to imaging with organic probes such as ICG and IRDye800 in the^800 nm NIR range and the 1,000-1,300 nm short end of NIR-II range,owing to minimized light scattering and autofluorescence background.Doping by cerium and other ions and phase engineering of Er^3+-based nanoparticles,combined with surface hydrophilic coating optimization can afford ultrabright,biocompatible NIR-IIb probe towards clinical translation for human use.The Nd^3+-based probes with NIR-II emission at 1,050 and 1,330 nm are also discussed,including Nd^3+doped nanocrystals and Nd^3+-organic ligand complexes.This review also points out future directions for further development of multi-functional RE NIR-II probes for biological imaging.

ID-OCTA:OCT angiography based on inverse SNR and decorrelation features

Optical coherence tomography angiography(OCTA)takes the flowing red blood cells(RBCs)as intrinsic contrast agents,enabling fast and three-dimensional visualization of vasculature per-fusion down to capillary level,without a requirement of exogenous fluorescent injection.Various motion-contrast OCTA algorithms have been proposed to effectively extract dynamic blood flow from static tissues utilizing the different components of OCT signals(including amplitude,phase and complex)with various operations(such as differential,variance and decorrelation).Those algorithms promote the application of OCTA in both clinical diagnosis and scientific research.The purpose of this paper is to provide a systematical review of OCTA based on the inverse SNR and decorrelation features(ID-OCTA),mainly including the OCTA contrast origins,ID-OCTA imaging,quantification and applications.

Effective and robust approach for fluorescence molecular tomography based on CoSaMP and SP_(3)model

Fluorescence molecular tomography(FMT)allows the detection and quantification of various biological processes in small animals in vrivo,which expands the horizons of pre clinical rescarch and drug development.Eficient three dimensional(3D)reconstruction algorithm is the key to accurate localization and quant ification of fAuorescent target in FMT.In this paper,3D recon-struction of FMT is regarded as a sparse signal recovery problem and the compressive sampling matching pursuit(CoSaMP)algorithm is adopted to obtain greedy recovery of fuorescent sig-nals.Moreover,to reduce the modeling error,the simplified spherical harmonics approximation to the radiative transfer equation(RTE),more specifically SP_(3),is utilized to describe light prop-agation in biological tissues.The performance of the proposed reconstruction method is thor-oughly evaluated by simulations on a 3D digital mouse model by comparing it with three representative greedy methods including orthogonal matching pursuit(OMP),stagewise OMP(StOMP),and regularized OMP(ROMP).The CoSaMP combined with SP_(3)shows an im-provement in reconstruction accuracy and exhibits distinct advantages over the comparative algorithms in multiple targets resolving.Stability analysis suggests that CoSaMP is robust to noise and performs stably with reduction of measurements.The feasibility and reoonstruction accuracy of the proposed method are further validated by phantom experimental data.

In vivo evaluation of laser-induced choroidal neovascularization in rats simultaneously using optical coherence tomography and photoacoustic microscopy

Determination of the precise location and the degree of the Choroidal neovascularization(CNV)lesion is essential for diagnosation Neovascular age-related macular degeneration(AMD)and evaluation the efficacy of treatment.Noninvasive imaging techniques with specific contrast for CNV evaluation are demanded.In this paper,two noninvasive imaging techniques,namely Optical coherence tomography(OCT)and Photoacoustic microscopy(PAM),are combined to provide specific detection of CNV for their complimentary contrast mechanisms.In vivo time-serial evaluation of Laser-induced CNV in rats is present at days 1,3,5,7,14,21 after laser photocoagulation is applied to the rat fundus.Both OCT and PAM show that the CNV increases to its maximum at day 7 and decreases at day 14.Quantification of CNV area and CNV thickness is given.The dual-modal information of CNV is consistent with the histologic evaluation by hematoxylin and eosin(H&E)staining.

The Matrix Transform for Reconstruction on Finite-Element-Based Photoacoustic Tomography

Numerical Finite-element method (FEM) based algorithms have been widely applied for the reconstruction of the photoacoustic image. As compared with the traditional analytic methods, the FEM based methods can be easily used to deal with problems with irregularly shaped imaging domain. However, the FEM based algorithms are usually computationally intensive because repeated manipulations of matrices with larger size are needed during the reconstruction process. To tackle such a problem, a novel method is proposed for reducing the size of the matrix to be inversed during the reconstruction process and hence speed up the inverse reconstruction without any sacrifice of the reconstruction accuracy.

PRELIMINARY STUDY ON SKIN CANCER DETECTION IN SENCAR MICE USING MUELLER OPTICAL COHERENCE TOMOGRAPHY

We report on the use of a fiber-based Mueller-matrix optical coherence tomography(OCT)system with continuous source-polarization modulation for in vivo imaging of early stages of skin cancer in SENCAR mice.A homemade hand-held probe with integrated optical scanning and beam delivering optics was coupled in the sample arm.The OCT images show the morphological changes in skin resulting from pre-cancerous papilloma formations that are consistent with histology,thus demonstrating the system’s potential for early skin cancer detection.

Multifunctional Fluorescent Magnetic Nanoparticles： Synthesis, Characterization and Targeted Cell Imaging Applications

Multifunctional fluorescent magnetic nanoparticles （Fe3O4@SiO2-PLLA-RhB/FA） with cell recognition ability were synthesized through conjugation of magnetic nanoparticles with folic acid （FA） and Rhodamine B. To verity their potential biomedical applications, biocompatibility as well as cell imaging applications of the multifunctional nanoparticles were further investigated. Results showed that these fluorescent magnetic nanoparticles are well bio- compatible with NIH-3T3 cells and HeLa cells. More importantly, these nanoparticles could be selectively taken up by HeLa cells （FA receptor positive） as evidenced by laser scanning confocal microscopy, suggesting their potential for biological imaging applications. Given their excellent biocompatibility and multifunctional characteristics, weexpect that the fluorescent magnetic nanoparticles could be promising for various biomedical applications.

Polyetherimide functionalized carbon dots with enhanced red emission in aqueous solution for bioimaging

Red emissive carbon dots(CDs)are highly desired for biological applications.However,serious luminescence quenching of red emissive CDs in aqueous solution greatly hinders their application in high performance biological imaging.Herein,we reported a facile strategy to realize enhanced red emission of CDs in aqueous solution by surface modification with polyetherimide(PEI)via microwave heating method.High photoluminescence quantum yield(PLQY)of 25%was realized from the PEI functionalized CDs(CDs@PEI)in aqueous solution.The proposed PEI functionalization strategy not only protects the red emission against water molecules quenching,but also reverses the surface charges from negativity to positivity to promote cellular uptake of CDs,leading to clear cell imaging in red fluorescence region.More important,CDs@PEI exhibits much better photostability than commercial red emissive dye(MitoT racker red)in cell fluorescent imaging.Potential application of CDs@PEI on fast staining of cells for clonogenic assay has also been demonstrated.

Donor-Acceptor Typed AIE Luminogens with Near-infrared Emission for Super-resolution Imaging

Aggregation-induced emission(AIE)luminogens(AIEgens)with high brightness in aggregates exhibit great potentials in biological imaging,but these AIEgens are seldom applied in super-resolution biological imaging,especially in the imaging by using the structural illumination microscope(SIM).Based on this consideration,we synthesized the donor-acceptor typed AIEgen of DTPA-BTN,which not only owns high brightness in the near-infrared(NIR)emission region from 600 nm to 1000 nm(photoluminescence quantum yield,PLQYs=11.35%),but also displays excellent photo-stability.In addition,AIE nanoparticles based on 4,7-ditriphenylamine-[1,2,5]-thiadiazolo[3,4-c]pyridine(DTPA-BTN)were also prepared with highly emissive features and excellent biocompatibility.Finally,the developed DTPA-BTN-based AIE nanoparticles were applied in the super-resolution cellular imaging via SIM,where much smaller full width at half-maximum values and high signal to noise ratios were obtained,indicating the superior imaging resolution.The results here imply that highly emissive AIEgens or AIE nanoparticles can be promising imaging agents for super-resolution imaging via SIM.

Polyoxometalates based nanocomposites for bioapplications

Health care and medical care have always been dominant topics in human society.The field of precision medicine,iatrotechnics revolution and timely on-demand detection have continued to evolve in response to increasing demands from the society.Furthermore,the emergence of innovative materials and their applications offer promising prospects for advancing global health.Polyoxometalates(POMs)are negatively-charged molecular metal oxides with well-defined structures,beautiful geometries and nanoscale sizes.Owing to their vast diversity in composition,structure,nuclearity and charge,they constitute a significant subcategory of inorganic clusters that contain bridging oxygen atoms between two or more metal ions.Nowadays,POMs based nanocomposites have been widely applied in the field of disease diagnosis,anticancer therapy and antibacterial therapy as new generation bioactive materials.In this review,the recent advances of POMs based nanocomposites in bioapplications are summarized and the future perspectives are discussed.