Review on Optical Imaging Techniques for Multispectral Analysis of Nanomaterials

Development of a novel technology for long-term culture and live imaging of excised human tissue

An integrated understanding of the structure and reactivity of cells, extracellular matrices, and appendages is important for elucidating their functions and mechanisms in our bodies. Three-dimensional imaging using immuno-fluorescent staining with decolorization technology aids in comprehending the internal structure of human organs. However, live imaging of skin dynamics using animal models is highly invasive and unsuitable for humans. The aim of this study was to establish a non-invasive live imaging method for excised human tissue. In this study, to maintain excised human skin tissue in a state similar to a living body, we developed a novel microneedle-based culture technique. This method was evaluated for cytotoxicity detection, inflammatory cytokine release, and tissue morphology. Using microneedles, we cultured excised skin tissue and observed cellular organelles, reactive oxygen species (ROS), and fibrous structures via fluorescent probes and autofluorescence. The microneedle technique prevented cell death and inflammation, enabling long-term culturing. We live-imaged various skin cells, extracellular matrices, and appendage structures, visualizing epidermal cell membranes, mitochondria, and ROS. Collagen and elastin fibers were observed using autofluorescence and second harmonic generation. This approach enabled live imaging for 5 d, providing insights into skin metabolism, regeneration, and responses to stimuli and drugs, ultimately advancing dermatological research.

Recent Advances in Reactive Oxygen Species -Mediated Near-Infrared Organic Long-Persistent Luminescence Imaging

Organic luminophores have found extensive applications in cellular and in vivo fluorescence imaging. However, their efficacy is often hindered by formidable challenges, including a low signal-to-noise ratio (SNR), susceptibility to false-positive signals, limited tissue penetration depth, and autofluorescence arising from non-negligible background interference. The emergence of near-infrared (NIR) afterglow imaging has addressed these problems. Organic afterglow imaging distinguishes by its unique capacity to emit light long after the cessation of external excitation, thereby exhibiting extraordinary persistence in luminescence. The integration of deep tissue penetration with prolonged luminescence in NIR organic long-persistent luminescent materials confers a distinct advantage for in vivo biological imaging, effectively minimizing the confounding effects of autofluorescence while enhancing spatial resolution for imaging in deep tissues, which is favorable for biosensing. In this review, we present a comprehensive summary of recent advancements in reactive oxygen species (ROS)-mediated NIR organic afterglow imaging, positioning this emerging technique as an exceptionally promising approach for in vivo biosensing, biological imaging, imaging-guided surgery, and therapeutic applications. Furthermore, we critically examine the challenges facing this field and propose future avenues for its continued evolution and refinement.

In Vivo Surface-Enhanced Transmission Raman Spectroscopy and Impact of Frozen Biological Tissues on Lesion Depth Prediction

Plasmonic surface-enhanced transmission Raman spectroscopy (SETRS) has emerged as a promising optical technique for detecting and predicting the depths of deep-seated lesions in biological tissues. However, in vivo studies using SETRS are scarce and typically show shallow penetration depths. Moreover, the optical parameters used in the prediction process are often derived from frozen samples and there is limited understanding of how freezing affects the optical properties of biological tissues and the accuracy of depth prediction in living models. In this work, we conduct in vivo SETRS measurements on thick abdominal tissue region of the live rats to investigate the impact of freezing on the measured optical properties for the purpose of depth prediction. First, we fabricated ultrahigh bright surface-enhanced Raman spectroscopy (SERS) nanotags and utilized a custom transmission Raman system. We then measured the change of optical attenuation at two different wavelengths (Δμ) for four types of rat tissues (including skin, fat, muscle, and liver) following freezing. The freezing process dramatically affects Δμ values, even after only 1 day of freezing. In contrast, Δμ values obtained from fresh samples enable precise localization of SERS lesion phantoms in the live rat with only 5% deviation. The total thickness of the live rat is 2.6 cm, which, to the best of our knowledge, is the highest value of in vivo SETRS studies so far. This work helps to fill the gap in the SERS field of tissue localization and optical coefficient studies in highly heterogeneous tissues, and demonstrates the potential of the SETRS technique to achieve precise clinical localization of deep lesions.

Nonadiabatic Excited-State Molecular Dynamics with an Explicit Solvent: NEXMD-SANDER Implementation

In this article, the nonadiabatic excited-state Molecular dynamics (NEXMD) package is linked with the SANDER package, provided by AMBERTOOLS. The combination of these software packages enables the simulation of photoinduced dynamics of large multichromophoric conjugated molecules involving several coupled electronic excited states embedded in an explicit solvent by using the quantum/mechanics/molecular mechanics (QM/MM) methodology. The fewest switches surface hopping algorithm, as implemented in NEXMD, is used to account for quantum transitions among the adiabatic excited-state simulations of the photoexcitation and subsequent nonadiabatic electronic transitions, and vibrational energy relaxation of a substituted polyphenylenevinylene oligomer (PPV3-NO2) in vacuum and methanol as an explicit solvent has been used as a test case. The impact of including specific solvent molecules in the QM region is also analyzed. Our NEXMD-SANDER QM/MM implementation provides a useful computational tool to simulate qualitatively solvent-dependent effects, like electron transfer, stabilization of charge-separated excited states, and the role of solvent reorganization in the molecular optical properties, observed in solution-based spectroscopic experiments.

Review on Photoacoustic Monitoring after Drug Delivery: From Label-Free Biomarkers to Pharmacokinetics Agents

Photoacoustic imaging (PAI) is an emerging noninvasive and label-free method for capturing the vasculature, hemodynamics, and physiological responses following drug delivery. PAI combines the advantages of optical and acoustic imaging to provide high-resolution images with multiparametric information. In recent decades, PAI's abilities have been used to determine reactivity after the administration of various drugs. This study investigates photoacoustic imaging as a label-free method of monitoring drug delivery responses by observing changes in the vascular system and oxygen saturation levels across various biological tissues. In addition, we discuss photoacoustic studies that monitor the biodistribution and pharmacokinetics of exogenous contrast agents, offering contrast-enhanced imaging of diseased regions. Finally, we demonstrate the crucial role of photoacoustic imaging in understanding drug delivery mechanisms and treatment processes.

Revolutionizing cancer therapy: nanoformulation of miRNA-34 - enhancing delivery and efficacy for various cancer immunotherapies: a review

Despite recent advancements in cancer therapies, challenges such as severe toxic effects, non-selective targeting, resistance to chemotherapy and radiotherapy, and recurrence of metastatic tumors persist. Consequently, there has been considerable effort to explore innovative anticancer compounds, particularly in immunotherapy, which offer the potential for enhanced biosafety and efficacy in cancer prevention and treatment. One such avenue of exploration involves the miRNA-34 (miR-34) family, known for its ability to inhibit tumorigenesis across various cancers. Dysregulation of miR-34 has been observed in several human cancers, and it is recognized as a tumor suppressor microRNA due to its synergistic interaction with the well-established tumor suppressor p53. However, challenges have arisen with the therapeutic application of miR-34a. These include its susceptibility to degradation by RNase in serum, limiting its ability to penetrate capillary endothelium and reach target cells, as well as reports of immunoreactive adverse reactions. Furthermore, unexpected side effects may occur, such as the accumulation of therapeutic miRNAs in healthy tissues due to interactions with serum proteins on nano-vector surfaces, nanoparticle breakdown in the bloodstream due to shearing stress, and unsuccessful extravasation of nanocarriers to target cells owing to interstitial fluid pressure. Despite these challenges, miR-34a remains a promising candidate for cancer therapy, and other members of the miR-34 family have also shown potential in inhibiting tumor cell proliferation. While the in vivo applications of miR-34b/c are limited, they warrant further exploration for oncotherapy. Recently, procedures utilizing nanoparticles have been developed to address the challenges associated with the clinical use of miR-34, demonstrating efficacy both in vitro and in vivo. This review highlights emerging trends in nanodelivery systems for miR-34 targeting cancer cells, offering insights into novel nanoformulations designed to enhance the anticancer therapeutic activity and targeting precision of miR-34. As far as current knowledge extends, no similar recent review comprehensively addresses the diverse nanoformulations aimed at optimizing the therapeutic potential of miR-34 in anticancer strategies.

Advanced Techniques for Liver Fibrosis Detection: Spectral Photoacoustic Imaging and Superpixel Photoacoustic Unmixing Analysis for Collagen Tracking

Liver fibrosis, a major global health issue, is marked by excessive collagen deposition that impairs liver function. Noninvasive methods for the direct visualization of collagen content are crucial for the early detection and monitoring of fibrosis progression. This study investigates the potential of spectral photoacoustic imaging (sPAI) to monitor collagen development in liver fibrosis. Utilizing a novel data-driven superpixel photoacoustic unmixing (SPAX) framework, we aimed to distinguish collagen presence and evaluate its correlation with fibrosis progression. We employed an established diethylnitrosamine (DEN) model in rats to study liver fibrosis over various time points. Our results revealed a significant correlation between increased collagen photoacoustic signal intensity and advanced fibrosis stages. Collagen abundance maps displayed dynamic changes throughout fibrosis progression. These findings underscore the potential of sPAI for the noninvasive monitoring of collagen dynamics and fibrosis severity assessment. This research advances the development of noninvasive diagnostic tools and personalized management strategies for liver fibrosis.

Mesoporous silica nanoparticles: a versatile carrier platform in lung cancer management

Mesoporous silica nanoparticles (MSNPs) are inorganic nanoparticles that have been comprehensively investigated and are intended to deliver therapeutic agents. MSNPs have revolutionized the therapy for various conditions, especially cancer and infectious diseases. In this article, the viability of MSNPs' administration for lung cancer therapy has been reviewed. However, certain challenges lay ahead in the successful translation such as toxicology, immunology, large-scale production, and regulatory matters have made it extremely difficult to translate such discoveries from the bench to the bedside. This review highlights recent developments, characteristics, mechanism of action and customization for targeted delivery. This review also covers the most recent data that sheds light on MSNPs' extraordinary therapeutic potential in fighting lung cancer as well as future hurdles.

A rapid multispectral endoscopic imaging system for in vivo assessment of the morphological and physiological characteristics of mouse intestines

Accurate assessment of blood content in biological tissues is critical for the diagnosis and monitoring of various diseases, including cardiovascular disease, tumors, trauma, and the success rate of organ transplants. In this study, a multispectral endoscopic imaging system was built for capturing tissue reflection optical images in 18 bands across the wavelength range from 400 nm to 760 nm, non-invasively. The system was characterized by six tri-channel narrowband filters installed in front of the light source to achieve spectral separation and was equipped with a specially designed color CCD for achieving a speed of 24 multispectral imaging cubes per second. A method based on linear matrix inversion was proposed to calibrate the CCD spectral response overlaps, while a spectral analysis algorithm was developed for evaluating blood content and detecting tissue composition. The developed system was implemented in an in vivo mouse model for illustrating the blood volume, blood oxygen saturation index, and scattering particle size of the intestinal wall mucosa. The observations not only helped us to understand the blood supply situation in the intestinal mucosa, but also further testified the feasibility of our presented system. Meanwhile, the developed system could provide critical non-invasive optical information for intracavitary cancer diagnosis, surgery guidance, and treatment assessment.

Targeted insertion and reporter transgene activity at a gene safe harbor of the human blood fluke, Schistosoma mansoni

The identification and characterization of genomic safe harbor sites (GSHs) can facilitate consistent transgene activity with minimal disruption to the host cell genome. We combined computational genome annotation and chromatin structure analysis to predict the location of four GSHs in the human blood fluke, Schistosoma mansoni, a major infectious pathogen of the tropics. A transgene was introduced via CRISPR-Cas-assisted homology-directed repair into one of the GSHs in the egg of the parasite. Gene editing efficiencies of 24% and transgene-encoded fluorescence of 75% of gene-edited schistosome eggs were observed. The approach advances functional genomics for schistosomes by providing a tractable path for generating transgenics using homology-directed, repair-catalyzed transgene insertion. We also suggest that this work will serve as a roadmap for the development of similar approaches in helminths more broadly.

Automated Laser-Fiber Coupling Module for Optical-Resolution Photoacoustic Microscopy

Photoacoustic imaging has emerged as a promising biomedical imaging technique that enables visualization of the optical absorption characteristics of biological tissues in vivo. Among the different photoacoustic imaging system configurations, optical-resolution photoacoustic microscopy stands out by providing high spatial resolution using a tightly focused laser beam, which is typically transmitted through optical fibers. Achieving high-quality images depends significantly on optical fluence, which is directly proportional to the signal-to-noise ratio. Hence, optimizing the laser-fiber coupling is critical. Conventional coupling systems require manual adjustment of the optical path to direct the laser beam into the fiber, which is a repetitive and time-consuming process. In this study, we propose an automated laser-fiber coupling module that optimizes laser delivery and minimizes the need for manual intervention. By incorporating a motor-mounted mirror holder and proportional derivative control, we successfully achieved efficient and robust laser delivery. The performance of the proposed system was evaluated using a leaf-skeleton phantom in vitro and a human finger in vivo, resulting in high-quality photoacoustic images. This innovation has the potential to significantly enhance the quality and efficiency of optical-resolution photoacoustic microscopy.

Functional photoacoustic imaging: from nano- and micro- to macro-scale

Functional photoacoustic imaging is a promising biological imaging technique that offers such unique benefits as scalable resolution and imaging depth, as well as the ability to provide functional information. At nanoscale, photoacoustic imaging has provided super-resolution images of the surface light absorption characteristics of materials and of single organelles in cells. At the microscopic and macroscopic scales. photoacoustic imaging techniques have precisely measured and quantified various physiological parameters, such as oxygen saturation, vessel morphology, blood flow, and the metabolic rate of oxygen, in both human and animal subjects. This comprehensive review provides an overview of functional photoacoustic imaging across multiple scales, from nano to macro, and highlights recent advances in technology developments and applications. Finally, the review surveys the future prospects of functional photoacoustic imaging in the biomedical field.

Vibrational Funnels for Energy Transfer in Organic Chromophores

Photoinduced intramolecular energy transfers in multichromophoric molecules involve nonadiabatic vibronic channels that act as energy transfer funnels. They commonly take place through specific directions of motion dictated by the nonadiabatic coupling vectors. Vibrational funnels may support persistent coherences between electronic states and sometimes delineate the presence of minor alternative energy transfer pathways. The ultimate confirmation of their role on the interchromophoric energy transfer can be achieved by performing nonadiabatic excited-state molecular dynamics simulations by selectively freezing the nuclear motions in question. Our results point out this strategy as a useful tool to identify and evaluate the impact of these vibrational funnels on the energy transfer processes and guide the in silico design of materials with tunable properties and enhanced functionalities. Our work encourages applications of this methodology to different chemical and biochemical processes such as reactive scattering and protein conformational changes, to name a few.

Review on ultrasound-guided photoacoustic imaging for complementary analyses of biological systems in vivo

Photoacoustic imaging has been developed as a new biomedical molecular imaging modality. Due to its similarity to conventional ultrasound imaging in terms of signal detection and image generation, dual-modal photoacoustic and ultrasound imaging has been applied to visualize physiological and morphological information in biological systems in vivo. By complementing each other, dual-modal photoacoustic and ultrasound imaging showed synergistic advances in photoacoustic imaging with the guidance of ultrasound images. In this review, we introduce our recent progresses in dual-modal photoacoustic and ultrasound imaging systems at various scales of study, from preclinical small animals to clinical humans. A summary of the works reveals various strategies for combining the structural information of ultrasound images with the molecular information of photoacoustic images.

Rational Design of a Self-Assembling High Performance Organic Nanofluorophore for Intraoperative NIR-II Image-Guided Tumor Resection of Oral Cancer

The first line of treatment for most solid tumors is surgical resection of the primary tumor with adequate negative margins. Incomplete tumor resections with positive margins account for over 75% of local recurrences and the development of distant metastases. In cases of oral cavity squamous cell carcinoma (OSCC), the rate of successful tumor removal with adequate margins is just 50-75%. Advanced real-time imaging methods that improve the detection of tumor margins can help improve success rates,overall safety, and reduce the cost. Fluorescence imaging in the second near-infrared (NIR-II) window has the potential to revolutionize the field due to its high spatial resolution, low background signal, and deep tissue penetration properties, but NIR-II dyes with adequate in vivo performance and safety profiles are scarce. A novel NIR-II fluorophore, XW-03-66, with a fluorescence quantum yield (QY) of 6.0% in aqueous media is reported. XW-03-66 self-assembles into nanoparticles (≈80 nm) and has a systemic circulation half-life (t_1/2 ) of 11.3 h. In mouse models of human papillomavirus (HPV)+ and HPV- OSCC, XW-03-66 outperformed indocyanine green (ICG), a clinically available NIR dye, and enabled intraoperative NIR-II image-guided resection of the tumor and adjacent draining lymph node with negative margins. In vitro and in vivo toxicity assessments revealed minimal safety concerns for in vivo applications.

Recent Advances in Photoacoustic Agents for Theranostic Applications

Photoacoustic agents are widely used in various theranostic applications. By evaluating the biodistribution obtained from photoacoustic images, the effectiveness of theranostic agents in terms of their delivery efficiency and treatment responses can be analyzed. Through this study, we evaluate and summarize the recent advances in photoacoustic-guided phototherapy, particularly in photothermal and photodynamic therapy. This overview can guide the future directions for theranostic development. Because of the recent applications of photoacoustic imaging in clinical trials, theranostic agents with photoacoustic monitoring have the potential to be translated into the clinical world.

Cancer bioimaging using dual mode luminescence of graphene/FA-ZnO nanocomposite based on novel green technique

Graphene based nanomaterials are explored in the field of cancer bioimaging and biomedical science and engineering. The luminescent nanostructures with a low toxicity and high photostability can be used as probes in bioimaging applications. This work is aimed to prepare graphene/folic acid-zinc oxide (GN/FA-ZnO) nanocomposite with dual-mode emissions (down-conversion and up-conversion) to be used in cancer bioimaging. The dual mode emissions offer long luminescence lifetime, multicolor emissions detected by the naked eyes after excitation and narrow band absorption and emission spectra. ZnO nanospheres and nanorods structures were prepared using co-precipitation technique and were conjugated with FA to separate the bulk graphite layers electrostatically into GN. The optical, morphological, surface charge and structural properties of the prepared nanostructures were investigated and discussed using different characterization techniques such as UV-visible spectroscopy, photoluminescence (PL) spectroscopy, scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), Zeta potential, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), and Fourier transform infrared (FTIR). GN/FA-ZnO nanocomposites were injected into Swiss albino mice implanted with Ehrlich Tumor and the bioimaging was investigated using photon imager and digital camera. The results showed clear fluorescence and confirmed that the green design of GN/FA-ZnO nanocomposite with targeting behavior was capable of selective bioimaging of the tumor. This study presented a novel dual mode emission nanocomposite for tumor targeting and is a promising strategy for the fabrication of a new design of spectral encoding.

Investigation of the Hue-Wavelength Response of a CMOS RGB-Based Image Sensor

In this study, a non-linear hue-wavelength (H-W) curve was investigated from 400 to 650 nm. To date, no study has reported on H-W relationship measurements, especially down to the 400 nm region. A digital camera mounted with complementary metal oxide semiconductor (CMOS) image sensors was used. The obtained digital images of the sample were based on an RGB-based imaging analysis rather than multispectral imaging or hyperspectral imaging. In this study, we focused on the raw image to reconstruct the H-W curve. In addition, several factors affecting the digital image, such as exposure time or international organization for standardization (ISO), were investigated. In addition, cross check of the H-W response using laser was performed. We expect that our method will be useful as an auxiliary method in the future for obtaining the fluor emission wavelength information.

Contrast Agents for Photoacoustic Imaging: A Review Focusing on the Wavelength Range

Photoacoustic imaging using endogenous chromophores as a contrast has been widely applied in biomedical studies owing to its functional imaging capability at the molecular level. Various exogenous contrast agents have also been investigated for use in contrast-enhanced imaging and functional analyses. This review focuses on contrast agents, particularly in the wavelength range, for use in photoacoustic imaging. The basic principles of photoacoustic imaging regarding light absorption and acoustic release are introduced, and the optical characteristics of tissues are summarized according to the wavelength region. Various types of contrast agents, including organic dyes, semiconducting polymeric nanoparticles, gold nanoparticles, and other inorganic nanoparticles, are explored in terms of their light absorption range in the near-infrared region. An overview of the contrast-enhancing capacity and other functional characteristics of each agent is provided to help researchers gain insights into the development of contrast agents in photoacoustic imaging.

Whole-Body Photoacoustic Imaging Techniques for Preclinical Small Animal Studies

Photoacoustic imaging is a hybrid imaging technique that has received considerable attention in biomedical studies. In contrast to pure optical imaging techniques, photoacoustic imaging enables the visualization of optical absorption properties at deeper imaging depths. In preclinical small animal studies, photoacoustic imaging is widely used to visualize biodistribution at the molecular level. Monitoring the whole-body distribution of chromophores in small animals is a key method used in preclinical research, including drug-delivery monitoring, treatment assessment, contrast-enhanced tumor imaging, and gastrointestinal tracking. In this review, photoacoustic systems for the whole-body imaging of small animals are explored and summarized. The configurations of the systems vary with the scanning methods and geometries of the ultrasound transducers. The future direction of research is also discussed with regard to achieving a deeper imaging depth and faster imaging speed, which are the main factors that an imaging system should realize to broaden its application in biomedical studies.

Review on Multispectral Photoacoustic Analysis of Cancer: Thyroid and Breast

In recent decades, photoacoustic imaging has been used widely in biomedical research, providing molecular and functional information from biological tissues in vivo. In addition to being used for research in small animals, photoacoustic imaging has also been utilized for in vivo human studies, achieving a multispectral photoacoustic response in deep tissue. There have been several clinical trials for screening cancer patients by analyzing multispectral responses, which in turn provide metabolomic information about the underlying biological tissues. This review summarizes the methods and results of clinical photoacoustic trials available in the literature to date to classify cancerous tissues, specifically of the thyroid and breast. From the review, we can conclude that a great potential exists for photoacoustic imaging to be used as a complementary modality to improve diagnostic accuracy for suspicious tumors, thus significantly benefitting patients’ healthcare.