Two-layered multiphoton microscopic imaging of cervical tissue

Current Trends and Advances in Nanoplatforms-Based Imaging for Cancer Diagnosis

The intersection of nanotechnology and biomedical imaging has ushered in a new era in the early detection and diagnosis of cancer which has revolutionized biomedical imaging by enhancing sensitivity, resolution, and targeting capability. This review presents a comprehensive overview of the latest developments and innovations in nanoplatforms-based imaging for cancer diagnosis, a burgeoning field that holds significant potential in improving cancer detection and treatment. Recently multimodal imaging techniques utilizing the unique properties of different types of nanoparticles are providing comprehensive diagnostic information. This multi-pronged approach allows for more precise tumor localization, size estimation, and growth rate calculation, offering a holistic view of the tumor and its environment. The primary focus of this review is on the recent progress in various types of nanoparticle-based imaging modalities, including optical, magnetic resonance, ultrasound, and nuclear imaging. Specific advancements in nanomaterial design for targeted imaging are highlighted, showing the improvement of precision targeting as an impact on the detection of cancer cells, even in early-stage tumors. A keen examination on the integration of diagnostic and therapeutic capabilities into single nano-based platforms for theranostics, underscoring their potential in personalized medicine is provided. The current challenges in the field, such as issues related to toxicity, biodistribution, and clearance of nanoparticles, and it explores ongoing research aimed at overcoming these hurdles. The growing body of research in this field highlights the promising future of nanoplatforms in improving the early detection and treatment of cancer.

Types of spectroscopy and microscopy techniques for cancer diagnosis: a review

Cancer is a life-threatening disease that has claimed the lives of many people worldwide. With the current diagnostic methods, it is hard to determine cancer at an early stage, due to its versatile nature and lack of genomic biomarkers. The rapid development of biophotonics has emerged as a potential tool in cancer detection and diagnosis. Using the fluorescence, scattering, and absorption characteristics of cells and tissues, it is possible to detect cancer at an early stage. The diagnostic techniques addressed in this review are highly sensitive to the chemical and morphological changes in the cell and tissue during disease progression. These changes alter the fluorescence signal of the cell/tissue and are detected using spectroscopy and microscopy techniques including confocal and two-photon fluorescence (TPF). Further, second harmonic generation (SHG) microscopy reveals the morphological changes that occurred in non-centrosymmetric structures in the tissue, such as collagen. Again, Raman spectroscopy is a non-destructive method that provides a fingerprinting technique to differentiate benign and malignant tissue based on Raman signal. Photoacoustic microscopy and spectroscopy of tissue allow molecule-specific detection with high spatial resolution and penetration depth. In addition, terahertz spectroscopic studies reveal the variation of tissue water content during disease progression. In this review, we address the applications of spectroscopic and microscopic techniques for cancer detection based on the optical properties of the tissue. The discussed state-of-the-art techniques successfully determines malignancy to its rapid diagnosis.

Quantification of gold nanoparticle accumulation in tissue by two-photon luminescence microscopy

Nanomedicine has emerged as a promising strategy to address some of the limitations of traditional biomedical sensing, imaging and therapy modalities. Its applicability and efficacy are, in part, hindered by the difficulty in both controllably delivering nanoparticles to specific regions and accurately monitoring them in tissue. Gold nanoparticles are among the most extensively used inorganic nanoparticles which benefit from high biocompatibility, flexible functionalization, strong and tunable resonant absorption, and production scalability. Moreover, their capability to enhance optical fields at their plasmon resonance enables local boosting of non-linear optical processes, which are otherwise very inefficient. In particular, two-photon induced luminescence (TPL) in gold offers high signal specificity for monitoring gold nanoparticles in a biological environment. In this article, we demonstrate that TPL microscopy provides a robust sub-micron-resolution technique able to quantify accumulated gold nanorods (GNRs) both in cells and in tissues. First, the temporal accumulation of GNRs with two different surface chemistries was measured in 786-O cells during the first 24 hours of incubation, and at different nanoparticle concentrations. Subsequently, GNR accumulation in mice, 6 h and 24 hours after tail vein injection, was quantified by TPL microscopy in biopsied tissue from kidney, spleen, liver and clear cell renal cell carcinoma (ccRCC) tumors, in good agreement with inductively coupled mass spectroscopy. Our data suggest that TPL microscopy stands as a powerful tool to understand and quantify the delivery mechanisms of gold nanoparticles, highly relevant to the development of future theranostic medicines.

Label-free imaging and spectroscopy for early detection of cervical cancer

The label-free imaging and spectroscopy method was studied on cervical unstained tissue sections obtained from 36 patients. The native fluorescence spectra of tissues are analyzed by the optical redox ratio (ORR), which is defined as fluorescence intensity ratio between NADH and FAD, and indicates the metabolism change with the cancer development. The ORRs of normal tissues are consistently higher than those of precancer or cancerous tissues. A criterion line of ORR at 5.0 can be used to discriminate cervical precancer/cancer from normal tissues. The sensitivity and specificity of the native fluorescence spectroscopy method for cervical cancer diagnosis are determined as 100% and 91%. Moreover, the native fluorescence spectroscopy study is much more sensitive on the healthy region of cervical precancer/cancer patients compared with the traditional clinical staining method. The results suggest label-free imaging and spectroscopy is a fast, highly sensitive and specific method on the detection of cervical cancer.

Layer-resolved colorectal tissues using nonlinear microscopy

In this work, multiphoton microscopy (MPM), based on the nonlinear optical processes two-photon excited fluorescence (TPEF) and second harmonic generation (SHG), was extended to evaluate the feasibility of using MPM to distinguish layers of the bowel wall. It was found that MPM has the ability to identify the four-layer microstructures of colorectal tissues including mucosa, submucosa, muscularis propria, and serosa as there are many intrinsic signal sources in each layer. Our results also showed the capability of using the quantitative analyses of MPM images for quantifying some feature parameters including the nuclear area, nuclear-to-cytoplasmic ratio, and optical redox ratio. This work demonstrates that MPM has the potential in noninvasively monitoring the development and progression of colorectal diseases and then guiding effective treatment.

Assessment of colloid response by nonlinear optical microscopy after preoperative radiochemotherapy for rectal carcinoma

Colloid response is a type of tumor response that occurs after preoperative radiochemotherapy for rectal carcinoma. Given its important influence on survival, the colloid response should be considered when estimating histopathological reactions. Here, multiphoton microscopy (MPM) was applied to evaluate the colloid response ex vivo. This study demonstrated that MPM has the capability to visualize the colloid response in the absence of labels and can, in particular, identify rare residual carcinomatous cells in mucin pools. These results highlight the potential of this nonlinear optical technique as a diagnostic tool for tumor response after neoadjuvant treatment.

Multiphoton microscopy for tumor regression grading after neoadjuvant treatment for colorectal carcinoma

AIM: To evaluate the feasibility of using multiphoton microscopy (MPM) to assess a tumor regression grading (TRG) system.

METHODS: Fresh specimens from seven patients with colorectal carcinoma undergoing neoadjuvant radiochemotherapy at the Fujian Medical University Union Hospital were obtained immediately after proctectomy. Specimens were serially sectioned (10 µm thickness) and used for MPM or stained with hematoxylin and eosin for comparison. Sections were imaged by MPM using 810 nm excitation, and images were collected in two wavelength channels corresponding to second-harmonic generation (SHG) and two-photon excited fluorescence (TPEF) signals. The ratio of these signal intensities was used to distinguish fibrosis from normal mucosal and serosal tissues.

RESULTS: TRG of specimens assessed by MPM were in complete agreement with histologic grading performed by a consulting pathologist. SHG and TPEF images clearly revealed collagen fibers and fragmented elastic fibers in the muscularis propria specimens following neoadjuvant radiochemotherapy. Additionally, blood vessel hyperplasia was observed as thickening and fibrosis of the intima and media, which was accompanied by minimal inflammatory cell infiltration. Furthermore, the SHG/TPEF ratio in stromal fibrosis (4.15 ± 0.58) was significantly higher than those in the normal submucosal (2.31 ± 0.52) and serosal (1.47 ± 0.10) tissues (P < 0.001 for both). Analysis of emission spectra from cancerous tumor cells revealed two peaks corresponding to nicotinamide adenine dinucleotide hydrogen and flavin adenine dinucleotide signals; the ratio of these values was 1.19 ± 0.02, which is close to a normal metabolic state.

CONCLUSION: MPM can be used to perform real-time diagnosis of tumor response after neoadjuvant treatment, and can be applied to evaluate TRG.

Second-harmonic generation imaging of cancer

The last 30 years has seen great advances in optical microscopy with the introduction of sophisticated fluorescence-based imaging methods such as confocal and multiphoton laser scanning microscopy. There is increasing interest in using these methods to quantitatively examine sources of intrinsic biological contrast including autofluorescent endogenous proteins and light interactions such as second-harmonic generation (SHG) in collagen. In particular, SHG-based microscopy has become a widely used quantitative modality for imaging noncentrosymmetric proteins such as collagen in a diverse range of tissues. Due to the underlying physical origin of the SHG signal, it is highly sensitive to collagen fibril/fiber structure and, importantly, to collagen-associated changes that occur in diseases such as cancer, fibrosis, and connective tissue disorders. An overview of SHG physics background and technologies is presented with a focused review on applications of SHG primarily as applied to cancer.

In vivo nonlinear spectral imaging as a tool to monitor early spectroscopic and metabolic changes in a murine cutaneous squamous cell carcinoma model

Timely detection of cutaneous squamous cell carcinoma with non-invasive modalities like nonlinear spectral imaging (NLSI) can ensure efficient preventive or therapeutic measures for patients. In this study, in vivo NLSI was used to study spectral characteristics in murine skin treated with 7, 12-dimethylbenz(a)anthracene. The results show that NLSI could detect emission spectral changes during the early preclinical stages of skin carcinogenesis. Analyzing these emission spectra using simulated band-pass filters at 450-460 nm and 525-535 nm, gave parameters that were expressed as a ratio. This ratio was increased and thus suggestive of elevated metabolic activity in early stages of skin carcinogenesis.

Fractal analysis of two-photon microscopic images for diagnosis of nasopharyngeal cancer

In this study, two-photon microscopy (TPM) was applied to obtain high-resolution, optically sectioned images with cellular morphology information from normal and cancerous nasopharyngeal tissue. Notable difference of nuclear-cytoplasmic ratio was found between these two groups. In particular, fractal dimension (FD) analysis based on TPM images showed good differentiation between normal and cancerous nasopharyngeal tissues. Our results indicate that TPM coupled with FD analysis methods has the potential to extract diagnostic features for label-free histological diagnosis.

Characteristics of scar margin dynamic with time based on multiphoton microscopy

Scar margins dynamic with time were quantitatively characterized using multiphoton microscopy (MPM). 2D large-area and 3D focused images of elastin and collagen at scar margins were obtained to extract quantitative parameters. An obvious boundary was observed at the scar margin, showing altered morphological patterns of elastin and collagen on both sides. Content alteration of elastin and collagen between the two sides of boundary were defined to characterize scar margins from different individuals. The statistical results from 15 normal scar samples strongly demonstrated that content alteration degree of elastin and collagen had decreasing tendency with the increase of patient age or scar duration, consistent with the fact of normal scars regressing spontaneously over time. It indicated that alteration degree can potentially serve as quantitative indicators to examine wound healing and scar progression over time. With the advent of clinical portable multiphoton endoscopes, the MPM technique can be applied in tracking scar formation and progression in vivo by examination of scar margin.

Pulse-modulated second harmonic imaging microscope quantitatively demonstrates marked increase of collagen in tumor after chemotherapy

Pulse-modulated second harmonic imaging microscopes (PM-SHIMs) exhibit improved signal-to-noise ratio (SNR) over conventional SHIMs on sensitive imaging and quantification of weak collagen signals inside tissues. We quantify the spatial distribution of sparse collagen inside a xenograft model of human acute myeloid leukemia (AML) tumor specimens treated with a new drug against receptor tyrosine kinase (ABT-869), and observe a significant increase in collagen area percentage, collagen fiber length, fiber width, and fiber number after chemotherapy. This finding reveals new insights into tumor responses to chemotherapy and suggests caution in developing new drugs and therapeutic regimens against cancers.

In vivo imaging of ovarian tissue using a novel confocal microlaparoscope

OBJECTIVE

The objective of the study was to develop a clinical confocal microlaparoscope for imaging ovary epithelium in vivo with the long-term objective of diagnosing cancer in vivo.

STUDY DESIGN

A confocal microlaparoscope was developed and used to image the ovaries of 21 patients in vivo using fluorescein sodium and acridine orange as the fluorescent contrast agents.

RESULTS

The device was tested in vivo and demonstrated to be safe and function as designed. Real-time cellular visualization of ovary epithelium was demonstrated.

CONCLUSION

The confocal microlaparoscope represents a new type of in vivo imaging device. With its ability to image cellular details in real time, it has the potential to aid in the early diagnosis of cancer. Initially the device may be used to locate unusual regions for guided biopsies. In the long term, the device may be able to supplant traditional biopsies and allow the surgeon to identify early-stage ovarian cancer.

QUANTITATIVE REDOX SCANNING OF TISSUE SAMPLES USING A CALIBRATION PROCEDURE

The fluorescence properties of reduced nicotinamide adenine dinucleotide (NADH) and oxidized flavoproteins (Fp) including flavin adenine dinucleotide (FAD) in the respiratory chain are sensitive indicators of intracellular metabolic states and have been applied to the studies of mitochondrial function with energy-linked processes. The redox scanner, a three-dimensional (3D) low temperature imager previously developed by Chance et al., measures the in vivo metabolic properties of tissue samples by acquiring fluorescence images of NADH and Fp. The redox ratios, i.e. Fp/(Fp+NADH) and NADH/(Fp+NADH), provided a sensitive index of the mitochondrial redox state and were determined based on relative signal intensity ratios. Here we report the further development of the redox scanning technique by using a calibration method to quantify the nominal concentration of the fluorophores in tissues. The redox scanner exhibited very good linear response in the range of NADH concentration between 165-1318μM and Fp between 90-720 μM using snap-frozen solution standards. Tissue samples such as human tumor mouse xenografts and various mouse organs were redox-scanned together with adjacent NADH and Fp standards of known concentration at liquid nitrogen temperature. The nominal NADH and Fp concentrations as well as the redox ratios in the tissue samples were quantified by normalizing the tissue NADH and Fp fluorescence signal to that of the snap-frozen solution standards. This calibration procedure allows comparing redox images obtained at different time, independent of instrument settings. The quantitative multi-slice redox images revealed heterogeneity in mitochondrial redox state in the tissues.

MITOCHONDRIAL REDOX IMAGING FOR CANCER DIAGNOSTIC AND THERAPEUTIC STUDIES

Mitochondrial redox states provide important information about energy-linked biological processes and signaling events in tissues for various disease phenotypes including cancer. The redox scanning method developed at the Chance laboratory about 30 years ago has allowed 3D high-resolution (~ 50 × 50 × 10 μm3) imaging of mitochondrial redox state in tissue on the basis of the fluorescence of NADH (reduced nicotinamide adenine dinucleotide) and Fp (oxidized flavoproteins including flavin adenine dinucleotide, i.e., FAD). In this review, we illustrate its basic principles, recent technical developments, and biomedical applications to cancer diagnostic and therapeutic studies in small animal models. Recently developed calibration procedures for the redox imaging using reference standards allow quantification of nominal NADH and Fp concentrations, and the concentration-based redox ratios, e.g., Fp/(Fp+NADH) and NADH/(Fp+NADH) in tissues. This calibration facilitates the comparison of redox imaging results acquired for different metabolic states at different times and/or with different instrumental settings. A redox imager using a CCD detector has been developed to acquire 3D images faster and with a higher in-plane resolution down to 10 μm. Ex vivo imaging and in vivo imaging of tissue mitochondrial redox status have been demonstrated with the CCD imager. Applications of tissue redox imaging in small animal cancer models include metabolic imaging of glioma and myc-induced mouse mammary tumors, predicting the metastatic potentials of human melanoma and breast cancer mouse xenografts, differentiating precancerous and normal tissues, and monitoring the tumor treatment response to photodynamic therapy. Possible future directions for the development of redox imaging are also discussed.