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1AbstractIn biomedical research, the outcome of longitudinal studies has been traditionally analyzed using the repeated measures analysis of variance (rm-ANOVA) or more recently, linear mixed models (LMEMs). Although LMEMs are less restrictive than rm-ANOVA as they can work with unbalanced data and non-constant correlation between observations, both methodologies assume a linear trend in the measured response. It is common in biomedical research that the true trend response is nonlinear and in these cases the linearity assumption of rm-ANOVA and LMEMs can lead to biased estimates and unreliable inference.In contrast, GAMs relax the linearity assumption of rm-ANOVA and LMEMs and allow the data to determine the fit of the model while also permitting incomplete observations and different correlation structures. Therefore, GAMs present an excellent choice to analyze longitudinal data with non-linear trends in the context of biomedical research. This paper summarizes the limitations of rm-ANOVA and LMEMs and uses simulated data to visually show how both methods produce biased estimates when used on data with non-linear trends. We present the basic theory of GAMs and using reported trends of oxygen saturation in tumors, we simulate example longitudinal data (2 treatment groups, 10 subjects per group, 5 repeated measures for each group) to demonstrate their implementation in R. We also show that GAMs are able to produce estimates with non-linear trends even when incomplete observations exist (with 40% of the simulated observations missing). To make this work reproducible, the code and data used in this paper are available at: https://github.com/aimundo/GAMs-biomedical-research.

Background Immunotherapy in colorectal cancer (CRC) regulates specific immune checkpoints and, when used in combination with chemotherapy, can improve patient prognosis. One specific immune checkpoint is the recruitment of circulating monocytes that differentiate into tumor-associated macrophages (TAMs) and promote tumor angiogenesis. Changes in vascularization can be non-invasively assessed via diffuse reflectance spectroscopy using hemoglobin concentrations and oxygenation in a localized tumor volume. In this study, we examine whether blockade of monocyte recruitment via CCL2 (macrophage chemoattractant protein-1) leads to enhanced sensitivity of 5-fluorouracil (5-FU) in a CT26-Balb/c mouse model of CRC. It was hypothesized that the blockade of TAMs will alter tumor perfusion, increasing chemotherapy response. A subcutaneous tumor model using Balb/c mice injected with CT26 colon carcinoma cells received either a saline or isotype control, anti-CCL2, 5-FU, or a combination of anti-CCL2 and 5-FU. Results Findings show that 12 days post-treatment, monocyte recruitment was significantly reduced by approximately 61% in the combination group. This shows that the addition of anti-CCL2 to 5-FU slowed the fold-change (change from the original measurement to the final measurement) in tumor volume from Day 0 to Day 12 (~ 5 fold). Modest improvements in oxygen saturation (~ 30%) were observed in the combination group. Conclusion The findings in this work suggest that the blockade of CCL2 is sufficient in the reduction of TAMs that are recruited into the tumor microenvironment and has the ability to modestly alter tumor perfusion during early-tumor response to treatment even though the overall benefit is relatively modest.

Ulcerative colitis (UC) is a gastrointestinal, autoimmune disease that causes ulceration and inflammation of the colon with an incidence of 10 out of every 100,000 people in North America and Western Europe. Though the specific cause is unknown, several studies have demonstrated that inflammatory cells as well as environmental variables, genetics, and lifestyle behaviors can play a role in the long-term inflammatory response. Researchers have commonly used immunohistochemistry, western blotting and gene sequencing to establish the cellular processes behind UC relapse and remission. However, because these destructive methods necessitate the removal of a sample, they can only be used on non-living tissues. The use of minimally invasive approaches to evaluate the

Ulcerative colitis (UC) is a gastrointestinal, autoimmune disease that causes ulceration and inflammation of the colon with an incidence 10 out of every 100,000 people in North America and Western Europe. Though the exact etiology is uncertain, a number of studies have shown that inflammatory cells along with environmental factors, genetics, and lifestyle habits can contribute to the sustained inflammatory response. In order to determine the cellular mechanism behind relapse and remission of UC, researchers have frequently employed immunohistochemistry, western blotting and gene sequencing, but these destructive analysis methods require the removal of a sample, necessarily limiting these methods to non-living tissues. There is an emerging interest in using minimally-invasive techniques to study the in vivo, longitudinal effects of UC on the mucosa in the colon. Here we have developed a mouse model of UC using dextran sulfate sodium and a minimally-invasive spectroscopy monitoring modality to study the changes in the tissue hemodynamics during active UC.

Colorectal cancer (CRC) is the fourth most common cancer type and is the second leading cause of cancer deaths annually in the United States. Conventional treatment options include postoperative (adjuvant) and preoperative (neoadjuvant) chemotherapy and radiotherapy. Although these treatment modalities have shown to decrease tumor burden, a major limitation to chemothearpy/radiotherapy is the high recurrence rate in patients. Immune-modulation strategies have emerged as a promising new therapeutic avenue to reduce this recurrence rate while minimizing undesirable systemic side effects. This review will focus specifically on the mechanisms of monoclonal antibodies: immune checkpoint inhibitors and cytokines, as well as current drugs approved by the Food and Drug Administration (FDA) and new clinical/pre-clinical trials. Finally, this review will investigate emerging methods used to monitor tumor response post-treatment.

The current paradigm for chemotherapy in the treatment of colorectal cancer (CRC) is based on the maximum-tolerated dose approach (MTD), which uses high doses of cytotoxic agents with the aim of killing tumor cells. However, the toxicity of MTD chemotherapy requires drug delivery in a cyclic manner with rest periods that allow the tumor to recover. In contrast, metronomic chemotherapy (MET) uses low but continuous doses that target the endothelial cells of tumors, thereby directly affecting the development of new blood vessels (angiogenesis). Because the potential impact of MET when used as neoadjuvant chemotherapy (NAC) in CRC has not been explored and contrasted with the effects in perfusion of the standard MTD regimen, this study uses an azoxymethane-induced primary model of CRC to assess changes in perfusion and angiogenic markers. Diffuse reflectance spectroscopy (DRS) was used to longitudinally quantify oxygen saturation (StO2) and compare these changes with the change in expression of VEGF-A between MET and MTD treatments. In the MTD group, an increase in StO2 from 65 to 81% was observed by week 4 of treatment and a reduction of VEGF-A expression from 81% to 16% was observed between weeks 4 and 6.

First-Generation College Students (FGCSs) face myriad challenges including the lack of parental guidance, economic and social burdens, isolation, decreased belongingness, and lowered self-confidence making them at an increased risk of dropping out of college compared to their Continuing College Students (CCSs) colleagues. In addition, being in a multidisciplinary Science, Technology, Engineering, and Mathematics (STEM) field such as Biomedical Engineering (BMEG) is another challenge as it requires the integration of several disciplines. This study aims to maximize FGCSs' success and retention in Biomedical Engineering. We hypothesize that STEM-tailored faculty and peer mentoring that is focused on academic and professional development will significantly increase BMEG FGCSs' academic and professional success and enhance their belongingness to the engineering community. Study participants were assigned to either group; faculty mentoring combined with academic coaching or peer mentoring combined with academic coaching. Both quantitative and qualitative data were collected using two surveys; pre-mentoring and post-mentoring. Both faculty mentoring and peer mentoring led to increasing FGCSs' confidence, belongingness, and involvement in professional opportunities. To tackle the added challenge of studying a multidisciplinary STEM field to the challenges facing FGCSs, a mentorship program that is focused on enhancing self-confidence, sense of belonging and augmenting professional development can be employed to ensure the success, integration, and retention of FGCSs in multidisciplinary STEM fields such as Biomedical Engineering.

Background Calcific aortic valve disease (CAVD) pathophysiology is a complex, multistage process, usually diagnosed at advanced stages after significant anatomical and hemodynamic changes in the valve. Early detection of disease progression is thus pivotal in the development of prevention and mitigation strategies. In this study, we developed a diet-based, non-genetically modified mouse model for early CAVD progression, and explored the utility of two-photon excited fluorescence (TPEF) microscopy for early detection of CAVD progression. TPEF imaging provides label-free, non-invasive, quantitative metrics with the potential to correlate with multiple stages of CAVD pathophysiology including calcium deposition, collagen remodeling and osteogenic differentiation. Methods Twenty-week old C57BL/6J mice were fed either a control or pro-calcific diet for 16 weeks and monitored via echocardiography, histology, immunohistochemistry, and quantitative polarized light imaging. Additionally, TPEF imaging was used to quantify tissue autofluorescence (A) at 755 nm, 810 nm and 860 nm excitation, to calculate TPEF 755–860 ratio (A860/525/(A755/460 + A860/525)) and TPEF Collagen-Calcium ratio (A810/525/(A810/460 + A810/525)) in the murine valves. In a separate experiment, animals were fed the above diets till 28 weeks to assess for later-stage calcification. Results Pro-calcific mice showed evidence of lipid deposition at 4 weeks and calcification at 16 weeks at the valve commissures. The valves of pro-calcific mice also showed positive expression for markers of osteogenic differentiation, myofibroblast activation, proliferation, inflammatory cytokines and collagen remodeling. Pro-calcific mice exhibited lower TPEF autofluorescence ratios, at locations coincident with calcification, that correlated with increased collagen disorganization and positive expression of osteogenic markers. Additionally, locations with lower TPEF autofluorescence ratios at 4 and 16 weeks exhibited increased calcification at later 28-week timepoints. Conclusions This study suggests the potential of TPEF autofluorescence metrics to serve as a label-free tool for early detection and monitoring of CAVD pathophysiology.

Significance: Many studies in colorectal cancer (CRC) use murine ectopic tumor models to determine response to treatment. However, these models do not replicate the tumor microenvironment of CRC. Physiological information of treatment response derived via diffuse reflectance spectroscopy (DRS) from murine primary CRC tumors provide a better understanding for the development of new drugs and dosing strategies in CRC. Aim: Tumor response to chemotherapy in a primary CRC model was quantified via DRS to extract total hemoglobin content (tHb), oxygen saturation (StO2), oxyhemoglobin, and deoxyhemoglobin in tissue. Approach: A multimodal DRS and imaging probe (0.78 mm outside diameter) was designed and validated to acquire diffuse spectra longitudinally—via endoscopic guidance—in developing colon tumors under 5-fluoruracil (5-FU) maximum-tolerated (MTD) and metronomic regimens. A filtering algorithm was developed to compensate for positional uncertainty in DRS measurements Results: A maximum increase in StO2 was observed in both MTD and metronomic chemotherapy-treated murine primary CRC tumors at week 4 of neoadjuvant chemotherapy, with 21 ± 6 % and 17 ± 6 % fold changes, respectively. No significant changes were observed in tHb. Conclusion: Our study demonstrates the feasibility of DRS to quantify response to treatment in primary CRC models.

A densely-packed, custom multi-pixel photodetector probe permits spatially resolved diffuse reflectance (SRDR) measurements of phantoms of varying thicknesses, showing high signal contrast between thin phantoms and high depth sensitivity.

Purpose: Colorectal cancer is the fourth most common cancer in the United States, accounting for more than 50,000 deaths annually1. The standard treatment is 5-fluorouracil (5-FU)-based chemotherapy, but emerging methods of immunotherapy have gained the attention of investigators and clinicians. A specific cytokine-based strategy for immunotherapy is the blockade of CCL2/MCP-1 (monocyte chemoattractant protein-1)2. CCL2 is a chemotactic cytokine that recruits circulating monocytes to the tumor microenvironment2. These monocytes differentiate into tumor-associated macrophages (TAMs), which promote pro-tumor functions including tumor growth, immunosuppression, and angiogenesis. CCL2 blockade in certain mouse models of cancer has been shown to reduce tumor burden but had not been studied in colorectal cancer. In this study, we examine how cytokine-targeted anti-CCL2 immunotherapy affects tumor-associated macrophage recruitment as well as the promotion of angiogenesis as a standalone and in combination with 5-FU. Methods: Nine-week-old Balb/c mice (n=13) were acclimated for a week in the Small Animal Facility at the University of Arkansas. CT26 cells, a murine colon carcinoma cell line, were cultured in RPMI-1640 media, supplemented with 10% bovine serum, 0.2% amphotericin B/gentamicin, and 1% antibiotic antimycotic solution. 1 × 106 CT26 cells were subcutaneously injected into the left flank of Balb/c mice (10 weeks old). The tumors grew to 75 mm3, upon which Balb/c mice were randomly divided into saline control, immunotherapy, chemotherapy, and combination (immunotherapy + chemotherapy) groups. The immunotherapy and chemotherapy groups were intraperitoneally injected with a 28G insulin syringe with anti-CCL2 and 5-FU at a concentration of 5.0 mg/kg/dose and 15mg/kg/dose, respectively. The control group was injected with an equal volume of sterile saline on days while the combination group received a dose of anti-CCL2 and 5-FU. Tumor-associated macrophages were quantified via immunohistochemistry using anti-CD68 and tumor vasculature was quantified using anti-CD31. Correlation plots were also created to determine a relationship between macrophage recruitment and new blood vessel formation. Results: There was a decrease in the total number of tumor-associated macrophages from Day 3 to 7 (33% decrease) when tumors were treated with anti-CCL2 and 5-FU. The area of vasculature in the combination group showed a slight decrease from Day 3 to Day 7 (29% decrease). There was a slight positive correlation between total macrophage recruitment and new blood vessel formation (R2 = 0.3041). Conclusion: Overall, we have demonstrated that anti-CCL2 in combination with 5-FU has modestly slowed tumor growth, reduced the area of vasculature, and decreased the number of recruited tumor-associated macrophages in a murine model of colorectal cancer. Acknowledgments: This material is based on work supported by the National Institutes of Health (1R15CA202662- 01), National Science Foundation CAREER award (CBET 1751554), and the Arkansas Biosciences Institute. Citation Format: Shelby N. Bess, Timothy J. Muldoon. Correlation between immune modulation of macrophage recruitment and new blood vessel formation in a subcutaneous murine mouse model of colorectal cancer [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr P009.

Background Colorectal cancer remains the second leading cause of cancer death in the United States, and increased risk in patients with ulcerative colitis (a subset of inflammatory bowel disease) has motivated studies into early markers of dysplasia. The development of clinically translatable multiphoton imaging systems has allowed for the potential of in vivo label-free imaging of epithelial crypt structures via autofluorescence and/or second harmonic generation (SHG). SHG has been used to investigate collagen structures in various types of cancer, though the changes that colorectal epithelial collagen structures undergo during tumor development, specifically colitis-associated tumors, have not been fully investigated. Methods This study used two murine models, using A/J mice, one for spontaneous carcinoma and one for colitis-associated carcinoma, to investigate and quantify SHG image features that could potentially inform future study designs of endoscopic multiphoton imaging systems. The spontaneous tumor model comprised a series of six weekly injections of azoxymethane (AOM model). The colitis-associated tumor model comprised a single injection of AOM, followed by cycles of drinking water with dissolved dextran sodium sulfate salt (AOM-DSS model). SHG images of freshly resected murine colon were acquired with a multiphoton imaging system, and image features, such as crypt size, shape and distribution, were quantified using an automated algorithm. Results The comparison of quantified features of crypt morphology demonstrated the ability of our quantitative image feature algorithms to detect differences between spontaneous (AOM model) and colitis-associated (AOM-DSS model) murine colorectal tissue specimens. There were statistically significant differences in the mean and standard deviation of nearest neighbor (distance between crypts) and circularity between the Control cohort, AOM and AOM-DSS cohorts. We also saw significance between AOM and AOM-DSS cohorts when calculating nearest neighbor in images acquired at fixed depths. Conclusion The results provide insight into the ability of SHG imaging to yield relevant data about the crypt microstructure in colorectal epithelium, specifically the potential to distinguish between spontaneous and colitis-associated murine models using quantification of crypt shape and distribution, informing future design of translational multiphoton imaging systems and protocols. Electronic supplementary material The online version of this article (10.1186/s12885-019-5639-8) contains supplementary material, which is available to authorized users.

Immunotherapy, an emerging field in cancer therapeutics, in colon cancer aims to reduce pre-surgical tumor burden by regulating host immune checkpoints, and when used in combination with neoadjuvant chemotherapy, may improve tumor therapeutic response. One such immune checkpoint is CCL2 (monocyte chemoattractant protein-1)-mediated recruitment of monocytes, which differentiate into tumor-associated macrophages (TAMs) in the tumor microenvironment that promote angiogenesis and tumorigenesis. Thus, CCL2 blockade may play an anti-tumor role via effects on tumor perfusion. However, there have been no studies investigating CCL2 blockade immunotherapy combined with chemotherapy in an animal model of colon cancer. Furthermore, there is a need to longitudinally assess tumor therapeutic response throughout treatment. In this study, CT26 murine colon carcinoma was injected into the flanks of Balb/c mice (n=80) to form tumor allografts. Mice in the key experimental group received combined chemotherapy (5-flurouracil) and immunotherapy (anti-CCL2), with appropriate controls. Tumor therapeutic response was monitored using diffuse reflectance spectroscopy (DRS) by measuring the tumor perfusion metrics, hemoglobin concentration and oxygenation. End-point immunohistochemical analysis was used to quantify TAM fraction (CD68 and DAPI), TAM polarization (iNOS and CD206), and hypoxia (pimonidazole) to spatially and temporally correlate to DRS results. The central hypothesis was that decreasing TAMs via CCL2 blockade alters tumor perfusion, thereby increasing tumor response to 5-fluorouracil. This study may potentially demonstrate an effective immunotherapy approach (CCL2 blockade) and a viable method to longitudinally and non-invasively assess tumor therapeutic response to such immunotherapy (DRS) in mouse allograft models of colon cancer.

Magnetohydrodynamics (MHD) is a unique approach for pumping fluids on a microscale and is highly suitable for enabling multiple functions for chemical analysis on a chip. An ionic current, j, is established in the fluid between selectively-activated electrodes in the presence of a magnetic field, B, that is perpendicular to the current, to generate a force, FB , orthogonal to j and B, through the right hand rule. FB is a body force that propels the liquid in the same direction through momentum transfer. We use microelectrodes, which are patterned into different, individually-addressable geometries on chips. Those electrodes are modified with poly(3,4-ethylenedioxythiophene), PEDOT, a conducting polymer, that converts the applied electronic current in the external circuit to ionic current in the liquid [1] via redox (R) processes and charging. A small NdFeB permanent magnet is placed under the chip to provide B. By strategic activation of the electrodes, fluid flow can be programmed. For example, we previously demonstrated that R-MHD can start, stop, reverse, adjust speed, and alter profiles of the fluid flow. We have also shown recently that R-MHD fluid flow can be diverted in a contactless way by magnetic field gradients when paramagnetic species are present [2]. In our presentation, we will discuss recent studies on using R-MHD to control the paths of individual microvolumes of fluids for different applications, which include chemical separations of mixtures of small biologically-relevant molecules as well as fluorescence imaging [3] and identification of cyanobacteria responsible for algal blooms in fresh water samples. Fluid manipulation and flow profiles under different experimental conditions and solvent and solution compositions will be described. These involve sustained and redirection of flow, adjacent counter flows, transverse paths, sampling, and injection. Acknowledgements: We are grateful for financial support from the National Science Foundation (CMI-1808286) and Arkansas Bioscience Institute, the major research component of the Arkansas Tobacco Settlement Proceeds Act of 2000. References [1] Khan, F. Z.; Fritsch, I. “Chip-Scale Electrodeposition and Analysis of Poly(3,4-ethylenedioxythiophene) (PEDOT) Films for Enhanced and Sustained Microfluidics Using DC-Redox-Magnetohydrodynamics”, Journal of The Electrochemical Society 2019, 166 (13), H615-H627. [2] Hähnel, V.; Khan, F. Z.; Mutschke, G.; Cierpka, C.; Uhlemann, M.; Fritsch, I. “Combining magnetic forces for contactless manipulation of fluids in microelectrode-microfluidic systems:, Scientific Reports 2019, 9:5103. [3] Khan, F. Z.; Hutcheson, J.; Hunter, C. J.; Powless, A. J. Benson, D.; Fritsch, I.*; Muldoon, T. J.* “Redox-Magnetohydrodynamically controlled fluid flow with poly(3,4-ethylenedioxythiophene) (PEDOT) coupled to an epitaxial light sheet confocal microscope for image cytometry applications”, Anal. Chem., 2018, 90(13), 7862-7870.

Low-cost imaging systems that utilize exogenous fluorescent dyes, such as acridine orange (AO), have recently been developed for use as point-of-care (POC) blood analyzers. AO-based fluorescence imaging exploits variations in emission wavelength within different cell types to enumerate and classify leukocyte subpopulations from whole blood specimens. This approach to leukocyte classification relies on accurate and reproducible colorimetric features, which have previously been demonstrated to be highly dependent on the cell staining protocols (such as specific AO concentration, timing, and pH). We have developed a light-sheet-based fluorescence imaging spectrometer, featuring a spectral resolution of 9 nm, with an automated spectral extraction algorithm as an investigative tool to study the spectral features from AO-stained leukocytes. Whole blood specimens were collected from human subjects, stained with AO using POC methods, and leukocyte spectra were acquired on a cell-by-cell basis. The post-processing method involves three steps: image segmentation to isolate individual cells in each spectral image, image quality control to exclude cells with low emission intensity, out-of-focus cells, and cellular debris, and the extraction of spectra for each cell. An increase in AO concentration was determined to contribute to the red-shift in AO-fluorescence, while varied pH values did not cause a change in fluorescence. In relation to the spectra of AO-stained leukocytes, there were corresponding red-shift trends associated with dye accumulation within acidic vesicles and at increasing incubation periods. The system presented here could guide future development of POC systems reliant on AO fluorescence and colorimetric features to identify leukocyte subpopulations in whole blood specimens.

Resistance to conventional antibiotics is a growing public health concern that is quickly outpacing the development of new antibiotics. This has led the Infectious Diseases Society of America (IDSA) to designate Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species as "ESKAPE pathogens" on the basis of the rapidly decreasing availability of useful antibiotics. This emphasizes the urgent need for alternative therapeutic strategies to combat infections caused by these and other bacterial pathogens. In this study, we used Staphylococcus aureus (S. aureus) as a proof-of-principle ESKAPE pathogen to demonstrate that an appropriate antibiotic (daptomycin) can be incorporated into polydopamine-coated gold nanocages (AuNC@PDA) and that daptomycin-loaded AuNC@PDA can be conjugated to antibodies targeting a species-specific surface protein (staphylococcal protein A; Spa) as a means of achieving selective delivery of the nanoconstructs directly to the bacterial cell surface. Targeting specificity was confirmed by demonstrating a lack of binding to mammalian cells, reduced photothermal and antibiotic killing of the Spa-negative species Staphylococcus epidermidis, and reduced killing of S. aureus in the presence of unconjugated anti-Spa antibodies. We demonstrate that laser irradiation at levels within the current safety standard for use in humans can be used to achieve both a lethal photothermal effect and controlled release of the antibiotic, thus resulting in a degree of therapeutic synergy capable of eradicating viable S. aureus cells. The system was validated using planktonic bacterial cultures of both methicillin-sensitive and methicillin-resistant S. aureus strains and subsequently shown to be effective in the context of an established biofilm, thus indicating that this approach could be used to facilitate the effective treatment of intrinsically resistant biofilm infections.

We present the merging of two technologies to perform continuous high-resolution fluorescence imaging of cellular suspensions in a deep microfluidics chamber with no moving parts. An epitaxial light sheet confocal microscope (e-LSCM) was used to image suspensions enabled by fluid transport via redox-magnetohydrodynamics (R-MHD). The e-LSCM features a linear solid state sensor, oriented perpendicular to the direction of flow, that can bin the emission across different numbers of pixels, yielding electronically adjustable optical sectioning. This, in addition to intensity thresholding, defines the axial resolution, which was validated with an optical phantom of polystyrene microspheres suspended in agarose. The linear fluid speed within the microfluidics chamber was uniform (0.16-2.9%) across the 0.5-1.0 mm lateral field of view (dependent upon the chosen magnification) with continuous acquisition. Also, the camera's linear exposure periods were controlled to ensure an accurate image aspect ratio across this span. Poly(3,4-ethylenedioxythiophene) (PEDOT) was electrodeposited as an immobilized redox film on electrodes of a chip for R-MHD, and the fluid flow was calibrated to specific linear speeds as a function of applied current. Images of leukocytes stained with acridine orange, a fluorescent, amphipathic vital dye that intercalates DNA, were acquired in the R-MHD microfluidics chamber with the e-LSCM to demonstrate imaging of biological samples. The combination of these technologies provides a miniaturizable platform for large sample volumes and high-throughput, image-based analysis without the requirement of moving parts, enabling development of robust, point-of-care image cytometry.

Spatial frequency domain imaging (SFDI) is a widefield, noncontact, and label-free imaging modality that is currently being explored as a new tool for longitudinal tracking of cancer therapies in the preclinical setting. We describe a two-layer look-up-table (LUT) inversion algorithm for SFDI that better accounts for the skin (top layer) and tumor (bottom layer) tissue geometry in subcutaneous tumor models. Monte Carlo (MC) simulations were conducted natively in the spatial frequency domain, avoiding discretization errors associated with Fourier or Hankel transforms of conventional MC simulation results. The two-layer LUT was validated using two-layer tissue mimicking optical phantoms, in which the optical property extractions of the bottom (tumor) layer were determined to be within 20% and 11% of the true values for μa and μs', respectively. A sensitivity analysis was conducted to evaluate how imperfect top layer estimates affect bottom-layer optical property extractions. Finally, the two-layer LUT was used to reanalyze a prior longitudinal data set, which revealed larger therapy-induced changes in optical scattering and a more hypoxic tumor environment compared to the homogeneous LUT. The two-layer LUT described here improves the accuracy of subcutaneous tumor imaging, and the general methodology can be applied for arbitrary multilayer SFDI applications.

Manual assessment of renal fibrosis via visual inspection represents a significant challenge even among expert pathologists. The goal of this project was to create a quantitative analysis program that could be used as a complementary tool for pathologists. The algorithm was applied to color images of renal needle core biopsy slides, at varying stages of disease, stained with either Masson's trichrome (MT) or collagen III immunohistochemistry (Coll3). Each image was split into colorimetric channels and the ratio of two of the corresponding channels was then compared to the overall tissue image. Results demonstrated that colorimetric ratios of red:blue for MT and green:red for Coll3 produced ranges between 1.3- 1.5 and 1.10-1.12, respectively, that successfully excluded non-fibrotic renal tissue and could therefore be used to create a quantitative analysis of renal fibrosis for comparison to pathologists' diagnosis.

Diffuse reflectance spectroscopy (DRS) has been used in murine studies to quantify tumor perfusion and therapeutic response. These studies frequently use inhaled isoflurane anesthesia, which depresses the respiration rate and results in the desaturation of arterial oxygen saturation, potentially affecting tissue physiological parameters. However, there have been no controlled studies quantifying the effect of isoflurane anesthesia on DRS-derived physiological parameters of murine tissue. The goal of this study was to perform DRS on Balb/c mouse (n = 10) tissue under various anesthesia conditions to quantify effects on tissue physiological parameters, including total hemoglobin concentration, tissue oxygen saturation, oxyhemoglobin and reduced scattering coefficient. Two independent variables were manipulated including metabolic gas type (pure oxygen vs. medical air) and isoflurane concentration (1.5 to 4.0%). The 1.5% isoflurane and 1 L/min oxygen condition most closely mimicked a no-anesthesia condition with oxyhemoglobin concentration within 89% ± 19% of control. The time-dependent effects of isoflurane anesthesia were tested, revealing that anesthetic induction with 4.0% isoflurane can affect DRS-derived physiological parameters up to 20 minutes post-induction. Finally, spectroscopy with and without isoflurane anesthesia was compared for colon tumor Balb/c-CT26 allografts (n = 5) as a representative model of subcutaneous murine tumor allografts. Overall, isoflurane anesthesia yielded experimentally-induced depressed oxyhemoglobin, and this depression was both concentration and time dependent. Investigators should understand the dynamic effects of isoflurane on tissue physiological parameters measured by DRS. These results may guide investigators in eliminating, limiting, or managing anesthesia-induced physiological changes in DRS studies in mouse models.

Spatial Frequency Domain Imaging (SFDI) is a Diffuse Optical Imaging (DOI) technique that is well suited for preclinical functional imaging. Recently, we have shown that SFDI can successfully be used for longitudinal monitoring of a prostate subcutaneous tumor xenograft, where we have applied a look-up-table (LUT) based approach to extract tissue absorption (μa) and scattering properties (μs’). This LUT assumes a semi-infinite homogeneous medium and simulates reflectance (Rd) in spatial domain, and scales Rd for all μa and μs’ of interest from a single Monte Carlo simulation. However, converting Rd to spatial frequency domain (SFD) and scaling for μs’ may introduces unacceptable errors. Most importantly, the homogeneous model fails to mimic the actual physiology of a subcutaneous tumor, which can be described as a two-layer medium with a thin skin layer above the tumor layer. To overcome these limitations, we have developed a Monte Carlo based two-layer LUT with a wide range of tumor (bottom) layer optical properties, and fixed skin (top) properties. The two-layer LUT will be validated by two-layer silicone phantoms and tested for sensitivity to inaccurate layer assumptions. Additionally, the homogeneous and two-layer LUTs will be used on a large mouse tumor database (n=54 mice monitored over 3 months) to identify how the two-layer LUT can improve accuracy of SFDI by more accurately reflecting in vivo physiology, and reducing discretization and scaling errors. Improved SFDI findings in small animals, in the long run, will help establish clinical DOI tools for early detection of chemotherapy efficacy during treatment.

Locally advanced adenocarcinomas located in the distal rectum are commonly treated via 5-fluorouracil (5-FU)-based neoadjuvant chemoradiation therapy (CRT). The occurrence of pre-operative pathological complete response, or the absence of any histological evidence of residual cancer, is seen in 15-27% of rectal cancer cases. Response to chemotherapeutic agents varies between patients, introducing the need for a system to predict optimal drug combinations. We propose a method of utilizing optical metabolic imaging of in vitro, primary tumor-derived, three-dimensional organoid culture to create specific drug sensitivity profiles, and to rapidly assess a patient’s potential response to drugs. Murine xenografts were developed in Swiss athymic nude mice, using human colorectal adenocarcinoma cell lines, implanted in the flank (RKO, ATCC). Tumors were excised upon reaching a volume of 500mm3 and processed for organoid culture. Organoids were subjected to longitudinal metabolic imaging of metabolic cofactors FAD and NADH for seven days. The resulting images were used to yield an optical redox value on a cell-by-cell basis, determined by the fluorescence intensity ratio of FAD/(FAD+NADH). This data infers proliferative index of the organoids. Beginning on day three, a control vehicle dimethyl sulfoxide, or the cytotoxic agent 5-FU, was added to the organoid growth media in wells, with metabolic imaging performed the same as previously stated. The optical redox values decreased due to the addition of 5-FU, which targets rapidly dividing cells and induces apoptosis. The changes in the optical redox histograms were correlated to markers of cell proliferation (Ki-67) and apoptosis (cleaved caspase-3).

Fiber bundle microendoscopic imaging of colorectal tissue has shown promising results, for both qualitative and quantitative analysis. A quantitative image quality control and image feature extraction algorithm was previously designed for quantitative image feature analysis of proflavine-stained ex vivo colorectal tissue. We investigated fluorescein as an alternative topical stain. Images of ex vivo porcine, caprine, and human colorectal tissue were used to compare microendoscopic images of tissue topically stained with fluorescein and proflavine solutions. Fluorescein was shown to be comparable for automated crypt detection, with an average crypt detection sensitivity exceeding 90% using a combination of three contrast limit pairs.

Recent fiber-bundle microendoscopy techniques enable non-invasive analysis of in vivo tissue using either imaging techniques or a combination of spectroscopy techniques. Combining imaging and spectroscopy techniques into a single optical probe may provide a more complete analysis of tissue health. In this article, two dissimilar modalities are combined, high-resolution fluorescence microendoscopy imaging and diffuse reflectance spectroscopy, into a single optical probe. High-resolution fluorescence microendoscopy imaging is a technique used to visualize apical tissue micro-architecture and, although mostly a qualitative technique, has demonstrated effective real-time differentiation between neoplastic and non-neoplastic tissue. Diffuse reflectance spectroscopy is a technique which can extract tissue physiological parameters including local hemoglobin concentration, melanin concentration, and oxygen saturation. This article describes the specifications required to construct the fiber-optic probe, how to build the instrumentation, and then demonstrates the technique on in vivo human skin. This work revealed that tissue micro-architecture, specifically apical skin keratinocytes, can be co-registered with its associated physiological parameters. The instrumentation and fiber-bundle probe presented here can be optimized as either a handheld or endoscopically-compatible device for use in a variety of organ systems. Additional clinical research is needed to test the viability of this technique for different epithelial disease states.

The role of valvular interstitial cell (VIC) architecture in regulating cardiac valve function and pathology is not well understood. VICs are known to be more elongated in a hypertensive environment compared to those in a normotensive environment. We have previously reported that valve tissues cultured under hypertensive conditions are prone to acute pathological alterations in cell phenotype and contractility. We therefore aimed to rigorously study the relationship between VIC shape, contractile output and other functional indicators of VIC pathology. We developed an in vitro model to engineer VICs to take on the same shapes as those seen in normal and hypertensive conditions. VICs with longer cellular and nuclear shapes, as seen in hypertensive conditions, had greater contractile response to endothelin-1 that correlated with increased anisotropy of the actin architecture. These elongated VICs also demonstrated altered cell metabolism through a decreased optical redox ratio, which coincided with increased cellular proliferation. In the presence of actin polymerization inhibitor, however, these functional responses were significantly reduced, suggesting the important role of cytoskeletal actin organization in regulating cellular responses to abnormal shape. Overall, these results demonstrate the relationship between cell shape, cytoskeletal and nuclear organization, with functional output including contractility, metabolism, and proliferation.

Intraepithelial dysplasia of the oral mucosa typically originates in the proliferative cell layer at the basement membrane and extends to the upper epithelial layers as the disease progresses. Detection of malignancies typically occurs upon visual inspection by non-specialists at a late-stage. In this manuscript, we validate a quantitative hybrid imaging and spectroscopy microendoscope to monitor dysplastic progression within the oral cavity microenvironment in a phantom and pre-clinical study. We use an empirical model to quantify optical properties and sampling depth from sub-diffuse reflectance spectra (450–750 nm) at two source-detector separations (374 and 730 μm). Average errors in recovering reduced scattering (5–26 cm−1) and absorption coefficients (0–10 cm−1) in hemoglobin-based phantoms were approximately 2% and 6%, respectively. Next, a 300 μm-thick phantom tumor model was used to validate the probe’s ability to monitor progression of a proliferating optical heterogeneity. Finally, the technique was demonstrated on 13 healthy volunteers and volume-averaged optical coefficients, scattering exponent, hemoglobin concentration, oxygen saturation and sampling depth are presented alongside a high-resolution microendoscopy image of oral mucosa from one volunteer. This multimodal microendoscopy approach encompasses both structural and spectroscopic reporters of perfusion within the tissue microenvironment and can potentially be used to monitor tumor response to therapy.

Qualitative screening for colorectal polyps via fiber bundle microendoscopy imaging has shown promising results, with studies reporting high rates of sensitivity and specificity, as well as low interobserver variability with trained clinicians. A quantitative image quality control and image feature extraction algorithm (QFEA) was designed to lessen the burden of training and provide objective data for improved clinical efficacy of this method. After a quantitative image quality control step, QFEA extracts field-of-view area, crypt area, crypt circularity, and crypt number per image. To develop and validate this QFEA, a training set of microendoscopy images was collected from freshly resected porcine colon epithelium. The algorithm was then further validated on ex vivo image data collected from eight human subjects, selected from clinically normal appearing regions distant from grossly visible tumor in surgically resected colorectal tissue. QFEA has proven flexible in application to both mosaics and individual images, and its automated crypt detection sensitivity ranges from 71 to 94% despite intensity and contrast variation within the field of view. It also demonstrates the ability to detect and quantify differences in grossly normal regions among different subjects, suggesting the potential efficacy of this approach in detecting occult regions of dysplasia.

Spatially–resolved diffuse reflectance (SRDR) measurements provide photon path information, and enable layered tissue analysis. This paper presents experimental SRDR measurements on two-layer PDMS skin tissue-mimicking phantoms of varying top layer thicknesses, and bulk phantoms of varying optical properties using concentric multi-pixel photodiode array (CMPA) probes, and corresponding forward Monte Carlo simulations. The CMPA is the most densely packed semiconductor SRDR probe reported to date. Signal contrasts between the single layer phantom and bi-layer phantoms with varying top layer thicknesses are as high as 80%. The mean error between the Monte Carlo simulations and the experiment is less than 6.2 %.

Two-photon excitation of label-free tissue is of increasing interest, as advances have been made in endoscopic clinical application of multiphoton microscopy, such as second harmonic generation (SHG) scanning endoscopy used to monitor cervical collagen in mice1. We used C57BL mice as a model to investigate the progression of gastrointestinal structures, specifically glandular area and circularity. We used multiphoton microscopy to image ex-vivo label-free murine colon, focusing on the collagen structure changes over time, in mice ranging from 10 to 20 weeks of age. Series of images were acquired within the colonic and intestinal tissue at depth intervals of 20 microns from muscularis to the epithelium, up to a maximum depth of 180 microns. The imaging system comprised a two-photon laser tuned to 800nm wavelength excitation, and the SHG emission was filtered with a 400/40 bandpass filter before reaching the photomultiplier tube. Images were acquired at 15 frames per second, for 200 to 300 cumulative frames, with a field of view of 261um by 261um, and 40mW at sample. Image series were compared to histopathology H&E slides taken from adjacent locations. Quantitative metrics for determining differences between murine glandular structures were applied, specifically glandular area and circularity.

We present a light sheet confocal microscope (LSCM) capable of high-resolution imaging of cell suspensions in a microfluidic environment. In lieu of conventional pressure-driven flow or mechanical translation of the samples, we have employed a novel method of fluid transport, redox-magnetohydrodynamics (redox-MHD). This method achieves fluid motion by inducing a small current into the suspension in the presence of a magnetic field via electrodes patterned onto a silicon chip. This on-chip transportation requires no moving parts, and is coupled to the remainder of the imaging system. The microscopy system comprises a 450 nm diode 20 mW laser coupled to a single mode fiber and a cylindrical lens that converges the light sheet into the back aperture of a 10x, 0.3 NA objective lens in an epi-illumination configuration. The emission pathway contains a 150 mm tube lens that focuses the light onto the linear sensor at the conjugate image plane. The linear sensor (ELiiXA+ 8k/4k) has three lateral binning modes which enables variable detection aperture widths between 5, 10, or 20 μm, which can be used to vary axial resolution. We have demonstrated redox-MHD-enabled light sheet microscopy in suspension of fluorescent polystyrene beads. This approach has potential as a high-throughput image cytometer with myriad cellular diagnostic applications.

In the non-keratinized epithelia, dysplasia typically arises near the basement membrane and proliferates into the upper epithelial layers over time. We present a non-invasive, multimodal technique combining high-resolution fluorescence imaging and broadband sub-diffuse reflectance spectroscopy (sDRS) to monitor health at various tissue layers. This manuscript focuses on characterization of the sDRS modality, which contains two source-detector separations (SDSs) of 374 μm and 730 μm, so that it can be used to extract in vivo optical parameters from human oral mucosa at two tissue thicknesses. First, we present empirical lookup tables (LUTs) describing the relationship between reduced scattering (μs′) and absorption coefficients (μa) and absolute reflectance. LUTS were shown to extract μs′ and μa with accuracies of approximately 4% and 8%, respectively. We then present LUTs describing the relationship between μs′, μa and sampling depth. Sampling depths range between 210–480 and 260–620 μm for the 374 and 730 μm SDSs, respectively. We then demonstrate the ability to extract in vivo μs′, μa, hemoglobin concentration, bulk tissue oxygen saturation, scattering exponent, and sampling depth from the inner lip of thirteen healthy volunteers to elucidate the differences in the extracted optical parameters from each SDS (374 and 730 μm) within non-keratinized squamous epithelia.