Antenatal oral glucose tolerance test abnormalities in the prediction of future risk of postpartum diabetes in women with gestational diabetes: Results from the LIVING study.

OBJECTIVES: To explore associations between type and number of abnormal glucose values on antenatal oral glucose tolerance test (OGTT) with postpartum diabetes in South Asian women diagnosed with gestational diabetes (GDM) using International Association of the Diabetes and Pregnancy Study Groups criteria. METHODS: This post-hoc evaluation of the Lifestyle Intervention IN Gestational Diabetes (LIVING) study, a randomized controlled trial, was conducted among women with GDM in the index pregnancy, across 19 centers in Bangladesh, India, and Sri Lanka. Postpartum diabetes (outcome) was defined on OGTT, using American Diabetes Association (ADA) criteria. RESULTS: We report data on 1468 women with GDM, aged 30.9 (5.0) years, and with median (interquartile range) follow-up period of 1.8 (1.4-2.4) years after childbirth following the index pregnancy. We found diabetes in 213 (14.5%) women with an incidence of 8.7 (7.6-10.0)/100 women-years. The lowest incidence rate was 3.8/100 women years, in those with an isolated fasting plasma glucose (FPG) abnormality, and highest was 19.0/100 women years in participants with three abnormal values. The adjusted hazard ratios for two and three abnormal values compared to one abnormal value were 1.73 (95% confidence interval [CI], 1.18-2.54; p = .005) and 3.56 (95% CI, 2.46-5.16; p < .001) respectively. The adjusted hazard ratio for the combined (combination of fasting and postglucose load) abnormalities was 2.61 (95% CI, 1.70-4.00; p < .001), compared to isolated abnormal FPG. CONCLUSIONS: Risk of diabetes varied significantly depending upon the type and number of abnormal values on antenatal OGTT. These data may inform future precision medicine approaches such as risk prediction models in identifying women at higher risk and may guide future targeted interventions.

CKD is the Major Cause of Death in Uddanam: A Population-Representative Study Using Smart Verbal Autopsy.

Introduction: Uddanam is an agricultural area with a high burden of chronic kidney disease of unknown etiology (CKDu). Despite reports of many deaths due to CKD in the lay press, the exact contribution of CKD to deaths remains uncertain because most deaths occur outside medical care. Methods: We used SmartVA automated verbal autopsy tool to ascertain the cause-specific mortality fractions among a 2419 subject-strong general population cohort of adult subjects in Uddanam between 2018 and 2022. Verbal autopsy interviews were conducted twice with the family members of the deceased. Results: A total of 133 deaths were recorded, giving a crude death rate of 5.5%, 10 times higher than that recorded in national surveys. CKD was responsible for 45% of all deaths, followed by ischemic heart disease (15%) and respiratory disease (6%). Conclusion: This study confirms CKD as the leading cause of mortality in this high CKD burden area and provides crucial data for public health decision-making and resource allocation.

TIE-GANs: single-shot quantitative phase imaging using transport of intensity equation with integration of GANs.

Significance: Artificial intelligence (AI) has become a prominent technology in computational imaging over the past decade. The expeditious and label-free characteristics of quantitative phase imaging (QPI) render it a promising contender for AI investigation. Though interferometric methodologies exhibit potential efficacy, their implementation involves complex experimental platforms and computationally intensive reconstruction procedures. Hence, non-interferometric methods, such as transport of intensity equation (TIE), are preferred over interferometric methods. Aim: TIE method, despite its effectiveness, is tedious as it requires the acquisition of many images at varying defocus planes. The proposed methodology holds the ability to generate a phase image utilizing a single intensity image using generative adversarial networks (GANs). We present a method called TIE-GANs to overcome the multi-shot scheme of conventional TIE. Approach: The present investigation employs the TIE as a QPI methodology, which necessitates reduced experimental and computational efforts. TIE is being used for the dataset preparation as well. The proposed method captures images from different defocus planes for training. Our approach uses an image-to-image translation technique to produce phase maps and is based on GANs. The main contribution of this work is the introduction of GANs with TIE (TIE:GANs) that can give better phase reconstruction results with shorter computation times. This is the first time the GANs is proposed for TIE phase retrieval. Results: The characterization of the system was carried out with microbeads of 4 µm size and structural similarity index (SSIM) for microbeads was found to be 0.98. We demonstrated the application of the proposed method with oral cells, which yielded a maximum SSIM value of 0.95. The key characteristics include mean squared error and peak-signal-to-noise ratio values of 140 and 26.42 dB for oral cells and 100 and 28.10 dB for microbeads. Conclusions: The proposed methodology holds the ability to generate a phase image utilizing a single intensity image. Our method is feasible for digital cytology because of its reported high value of SSIM. Our approach can handle defocused images in such a way that it can take intensity image from any defocus plane within the provided range and able to generate phase map.

The incidence and risk factors of postpartum diabetes in women from Bangladesh, India and Sri Lanka (South Asia) with prior gestational diabetes mellitus: Results from the LIVING study.

AIM: To study, the incidence and risk factors for postpartum diabetes (DM), in women with gestational diabetes mellitus (GDM) from South Asia (Bangladesh, India and Sri Lanka), followed for nearly two years after delivery. METHODS: Women with prior GDM diagnosed using IADPSG criteria were invited at 19 centres across Bangladesh, India and Sri Lanka for an oral glucose tolerance test (OGTT) following childbirth, and were enrolled in a randomized controlled trial. The glycaemic category (outcome) was defined from an OGTT based on American Diabetes Association criteria. RESULTS: Participants (n = 1808) recruited had a mean ± SD age of 31.0 ± 5.0 years. Incident DM was identified, between childbirth and the last follow-up, in 310 (17.1 %) women [incidence 10.75/100 person years], with a median follow-up duration of 1.82 years after childbirth. Higher age, lower education status, higher prior pregnancy count, prior history of GDM, family history of DM, and postpartum overweight/obese status were significantly associated with incident DM. Women in Bangladesh had a higher cumulative incidence of DM [16.49/100 person years] than in Sri Lanka [12.74/100 person years] and India [7.21/100 person years]. CONCLUSIONS: A high incidence of DM was found in women with prior GDM in South Asia, with significant variation between countries. Women from Bangladesh had a significantly higher pregnancy count, family history of DM and overweight/obese status, despite having significantly lower age, which could be responsible for their higher rates of DM. Registration of this study: The study was registered with the Clinical Trials Registry of India (CTRI/2017/06/008744), Sri Lanka Clinical Trials Registry (SLCTR/2017/001), and ClinicalTrials.gov (NCT03305939).

How do diverse low-income and middle-income countries implement primary healthcare team integration to support the delivery of comprehensive primary health care? A mixed-methods study protocol from India, Mexico and Uganda.

INTRODUCTION: Attainment of universal health coverage is feasible via strengthened primary health systems that are comprehensive, accessible, people-centred, continuous and coordinated. Having an adequately trained, motivated and equipped primary healthcare workforce is central to the provision of comprehensive primary healthcare (CPHC). This study aims to understand PHC team integration, composition and organisation in the delivery of CPHC in India, Mexico and Uganda. METHODS AND ANALYSIS: A parallel, mixed-methods study (integration of quantitative and qualitative results) will be conducted to gain an understanding of PHC teams. Methods include: (1) Policy review on PHC team composition, organisation and expected comprehensiveness of PHC services, (2) PHC facility review using the WHO Service Availability and Readiness Assessment, and (3) PHC key informant interviews. Data will be collected from 20, 10 and 10 PHCs in India, Mexico and Uganda, respectively, and analysed using descriptive methods and thematic analysis approach. Outcomes will include an in-depth understanding of the health policies for PHC as well as understanding PHC team composition, organisation and the delivery of comprehensive PHC. ETHICS AND DISSEMINATION: Approvals have been sought from the Institutional Ethics Committee of The George Institute for Global Health, India for the Indian sites, School of Medicine Research Ethics Committee at Makerere University for the sites in Uganda and the Research, Ethics and Biosecurity Committees of the Mexican National Institute of Public Health for the sites in Mexico. Results will be shared through presentations with governments, publications in peer-reviewed journals and presentations at conferences.

Quantifying viscosity and elasticity using holographic imaging by Rayleigh wave dispersion.

Viscoelasticity is an important diagnostic parameter to investigate physiological dysfunctions in biological tissues. This Letter reports the quantification of viscoelastic parameters by Rayleigh wave tracing on the surface of tissue-mimicking phantoms using holographic imaging. The Rayleigh wave is induced by an electromechanical actuator on the surface of oil-in-gelatin phantoms and a biological tissue sample followed by holographic imaging and reconstruction of the wave. The frequency-dependent velocity dispersion is fitted to a Voigt model for the quantification of viscous and elastic moduli. The viscoelastic parameters calculated by the proposed method are validated by comparing the results from a conventional mechanical rheometer.

Cost-Effectiveness of Population Screening Programs for Cardiovascular Diseases and Diabetes in Low- and Middle-Income Countries: A Systematic Review.

Almost all low- and middle-income countries (LMICs) have instated a program to control and manage non-communicable diseases (NCDs). Population screening is an integral component of this strategy and requires a substantial chunk of investment. Therefore, testing the screening program for economic along with clinical effectiveness is essential. There is significant proof of the benefits of incorporating economic evidence in health decision-making globally, although evidence from LMICs in NCD prevention is scanty. This systematic review aims to consolidate and synthesize economic evidence of screening programs for cardiovascular diseases (CVD) and diabetes from LMICs. The study protocol is registered on PROSPERO (CRD42021275806). The review includes articles from English and Chinese languages. An initial search retrieved a total of 2,644 potentially relevant publications. Finally, 15 articles (13 English and 2 Chinese reports) were included and scrutinized in detail. We found 6 economic evaluations of interventions targeting cardiovascular diseases, 5 evaluations of diabetes interventions, and 4 were combined interventions, i.e., screening of diabetes and cardiovascular diseases. The study showcases numerous innovative screening programs that have been piloted, such as using mobile technology for screening, integrating non-communicable disease screening with existing communicable disease screening programs, and using community health workers for screening. Our review reveals that context is of utmost importance while considering any intervention, i.e., depending on the available resources, cost-effectiveness may vary-screening programs can be made universal or targeted just for the high-risk population.

Effects of a Lifestyle Intervention to Prevent Deterioration in Glycemic Status Among South Asian Women With Recent Gestational Diabetes: A Randomized Clinical Trial.

Importance: Women with recent gestational diabetes (GDM) have increased risk of developing type 2 diabetes. Objective: To investigate whether a resource-appropriate and context-appropriate lifestyle intervention could prevent glycemic deterioration among women with recent GDM in South Asia. Design, Setting, and Participants: This randomized, participant-unblinded controlled trial investigated a 12-month lifestyle intervention vs usual care at 19 urban hospitals in India, Sri Lanka, and Bangladesh. Participants included women with recent diagnosis of GDM who did not have type 2 diabetes at an oral glucose tolerance test (OGTT) 3 to 18 months postpartum. They were enrolled from November 2017 to January 2020, and follow-up ended in January 2021. Data were analyzed from April to July 2021. Interventions: A 12-month lifestyle intervention focused on diet and physical activity involving group and individual sessions, as well as remote engagement, adapted to local context and resources. This was compared with usual care. Main Outcomes and Measures: The primary outcome was worsening category of glycemia based on OGTT using American Diabetes Association criteria: (1) normal glucose tolerance to prediabetes (ie, impaired fasting glucose or impaired glucose tolerance) or type 2 diabetes or (2) prediabetes to type 2 diabetes. The primary analysis consisted of a survival analysis of time to change in glycemic status at or prior to the final patient visit, which occurred at varying times after 12 months for each patient. Secondary outcomes included new-onset type 2 diabetes and change in body weight. Results: A total of 1823 women (baseline mean [SD] age, 30.9 [4.9] years and mean [SD] body mass index, 26.6 [4.6]) underwent OGTT at a median (IQR) 6.5 (4.8-8.2) months postpartum. After excluding 160 women (8.8%) with type 2 diabetes, 2 women (0.1%) who met other exclusion criteria, and 49 women (2.7%) who did not consent or were uncontactable, 1612 women were randomized. Subsequently, 11 randomized participants were identified as ineligible and excluded from the primary analysis, leaving 1601 women randomized (800 women randomized to the intervention group and 801 women randomized to usual care). These included 600 women (37.5%) with prediabetes and 1001 women (62.5%) with normoglycemia. Among participants randomized to the intervention, 644 women (80.5%) received all program content, although COVID-19 lockdowns impacted the delivery model (ie, among 644 participants who engaged in all group sessions, 476 women [73.9%] received some or all content through individual engagement, and 315 women [48.9%] received some or all content remotely). After a median (IQR) 14.1 (11.4-20.1) months of follow-up, 1308 participants (81.2%) had primary outcome data. The intervention, compared with usual care, did not reduce worsening glycemic status (204 women [25.5%] vs 217 women [27.1%]; hazard ratio, 0.92; [95% CI, 0.76-1.12]; P = .42) or improve any secondary outcome. Conclusions and Relevance: This study found that a large proportion of women in South Asian urban settings developed dysglycemia soon after a GDM-affected pregnancy and that a lifestyle intervention, modified owing to the COVID-19 pandemic, did not prevent subsequent glycemic deterioration. These findings suggest that alternate or additional approaches are needed, especially among high-risk individuals. Trial Registration: Clinical Trials Registry of India Identifier: CTRI/2017/06/008744; Sri Lanka Clinical Trials Registry Identifier: SLCTR/2017/001; and ClinicalTrials.gov Identifier: NCT03305939.

Surface wave elastography using high speed full-field optical interferometry.

The assessment of mechanical stiffness is an essential diagnostic tool for investigating the biomechanical properties of biological tissues. Surface wave elastography (SWE) is an emerging technique to quantify elastic properties of tissues in clinical diagnosis. High-speed optical imaging combined with SWE has enormous potential in quantifying the elastic properties of tissues at microscale resolutions. In this study, we implement surface wave elastography using high-speed optical interferometry to characterize the elastic properties of tissue-mimicking phantoms andex-vivonative caprine liver tissue by imaging the surface wave induced by an electromechanical actuator. The sinusoidal mechanical excitations ranging from 120 Hz to 1.2 kHz on the surface of tissues are captured using a high-speed camera with a frame rate of 4 kHz at micrometer resolutions. The surface wavefront reconstruction is performed using a phase-shifting algorithm and linear regression is used to calculate the surface wave velocity. The mechanical stiffness estimated from the optical system is compared with the results of mechanical compression testing measurements. The results from this multimodal platform combining optical interferometry and vibrational spectroscopy using SWE are highly promising towards a non-invasive or minimally invasive imaging forin-vivoandex-vivomechanical characterization of tissues with future clinical applications.

Gender, health and ageing in Fiji: a mixed methods analysis.

BACKGROUND: Women are disadvantaged by ageing: older women are more likely than older men to suffer from ill-health, have less access to health care and suffer discrimination within the health care system. Globally, there is a dearth of health research on gender and ageing with substantial knowledge gaps in low and middle-income country contexts. Part of a wider investigation on health and ageing in Fiji, our objective was to identify and describe gendered differences in healthy ageing in this Pacific Island context. We believe this to be the first such study in the Pacific region. METHODS: Applying a health systems lens, we used a mixed-methods approach, encompassing analysis of cause of death data; focus group discussion to gather community and family attitudes to health services; and policy analysis, and then used data triangulation techniques to draw out key themes and insights. RESULTS: We found that gender affects health outcomes among older persons, attitudes towards and experience of healthy ageing, and an older person's access to and use of health services. We also found that while Fiji's policy response to ageing has recognised the importance of gender, to-date there has been limited action to address gender differences. Gender (as oppose to sex differences) has direct and indirect implications for the health of older Fijians, while gendered inequalities and patriarchal norms appear to affect both men and women's experience of ageing and the health system response. Further, gender and age discrimination may be intersecting, intensifying their separate effects. CONCLUSION: This study demonstrates the feasibility and importance of applying a gender lens to the study of healthy ageing. Our findings from Fiji may be relevant to other island nations in the south Pacific which share similar challenges of population ageing, a constrained health budget and geographically-dispersed populations. The data triangulation methodology may be considered an efficient and insightful way to examine gendered responses to healthy ageing elsewhere.

Iontophoresis mediated localized delivery of liposomal gold nanoparticles for photothermal and photodynamic therapy of acne.

Acne is one of the common dermatological skin inflammatory conditions. The current therapeutic modalities for the treatment of acne include the administration of antibiotics and anti-inflammatory agents. The rising instance of antibiotic resistance in acne strains has led to the exploration of alternative therapeutic modalities. In the current study, we have employed a liposomal gold nanoparticle entrapping curcumin (Au Lipos Cur NPs) for dual light-mediated therapy for the treatment of acne. These nanoparticles exerted a positive zeta potential that enabled their localized follicular delivery by iontophoresis. The localized deposition of Au Lipos NPs leads to photothermal transduction causing destruction of sebaceous glands. Furthermore, when the nanoparticles were assessed in vitro by sequential irradiation with NIR and blue light, it resulted in significant inhibition of bacterial growth. Thus the dual light-mediated therapy by Au Lipos Cur NPs can form a potential therapeutic modality for the efficient treatment of recurrent acne.

Thickening of Ectatic Cornea through Regeneration Using Decellularized Corneal Matrix Injectable Hydrogel: A Strategic Advancement to Mitigate Corneal Ectasia.

Ectatic corneal diseases are a group of eye disorders characterized by progressive thinning and outward bulging of the cornea, resulting in vision impairment. A few attempts have been made to use cornea-derived extracellular matrix hydrogels for corneal tissue engineering; however, no studies have investigated its application in corneal ectasia. In this study, we have first developed an animal surgical model that mimics a few specific phenotypes of ectatic cornea. Later, we investigated the potential of decellularized cornea matrix hydrogels (dCMH) from both human and bovine sources in increasing the thickness of the cornea in the developed surgical model. Our data advocate that surgical stromal depletion can be followed to establish ectatic models and can also provide information on the biocompatibility of materials, its integration with native stroma, degradation over time, and tissue remodeling. We observed that dCMH from both sources could integrate with ectatic thin corneal stroma and helps in regaining the thickness by regenerating a reasonably functional and transparent stroma; however, no significant difference was spotted between the dCMH made from human and bovine corneal tissue sources. Hence, this study is a promising step toward developing a non-invasive technique for the treatment of corneal ectasia by using dCMH.

Qualitative enquiry on irregular intake of antihypertensive medications to inform a model of care to improve blood pressure control.

Background: A large proportion of people with hypertension do not take medications regularly. There is little understanding of this complex behaviour in India.Methods: A descriptive qualitative study was conducted in two districts of Andhra Pradesh, India, to explore the reasons for irregular intake of anti-hypertensive drugs from patient's and health care provider's (HCP) perspectives. In-depth interviews and focus group discussions were carried out among HCPs and patients with irregular drug intake.Results: The major themes that emerged were: (i) patient's perception of immediate relief and poor awareness about the disease, (ii) patient's misconceptions about the drug and fear of life long medications, (iii) busy schedule and forgetfulness, (iv) health system factors such as lack of patient counselling, high cost of care and non-availability of medicines, and (v) lack of peer/family/social support and social stigma.Conclusion: Better patient education and counselling services and active engagement of family members and peers are needed to improve medication adherence. The NPCDCS program should implement mechanisms to assess and monitor adherence to medications in chronic diseases particularly for hypertension.Impact: Currently there is no strategy to ensure medication adherence in India. The results of the study will be utilized in developing a community model of care to improve the level of adherence and better control of blood pressure.KEYWORDS: hypertension; medication adherence; compliance; qualitative study.

Dual-modality microfluidic biosensor based on nanoengineered mesoporous graphene hydrogels.

A dual-modality microfluidic biosensor is fabricated using a mesoporous nanostructured cysteine-graphene hydrogel for the quantification of human cardiac myoglobin (cMb). In this device, the nanoengineered mesoporous l-cysteine-graphene (Cys-RGO) hydrogel performs the role of a dual-modality sensing electrode for the measurements conducted using differential pulse voltammetry and surface plasmon resonance (SPR) techniques. High surface reactivity, mesoporous structure and fast electron transfer combined with good reaction kinetics of the graphene hydrogel in this device indicate excellent performance for the detection of human cardiac myoglobin in serum samples. In electrochemical modality, this microfluidic chip exhibits a high sensitivity of 196.66 µA ng-1 mL cm-2 for a linear range of concentrations (0.004-1000 ng mL-1) with a low limit of detection (LOD) of 4 pg mL-1 while the SPR technique shows a LOD of 10 pg mL-1 for cMb monitoring in the range 0.01-1000 ng mL-1. The intra-assay coefficient of variation was less than 8% for standard samples and 9% for real serum samples, respectively. This Cys-RGO hydrogel-based microfluidic SPR chip allows real-time dynamic tracking of cMb molecules with a high association constant of 4.93 ± 0.2 × 105 M-1 s-1 and a dissociation constant of 1.37 ± 0.08 × 10-4 s-1, self-verification, reduced false readout, and improved detection reliability.

Echocardiogram Analysis Using Motion Profile Modeling.

Echocardiography is a widely used and cost-effective medical imaging procedure that is used to diagnose cardiac irregularities. To capture the various chambers of the heart, echocardiography videos are captured from different angles called views to generate standard images/videos. Automatic classification of these views allows for faster diagnosis and analysis. In this work, we propose a representation for echo videos which encapsulates the motion profile of various chambers and valves that helps effective view classification. This variety of motion profiles is captured in a large Gaussian mixture model called universal motion profile model (UMPM). In order to extract only the relevant motion profiles for each view, a factor analysis based decomposition is applied to the means of the UMPM. This results in a low-dimensional representation called motion profile vector (MPV) which captures the distinctive motion signature for a particular view. To evaluate MPVs, a dataset called ECHO 1.0 is introduced which contains around 637 video clips of the four major views: a) parasternal long-axis view (PLAX), b) parasternal short-axis (PSAX), c) apical four-chamber view (A4C), and d) apical two-chamber view (A2C). We demonstrate the efficacy of motion profile-vectors over other spatio-temporal representations. Further, motion profile-vectors can classify even poorly captured videos with high accuracy which shows the robustness of the proposed representation.

Label-free nanoscale characterization of red blood cell structure and dynamics using single-shot transport of intensity equation.

We report the results of characterization of red blood cell (RBC) structure and its dynamics with nanometric sensitivity using transport of intensity equation microscopy (TIEM). Conventional transport of intensity technique requires three intensity images and hence is not suitable for studying real-time dynamics of live biological samples. However, assuming the sample to be homogeneous, phase retrieval using transport of intensity equation has been demonstrated with single defocused measurement with x-rays. We adopt this technique for quantitative phase light microscopy of homogenous cells like RBCs. The main merits of this technique are its simplicity, cost-effectiveness, and ease of implementation on a conventional microscope. The phase information can be easily merged with regular bright-field and fluorescence images to provide multidimensional (three-dimensional spatial and temporal) information without any extra complexity in the setup. The phase measurement from the TIEM has been characterized using polymeric microbeads and the noise stability of the system has been analyzed. We explore the structure and real-time dynamics of RBCs and the subdomain membrane fluctuations using this technique.

Microporous Nanocomposite Enabled Microfluidic Biochip for Cardiac Biomarker Detection.

This paper demonstrates an ultrasensitive microfluidic biochip nanoengineered with microporous manganese-reduced graphene oxide nanocomposite for detection of cardiac biomarker, namely human cardiac troponin I. In this device, the troponin sensitive microfluidic electrode consisted of a thin layer of manganese-reduced graphene oxide (Mn3O4-RGO) nanocomposite material. This nanocomposite thin layer was formed on surface of a patterned indium tin oxide substrate after modification with 3-aminopropyletriethoxysilane and was assembled with a polydimethylsiloxane-based microfluidic system. The nanoengineered microelectrode was functionalized with antibodies specific to cardiac troponin I. The uniformly distributed flower-shaped nanostructured manganese oxide (nMn3O4) onto RGO nanosheets offered large surface area for enhanced loading of antibody molecules and improved electrochemical reaction at the sensor surface. This microfluidic device showed an excellent sensitivity of log [87.58] kΩ/(ng mL-1)/cm2 for quantification of human cardiac troponin I (cTnI) molecules in a wide detection range of 0.008-20 ng/mL. This device was found to have high stability, high reproducibility, and minimal interference with other biomarkers cardiac troponin C and T, myoglobin, and B-type natriuretic peptide. These advantageous features of the Mn3O4-RGO nanocomposite, in conjunction with microfluidic integration, enabled a promising microfluidic biochip platform for point-of-care detection of cardiac troponin.

Quantitative phase imaging of live cells with near on-axis digital holographic microscopy using constrained optimization approach.

We demonstrate a single-shot near on-axis digital holographic microscope that uses a constrained optimization approach for retrieval of the complex object function in the hologram plane. The recovered complex object is back-propagated from the hologram plane to image plane using the Fresnel back-propagation algorithm. A numerical aberration compensation algorithm is employed for correcting the aberrations in the object beam. The reference beam angle is calculated automatically using the modulation property of Fourier transform without any additional recording. We demonstrate this approach using a United States Air Force (USAF) resolution target as an object on our digital holographic microscope. We also demonstrate this approach by recovering the quantitative phase images of live yeast cells, red blood cells and dynamics of live dividing yeast cells.

Optofluidic bioimaging platform for quantitative phase imaging of lab on a chip devices using digital holographic microscopy.

We propose a versatile 3D phase-imaging microscope platform for real-time imaging of optomicrofluidic devices based on the principle of digital holographic microscopy (DHM). Lab-on-chip microfluidic devices fabricated on transparent polydimethylsiloxane (PDMS) and glass substrates have attained wide popularity in biological sensing applications. However, monitoring, visualization, and characterization of microfluidic devices, microfluidic flows, and the biochemical kinetics happening in these devices is difficult due to the lack of proper techniques for real-time imaging and analysis. The traditional bright-field microscopic techniques fail in imaging applications, as the microfluidic channels and the fluids carrying biological samples are transparent and not visible in bright light. Phase-based microscopy techniques that can image the phase of the microfluidic channel and changes in refractive indices due to the fluids and biological samples present in the channel are ideal for imaging the fluid flow dynamics in a microfluidic channel at high resolutions. This paper demonstrates three-dimensional imaging of a microfluidic device with nanometric depth precisions and high SNR. We demonstrate imaging of microelectrodes of nanometric thickness patterned on glass substrate and the microfluidic channel. Three-dimensional imaging of a transparent PDMS optomicrofluidic channel, fluid flow, and live yeast cell flow in this channel has been demonstrated using DHM. We also quantify the average velocity of fluid flow through the channel. In comparison to any conventional bright-field microscope, the 3D depth information in the images illustrated in this work carry much information about the biological system under observation. The results demonstrated in this paper prove the high potential of DHM in imaging optofluidic devices; detection of pathogens, cells, and bioanalytes on lab-on-chip devices; and in studying microfluidic dynamics in real time based on phase changes.