Numerous developments in optical biomedical imaging research utilizing gold nanostructures as contrast agents have advanced beyond basic research towards demonstrating potential as diagnostic tools; some of which are translating into clinical applications. Recent advances in optics, lasers and detection instrumentation along with the extensive, yet developing, knowledge-base in tailoring the optical properties of gold nanostructures has significantly improved the prospect of near-infrared (NIR) optical detection technologies. Of particular interest are optical coherence tomography (OCT), photoacoustic imaging (PAI), multispectral optoacoustic tomography (MSOT), Raman spectroscopy (RS) and surface enhanced spatially offset Raman spectroscopy (SESORS), due to their respective advancements. Here we discuss ...

Non-muscle-invasive bladder cancer affects millions of people worldwide, resulting in significant discomfort to the patient and potential death. Today, cystoscopy is the gold standard for bladder cancer assessment, using white light endoscopy to detect tumor suspected lesion areas, followed by resection of these areas and subsequent histopathological evaluation. Not only does the pathological examination take days, but due to the invasive nature, the performed biopsy can result in significant harm to the patient. Nowadays, optical modalities, such as optical coherence tomography (OCT) and Raman spectroscopy (RS), have proven to detect cancer in real time and can provide more detailed clinical ...

The retina consists of multiple layers of different types of cells; the inner layer is known as the retinal nerve fiber layer (RNFL) and it consists of unmyelinated optic nerve axons coming from the retinal ganglion cells. Optical coherence tomography (OCT) is able to detect subtle changes in the thickness of the retina by means of infrared light reflection, representing retinal and optic nerve damage in neuro-ophthalmology pathologies. In recent years, different research has suggested that retinal OCT is a sensitive and useful tool to measure axonal damage after optic neuropathy and to understand the process of neurodegeneration in multiple ...

Multimodal imaging platforms offer a vast array of tissue information in a single image acquisition by combining complementary imaging techniques. By merging different systems, better tissue characterization can be achieved than is possible by the constituent imaging modalities alone. The combination of optical coherence tomography (OCT) with non-linear optical imaging (NLOI) techniques such as two-photon excited fluorescence (TPEF), second harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS) provides access to detailed information of tissue structure and molecular composition in a fast, label-free and non-invasive manner. We introduce a multimodal label-free approach for morpho-molecular imaging and spectroscopy and validate the ...

Optical coherence tomography angiography (OCTA) is a relatively novel functional extension of the widely accepted ophthalmic imaging tool named optical coherence tomography (OCT). Since OCTA’s debut in ophthalmology, researchers have also been trying to expand its translational application into dermatology. The ability of OCTA in resolving microvasculature has shown promising results in imaging skin diseases. Meanwhile, photoacoustic imaging (PAI), which uses laser pulse induced ultrasound waves as the signal, has been studied to differentiate human skin layers and to help skin disease diagnosis. This perspective article gives a short review of OCTA and PAI in the field of photodermatology ...

The solid concentration of pulmonary mucus (wt%) is critical to respiratory health. In patients with respiratory disease, such as Cystic Fibrosis (CF) and Chronic Obstructive Pulmonary Disorder (COPD), mucus hydration is impaired, resulting in high wt%. Mucus with high wt% is a hallmark of pulmonary disease that leads to obstructed airways, inflammation, and infection. Methods to measure mucus hydration in situ and in real-time are needed for drug development and personalized therapy. We employed plasmonic gold nanorod (GNR) biosensors that intermittently collide with macromolecules comprising the mucus mesh as they self-diffuse, such that GNR translational diffusion ( D T ) is sensitive ...

Biopsy based diagnosis of oral precancers like leukoplakia (OLK) and submucous fibrosis (OSF) as well as squamous cell carcinoma (OSCC) suffers from observer specific variability. Present work explored the utility of intensity and textural features from optical coherence tomography (OCT) images after specific feature subset selection for precise classification of oral lesions using variants of support vector machine. Concomitant application of Fourier transform infrared (FTIR) spectroscopy for endorsing global biochemical signatures, and histochemistry was performed further for value addition of the OCT findings. Immunohistochemical findings for characterization of specific local molecular alteration were also included in this. Result suggested that ...

Heterogeneous Au-Fe3O4 dumbbell nanoparticles (NPs) are composed of Au NP and Fe3O4 NP that brings in optical and magnetic property respectively. This article reports the engineering of Au-Fe3O4 NPs as gene carriers for magnetic gene transfection as well as contrast agents for micro-optical coherence tomography (µOCT). As a proof-of-concept, Au-Fe3O4 NPs are used to deliver green fluorescent protein to HEK 293T cells and their entrance into the cells is monitored through µOCT.

Tuning the localized surface plasmon modes of gold nanostructures to be in resonance with near-infrared incident light is desirable in various applications such as biosensing, biomedicine/therapy and opto-electronic devices. Unfortunately, current methods for regulating the plasmon modes of gold nanoparticles still suffer from poor controllability and reproducibility. Here, we developed a facile and effective method to precisely tailor the plasmon mode of gold triangular nanoprisms (GTNPs) by simply exposing them to O 3 atmosphere. The resonant wavelength of the plasmon mode sustained by the GTNPs can be steadily tuned over a broad spectral range varying from 1010 nm to ...

Polymer microneedles (MNs) have gained increasing attention as a minimally invasive method for efficiently delivering drugs and vaccines in a patient-friendly manner. Herein, an easy and mild process with O2 plasma treatment was used to fabricate polyvinylpyrrolidone (PVP)/polyvinyl alcohol (PVA) MN patches, and efficient, sustained transdermal delivery was achieved. The diffusion rate of the entrained molecules could be controlled by adjusting the ratio of PVP/PVA. Optical coherence tomography was used to monitor the in vitro penetration in real time and to measure the penetration depth. Rhodamine 6G and fluorescein isothiocyanate-labeled bovine serum albumin (BSA-FITC) were used to explore ...

Optical coherence tomography velocimetry combined with a rheometer and optical modulation techniques provides increased sensitivity to the low shear rate motion of complex fluid systems. Optical modulation coupled with a new interferometer design yields improved signal to noise ratios and is demonstrated with optically opaque colloidal suspensions. Thus the measureable range of shear velocities with complex fluids can be as low as ~40 µms-1, more than an order of magnitude improvement on the previous lower limit of ~700 µms-1. Furthermore the apparatus demonstrates improved sensitivity to the measurement of velocity. The instrument was used to study two hard sphere colloidal ...

Optical coherence tomography (OCT) is a non-invasive interferometry imaging technique with micrometre scale resolution at millimetre scale penetration depths in highly scattering tissues. This study describes a new evolution of OCT, termed molecular optical coherence phase microscopy (molecular OCPM), which is capable of imaging expression of molecular markers at the cellular level using gold nanorods as photothermal imaging agents. Gold nanorods were selected as the OCPM molecular photothermal imaging agents due to their excellent photothermal energy conversion efficiency and tuneable plasmon bands. The gold nanorods were surface functionalized to achieve efficient and specific targeting of the tyrosine kinase human epidermal ...

Depth resolved label-free detection of structural changes with nanoscale sensitivity is an outstanding problem in the biological and physical sciences and has significant applications in both the fundamental research and healthcare diagnostics arenas. Here we experimentally demonstrate a novel label-free depth resolved sensing technique based on optical coherence tomography (OCT) to detect structural changes at the nanoscale. Structural components of the 3D object, spectrally encoded in the remitted light, are transformed from the Fourier domain into each voxel of the 3D OCT image without compromising sensitivity. Spatial distribution of the nanoscale structural changes in the depth direction is visualized in ...

Although many of the molecular mechanisms that regulate tissue assembly in the embryo have been delineated, the physical forces that couple these mechanisms to actual changes in tissue form remain unclear. Qualitative studies suggest that mechanical loads play a regulatory role in development, but clear quantitative evidence has been lacking. This is partly owing to the complex nature of these problems – embryonic tissues typically undergo large deformations and exhibit evolving, highly viscoelastic material properties. Still, despite these challenges, new disruptive technologies are enabling study of the mechanics of tissue assembly in unprecedented detail. Here, we present novel experimental techniques that ...

Inflammatory bowel disease including Crohn’s disease and ulcerative colitis resemble a large burden for patients due to the chronic course of disease. Therefore, there is an urgent need to explore new potential drugs and to develop new treatment options. Usually, evaluation of therapeutic potential is performed in murine models of colitis with the challenge of a valid assessment of the inflammation process and the therapeutic response. Digital holographic microscopy (DHM) enables strain-free quantitative phase contrast imaging and provides tissue density assessment by measuring optical path length delay and accordingly refractive index. Dextran sodium sulphate induced colitis was performed in ...

Microfluidic devices have undergone rapid development in recent years and provide a lab-on-a-chip solution for many biomedical and chemical applications. Optical imaging techniques are essential in microfluidics for observing and extracting information from biological or chemical samples. Traditionally, imaging in microfluidics is achieved by bench-top conventional microscopes or other bulky imaging systems. More recently, many novel compact microscopic techniques have been developed to provide a low-cost and portable solution. In this review, we provide an overview of optical imaging techniques used in microfluidics followed with their applications. We first discuss bulky imaging systems including microscopes and interferometer-based techniques, then we ...

We used optical coherence tomography velocimetry inside a fluids rheometer to study the rheology of a family of polyacrylamide (PAM) solutions that contain different polymer molecular weights and concentrations, with picolitre probing volumes. The linear velocity profiles obtained from low molecular weight samples, characteristic of Newtonian fluids under shear, become shear-banded when longer polymer chains (molecular weights 5000000 and above) are used at sufficiently high concentrations. Upon increasing the concentration further, shear-banding becomes less dominant and significant wall-slip takes place on the two plates of the rheometer. We describe the shear-banding and wall-slip phenomena in our samples in terms of ...

We present a one-step flow process to synthesize biocompatible gold nanorods with tunable absorption and bio-compatible surface ligands. Photothermal optical coherence tomography (OCT) of human breast tissue is demonstrated successfully using tailored gold nanorods designed to have strong absorption in the near infrared wavelength range.