An Active and Soft Hydrogel Actuator to Stimulate Live Cell Clusters by Self-folding.

The hydrogels are widely used in various applications, and their successful uses depend on controlling the mechanical properties. In this study, we present an advanced strategy to develop hydrogel actuator designed to stimulate live cell clusters by self-folding. The hydrogel actuator consisting of two layers with different expansion ratios were fabricated to have various curvatures in self-folding. The expansion ratio of the hydrogel tuned with the molecular weight and concentration of gel-forming polymers, and temperature-sensitive molecules in a controlled manner. As a result, the hydrogel actuator could stimulate live cell clusters by compression and tension repeatedly, in response to temperature. The cell clusters were compressed in the 0.7-fold decreases of the radius of curvature with 1.0 mm in room temperature, as compared to that of 1.4 mm in 37 °C. Interestingly, the vascular endothelial growth factor (VEGF) and insulin-like growth factor-binding protein-2 (IGFBP-2) in MCF-7 tumor cells exposed by mechanical stimulation was expressed more than in those without stimulation. Overall, this new strategy to prepare the active and soft hydrogel actuator would be actively used in tissue engineering, drug delivery, and micro-scale actuators.

Preliminary study of optical coherence tomography imaging to identify microscopic extrathyroidal extension in patients with papillary thyroid carcinoma.

BACKGROUND AND OBJECTIVES: We evaluated the feasibility of using optical coherence tomography (OCT), to identify microscopic extrathyroidal extension (mETE) in ex vivo thyroidectomy specimens of patients who underwent thyroidectomy for the treatment of papillary thyroid carcinoma (PTC). METHODS: A total of 170 ex vivo OCT images of the tumor, were acquired just after completion of thyroidectomy in 17 patients. The OCT images of each patient were separately evaluated by two blinded investigators, and the outcomes were compared with the histopathology reports. RESULTS: The sensitivity and specificity of mETE identification from the OCT images were 81.4% and 86.0%, respectively, for the first investigator, and 82.9% and 87.0%, respectively, for the second investigator. Substantial agreement between the investigators was verified by Cohen's κ (Cohen's κ = 0.772). CONCLUSION: In this preliminary study of a limited series of ex vivo thyroidectomy specimens, we verified the feasibility of OCT as a method of identifying mETE in patients with PTC.

Detection of vesicant-induced upper airway mucosa damage in the hamster cheek pouch model using optical coherence tomography.

Hamster cheek pouches were exposed to 2-chloroethyl ethyl sulfide [CEES, half-mustard gas (HMG)] at a concentration of 0.4, 2.0, or 5.0 mg/ml for 1 or 5 min. Twenty-four hours post-HMG exposure, tissue damage was assessed by both stereomicrography and optical coherence tomography (OCT). Damage that was not visible on gross visual examination was apparent in the OCT images. Tissue changes were found to be dependent on both HMG concentration and exposure time. The submucosal and muscle layers of the cheek pouch tissue showed the greatest amount of structural alteration. Routine light microscope histology was performed to confirm the OCT observations.

Detection and monitoring of early airway injury effects of half-mustard (2-chloroethylethylsulfide) exposure using high-resolution optical coherence tomography.

Optical coherence tomography (OCT) is a noninvasive, high-resolution imaging technology capable of delivering real-time, near-histologic images of tissues. Mustard gas is a vesicant-blistering agent that can cause severe and lethal damage to airway and lungs. The ability to detect and assess airway injury in the clinical setting of mustard exposure is currently limited. The purpose of this study is to assess the ability to detect and monitor progression of half-mustard [2-chloroethylethylsulfide (CEES)] airway injuries with OCT techniques. A ventilated rabbit mustard exposure airway injury model is developed. A flexible fiber optic OCT probe is introduced into the distal trachea to image airway epithelium and mucosa in vivo. Progression of airway injury is observed over eight hours with OCT using a prototype time-domain superluminescent diode OCT system. OCT tracheal images from CEES exposed animals are compared to control rabbits for airway mucosal thickening and other changes. OCT detects the early occurrence and progression of dramatic changes in the experimental group after exposure to CEES. Histology and immunofluorescence staining confirms this finding. OCT has the potential to be a high resolution imaging modality capable of detecting, assessing, and monitoring treatment for airway injury following mustard vesicant agent exposures.

Evaluation of rabbit tracheal inflammation using optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) is an evolving technology that is capable of delivering real-time, high-resolution images of tissues. The purpose of this study was to evaluate the feasibility of using OCT for detecting airway pathology in a septic animal model. METHODS: The tracheas of New Zealand white rabbits were inoculated endobronchially with various concentrations of live Streptococcus pneumoniae bacteria. After the development of pneumonia/sepsis, the animals were killed. OCT tracheal images and corresponding histologic specimens from these experimental animals were compared to control rabbit tracheas for morphologic features and quantitative tracheal mucosal thickness measurements. RESULTS: The results revealed significant airway mucosal thickening in the experimental group that was consistent with tracheal edema. Morphologic changes, including epithelial denuding and mucosal sloughing, were evident in regions of the experimental tracheas. CONCLUSION: This study suggests that OCT is a potentially valuable imaging modality that is capable of evaluating superficial airway pathology with high-resolution in vivo images. Numerous applications of OCT can be envisioned in the realm of pulmonary medicine and thoracic surgery that may substantially increase the precision and accuracy of current bronchoscopic diagnostic and surgical techniques.

Feasibility of three-dimensional optical coherence tomography and optical Doppler tomography of malignancy in hamster cheek pouches.

OBJECTIVE: Hamster cheek pouches (HCP) with various degrees of 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced dysplasia and malignancies were imaged with OCT/ODT in vivo and in vitro to assess the potential for three-dimensional high-resolution optical localization of airway malignancy. BACKGROUND DATA: Optical coherence tomography (OCT)/optical doppler tomography (ODT) provide potential capability for real-time in vivo high-resolution (2-20 microm) cross-sectional imaging of tissues and spatially resolved blood flow in microvasculature for pathology diagnostics. METHODS: DMBA was applied to the right side of the cheek pouch (HCP), and mineral oil (control) to the left side three times weekly for 10-18 weeks in Syrian Golden Hamsters using a standard protocol for malignancy induction. HCP were imaged in vivo with OCT/ODT as well as in vitro post-excision, using a prototype 1310-nm broadband superluminescent diode-based OCT/ODT device constructed in our laboratory. Three-dimensional images were constructed, and compared to standard and three-dimensional histology hematoxylin and eosin staining. RESULTS AND CONCLUSION: OCT imaging offered exceptional resolution of the HCP to depths of 1-2 mm and confirmed ability to detect dysplasia and malignancy. Three-dimensional OCT images were readily constructed, allowing visualization of extent and localization of tumor margins. ODT demonstrated increased vascularity in the area of neoplasia. OCT/ODT is a promising new technology for oral airway diagnostics.

Noninvasive imaging of oral premalignancy and malignancy.

Early detection of cancer and its precursors remains the best way to ensure patient survival and quality of life. Our specific aim is to test a multimodality approach to noninvasive diagnostics of oral premalignancy and malignancy. In the hamster cheek pouch model (120 hamsters), in vivo optical coherence tomography (OCT) and optical Doppler tomography (ODT) map epithelial, subepithelial, and vascular change throughout carcinogenesis. In vivo multiwavelength multiphoton (MPM) and second-harmonic generated (SHG) fluorescence techniques provided parallel data on surface and subsurface tissue structure, specifically collagen presence and structure, cellular presence, and vasculature. Images are diagnosed by two blinded, prestandardized investigators using a scale from 0 to 6 for all modalities. After sacrifice, histopathology is evaluated on a scale of 0 to 6. Imaging data are reproducibly obtained with good accuracy. Carcinogenesis-related structural and vascular changes are clearly visible to tissue depths of 2 mm. Sensitivity (OCT/ODT alone, 71 to 88%; OCT+MPMSHG, 79 to 91%) and specificity (OCT alone, 62 to 83%; OCT+MPMSHG, 67 to 90%) compare well with conventional techniques. Our conclusions are that OCT/ODT and MPM/SHG are promising noninvasive in vivo diagnostic modalities for oral dysplasia and malignancy.

Evaluation of tracheal imaging by optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) is a new technology capable of generating high resolution cross-sectional images of complex tissue in real time. Analogous to ultrasound, OCT measures backscattered light intensity using coherence interferometery to construct topographical images of complex tissue. Since OCT uses infrared light rather than acoustic waves, its spatial resolution is exceptionally high (2-10 microm). Recent advances in data acquisition, analysis, and processing enable real-time imaging, and make OCT a potentially valuable tool for pulmonary airway diagnostic applications, including assisting directed airway biopsies. OBJECTIVE: This study evaluates feasibility of OCT for delineating proximal airway microstructures in various animal as well as human tracheas. METHODS: Excised trachea samples from New Zealand white rabbits, Duroc pigs, and human trachea were imaged using a compact, 1,300-nm broad-band superluminescent-diode-based prototype fiber OCT device we constructed. The resulting structural OCT images were compared to conventional hematoxilin and eosin (HE) stained histological sections from the same samples. RESULTS: OCT was able to delineate microstructures such as the epithelium, mucosa, cartilage, and glands in all samples. CONCLUSION: These findings suggest that integration of OCT with flexible fiberoptic bronchoscopy could enhance pulmonary diagnostic medicine and detection of pathologic tissue changes in various respiratory diseases.

In vivo optical coherence tomography for the diagnosis of oral malignancy.

BACKGROUND AND OBJECTIVE: Oral cancer results in 10,000 U.S. deaths annually. Improved highly sensitive diagnostics allowing early detection of oral cancer would benefit patient survival and quality of life. Objective was to investigate in vivo non-invasive optical coherence tomography (OCT) techniques for imaging and diagnosing neoplasia-related epithelial, sub-epithelial changes throughout carcinogenesis. STUDY DESIGN/MATERIALS AND METHODS: In the standard hamster cheek pouch model for oral carcinogenesis (n = 36), in vivo OCT was used to image epithelial and sub-epithelial change. OCT- and histopathology-based diagnoses on a scale of 0 (healthy) to 6 (squamous cell carcinoma, SCC) were performed at all stages throughout carcinogenesis by two blinded investigators. RESULTS: Epithelial, sub-epithelial structures were clearly discernible using OCT. OCT diagnosis agreed with the histopathological gold standard in 80% of readings. CONCLUSION: In vivo OCT demonstrates excellent potential as a diagnostic tool in the oral cavity.

Imaging wound healing using optical coherence tomography and multiphoton microscopy in an in vitro skin-equivalent tissue model.

Laser thermal injury and subsequent wound healing in organotypic, skin-equivalent tissue models were monitored using optical coherence tomography (OCT), multiphoton microscopy (MPM), and histopathology. The in vitro skin-equivalent raft tissue model was composed of dermis with type I collagen and fibroblast cells and epidermis of differentiated keratinocytes. Noninvasive optical imaging techniques were used for time-dependent, serial measurements of matrix destruction and reconstruction and compared with histopathology. The region of laser thermal injury was clearly delineated in OCT images by low signal intensity. High resolution MPM imaging using second-harmonic generation revealed alterations in collagen microstructure organization with subsequent matrix reconstruction. Fibroblast cell migration in response to injury was monitored by MPM using two-photon excited fluorescence. This study illustrates the complementary features of linear and nonlinear light-tissue interaction in intrinsic signal optical imaging and their use for noninvasive, serial monitoring of wound healing processes in biological tissues.