Generalized Fringe-to-Phase Framework for Single-Shot 3D Reconstruction Integrating Structured Light with Deep Learning.

Three-dimensional (3D) shape acquisition of objects from a single-shot image has been highly demanded by numerous applications in many fields, such as medical imaging, robotic navigation, virtual reality, and product in-line inspection. This paper presents a robust 3D shape reconstruction approach integrating a structured-light technique with a deep learning-based artificial neural network. The proposed approach employs a single-input dual-output network capable of transforming a single structured-light image into two intermediate outputs of multiple phase-shifted fringe patterns and a coarse phase map, through which the unwrapped true phase distributions containing the depth information of the imaging target can be accurately determined for subsequent 3D reconstruction process. A conventional fringe projection technique is employed to prepare the ground-truth training labels, and part of its classic algorithm is adopted to preserve the accuracy of the 3D reconstruction. Numerous experiments have been conducted to assess the proposed technique, and its robustness makes it a promising and much-needed tool for scientific research and engineering applications.

Single-shot 3D shape acquisition using a learning-based structured-light technique.

Learning three-dimensional (3D) shape representation of an object from a single-shot image has been a prevailing topic in computer vision and deep learning over the past few years. Despite extensive adoption in dynamic applications, the measurement accuracy of the 3D shape acquisition from a single-shot image is still unsatisfactory due to a wide range of challenges. We present an accurate 3D shape acquisition method from a single-shot two-dimensional (2D) image using the integration of a structured-light technique and a deep learning approach. Instead of a direct 2D-to-3D transformation, a pattern-to-pattern network is trained to convert a single-color structured-light image to multiple dual-frequency phase-shifted fringe patterns for succeeding 3D shape reconstructions. Fringe projection profilometry, a prominent structured-light technique, is employed to produce high-quality ground-truth labels for training the network and to accomplish the 3D shape reconstruction after predicting the fringe patterns. A series of experiments has been conducted to demonstrate the practicality and potential of the proposed technique for scientific research and industrial applications.

An Oral-mucosa-on-a-chip sensitively evaluates cell responses to dental monomers.

Knowledge of human gingival cell responses to dental monomers is critical for the development of new dental materials. Testing standards have been developed to provide guidelines to evaluate biological functionality of dental materials and devices. However, one shortcoming of the traditional testing platforms is that they do not recapitulate the multi-layered configuration of gingiva, and thus cannot evaluate the layer-specific cellular responses. An oral mucosa-chip with two cell layers was previously developed as an alternative platform to assess the oral mucosa responses to dental biomaterials. The mucosa-chip consists of an apical keratinocyte layer attached to a fibroblast-embedded collagen hydrogel through interconnecting pores in a three-microchannel network. Here, cell responses in the mucosa-chip were evaluated against 2-hydroxyethyl methacrylate (HEMA), a common monomer used in restorative and aesthetic dentistry. The response of mucosal cell viability was evaluated by exposing the chip to HEMA of concentrations ranging from 1.56 to 25 mM and compared to cells in conventional well-plate monoculture. The co-cultured cells were then stained and imaged with epifluorescence and confocal microscopy to determine the layer-specific responses to the treatment. Mucosa-chips were demonstrated to be more sensitive to assess HEMA-altered cell viability than well-plate cultures, especially at lower doses (1.56 and 6.25 mM). The findings suggest that the mucosa-chip is a promising alternative to traditional platforms or assays to test a variety of biomaterials by offering a multi-layered tissue geometry, accessible layer-specific information, and higher sensitivity in detecting cellular responses.

MIMONet: Structured-light 3D shape reconstruction by a multi-input multi-output network.

Reconstructing 3D geometric representation of objects with deep learning frameworks has recently gained a great deal of interest in numerous fields. The existing deep-learning-based 3D shape reconstruction techniques generally use a single red-green-blue (RGB) image, and the depth reconstruction accuracy is often highly limited due to a variety of reasons. We present a 3D shape reconstruction technique with an accuracy enhancement strategy by integrating the structured-light scheme with deep convolutional neural networks (CNNs). The key idea is to transform multiple (typically two) grayscale images consisting of fringe and/or speckle patterns into a 3D depth map using an end-to-end artificial neural network. Distinct from the existing autoencoder-based networks, the proposed technique reconstructs the 3D shape of target using a refinement approach that fuses multiple feature maps to obtain multiple outputs with an accuracy-enhanced final output. A few experiments have been conducted to verify the robustness and capabilities of the proposed technique. The findings suggest that the proposed network approach can be a promising 3D reconstruction technique for future academic research and industrial applications.

Microstructural densification and alignment by aspiration-ejection influence cancer cell interactions with three-dimensional collagen networks.

Extracellular matrix microstructure and mechanics are crucial to breast cancer progression and invasion into surrounding tissues. The peritumor collagen network is often dense and aligned, features which in vitro models lack. Aspiration of collagen hydrogels led to densification and alignment of microstructure surrounding embedded cancer cells. Two metastasis-derived breast cancer cell lines, MDA-MB-231 and MCF-7, were cultured in initially 4 mg/ml collagen gels for 3 days after aspiration, as well as in unaspirated control hydrogels. Videomicroscopy during aspiration, and at 0, 1, and 3 days after aspiration, epifluorescence microscopy of phalloidin-stained F-actin cytoskeleton, histological sections, and soluble metabolic byproducts from constructs were collected to characterize effects on the embedded cell morphology, the collagen network microstructure, and proliferation. Breast cancer cells remained viable after aspiration-ejection, proliferating slightly less than in unaspirated gels. Furthermore, MDA-MB-231 cells appear to partially relax the collagen network and lose alignment 3 days after aspiration. Aspiration-ejection generated aligned, compact collagen network microstructure with immediate cell co-orientation and higher cell number density apparently through purely physical means, though cell-collagen contact guidance and network remodeling influence cell organization and collagen network microstructure during subsequent culture. This study establishes a platform to determine the effects of collagen density and alignment on cancer cell behavior, with translational potential for anticancer drug screening in a biomimetic three-dimensional matrix microenvironment, or implantation in preclinical models.

Interfacial Electrofabrication of Freestanding Biopolymer Membranes with Distal Electrodes.

Using electrical signals to guide materials' deposition has a long-standing history in metal coating, microchip fabrication, and the integration of organics with devices. In electrodeposition, however, the conductive materials can be deposited only onto the electrode surfaces. Here, an innovative process is presented to electrofabricate freestanding biopolymer membranes at the interface of electrolytes without any supporting electrodes at the fabrication site. Chitosan, a derivative from the naturally abundant biopolymer chitin, has been broadly explored in electrodeposition for integrating biological entities onto microfabricated devices. It is widely believed that the pH gradients generated at the cathode deprotonate the positively charged chitosan chains into a film on the cathode surface. The interfacial electrofabrication with pH indicators, however, demonstrated that the membrane growth was driven by the instantaneous flow of hydroxyl ions from the ambient alginate solution, rather than the slow propagation of pH gradients from the cathode surface. This interfacial electrofabrication produces freestanding membrane structures and can be expanded to other materials, which presents a new direction in using electrical signals for manufacturing.

Recombinant Human Keratinocyte Growth Factor Ameliorates Cancer Treatment-Induced Oral Mucositis on a Chip.

Oral mucositis (OM) is a severe complication of cancer therapies caused by off-target cytotoxicity. Palifermin, which is recombinant human keratinocyte growth factor (KGF), is currently the only mitigating treatment available to a subset of OM patients. This study used a previously established model of oral mucositis on a chip (OM-OC) comprised of a confluent human gingival keratinocytes (GIE) layer attached to a basement membrane-lined subepithelial layer consisting of human gingival fibroblasts (HGF) and human dermal microvascular endothelial cells (HMEC) on a stable collagen I gel. Cisplatin, radiation, and combined treatments are followed by a recovery period in the OM-OC to determine possible cellular and molecular mechanisms of OM under effects of KGF. Cancer treatments affected the keratinocyte layer, causing death and epithelial barrier loss. Both keratinocytes and subepithelial cells died rapidly, as evidenced by propidium iodide staining. In response to radiation exposure, cell death occurred in the apical epithelial layer, predominantly, within 24h. Cisplatin exposure predominantly promoted death of basal epithelial cells within 32-36h. Presence of KGF in OM-OC protected tissues from damage caused by cancer treatments in a dose-dependent manner, being more effective at 10 ng/mL. As verified by F-actin staining and the Alamar Blue assay, KGF contributed to epithelial survival and induced proliferation of GIE and HGF as well as HMEC within 120h. When the expression of eighty inflammatory cytokines is evaluated at OM induction (Day 12) and resolution (Day 18) stages in OM-OC, some cytokines are identified as potential novel therapeutic targets. In comparison with chemoradiation exposure, KGF treatment showed a trend to decrease IL-8 and TNF-a expression at Day 12 and 18, and TGF-ß1 at Day 18 in OM-OC. Taken together, these findings support the utility of OM-OC as a platform to model epithelial damage and evaluate molecular mechanisms following OM treatment.

Programmable Physical Properties of Freestanding Chitosan Membranes Electrofabricated in Microfluidics.

Microfluidic-integrated freestanding membranes with suitable biocompatibility and tunable physicochemical properties are in high demand for a wide range of life science and biological studies. However, there is a lack of facile and rapid methods to integrate such versatile membranes into microfluidics. A recently invented interfacial electrofabrication of chitosan membranes offers an in-situ membrane integration strategy that is flexible, controllable, simple, and biologically friendly. In this follow-up study, we explored the ability to program the physical properties of these chitosan membranes by varying the electrofabrication conditions (e.g., applied voltage and pH of alginate). We found a strong association between membrane growth rate, properties, and fabrication parameters: high electrical stimuli and pH of alginate resulted in high optical retardance and low permeability, and vice versa. This suggests that the molecular alignment and density of electrofabricated chitosan membranes could be actively tailored according to application needs. Lastly, we demonstrated that this interfacial electrofabrication could easily be expanded to produce chitosan membrane arrays with higher uniformity than the previously well-established flow assembly method. This study demonstrates the tunability of the electrofabricated membranes' properties and functionality, thus expanding the utility of such membranes for broader applications in the future.

Oral mucositis on a chip: modeling induction by chemo- and radiation treatments and recovery.

Oral mucositis (OM) is a debilitating complication affecting roughly 70% of head and neck cancer patients receiving chemotherapy and/or radiation treatment. No broadly effective preventative treatment for OM exists. Therefore, anin vitromodel of cancer treatment-induced OM would aid studies into possible origins of the pathology and future drug targets to ameliorate it. In this study, we present a microfluidic oral mucosa triculture tissue construct consisting of a keratinocyte layer attached to a subepithelial fibroblast and endothelial cell-embedded collagen gel. To address the typically low stability of mucosal constructs in microfluidics, ruthenium-catalyzed photocrosslinking was implemented to strengthen the collagen gel and prevent the invasion of keratinocytes, thus maintaining tissue construct geometry and oral mucosa barrier function for over 18 d of culture. Next, the OM chip was exposed to cisplatin (day 10) and damaging radiation (day 11, ± cisplatin at day 10), mimicking damage from cancer therapy. Damage to and then recovery of the tissue layers and function were observed over days 11-18. Therefore, several important features of OM induction and resolution were modeled in microfluidic culture. The OM model on a chip allows for more sophisticated studies into mechanisms of OM and potential treatments.

Bacterial chemotaxis in static gradients quantified in a biopolymer membrane-integrated microfluidic platform.

Chemotaxis is a fundamental bacterial response mechanism to changes in chemical gradients of specific molecules known as chemoattractant or chemorepellent. The advancement of biological platforms for bacterial chemotaxis research is of significant interest for a wide range of biological and environmental studies. Many microfluidic devices have been developed for its study, but challenges still remain that can obscure analysis. For example, cell migration can be compromised by flow-induced shear stress, and bacterial motility can be impaired by nonspecific cell adhesion to microchannels. Also, devices can be complicated, expensive, and hard to assemble. We address these issues with a three-channel microfluidic platform integrated with natural biopolymer membranes that are assembled in situ. This provides several unique attributes. First, a static, steady and robust chemoattractant gradient was generated and maintained. Second, because the assembly incorporates assembly pillars, the assembled membrane arrays connecting nearby pillars can be created longer than the viewing window, enabling a wide 2D area for study. Third, the in situ assembled biopolymer membranes minimize pressure and/or chemiosmotic gradients that could induce flow and obscure chemotaxis study. Finally, nonspecific cell adhesion is avoided by priming the polydimethylsiloxane (PDMS) microchannel surfaces with Pluronic F-127. We demonstrated chemotactic migration of Escherichia coli as well as Pseudomonas aeruginosa under well-controlled easy-to-assemble glucose gradients. We characterized motility using the chemotaxis partition coefficient (CPC) and chemotaxis migration coefficient (CMC) and found our results consistent with other reports. Further, random walk trajectories of individual cells in simple bright field images were conveniently tracked and presented in rose plots. Velocities were calculated, again in agreement with previous literature. We believe the biopolymer membrane-integrated platform represents a facile and convenient system for robust quantitative assessment of cellular motility in response to various chemical cues.

Flow-assembled chitosan membranes in microfluidics: recent advances and applications.

The integration of membranes in microfluidic devices has been extensively exploited for various chemical engineering and bioengineering applications over the past few decades. To augment the applicability of membrane-integrated microfluidic platforms for biomedical and tissue engineering studies, a biologically friendly fabrication process with naturally occurring materials is highly desired. The in situ preparation of membranes involving interfacial reactions between parallel laminar flows in microfluidic networks, known as the flow-assembly technique, is one of the most biocompatible approaches. Membranes of many types with flexible geometries have been successfully assembled inside complex microchannels using this facile and versatile flow-assembly approach. Chitosan is a naturally abundant polysaccharide known for its pronounced biocompatibility, biodegradability, good mechanical stability, ease of modification and processing, and film-forming ability under near-physiological conditions. Chitosan membranes assembled by flows in microfluidics are freestanding, robust, semipermeable, and well-aligned in microstructure, and show high affinity to bioactive reagents and biological components (e.g. biomolecules, nanoparticles, or cells) that provide facile biological functionalization of microdevices. Here, we discuss the recent developments and optimizations in the flow-assembly of chitosan membranes and chitosan-based membranes in microfluidics. Furthermore, we recapitulate the applications of the chitosan membrane-integrated microfluidic platforms dedicated to biology, biochemistry, and drug release fields, and envision the future developments of this important platform with versatile functions.

Tuning the porosity of biofabricated chitosan membranes in microfluidics with co-assembled nanoparticles as templates.

Biopolymer membranes assembled in microfluidic devices offer many biological process- and analysis-related applications. One of the key characteristics of bio-fabricated membranes is their porosity, which regulates the transport of molecules, ions, or particles and contributes to their semi-permeability and selectivity. This study aims to tune the porosity of biofabricated chitosan membranes (CM) using incorporated nanoparticles as templates. CM with polystyrene nanoparticles (CM-np) were assembled by flow in microchannel networks. The membranes with incorporated nanoparticles were crosslinked with glutaraldehyde, and then the nanoparticles were dissolved with dimethyl sulfoxide. The in situ synthesized porous CM (pCM) were characterized with scanning electron microscopy and polarized light microscopy. Permeability tests confirmed the increased pore sizes of the pCM and enhanced permeability to macromolecules. Sharper static gradients in three-channel microfluidic devices were demonstrated with the pCM as compared to those with the original CM. The capability to customize the porosity of flow-assembled, freestanding and robust biopolymer membranes inside a microfluidic network is attractive and broadens the applications of these membranes in biomolecular and cellular studies.

Immobilization of Antimicrobial Silver and Antioxidant Flavonoid as a Coating for Wound Dressing Materials.

PURPOSE: The aim of this study is to develop a new coating for wound dressings that is comprised of antimicrobial silver (Ag) and antioxidant flavonoid quercetin (Q). METHODS: Dip-coating was used to apply the coating on cotton gauge as a model dressing. Ag was immobilised using polydopamine as a priming and catalytic layer followed by coating of quercetin that was incorporated in a functionalized polydimethylsiloxane. The coating was investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and release assay. The antimicrobial activity of quercetin and Ag was tested against Staphylococcus aureus (S. aureus). A surgical wound model on mice was used to evaluate the effects of the coated dressing on wound healing rates and tissue histology. RESULTS: Ag and quercetin showed enhanced antimicrobial activity against S. aureus when used in combination. Ag and quercetin were successfully immobilized onto the fibre of the dressing using the dip-coating process. The coating released Ag and quercetin over 8 days and showed strong antioxidant activity. In the wound healing model, complete wound closure was achieved in 12 days in the group receiving coated dressing and was associated with an enhancement in tissue remodelling and neo-angiogenesis and the reduction in tissue inflammation. CONCLUSION: These new antimicrobial-antioxidant coatings may be promising in the development of advanced wound care therapies.