3D printed biomimetic cochleae and machine learning co-modelling provides clinical informatics for cochlear implant patients.

Cochlear implants restore hearing in patients with severe to profound deafness by delivering electrical stimuli inside the cochlea. Understanding stimulus current spread, and how it correlates to patient-dependent factors, is hampered by the poor accessibility of the inner ear and by the lack of clinically-relevant in vitro, in vivo or in silico models. Here, we present 3D printing-neural network co-modelling for interpreting electric field imaging profiles of cochlear implant patients. With tuneable electro-anatomy, the 3D printed cochleae can replicate clinical scenarios of electric field imaging profiles at the off-stimuli positions. The co-modelling framework demonstrated autonomous and robust predictions of patient profiles or cochlear geometry, unfolded the electro-anatomical factors causing current spread, assisted on-demand printing for implant testing, and inferred patients' in vivo cochlear tissue resistivity (estimated mean = 6.6 kΩcm). We anticipate our framework will facilitate physical modelling and digital twin innovations for neuromodulation implants

Cancer cell migration on straight, wavy, loop and grid microfibre patterns

Cell migration plays an important role in physiological and pathological processes where the fibrillar morphology of extracellular matrices (ECM) could regulate the migration dynamics. To mimic the morphological characteristics of fibrillar matrix structures, low-voltage continuous electrospinning was adapted to construct straight, wavy, looped and gridded fibre patterns made of polystyrene (of fibre diameter ca. 3 μm). Cells were free to explore their different shapes in response to the directly-adhered fibre, as well as to the neighbouring patterns. For all the patterns studied, analysing cellular migration dynamics of MDA-MB-231 (a highly migratory breast cancer cell line) demonstrated two interesting findings: first, although cells dynamically adjust their shapes and migration trajectories in response to different fibrillar environments, their average step speed is minimally affected by the fibre global pattern; secondly, a switch in behaviour was observed when the pattern features approach the upper limit of the cell body's minor axis, reflecting that cells' ability to divert from an existing fibre track is limited by the size along the cell body's minor axis. It is therefore concluded that the upper limit of cell body's minor axis might act as a guide for the design of microfibre patterns for different purposes of cell migration.</p

3D Printing of Soft and Biological Materials: Applications to Human Cochlear Modelling and Beyond

3D printing has emerged as a promising tool for on-demand and rapid fabrication of materials. The field of soft material printing typically utilises inks that exhibit viscoelastic properties with elastic moduli in the kPa – MPa range, such as hydrogels and elastomers. Although soft material printing has been frequently used for creating biomimetic mini tissues, its ability to imitate organ functions as a direct result of organ anatomy is yet to be fully realised, and continued innovation in printing method and flexible machinery are needed to drive the field forward. My PhD thesis focuses on advancing the field of soft material printing. Specifically, there are three main scopes in my work. Firstly, I developed an affordable and fully customisable extrusion-based printing platform for soft materials. The platform is equipped with multiple printheads for heterogeneous construct printing, and heating systems and a UV module for tuning the material rheology during and after printing. A detailed assembly instruction and the software design are provided, hence new users can facilely replicate the platform and contribute to the continued development of the platform. In summary, it is anticipated that this entirely hackable platform can facilitate the widespread adoption of the technology, overcoming the cost and flexibility barriers presented in commercial systems. Secondly, to realise the potential of 3D printing for imitating physiological phenomena related to anatomical structures, I created 3D printed cochleae that exhibit similar electro-anatomical features resembling human cochleae. These biomimetic cochlear models were integrated with machine learning to advance clinical predictions of ‘current spread’ for cochlear implant (CI) patients. The co-modelling framework demonstrated autonomous predictions of patient electric field imaging profile or cochlear geometry, unfolded the electro-anatomical factors causing CI stimulus spread, assisted on-demand printing for CI testing, and inferred patients’ in vivo cochlear tissue resistivity by CI telemetry. This framework might facilitate physical modelling and digital twin innovations for neuromodulation implants in healthcare. Lastly, I demonstrate the high flexibility and versatile functionalities of the custom-made 3D extrusion printing platform. Apart from 3D CAD models, the standard geometry input used in 3D printing, the platform accepts unconventional geometry inputs to suit different needs, including coordinates, equations and pictures. Advanced operations, such as liquid dispensing, printing with variable speed and non-planar printing, are permitted with the platform. With the aid of support baths, heating and UV tools, a wide variety of soft materials, including naturally derived hydrogels, pH-responsive hydrogels and elastomers, were successfully printed using the platform. Overall, the perspective provided in this work might guide new users to efficiently design printing processes for soft materials that do not possess suitable rheological and mechanical properties for creating 3D structures with conventional extrusion methods

Microcapillary cell extrusion deposition with picolitre dispensing resolution.

UNLABELLED: Extrusion-based cell deposition has become a prominent technique for expanding bioprinting applications. However, the associated print resolution in the order of nanolitre or above has been a limiting factor. The demand for improving print resolution towards the scale of a single cell has driven the development of precision nozzle extrusion, although the benefits gained remain ambiguous. Here, aided by in situ imaging, we investigated the dynamics of cell organisation through an extrusion-based microcapillary tip with picolitre precision through in-air or immersion deposition. The microcapillary extrusion setup, termed 'Picodis', was demonstrated by generating droplets of colouring inks immersed in an immiscible medium. Next, using 3T3 fibroblast cells as an experimental model, we demonstrated the deposition of cell suspension, and pre-aggregated cell pellets. Then, the dynamic organisation of cells within the microcapillary tip was described, along with cell ejection and deposition upon exiting the tip opening. The vision-assisted approach revealed that when dispersed in a culture medium, the movements of cells were distinctive based on the flow profiles and were purely driven by laminar fluid flow within a narrow tip. The primary process limitations were cell sedimentation, aggregation and compaction, along with trapped air bubbles. The use of picolitre-level resolution microcapillary extrusion, although it provides some level of control for a small number of cells, does not necessarily offer a reliable method when a specified number of cells are required. Our study provides insights into the process limitations of high-resolution cell ink extrusion, which may be useful for optimising biofabrication processes of cell-laden constructs for biomedical research. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s42242-022-00205-3

A hackable, multi-functional, and modular extrusion 3D printer for soft materials.

Three-dimensional (3D) printing has emerged as a powerful tool for material, food, and life science research and development, where the technology's democratization necessitates the advancement of open-source platforms. Herein, we developed a hackable, multi-functional, and modular extrusion 3D printer for soft materials, nicknamed Printer.HM. Multi-printhead modules are established based on a robotic arm for heterogeneous construct creation, where ink printability can be tuned by accessories such as heating and UV modules. Software associated with Printer.HM were designed to accept geometry inputs including computer-aided design models, coordinates, equations, and pictures, to create prints of distinct characteristics. Printer.HM could further perform versatile operations, such as liquid dispensing, non-planar printing, and pick-and-place of meso-objects. By 'mix-and-match' software and hardware settings, Printer.HM demonstrated printing of pH-responsive soft actuators, plant-based functional hydrogels, and organ macro-anatomical models. Integrating affordability and open design, Printer.HM is envisaged to democratize 3D printing for soft, biological, and sustainable material architectures

Modeling Structural Elements and Functional Responses to Lymphatic-Delivered Cues in a Murine Lymph Node on a Chip.

Publication status: PublishedFunder: WD Armstrong FoundationLymph nodes (LNs) are organs of the immune system, critical for maintenance of homeostasis and initiation of immune responses, yet there are few models that accurately recapitulate LN functions in vitro. To tackle this issue, an engineered murine LN (eLN) has been developed, replicating key cellular components of the mouse LN; incorporating primary murine lymphocytes, fibroblastic reticular cells, and lymphatic endothelial cells. T and B cell compartments are incorporated within the eLN that mimic LN cortex and paracortex architectures. When challenged, the eLN elicits both robust inflammatory responses and antigen-specific immune activation, showing that the system can differentiate between non specific and antigen-specific stimulation and can be monitored in real time. Beyond immune responses, this model also enables interrogation of changes in stromal cells, thus permitting investigations of all LN cellular components in homeostasis and different disease settings, such as cancer. Here, how LN behavior can be influenced by murine melanoma-derived factors is presented. In conclusion, the eLN model presents a promising platform for in vitro study of LN biology that will enhance understanding of stromal and immune responses in the murine LN, and in doing so will enable development of novel therapeutic strategies to improve LN responses in disease

Deployable extrusion bioprinting of compartmental tumoroids with cancer associated fibroblasts for immune cell interactions.

Funder: Cambridge Trust; doi: http://dx.doi.org/10.13039/501100003343Funder: Chinese Scholars CouncilFunder: Medical Research Council; doi: http://dx.doi.org/10.13039/501100000265Funder: W.D Armstrong TrustRealizing the translational impacts of three-dimensional (3D) bioprinting for cancer research necessitates innovation in bioprinting workflows which integrate affordability, user-friendliness, and biological relevance. Herein, we demonstrate 'BioArm', a simple, yet highly effective extrusion bioprinting platform, which can be folded into a carry-on pack, and rapidly deployed between bio-facilities. BioArm enabled the reconstruction of compartmental tumoroids with cancer-associated fibroblasts (CAFs), forming the shell of each tumoroid. The 3D printed core-shell tumoroids showedde novosynthesized extracellular matrices, and enhanced cellular proliferation compared to the tumour alone 3D printed spheroid culture. Further, thein vivophenotypes of CAFs normally lost after conventional 2D co-culture re-emerged in the bioprinted model. Embedding the 3D printed tumoroids in an immune cell-laden collagen matrix permitted tracking of the interaction between immune cells and tumoroids, and subsequent simulated immunotherapy treatments. Our deployable extrusion bioprinting workflow could significantly widen the accessibility of 3D bioprinting for replicating multi-compartmental architectures of tumour microenvironment, and for developing strategies in cancer drug testing in the future

Hydrogel Bioadhesives with Extreme Acid-Tolerance for Gastric Perforation Repairing

Hydrogel bioadhesives have emerged as one of the most promising alternatives to sutures and staples for wound sealing and repairing, owing to their unique advantages in biocompatibility, mechanical compliance and minimally invasive manipulation. However, only a few hydrogel bioadhesives have been successfully used for gastric perforation repairing, due to their undesirable swelling when in direct contacting with extremely acidic gastric fluids, thereby accompanying with a graduallydeteriorated adhesion performance. Herein, we develop an acid-tolerant hydrogels (ATGels) bioadhesive, which integrates two distinct components, an acid-tolerant hydrogel substrate and an adhesive polymer brush layer. The ATGels bioadhesive could form instant, atraumatic, fluid-tight and sutureless sealing of gastric perforation, and enable robust biointerfaces in direct contact with gastric fluids, addressing the key limitations with sutures and commercially-available tissue adhesives. Moreover, in vivo investigation on gastric perforation of rat model validates the proposed acid-tolerant bioadhesion, and identifies the mechanisms for accelerated gastric perforation repairing through alleviated inflammation, which suppressed fibrosis and enhanced angiogenesis

Research data supporting "3D Printing of Liquid Crystalline Hydroxypropyl Cellulose – Toward Tunable and Sustainable Volumetric Photonic Structures"

This dataset includes all the data used in order to develop a 3D printing method for liquid crystalline hydroxypropyl cellulose. These include images of samples presented as well as spectral and measurement data. Spectral data are presented in matlab files (.mat), and each entry in the file includes all the data required to construct one spectrum, including raw data, reference, and background measurements. Proton NMR data are presented as both text files (.txt) for easy interpretation and native Topspin folders. The text files represent NMR data that has been Fourier transformed, phase and baseline corrected while the Topspin folders include the raw data as well as the configurations for the NMR measurements.This work was funded additionally by a Croucher Cambridge International Scholarship to C.L.C.C.; by a WD Armstrong Trust Studentship and a Macao Postgraduate Scholarship to I.M.L