Biopolymeric Coatings for Local Release of Therapeutics from Biomedical Implants

Funding Information: S.T., B.M., and J.C. contributed equally to this work. The authors are grateful for funding received from the Australian Research Council Centre of Excellence program (Project Number CE 140100012). J.C. acknowledges the European Research Council Starting Grant (ERC‐StG‐2019‐848325). S.N. and F.D. acknowledge the financial support of Australian Research Council through DP200102164. Publisher Copyright: © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.The deployment of structures that enable localized release of bioactive molecules can result in more efficacious treatment of disease and better integration of implantable bionic devices. The strategic design of a biopolymeric coating can be used to engineer the optimal release profile depending on the task at hand. As illustrative examples, here advances in delivery of drugs from bone, brain, ocular, and cardiovascular implants are reviewed. These areas are focused to highlight that both hard and soft tissue implants can benefit from controlled localized delivery. The composition of biopolymers used to achieve appropriate delivery to the selected tissue types, and their corresponding outcomes are brought to the fore. To conclude, key factors in designing drug-loaded biopolymeric coatings for biomedical implants are highlighted.publishersversionepub_ahead_of_prin

Electroactive Fibre Sensor Systems for Fluidics

Due to an increasing demand for development of cost-effective portable microfluidics using textile substrates, a foundation study on the effect of fibre surface chemistry on the performance of textiles was undertaken to elucidate its applicability to textile-based microfluidics (Chapter 3). Composite fibres consisting of low-density polyethylene (LDPE) fibres with liquid crystalline graphene oxide (LCGO) fillers, at a range of loadings, were successfully prepared by a melt spinning process and then incorporated in parallel with commercial polyester yarns (PET), via a tubular knitting process, to produce 3D textile-based microfluidic structures. It was shown that the LCGO filler increased the surface polarity of fibres, as a result of accumulation of oxygen on the polymer surface, and the increase in O/C ratio amplified the surface and inter-fibre capillary fluid driving force in textile structure. Fluid was shown to move up to 6x faster in 3D knitted structures comprised of 5w/w% LCGO/LDPE fibre compared to the knitted structure without any composite fibre. It was demonstrated that the ion rejection and/or absorption phenomenon which occur between fluid ions and fibre surface functional groups played the most important role in determination of fluid flow rate. The flow rate achievable was found to be proportional to the LCGO loading, providing the potential to control flow through fibre composition. Significantly, using this approach fluid pumping of fluid against a gravity feed head height (anti-gravitational) was observed as a consequence of the LCGO filler interactions at the surface of the LDPE/LCGO composite fibres. Recently, electric fields have been used to move or separate analytes in textile-based microfluidics to achieve a precise control over the fluid flow. However, applying electric fields to move or separate solutes within fluids typically results in Joule-heating which adversely affects the efficiency of the separations. In this thesis, the idea of preparing thermally conducting fibres and assembling them into 3D textile structures to facilitate dissipating the Joule-heating was investigated (Chapter 4) using LDPE/LCGO composite fibres, where LCGO was partially reduced to impart improved thermal conductivity. LCGO/LDPE composite fibres were successfully prepared and incorporated into a 3D PET knitted structures and their capability to dissipate the Joule-heating in electrofluidic experiments probed. Monitoring the temperature change during electrofluidic experiments showed that incorporation of reduced LCGO/LDPE fibres into 3D knitted structures resulted in lower temperature rise during the experiments and more importantly, final temperature decreased by an increase in the LCGO loading. However, loading more than 5 w/w% LCGO into LDPE fibres, utilising a powder coating and melt spinning approach, proved to be impractical due to agglomeration of LCGO within composite fibres resulting in poor mechanical properties and therefore limited knittability. To eliminate the issue of poor filler distribution, a solvent-based wet-spinning technique was adopted (Chapter 5). A solvent processable non cross-linked biocompatible grade polyurethane (PU) elastomer was filled with LCGO to produce LCGO/PU fibres. These fibres were successfully incorporated into 3D knitted structures in parallel to the PET yarns and then chemically reduced to improve thermal conductivity. The ability of the reduced LCGO/PU composite fibres as heat dissipators was shown to be limited by their electrical conductivity. Fibres were shown to become effective in Joule-heating dissipation at the point that they became electrically conductive resulting in potential short-circuits which should be avoided in high voltage electrofluidic experiments. As a consequence, boron nitride nanopowder (BNNP) filler was chosen to make BNNP/PU composite fibres as it was thermally conducting but electrically insulating (band gap of ~ 5 eV). It was shown that incorporating BNNP/PU composite fibres into 3D textile structures effectively dissipated the heat generated by Joule-heating and kept the textile structure at low temperature during electrofluidic experiments. This novel idea of utilizing thermally conducting fibres into textile-based microfluidics could be an advantageous for fibre based capillary electrophoresis studies specifically when proteins, living cells and thermosensitive analytes are being used. Textile substrates have been widely used to make wearable electrochemical sensors. Therefore, as a proof-of-concept study, two different 3D textile designs (utilizing knitting and braiding techniques) with integrated electrodes as potential wearable electrochemical sensors were investigated (Chapter 6). The electrochemical behaviour of stainless steel (SS) filament working electrodes were shown to be far from ideal (or reversible). These filaments were surface modificated by the electrodeposition of polypyrrole and gold nanoparticles to give improved electrode surface responses. These modified electrodes were successfully incorporated into 3D braided structures, whereby all electrodes were not in direct electrical contact, consisting of two parallel SS (counter and working) electrodes with the addition of a silver-coated nylon yarn as pseudo reference electrode. This braided 3 electrode system was shown to be a functional 3D textile platform capable of electrochemical detection in a similar manner as a classical 3-electrode electrochemical system. In an alternative approach, a 3D knitted structure with 3 separate conductive strips, i.e. two SS yarn and a silver-plated nylon in the middle separated by insulating yarns, was successfully created to perform amperometric detection under a gravity assisted electrolyte flow system. In summary, this thesis demonstrates the feasibility of the approaches investigated and their incorporation into textile structures. Significantly the approaches shown are relatively simple to fabricate, cheap, flexible and easily incorporated into textile systems to provide real time sensing and monitoring, fluid transportation and heat dissipation, all of which are critical for the implementation of textiles into active and functional devices

Image segmentation based determination of elastane core yarn diameter

Yarn diameter is one of the key knitted fabric parameters, whose accurate determination, however, continues to be a difficult task. The goal of the study presented was to calculate the diameter of dry and wet relaxed yarns with and without incorporated elastane using image-processing and -analysis tools implemented in MATLAB. Compared to the images of wet relaxed samples, a much more sophisticated segmentation approach had to be implemented for dry relaxed yarn images due to their weaker yarn-background contrast. The values calculated were compared with those obtained with the conventional yarn thickness determination method developed by Sadikov. Linear correlation between the two techniques was found to be substantial - coefficients of determination for the yarn diameters of the wet and dry relaxed samples were 0.87 and 0.72, respectively. Unlike Sadikov\u27s method, our newly developed technique calculates yarn core diameter without hairiness

A bladder-free, non-fluidic, conductive McKibben artificial muscle operated electrothermally

Fluidic McKibben artificial muscles that operate pneumatically or hydraulically provide excellent performance, but require bulky pumps/compressors, valves and connecting lines. Use of a pressure generating material, such as thermally expanding paraffin wax, can eliminate the need for these pumps and associated infrastructure. Here we further develop this concept by introducing the first bladderless McKibben muscle wherein molten paraffin is contained by surface tension within a tailored braid. Incorporation of electrically conductive wires in the braid allows for convenient Joule heating of the paraffin. The muscle is light (0.14 g) with a diameter of 1.4mm and is capable of generating a tensile stress of 50 kPa (0.039 N) in 20 s. The maximum contraction strain of 10% (7.6 kPa given load) was achieved in 60 s with an applied electrical power of 0.35 W

Facile development of a fiber-based electrode for highly selective and sensitive detection of dopamine

A facile one-step method was used to create a selective and sensitive electrode for dopamine (DA) detection based upon a stainless steel (SS) filament substrate and reduced graphene oxide (rGO). The electrode successfully and selectively detects DA in the presence of uric acid and ascorbic acid without the need of a Nafion coating. The proposed electrode is easy to fabricate, low-cost, flexible and strong. The rGO-SS electrode could also be incorporated into a 3-dimensional braided structure enabling DA detection in a two-electrode fibre system. The sensor is an excellent candidate for production of affordable, robust and flexible wearable and portable sensor and expands the application of textiles in point of care diagnostic devices

3D braided yarns to create electrochemical cells

The demands for new configurations of electrochemical cells continue to grow and novel approaches are being enabled by the advent of new electromaterials and novel fabrication strategies. Wearable energy storage devices that can be seamlessly integrated into garments are a critical component of the wearable electronics genre. Recently, flexible yarn supercapacitors have attracted significant attention due to their ability to be integrated into fabrics, or stitched into existing textiles. Large-scale production of yarn supercapacitors using conventional manufacturing processes, however, is still a challenge. Here, we introduce the use of braiding technology to achieve a predetermined arrangement of fibre electrodes, the basis of a mass fabrication protocol to produce specific electrochemical cells: wearable supercapacitors. The resultant supercapacitors show a high capacitance of 1.71 mF cm- 1. The structure is highly flexible with a 25% capacitance loss recorded after 1000 bending cycles

Thermally drawn polycaprolactone fibres with customised cross sections

There is growing demand for biodegradable polymer fibres in tissue engineering and nerve regeneration. We demonstrate a scalable and inexpensive fabrication technique to produce polycaproactone (PCL) fibres using fibredrawing technique. Here we report on the first successful drawing of hollow-core and solid-core PCL fibres of different cross sections. The demonstrated capacity to tailor the surface morphology of PCL fibres, together with their biodegradability and tissue compatibility, makes them a unique material base for tissue engineering and nerve regeneration applications

Performance Optimization of Polymer Fibre Actuators for Soft Robotics

Analytical modeling of soft pneumatic actuators constitutes a powerful tool for the systematic design and characterization of these key components of soft robotics. Here, we maximize the quasi-static bending angle of a soft pneumatic actuator by optimizing its cross-section for a fixed positive pressure inside it. We begin by formulating a general theoretical framework for the analytical calculation of the bending angle of pneumatic actuators with arbitrary cross-sections, which is then applied to an actuator made of a circular polymer tube and an asymmetric patch in the shape of a hollow-cylinder sector on its outer surface. It is shown that the maximal bending angle of this actuator can be achieved using a wide range of patches with different optimal dimensions and approximately the same cross-sectional area, which decreases with pressure. We also calculate the optimal dimensions of thin and small patches in thin pneumatic actuators. Our analytical results lead to clear design guidelines, which may prove useful for engineering and optimization of the key components of soft robotics with superior features

Life-Saving Threads: Advances in Textile-Based Analytical Devices

Novel approaches that incorporate electrofluidic and microfluidic technologies are reviewed to illustrate the translation of traditional enclosed structures into open and accessible textile based platforms. Through the utilization of on-fiber and on-textile microfluidics, it is possible to invert the typical enclosed capillary column or microfluidic chip platform, to achieve surface accessible efficient separations and fluid handling, while maintaining a microfluidic environment. The open fiber/textile based fluidics approach immediately provides new possibilities to interrogate, manipulate, redirect, extract, characterize, and quantify solutes and target species at any point in time during such processes as on-fiber electrodriven separations. This approach is revolutionary in its simplicity and provides many potential advantages not otherwise afforded by the more traditional enclosed platforms