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The creation of reagentless protein-based biosensors that are capable of monitoring molecular analytes directly in bodily fluids could revolutionize our understanding of biology and personalized health monitoring.

The development of electroactive cell-laden hydrogels (bioscaffolds) has gained interest in neural tissue engineering research due to their inherent electrical properties that can induce the regulation of cell behaviour. Hydrogels combined with electrically conducting materials can respond to external applied electric fields, where these stimuli can promote electro-responsive cell growth and proliferation. A successful neural interface for electrical stimulation should present the desired stable electrical properties, such as high conductivity, low impedance, increased charge storage capacity and similar mechanical properties related to a target neural tissue. We report how different electrical stimulation protocols can impact neuronal cells' survival and proliferation when using cell-laden GelMA/GO hydrogels. The rat pheochromocytoma cell line, PC12s encapsulated into hydrogels showed an increased proliferation behaviour with increasing current amplitudes applied. Furthermore, the presence of GO in GelMA hydrogels enhanced the metabolic activity and DNA content of PC12s compared with GelMA alone. Similarly, hydrogels provided survival of encapsulated cells at higher current amplitudes when compared to cells seeded onto ITO flat surfaces, which expressed significant cell death at a current amplitude of 2.50 mA. Our findings provide new rational choices for electroactive hydrogels and electrical stimulation with broad potential applications in neural tissue engineering research.

Improving outcomes for cancer patients during treatment and monitoring for cancer recurrence requires personalized care which can only be achieved through regular surveillance for biomarkers. Unfortunately, routine detection for blood-based biomarkers is cost-prohibitive using currently specialized laboratories. Using a rapid self-assembly sensing interface amenable to methods of mass production, we demonstrate the ability to detect and quantify a small carbohydrate-based cancer biomarker, Tn antigen (αGalNAc-Ser/Thr) in a small volume of blood, using a test format strip reminiscent of a blood glucose test. The detection of Tn antigen at picomolar levels is achieved through a new transduction mechanism based on the impact of Tn antigen interactions on the molecular dynamic motion of a lectin cross-linked lubricin antifouling brush. In tests performed on retrospective blood plasma samples from patients presenting three different tumor types, differentiation between healthy and diseased patients was achieved, highlighting the clinical potential for cancer monitoring.

There are numerous biomedical applications where the interfacial shearing of surfaces can cause wear and friction, which can lead to a variety of medical complications such as inflammation, irritation, and even bacterial infection. We introduce a novel nanomaterial additive comprised of two-dimensional graphene oxide nanosheets (2D-NSCs) coated with lubricin (LUB) to reduce the amount of tribological stress in biomedical settings, particularly at low shear rates where boundary lubrication dominates. LUB is a glycoprotein found in the articular joints of mammals and has recently been discovered as an ocular surface boundary lubricant. The ability of LUB to self-assemble into a "telechelic" brush layer on a variety of surfaces was exploited here to coat the top and bottom surfaces of the ultrathin 2D-NSCs in solution, effectively creating a biopolymer-coated nanosheet. A reduction in friction of almost an order of magnitude was measured at a bioinspired interface. This reduction was maintained after repeated washing (5×), suggesting that the large aspect ratio of the 2D-NSCs facilitates effective lubrication even at diluted concentrations. Importantly, and unlike LUB-only treatment, the lubrication effect can be eliminated over 15 rinsing cycles, suggesting that the LUB-coated 2D-NSCs do not exhibit any binding interactions with the shearing surfaces. The effective lubricating properties of the 2D-NSCs combined with full reversibility through rinsing make the LUB-coated 2D-NSCs an intriguing candidate as a lubricant for biomedical applications.

Biodegradable polymers have been widely used in tissue engineering with the potential to be replaced by regenerative tissue. While conventional bionic interfaces are designed to be implanted in living tissue and organs permanently, biocompatible and biodegradable electronic materials are now progressing a paradigm shift towards transient and regenerative bionic engineering. For example, biodegradable bioelectronics can monitor physiologies in a body, transiently rehabilitate disease symptoms, and seamlessly form regenerative interfaces from synthetic electronic devices to tissues by reducing inflammatory foreign-body responses. Conventional electronic materials have not readily been considered biodegradable. However, several strategies have been adopted for designing electroactive and biodegradable materials systems: (1) conductive materials blended with biodegradable components, (2) molecularly engineered conjugated polymers with biodegradable moieties, (3) naturally derived conjugated biopolymers, and (4) aqueously dissolvable metals with encapsulating layers. In this review, we endeavor to present the technical bridges from electrically active and biodegradable material systems to edible and biodegradable electronics as well as transient bioelectronics with pre-clinical bio-instrumental applications, including biodegradable sensors, neural and tissue engineering, and intelligent drug delivery systems.

Neural interfaces are well-established as a tool to understand the behaviour of the nervous system via recording and stimulation of living neurons, as well as serving as neural prostheses.

Self-assembled lubricin (LUB) monolayers are an effective antiadhesive coating for biomedical applications. Long deposition times and limited control over the monolayer grafting density remain impediments to commercialization and applications in advanced sensor technologies. This work describes a novel potential pulse-facilitated coating method that reduces coating times to mere seconds while also providing high-level control over the achieved grafting density. This is the first time that the potential pulse-facilitated method is applied for direct assembling of a large and complex polyelectrolyte.

Ultrashort self-assembling peptides of typically less than 5 amino acids in length can be modified with highly aromatic protecting groups such as Fluorenylmethyloxycarbonyl (Fmoc) resulting in the rapid formation of nanofibrillar hydrogels. These hydrogels show great promise as scaffolds for tissue engineering and 3D cell culture. If further modified with bioactive peptide sequences, the hydrogels can be used to promote and control cell adhesion, and even support the ability for cultured mesenchymal stem cells (MSCs) to differentiate into therapeutically useful lineages, such as chondrocytes. Whilst there have been numerous examples of how the addition of such sequences can promote the bioactivity of cultured cells, the effect adding these sequences has on the nanoarchitecture, mechanical properties and stability of the resultant hydrogels is less well explored. Here, we have performed a series of experiments investigating the effect incorporating stoichiometric amounts of Fmoc-Arg-Gly-Asp (Fmoc-RGD) into Fmoc-Phe-Phe (Fmoc-FF) hydrogels has on nanofibril morphology, and the rheological properties and stability of the formed gels. Furthermore, we correlate these variations in nano-architectural and mechanical properties with their ability to support the culture of clinically valuable bone marrow derived human mesenchymal stem cells (hMSCs). Our results show that at relatively low concentrations Fmoc-RGD is incorporated into the self-assembled Fmoc-FF nanofibrils creating biocompatible hydrogels capable of supporting hMSC growth for up to a week. At increased concentrations of Fmoc-RGD, incorporation into the nanofibrils is lost and the hydrogels that form are no longer stable enough to support the culture of hMSCs for multiple days. These findings shed light on the importance of balancing the positive effects of adding bioactive ligands to 3D scaffolds with the negative effects these ligands can have on the stability and mechanical properties of these scaffolds. Further, the findings will have implications for the choice of ultrashort peptide scaffolds for tissue engineering applications to support MSCs towards chondrogenic differentiation, and their application as gel-cell constructs in cartilage tissue engineering for osteoarthritis.

Electroactive polymers (EAPs) have been investigated as materials for use in a range of biomedical applications, ranging from cell culture, electrical stimulation of cultured cells as well as controlled delivery of growth factors and drugs. Despite their excellent drug delivery ability, EAPs are susceptible to biofouling thus they often require surface functionalisation with antifouling coatings to limit unwanted non-specific protein adsorption. Here we demonstrate the surface modification of para toluene sulfonate (pTS) doped polypyrrole with the glycoprotein lubricin (LUB) to produce a self-assembled coating that both prevents surface biofouling while also serving as a high-capacity reservoir for cationic drugs which can then be released passively via diffusion or actively via an applied electrical potential. We carried out our investigation in two parts where we initially assessed the antifouling and cationic drug delivery ability of LUB tethered on a gold surface using quartz crystal microbalance with dissipation monitoring (QCM) to monitor molecular interactions occurring on a gold sensor surface. After confirming the ability of tethered LUB nano brush layers on a gold surface, we introduced an electrochemically grown EAP layer to act as the immobilisation surface for LUB before subsequently introducing the cationic drug doxorubicin hydrochloride (DOX). The release of cationic drug was then investigated under passive and electrochemically stimulated conditions. High-performance liquid chromatography (HPLC) was then carried out to quantify the amount of DOX released. It was shown that the amount of DOX released from nano brush layers of LUB tethered on gold and EAP surfaces could be increased by up to 30% per minute by applying a positive electrochemically stimulating pulse at 0.8 V for one minute. Using bovine serum albumin (BSA), we show that DOX loaded LUB tethered on para toluene sulfonic acid (pTS) doped polypyrrole retained antifouling ability of up to 75% when compared to unloaded tethered LUB. This work demonstrates the unique, novel ability of tethered LUB to actively participate in the delivery of cationic therapeutics on different substrate surfaces. This study could lead to the development of versatile multifunctional biomaterials for use in wide range of biomedical applications, such as dual drug delivery and lubricating coatings, dual drug delivery and antifouling coatings, cellular recording and stimulation.

The human tissues most sensitive to electrical activity such as neural and muscle tissues are relatively soft, and yet traditional conductive materials used to interface with them are typically stiffer by many orders of magnitude. Overcoming this mismatch, by creating both very soft and electroactive materials, is a major challenge in bioelectronics and biomaterials science. One strategy is to imbue soft materials, such as hydrogels, with electroactive properties by adding small amounts of highly conductive nanomaterials. However, electroactive hydrogels reported to date have required relatively large volume fractions (>1%) of added nanomaterial, have shown only modest electroactivity, and have not been processable via additive manufacturing to create 3D architectures. Here, we describe the development and characterization of improved biocompatible photo-cross-linkable soft hybrid electroactive hydrogels based on gelatin methacryloyol (GelMA) and large area graphene oxide (GO) flakes, which resolve each of these three limitations. The addition of very small amounts (less than a 0.07% volume fraction) of GO to a 5% w/v GelMA hydrogel resulted in a dramatic (∼35-fold) decrease in the impedance at 1 Hz compared with GelMA alone. The GelMA/GO coated indium tin oxide (ITO) electrode also showed a considerable reduction in the impedance at 1 kHz (down to 170 Ω compared with 340 Ω for the GelMA-coated ITO), while charge injection capacity increased more than 6-fold. We attribute this enhanced electroactivity to the increased electroactive surface area contributed by the GO. Despite this dramatic change in electroactivity, the GelMA/GO composite hydrogels' mechanical properties were only moderately affected. Mechanical properties increased by ∼2-fold, and therefore, the hydrogels' desired softness of

Although there exist numerous established laboratory-based technologies for sample diagnostics and analyte detection, many medical and forensic science applications require point of care based platforms for rapid on-the-spot sample analysis. Electrochemical biosensors provide a promising avenue for such applications due to the portability and functional simplicity of the technology. However, the ability to develop such platforms with the high sensitivity and selectivity required for analysis of low analyte concentrations in complex biological samples remains a paramount issue in the field of biosensing. Nonspecific adsorption, or fouling, at the electrode interface via the innumerable biomolecules present in these sample types (i.e., serum, urine, blood/plasma, and saliva) can drastically obstruct electrochemical performance, increasing background "noise" and diminishing both the electrochemical signal magnitude and specificity of the biosensor. Consequently, this review aims to discuss strategies and concepts used throughout the literature to prevent electrode surface fouling in biosensors and to communicate the nature of the antifouling mechanisms by which they operate. Evaluation of each antifouling strategy is focused primarily on the fabrication method, experimental technique, sample composition, and electrochemical performance of each technology highlighting the overall feasibility of the platform for point of care based diagnostic/detection applications.

Carbon-based symmetric supercapacitors (SCs) are known for their high power density and long cyclability, making them an ideal candidate for power sources in new-generation electronic devices. To boost their electrochemical performances, deriving activated carbon doped with heteroatoms such as N, O, and S are highly desirable for increasing the specific capacitance. In this regard, activated carbon (AC) self-doped with heteroatoms is directly derived from bio-waste (lima-bean shell) using different KOH activation processes. The heteroatom-enriched AC synthesized using a pretreated carbon-to-KOH ratio of 1:2 (ONS@AC-2) shows excellent surface morphology with a large surface area of 1508 m2 g-1 . As an SC electrode material, the presence of heteroatoms (N and S) reduces the interfacial charge-transfer resistance and increases the ion-accessible surface area, which inherently provides additional pseudocapacitance. The ONS@AC-2 electrode attains a maximum specific capacitance (Csp ) of 342 F g-1 at a specific current of 1 Ag-1 in 1 m NaClO4 electrolyte at the wide potential window of 1.8 V. Moreover, as symmetric SCs the ONS@AC-2 electrode delivers a maximum specific capacitance (Csc ) of 191 F g-1 with a maximum specific energy of 21.48 Wh kg-1 and high specific power of 14 000 W kg-1 and excellent retention of its initial capacitance (98 %) even after 10000 charge/discharge cycles. In addition, a flexible supercapacitor fabricated utilizing ONS@AC-2 electrodes and a LiCl/polyvinyl alcohol (PVA)-based polymer electrolyte shows a maximum Csc of 119 F g-1 with considerable specific energy and power.

Graphene oxide (GO) and other 2D-nanosheet materials exhibit a range of useful physical, chemical, electrical, and optical properties that may usher in the next generation of biomedical, bioimaging...

The electrochemical sensing of clonazepam in samples of unprocessed saliva is reported, using commercially available reduced graphene oxide (rGO) screen printed electrodes (SPEs). The rGO electrodes were modified with self-assembled lubricin (LUB) antiadhesive coatings that function as a size-selective molecular sieve that partitions small molecule analytes from large fouling molecules at the electrode-fluid interface. By mitigating the adverse effects of protein fouling, these LUB coatings enable direct, reliable, and quantitative electrochemical measurements of clonazepam concentrations in untreated saliva, which was not possible with uncoated rGO electrodes in identical tests. The proposed assay design, which is suitable for disposable point-of-care diagnostics requires no sample pre-treatment and shows a linear detection response over a concentration range of 25–250 nM with a correlation coefficient of R2=0.987 and a limit of detection (LoD) of 16.67 nM. The swab-based sample acquisition method paired with the antifouling properties of the LUB coatings provide a cost effective and practical biosensing platform for assessing electroactive drug concentrations in saliva in a point-of-care setting.

Surface fouling is a major problem faced by bionic implants (e.g., cochlear implants, pacemakers), where the adsorption of unwanted biomolecules has a detrimental effect on interfacial charge transfer processes, which severely impairs their capacity to sense and transmit electrical signals with high fidelity. Polypyrrole (PPy) is a conductive polymer whose naturally high impedance, ionic and electric conductivity, mechanical "softness", and biocompatibility make it a leading candidate for next-generation neural electrode interfaces. However, PPy (and related conductive polymer) surfaces are susceptible to surface fouling upon exposure to biological fluids (e.g., blood, perilymph, saliva), which compromises performance and shortens its expected working lifespan. Here, we report the ability of lubricin (LUB) coatings, a rapidly self-assembling, biological antiadhesive glycoprotein, to mitigate the harmful electrochemical effects caused by the surface fouling of electrochemically grown PPy films. LUB, a biological antiadhesive glycoprotein, undergoes rapid self-assembly and adheres strongly to most interfaces, including PPy, resulting in an easy-to-apply and highly efficacious coating. The LUB-coated PPy electrodes are electrochemically characterized, and its antifouling properties are assessed against concentrated solutions of bovine serum albumin (BSA) and following long-term exposure to artificial perilymph (AP). Periodic impedance measurement conducted over 6 days in AP solution demonstrates the high stability and capacity of the LUB coatings to maintain stable impedance values under real-world mimicking conditions.

In the field of bionics, the long-term effectiveness of implantable bionic interfaces depends upon maintaining a "clean" and unfouled electrical interface with biological tissues. Lubricin (LUB) is an innately biocompatible glycoprotein with impressive antifouling properties. Unlike traditional antiadhesive coatings, LUB coatings do not passivate electrode surfaces, giving LUB coatings great potential for controlling surface fouling of implantable electrode interfaces. This study characterizes the antifouling properties of bovine native LUB (N-LUB), recombinant human LUB (R-LUB), hyaluronic acid (HA), and composite coatings of HA and R-LUB (HA/R-LUB) on gold electrodes against human primary fibroblasts and chondrocytes in passive and electrically stimulated environments for up to 96 h. R-LUB coatings demonstrated highly effective antifouling properties, preventing nearly all adhesion and proliferation of fibroblasts and chondrocytes even under biphasic electrical stimulation. N-LUB coatings, while showing efficacy in the short term, failed to produce sustained antifouling properties against fibroblasts or chondrocytes over longer periods of time. HA/R-LUB composite films also demonstrated highly effective antifouling performance equal to the R-LUB coatings in both passive and electrically stimulated environments. The high electrochemical stability and long-lasting antifouling properties of R-LUB and HA/R-LUB coatings in electrically stimulating environments reveal the potential of these coatings for controlling unwanted cell adhesion in implantable bionic applications.

© 2021 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ Rational design and synergistic interactions between the electrode and electroactive materials have a huge impact on elevating the energy storage performance of supercapacitor devices. Herein, selenium enriched hybrid NiSe2@Fe3Se4 (NFS) nanocomposites have been facilely deposited on Ni-foam using chemical bath deposition (CBD) technique. The NiSe2@Fe3Se4 hybrid composites exhibited better electrochemical performance than that of monometallic selenides (NiSe2 and Fe3Se4), which can be attributed to the synergy effect and improved conductivity of polymetallic ions over the Ni foam substrate. The effect of NFS deposition time on Ni foam was studied and it greatly influences the morphological and electrochemical performances. Specifically, the NFS deposited for 36 h (NFS@36 h) provides a maximum areal capacity of 6.05 C cm-2 at 6 mA cm-2, which is almost four-fold higher than that of pure NiSe2 (0.168 C cm-2) and Fe3Se4 (1.46 C cm-2). Furthermore, a hybrid supercapacitor (HSC) is assembled utilizing the NFS@36 h as a positive electrode and biomass derived O, N enriched activated carbon as a negative electrode with an aqueous electrolyte. With a high-mass loading of 21.5 mg cm-2, the device demonstrates superior specific energy of 52 W h kg-1 at 398 W kg-1 specific power and even maintained 19 W h kg-1 at a maximum specific 8000 W kg-1. Furthermore, the device exhibited excellent cycling durability with ~ 92% of specific capacitance retention for 10,000 charge/discharge cycles at 5 A g-1. Besides, the HSCs have been successfully illuminated several light emitting diodes (LEDs) and portable displays demonstrating superior energy storage performance.

A significant challenge of liquid phase exfoliation (LPE) of graphite to yield graphene resides in the fact that most conventional solvents used are high boiling points and thus extremely difficult to eliminate, especially during processing of graphene into composites or films. Here, we advance the ability to produce high yield graphene in a low boiling point organic solvent, chloroform, using core-substituted naphthalene diimides (cNDIs). Through the use of cNDIs it is possible to obtain high graphene concentrations of up to 0.13 mg/mL in chloroform. This yield represents a 69% improvement from graphene yields previously obtained in chloroform using unsubstituted NDIs. Characterisation of the products by UV-Vis, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) support the use of cNDIs as an appropriate exfoliating agent in chloroform.

Lubricin (LUB, aka PRG4), a mucin-like glycoprotein, is best known for the significant role it plays in the boundary lubrication, wear protection, and adhesion control systems in human joints. However, LUB exhibits a number of diverse and useful properties, including a remarkable ability to self-assemble into a telechelic brush structure onto virtually any substrate. This self-assembly behavior has spawned the emergence of numerous nontraditional applications of LUB coatings in numerous areas such as microfluidics, electrochemical sensors, contact lenses, antifouling surfaces, and bionic neural interfaces. Although LUB will readily self-assemble on most substrates, it has become apparent that the substrate has a significant influence on the LUB layer's demonstrated lubrication, antiadhesion, electrokinetic, and size-selective transport properties; however, investigations into LUB-substrate interactions and how they influence the self-assembled LUB layer structure remain a neglected aspect of LUB research. This study utilizes AFM force spectroscopy to directly assess the adhesion energy of LUB molecules adsorbed to a wide variety of different substrates which include inorganic, polymeric, and metallic materials. An analysis of the steric repulsive forces measured on approach provides a qualitative assessment of the LUB layer's mechanical modulus, related to the chain packing density, across substrates. These modulus measurements, combined with characteristic features and the dwell time dependence of the LUB adhesion forces provide insight into the organization and uniformity of the LUB brush structure. The results of these measurements indicate that LUB interactions with different substrates are highly variable and substrate-specific, resulting in a surprisingly broad spectrum of adhesion energies and layer properties (i.e., chain density, uniformity, etc.) which are not, themselves, correlated or easily predicted by substrate properties. In addition, this study finds exceptionally poor LUB adhesion to both mica and poly(methyl methacrylate) surfaces that remain widely used substrates for constructing model surfaces in fundamental tribology studies which may have significant implications for the findings of a number of foundational studies into LUB tribology and molecular synergies.

Growth factors play a crucial role in tissue engineering by directing the fate of cells and allowing the formation of tissues. Understanding the key requirements for growth factor delivery can point the way towards novel tissue engineering platforms. Growth factor suffer from a tendency to lose their bioactivity upon environmental and physical changes. The need for biomaterials that can preserve the native form of growth factor has directed interest towards hydrogels (e.g. gelatin, alginate) and hydrophobic polymers (e.g. polycaprolactone). In recent advances, the use of composite materials such as PCL-chitosan (hydrogel-hydrophobic polymer) and gelatin-alginate (hydrogel-hydrogel polymers) has opened the possibility of fine tuning the delivery systems. Other current research is exploring new delivery strategies for growth factors such as the use of bioreactors and delivery by molecule-recognition. In particular, systems that allow the delivery of growth factors in a 3-dimensional manner are promising compared to conventional methods. This review analyses the biological considerations, material selection, and delivery strategies that have been established as the pivotal components for growth factor delivery and will support the next generation of tissue engineering platforms by providing a comprehensive landscape for the growth factor delivery field. The last part of the review discusses the current challenges and promising future directions for delivering growth factors.

Biofouling on surfaces compromises the function of biomedical devices whose function involves contact with biological fluids. In the context of electrochemical devices, proteins are attracted to the surface via coaction of various forces (hydrogen bond, hydrophobic effect, and other polar interactions) and protein interaction with the surface can significantly alter the surface chemistry. In response to this issue, we have developed an efficient anti-biofouling surface that employs a glycoprotein, lubricin (LUB), and which generates low impedance layers compatible with electrochemical applications. Herein, we investigate how different LUB densities on platinum (Pt) electrodes affect the surface electrochemistry and its ability to prevent nonspecific adsorption of protein to the surface. Surfaces with higher densities of LUB were more resistant to protein adsorption. The LUB modified Pt electrodes were challenged in artificial perilymph (AP) media under passive and electrically stimulated conditions over 7-day periods throughout which the LUB layer retained its anti-biofouling and surface coating stability.

Alginate has been a biologically viable option for controlled local delivery of bioactive molecules in vitro and in vivo. Specific bioactive molecule release profiles are achieved often by controlling polymer composition/concentration, which also determines the modulus of hydrogels. This largely limits alginate-mediated bioactive molecule delivery to single-factors of uniform concentration applications, rather than applications that may require (multiple) bioactive molecules delivered at a concentration gradient for chemotactic purposes. Here we report a two-phase PLGA/alginate delivery system composed of protein-laden poly-d,l-lactic-co-glycolic acid (PLGA) microspheres wet-spun into alginate fibres. Fluorescein isothiocyanate-conjugated bovine serum albumin (FITC-BSA) was used as a model protein and the developed structures were characterized. The fabrication system devised was shown to produce wet-spun fibres with a protein concentration gradient (G-Alg/PLGA fibre). The two-phase delivery matrices display retarded FITC-BSA release in both initial and late stages compared to release from the PLGA microspheres or alginate fibre alone. In addition, incorporation of higher concentrations of protein-loaded PLGA microspheres increased protein release compared to the fibres with lower concentrations of BSA-loaded microspheres. The "programmable" microsphere concentration gradient fibre methodology presented here may enable development of novel alginate scaffolds with the ability to guide tissue regeneration through tightly-controlled release of one or more proteins in highly defined spatio-temporal configurations.

Controlling the release of bioactive agents has important potential applications in tissue engineering. While microspheres have been investigated to manipulate release rates, the majority of these investigations have been based on delivery into aqueous media, whereas the cellular environment in tissue engineering is more typically a hydrogel scaffold. If drug-loaded microspheres are introduced within scaffolds to deliver biologically active substances in situ, it is crucial to understand how the release rate is influenced by interactions between the microspheres and the scaffold. Here, we report the fabrication and characterization of a biodegradable scaffold that contains composite microspheres and is suitable for biological applications. Our approach evaluates the influence on the release profile of a model drug (FITC-dextran sulfate) from alginate and PCL-alginate microspheres within a hydrogel construct forming a secondary encapsulation. Increasing the degree of crosslinking in the secondary encapsulation matrix led to a slower cumulative release from 36% to 15%, from the alginate microspheres, whereas a decrease from 26% to 6% was observed for the PCL-alginate microspheres. These results suggest that the release of bioactive molecules can be fine tuned by independently engineering the properties of the scaffold and microspheres.

The development and study of advanced methods to encapsulate and provide a controlled release of drugs and bioactive agents provide the opportunity to deliver active factors in situ. This acute delivery requires systems to be able to precisely control the release rate, however this has been challenging to achieve using a single component system. We developed novel Polycaprolactone (PCL) porous templates to control the release of encapsulated alginate hydrogel containing water-soluble molecules of different molecular weights. The presence of molecule-loaded alginate within the PCL porous templates was confirmed by infrared spectroscopy, fluorescence imaging and scanning electron microscopy. The influence of the molecular weight of the encapsulated molecule was investigated. The release profile of PCL-alginate displayed significant improvement on slowing the release of molecules of different molecular weight when compared with alginate alone. Based on the results, we can suggest that PCL porous templates can be a promising candidate to form composite delivery systems carrying high molecular weight hydrophilic agents for tissue engineering and drug delivery applications.

Skeletal muscle is a functional tissue that accounts for approximately 40% of the human body mass. It has remarkable regenerative potential, however, trauma and volumetric muscle loss, progressive disease and aging can lead to significant muscle loss that the body cannot recover from. Clinical approaches to address this range from free-flap transfer for traumatic events involving volumetric muscle loss, to myoblast transplantation and gene therapy to replace muscle loss due to sarcopenia and hereditary neuromuscular disorders, however, these interventions are often inadequate. The adoption of engineering paradigms, in particular materials engineering and materials/tissue interfacing in biology and medicine, has given rise to the rapidly growing, multidisciplinary field of bioengineering. These methods have facilitated the development of new biomaterials that sustain cell growth and differentiation based on bionic biomimicry in naturally occurring and synthetic hydrogels and polymers, as well as additive fabrication methods to generate scaffolds that go some way to replicate the structural features of skeletal muscle. Recent advances in biofabrication techniques have resulted in significant improvements to some of these techniques and have also offered promising alternatives for the engineering of living muscle constructs ex vivo to address the loss of significant areas of muscle. This review highlights current research in this area and discusses the next steps required towards making muscle biofabrication a clinical reality.

Smart drug delivery systems represent state-of-the-art approaches for targeted therapy of life-threatening diseases such as cancer and cardiovascular diseases. Stimuli-responsive on-demand release of therapeutic agents at the diseased site can significantly limit serious adverse effects. In this study, we engineered a near-infrared (NIR) light-responsive liposomal gold nanorod-containing platform for on-demand delivery of proteins using a hybrid formulation of ultrasmall gold nanorods (AuNRs), thermosensitive phospholipid (DPPC) and non-ionic surfactant (Brij58). In light-triggered release optimization studies, 55.6% (± 4.8) of a FITC-labelled model protein, ovalbumin (MW 45 kDa) was released in 15 min upon NIR irradiation (785 nm, 1.35 W/cm2 for 5 min). This platform was then utilized to test on-demand delivery of urokinase-plasminogen activator (uPA) for bleeding-free photothermally-assisted thrombolysis, where the photothermal effect of AuNRs would synergize with the released uPA in clot lysis. Urokinase light-responsive liposomes showed 80.7% (± 4.5) lysis of an in vitro halo-clot model in 30 min following NIR irradiation (785 nm, 1.35 W/cm2 for 5 min) compared to 36.3% (± 4.4) and 15.5% (± 5.5) clot lysis from equivalent free uPA and non-irradiated liposomes respectively. These results show the potential of low-dose, site-specific thrombolysis via the combination of light-triggered delivery/release of uPA from liposomes combined with photothermal thrombolytic effects from gold nanorods. In conclusion, newly engineered, gold nanorod-based, NIR light-responsive liposomes represent a promising drug delivery system for site-directed, photothermally-stimulated therapeutic protein release.

The ability to prevent or minimize the accumulation of unwanted biological materials on implantable medical devices is important in maintaining the long-term function of implants. To address this issue, there has been a focus on materials, both biological and synthetic, that have the potential to prevent device fouling. In this review, we introduce a glycoprotein called lubricin and report on its emergence as an effective antifouling coating material. We outline the versatility of lubricin coatings on different surfaces, describe the physical properties of its monolayer structures, and highlight its antifouling properties in improving implant compatibility as well as its use in treatment of ocular diseases and arthritis. This review further describes synthetic polymers mimicking the lubricin structure and function. We also discuss the potential future use of lubricin and its synthetic mimetics as antiadhesive biomaterials for therapeutic applications.

Mesenchymal stem cell therapies show great promise in regenerative medicine. However, to generate clinically relevant numbers of these stem cells, significant in vitro expansion of the cells is required before transplantation into the affected wound or defect. The current gold standard protocol for recovering in vitro cultured cells involves treatment with enzymes such as trypsin which can affect the cell phenotype and ability to interact with the environment. Alternative enzyme free methods of adherent cell recovery have been investigated, but none match the convenience and performance of enzymatic detachment. In this work we have developed a synthetically simple, low cost cell culture substrate functionalized with gold nanorods that can support cell proliferation and detachment. When these nanorods are irradiated with biocompatible low intensity near infrared radiation (785 nm, 560 mWcm-2) they generate localized surface plasmon resonance induced nanoscale heating effects which trigger detachment of adherent mesenchymal stem cells. Through simulations and thermometry experiments we show that this localized heating is concentrated at the cell-nanorod interface, and that the stem cells detached using this technique show either similar or improved multipotency, viability and ability to differentiate into clinically desirable osteo and adipocytes, compared to enzymatically harvested cells. This proof-of-principle work shows that photothermally mediated cell detachment is a promising method for recovering mesenchymal stem cells from in vitro culture substrates, and paves the way for further studies to scale up this process and facilitate its clinical translation. STATEMENT OF SIGNIFICANCE: New non-enzymatic methods of harvesting adherent cells without damaging or killing them are highly desirable in fields such as regenerative medicine. Here, we present a synthetically simple, non-toxic, infra-red induced method of harvesting mesenchymal stem cells from gold nanorod functionalized substrates. The detached cells retain their ability to differentiate into therapeutically valuable osteo and adipocytes. This work represents a significant improvement on similar cell harvesting studies due to: its simplicity; the use of clinically valuable stem cells as oppose to immortalized cell lines; and the extensive cellular characterization performed. Understanding, not just if cells live or die but how they proliferate and differentiate after photothermal detachment will be essential for the translation of this and similar techniques into commercial devices.

The encapsulation of growth factors is an important component of tissue engineer- ing. Using microspheres is a convenient approach in which the dose of factors can be regulated by increasing or decreasing the number of encapsulated microspheres. Moreover, microspheres offer the possibility of delivering the growth factors directly to the target site. However, the fabrication of microspheres by traditional emulsion methods is largely variable due to the experimental procedure. We have developed a protocol using a commercially available microfluidic system that allows formation of tunable particle-size droplets loaded with growth factors. The methodology includes a guide for preparing an alginate-growth factors solution followed by the specific set-up needed for using the microfluidic system to form the microspheres. The pro- cedure also includes a unique post-crosslinking process without pH modification. These methods allow the preservation of integrity and bioactivity of the growth factors tested (BMP-6 and TGFβ -3) and their subsequent sustained delivery.•The protocol can be tuned to form particles of various sizes.•The gentle post-crosslinking process allows conformational integrity of various bioactive molecules., Graphical abstract Image, graphical abstract

Additive biofabrication (3D bioprinting) makes it possible to create scaffolds with precise geometries, control over pore interconnectivity and architectures that are not possible with conventional techniques. Inclusion of cells within the ink to form a “bio-ink” presents the potential to print 3D structures that can be implanted into damaged/diseased tissue to promote highly controlled cell-based regeneration and repair. The properties of an ‘ink’ are defined by its formulation and critically influence the delivery and integrity of structure formed. Importantly, the ink properties need to conform to biological requirements necessary for the cell system that they are intended to support and it is often challenging to find conditions for printing that facilitate this critical aspect of tissue bioengineering. In this study, alginate (Alg) was selected as the major component of the ‘bio-ink’ formulations for extrusion printing of cells. The rheological properties of alginate-gelatin (Alg-Gel) blends were compared with pre-crosslinked alginate and alginate solution to establish their printability whilst maintaining their ability to support optimal cell growth. Pre-crosslinked alginate on its own was liquid-like during printing. However, by controlling the temperature, Alg-Gel formulations had higher viscosity, storage modulus and consistency which facilitated higher print resolution/precision. Compression and indentation testing were used to examine the mechanical properties of alginate compared to Alg-Gel. Both types of gels yielded similar results with modulus increasing with alginate concentration. Decay in mechanical properties over time suggests that Alg-Gel slowly degrades in cell culture media with more than 60% decrease in initial modulus over 7 days. The viability of primary myoblasts delivered as a myoblast/Alg-Gel bio-ink was not affected by the printing process, indicating that the Alg-Gel matrix provides a potential means to print 3D constructs that may find application in myoregenerative applications.

The development of inherently conducting polymers as controllable/programmable drug delivery systems has attracted significant interest in medical bionics, and the interfacial properties of the polymers, in particular, protein adsorption characteristics, is integral to the stability of the overall performance. Herein we report a hybrid conducting system based on polypyrrole doped with an anti-inflammatory prodrug, dexamethasone phosphate (DexP), upon which post-surface modification was conducted to render the polymer more biostable. We firstly investigated the influence of the current density and DexP concentration on the physiochemical properties and surface characteristics of the resulting polymer films. Films were then surface modified with thiolated poly(ethylene glycol). The influence of surface modification on inhibition of nonspecific protein adsorption to the polymer surfaces was evaluated using electrochemistry and quartz crystal microbalance. Furthermore, studies were undertaken to examine the effect of surface coatings on the drug release behaviour triggered by electrical stimulation. Our results demonstrated that both the physiochemical and interfacial properties of conducting polymers can be modulated to enhance the performance of the materials as biocompatible drug delivery systems. This provides important insight into molecular engineering of conducting polymers to facilitate their applications in medical bionics.

Three-dimensional (3D) printing is a fast-growing additive manufacturing process, which is transforming not only the pharmaceutical sector but also the fabrication of goods across various fields such as material sciences and engineering, and biomedical and biocompatible structure components. In the pharmaceutical industry the 3D printing technology plays a pivotal role in the manufacturing of customized pharmaceutics. Examples of precise manufacturing of individually developed dosage forms encompass drug delivery systems (DDSs) with accelerated release profiles, adjustable and personalized dosage forms as well as cell-based materials for tissue engineering and regenerative medicine. This chapter presents 3D printing as a method to fabricate DDSs. The term “DDS” in this chapter refers to any combination of drugs and excipients (e.g., polymers and ceramics) in any format (i.e., tablet, pellet, mesh, fiber, etc.) that can be utilized to deliver therapeutics. The chapter covers the main progress made in the past years using the following techniques: direct write: pressure-assisted systems, fused deposition modeling, and inkjet printing.

Metal-phenolic networks (MPNs) are a versatile class of organic-inorganic hybrid systems that are generating interest for applications in catalysis, bioimaging, and drug delivery. These self-assembled MPNs possess metal-coordinated structures and may potentially serve as redox-responsive platforms for triggered disassembly or drug release. Therefore, a comprehensive study of the reduction and oxidation behavior of MPNs for evaluating their redox responsiveness, specific conditions required for their disassembly, and the kinetics of metal ion release, is necessary. Using a representative MPN gallic acid-iron (GA/FeIII) system, we conducted electrochemical studies to provide fundamental insights into the redox behavior of these MPNs. We demonstrate that GA/FeIII is redox active, and evaluate its electrochemical reversibility, identify the oxidation state of the redox-active species, and provide information regarding the stability of the networks toward reductive stimuli and specific redox conditions required for the "on-off" or continuous release of FeIII. Overall, through studying the redox properties of GA/FeIII films, we advance the understanding of multifunctional iron-containing MPN platforms that may have practical significance for biologically relevant applications.

Advances in neurotransmitter detection have emerged to improve the diagnosis of mental disorders promptly and offer timely clinical treatment. However, quantifying the neurotransmitter simplifies as fast diagnosis, inexpensive operational costs, less time-consuming and miniaturized design with high configurations. Herein, amperometric detection of dopamine and epinephrine was assessed using a novel surface modified Cu mesh electrode decorated with B, N doped graphene quantum dots (B, N-GQD). The electro-polymerization PEDOT supported with B, N-GQD has been employed to fabricate modified Cu mesh to form the biosensor electrodes. The result indicated a linear steady-state response towards B, N-GQD/PEDOT/CuO modified Cu mesh electrode that exhibited a sensitivity 0.76 μA μM−1 cm−2 and a low limit of detection of 0.270 μM (S/N = 3) for the detection of dopamine. Similarly, in epinephrine detection, the B, N-GQD/PEDOT/CuO modified Cu mesh electrode revealed a high sensitivity of 2.44 μA μM−1 cm−2 and a low limit of detection of 0.084 μM (S/N = 3), respectively. Furthermore, the surface modified electrode showed excellent performance in interference and recovery test in urine samples. The surface modified Cu mesh electrode shows promise in sensing biomolecules due to the benefits of low cost and versatility for practical applications.

Graphene derived from readily available graphite is viewed as the most effective route for large-scale production, due to the low cost of the raw material. However, the difficulty in achieving complete exfoliation, as well as the intrinsic insolubility of graphite, remains a key challenge. Herein, we describe a single-step approach to effectively disrupt and cleave the network of π–π interactions, induce the exfoliation of graphite and disperse the resulting exfoliated material in organic solvents, all driven by electron rich (graphene) donor-acceptor interactions. This is achieved through the addition of specially synthesised non-polar, branched, electron-deficient aromatic acceptor molecules. Minimal energy input through mild manual grinding of graphite with the tailored acceptor induces donor-acceptor interactions that preferentially affect the π−π system in graphite resulting in solid phase exfoliation. Graphite exfoliation and dispersion formation is further improved after mild bath sonication (30 min) of the acceptor-graphite composite in a solvent leading to 1250% increment in yield in NMP solvent for instance. The use of electron acceptors allows high concentration dispersions, not only in high boiling point solvents, whose surface energy generally matches that of graphene but also in a low boiling point solvent with mediocre properties.

Conducting polymers are good candidates for electronic biomedical devices such as biosensors, artificial nerves, and electrodes for brain tissue. Functionalizing the conducting polymer surface with bioactive molecules can limit adverse immune reactions to the foreign body and direct tissue integration. In this work, we demonstrate a simple one-step method to attach biomolecules covalently to a conductive polymer. Electrochemically synthesized polypyrrole was activated using plasma immersion ion implantation (PIII) in nitrogen. A short treatment with relatively low ion fluence (20 s) was found to enable direct covalent immobilization of protein upon incubation in a protein solution, while the protein is easily removed from untreated polypyrrole by washing in buffer. The covalent nature of the protein immobilization was demonstrated by its resistance to elution when repeatedly washed with SDS detergent. Changes in the surface properties and their evolution with time after PIII activation were studied by a combination of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), cyclic voltammetry, and water contact angle measurements. Notable changes in the chemistry of the modified layer in polypyrrole include the appearance of nitrile groups that gradually disappear with time and oxidation of the surface that increases over time in air. The kinetics of surface energy are consistent with the generation of radicals in the modified layer that are lost predominantly through oxidation. The conductivity of the modified surface layer (64 nm in thickness) decreases for low fluence treatments and is partially restored after high fluence treatment. This simple surface modification process opens up the possibility of creating biologically active interfaces for electro-stimulating biomedical devices and electrical sensing of neurological processes.

Application of rare earth conversion coatings as a surface treatment for magnesium has been the subject of several studies revealing the potential to act as an effective passivating layer. Herein a mechanistic study is presented on the formation of a rare earth conversion layer based on Pr(NO3)3 on AZ80X magnesium alloy in simulated biological (buffered) solution. Scanning electrochemical microscopy (SECM) was used to investigate the insulating properties and degradation behaviour of the Pr conversion layer. The self-healing properties of the conversion layer in the presence of Pr3+ were also studied using SECM. Results revealed the self-healing characteristic of the Pr conversion film in the presence of active, Pr3+, species. The Pr conversion layer provided passivation in the short term by producing an electrochemically inert and insulating layer. SECM results in potentiometric mode elucidated the role of near surface pH in the formation of the conversion coating. Keywords: Scanning electrochemical microscopy, Magnesium alloy, Praseodymium oxide, Passivation, Conversion coating, Self-healing