Biomedical Engineering - Research Publications
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ItemP015 The effects of cathodal transcranial direct current stimulation in patienst with focal epilepsy (a pilot study)‘(Elsevier, 2017-03)Introduction: Over 65 million people live with epilepsy worldwide. Unfortunately, seizures can not be adequately controlled in a third of the affected individuals. Therefore, there is a definite need for adjunctive or alternative therapeutic approaches in this group of patients to control the recurrence of seizure attacks. Modulation of dysfunctional electrical brain activity by transcranial direct current stimulation (tDCS) seems to be a potentially valuable non-invasive alternative for epilepsy treatment in this population. Objectives: This pilot study aimed to assess the effects of a novel protocol called within-session repeated c-tDCS (9 min treatment - 20 min rest - 9 min treatment) on patients with focal epilepsy. Method: We conducted a small pilot study in patients admitted to the Video-EEG Monitoring Unit at the Royal Melbourne Hospital and as out patients at this hospital or St Vincent Hospital. Thirty patients have participated in this study to date. Twenty patients with focal epilepsy received one session of c-tDCS (9–20-9 protocol) over the temporal lobe in the affected hemisphere. One participant received c-tDCS on two consecutive days. The other nine patients received one session of sham tDCS with the same electrode montage and protocol. Short interval intracortical inhibition or SICI was measured with paired-pulse transcranial magnetic stimulation (TMS) before and after the tDCS intervention in 18 participants. Motor evoked potentials were recorded from first dorsal interosseous muscle in these participants. Participants were asked to record the time and the number of their seizures post tDCS treatment for 4 weeks in a seizure diary. Twenty-four participants returned their diaries. Results: All patients tolerated the c-tDCS protocol very well. One-way ANOVA showed that SICI was increased significantly in the experimental group compared to the sham group (F = 10.3, p = 0.005) (Fig. 1). The mean response ratio was −48.4 (SD = 54) for the experimental group vs. −8.3 (SD = 16.7) for sham group
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ItemCovalent Incorporation of Heparin Improves Chondrogenesis in Photocurable Gelatin-Methacryloyl Hydrogels(WILEY-V C H VERLAG GMBH, 2017-12)Multicomponent gelatin-methacryloyl (GelMA) hydrogels are regularly adopted for cartilage tissue engineering (TE) applications, where optimizing chemical modifications for preserving biofunctionality is often overlooked. This study investigates the biological effect of two different modification methods, methacrylation and thiolation, to copolymerize GelMA and heparin. The native bioactivity of methacrylated heparin (HepMA) and thiolated heparin (HepSH) is evaluated via thromboplastin time and heparan sulfate-deficient myeloid cell-line proliferation assay, demonstrating that thiolation is superior for preserving anticoagulation and growth factor signaling capacity. Furthermore, incorporating either HepMA or HepSH in chondrocyte-laden GelMA hydrogels, cultured for 5 weeks under chondrogenic conditions, promotes cell viability and chondrocyte phenotype. However, only GelMA-HepSH hydrogels yield significantly greater differentiation and matrix deposition in vitro compared to GelMA. This study demonstrates that thiol-ene chemistry offers a favorable strategy for incorporating bioactives into gelatin hydrogels as compared to methacrylation while furthermore highlighting GelMA-HepSH hydrogels as candidates for cartilage TE applications.
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ItemUnicortical and bicortical plating in the fixation of comminuted fractures of the clavicle: a biomechanical study(WILEY, 2017-11)BACKGROUND: Intraoperative neurovascular complications with clavicle fracture fixation are often due to far cortex penetration by drills and screws, but could be avoided using a unicortical construct. The objective of this study was to compare the bending and torsional strength of a unicortical locking screw plate construct and a hybrid (with central locked and outer non-locked long oblique screws) unicortical plate construct for clavicle fracture fixation with that of a conventional bicortical locking screw construct of plate fixation. METHODS: Twenty-four human clavicle specimens were harvested and fractured in a comminuted mid-shaft butterfly configuration. Clavicles were randomly allocated to three surgical fixation groups: unicortical locking screw, bicortical locking screw and hybrid unicortical screw fixation. Clavicles were tested in torsion and cantilever bending. Construct bending and torsional stiffness were measured, as well as ultimate strength in bending. RESULTS: There were no significant differences in bending stiffness or ultimate bending moment between all three plating techniques. The unicortical locked construct had similar torsional stiffness compared with the bicortical locked construct; however, the hybrid technique was found to have significantly lower torsional stiffness to that of the bicortical locking screw construct (mean difference: 87.5 Nmm/degree, P = 0.028). CONCLUSIONS: Unicortical locked screw plate fixation and hybrid unicortical plating fixation with centrally locked screws and outer long, oblique screws may alleviate far cortex penetration, protecting nearby anatomical structures, and may ease implant removal and conversion to bicortical fixation for revision surgery; however, use of long oblique screws may increase the risk of early loosening under torsion.
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ItemTriggered and Tunable Hydrogen Sulfide Release from Photogenerated Thiobenzaldehydes(WILEY-V C H VERLAG GMBH, 2017-08-22)Hydrogen sulfide (H2 S) has been identified as an important cell-signaling mediator and has a number of biological functions, such as vascular smooth muscle relaxation, neurotransmission, and regulation of inflammation. A facile and versatile approach for H2 S production initiated by light irradiation and controlled by reaction with an amine or an amino acid was developed. The donor was synthesized in a one-pot reaction, and simple crystallization led to a yield of approximately 90 %. The synthetic strategy is scalable and versatile, and the H2 S donors can be expressed ina number of different molecular and macromolecular forms, including crystalline small-molecule compounds, water-soluble polymers, polystyrene films, and hydrogels. The H2 S donors based on polystyrene film and hydrogel were used as cell-culture scaffolds. The H2 S donor based on water-soluble polymer was applied in photocontrolled inhibition of P-selectin expression on human platelets and subsequent regulation of platelet aggregation. This study provides the simplest controllable H2 S source to study its biological functions. The developed materials are also new therapeutic platforms to deliver H2 S, as there is no accumulation of toxic byproducts, and the donor materials from polystyrene films and hydrogels can be readily removed after releasing H2 S.
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ItemFace shield design against blast-induced head injuries(WILEY, 2017-12)Blast-induced traumatic brain injury has been on the rise in recent years because of the increasing use of improvised explosive devices in conflict zones. Our study investigates the response of a helmeted human head subjected to a blast of 1 atm peak overpressure, for cases with and without a standard polycarbonate (PC) face shield and for face shields comprising of composite PC and aerogel materials and with lateral edge extension. The novel introduction of aerogel into the laminate face shield is explored and its wave-structure interaction mechanics and performance in blast mitigation is analysed. Our numerical results show that the face shield prevented direct exposure of the blast wave to the face and help delays the transmission of the blast to reduce the intracranial pressures (ICPs) at the parietal lobe. However, the blast wave can diffract and enter the midface region at the bottom and side edges of the face shield, resulting in traumatic brain injury. This suggests that the bottom and sides of the face shield are important regions to focus on to reduce wave ingress. The laminated PC/aerogel/PC face shield yielded higher peak positive and negative ICPs at the frontal lobe, than the original PC one. For the occipital and temporal brain regions, the laminated face shield performed better than the original. The composite face shield with extended edges reduced ICP at the temporal lobe but increases ICP significantly at the parietal lobe, which suggests that a greater coverage may not lead to better mitigating effects.
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ItemPromoting Endothelialization of Polymeric Cardiovascular Biomaterials(WILEY-V C H VERLAG GMBH, 2017-04)The lack of a blood compatible synthetic interface is one of the largest unaddressed challenges in the field of biomaterials science. This technological shortcoming hinders the successful clinical application of small diameter vascular grafts and other cardiovascular devices such as stents and artificial heart valves. Therefore, intensive research activities are ongoing to develop polymer materials with improved blood compatibility. One attractive strategy to improve the blood compatibility of an interface is to design surfaces that promote the development of an endothelium, the monolayer of endothelial cells that line our native vasculature and is responsible for blood compatibility. This article describes the recent strategies that have been used to generate polymeric materials that promote the development of an endothelium, discusses shortcomings in the field, and proposes future directions of research that can be undertaken to design next generation polymeric biomaterial that promote endothelialization. image
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ItemFlexible polygon-mirror based laser scanning microscope platform for multiphoton in-vivo imaging(WILEY-V C H VERLAG GMBH, 2017-11)Commercial microscopy systems make use of tandem scanning i.e. either slow or fast scanning. We constructed, for the first time, an advanced control system capable of delivering a dynamic line scanning speed ranging from 2.7 kHz to 27 kHz and achieve variable frame rates from 5 Hz to 50 Hz (512 × 512). The dynamic scanning ability is digitally controlled by a new customized open-source software named PScan1.0. This permits manipulation of scanning rates either to gain higher fluorescence signal at slow frame rate without increasing laser power or increase frame rates to capture high speed events. By adjusting imaging speed from 40 Hz to 160 Hz, we capture a range of calcium waves and transient peaks from soma and dendrite of single fluorescence neuron (CAL-520AM). Motion artifacts arising from respiratory and cardiac motion in small animal imaging reduce quality of real-time images of single cells in-vivo. An image registration algorithm, integrated with PScan1.0, was shown to perform both real time and post-processed motion correction. The improvement is verified by quantification of blood flow rates. This work describes all the steps necessary to develop a high performance and flexible polygon-mirror based multiphoton microscope system for in-vivo biological imaging.
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