Mechanical characterisation of biological materials using Brillouin microscopy

Biomechanics studies how biomaterials deform subjected to external loads. Most techniques used in biomechanics require direct contact or lack of subcellular resolution. By contrast, Brillouin microscopy is a contactless and label-free technique used to characterise mechanical properties of cells and tissues. Despite Brillouin microscopy measuring longitudinal modulus M , an empirical power law has been widely used to interpret Brillouin measurements as stiffness. In this thesis, we focused on the interpretation and relevance between the Brillouin microscopy measurements and quasi-static mechanical properties using hydrogels and cells. To investigate how Brillouin measurements relate to the mechanical properties of biological materials, we use hydrogels that approximate the mechanics of biphasic hydrated materials. By varying water content ε and Young’s modulus E in hydrogels, we found Brillouin measurements reflect changes in ε and the relationship between M and E arises due to their mutual dependence on ε. We further used binary mixture theory and polymer theory to explain the underlying physics. However, cells are neither passive nor homogeneous, we discussed the assumptions required to relate M and E to contextualise measurements made. We varied the osmotically active water content ε^* of cells by controlling the external osmotic stress whilst measuring M and E. We found both M and E depends on ε^* in a manner that can be explained by binary mixture theory and the ideal gas law. However, the correlation between M and E does not always exist when comparing different cellular components. Furthermore, we also assessed the potential of using Brillouin microscopy as an early diagnostic tool to detect the structural changes of ECM degradation in osteoarthritis (OA). To mimic OA, porcine cartilage was digested by enzyme and our results show that Brillouin microscopy can detect the structure change in OA and hence Brillouin microscopy could develop to a minimally-invasive arthroscope.Open Acces

CELL SURFACE COATINGS FOR MAMMALIAN CELL-BASED THERAPEUTIC DELIVERY

The cell plasma membrane is an interactive interface playing an important role in regulating cell-to-cell, cell-to-tissue contact, and cell-to-environment responses. This environment-responsive phospholipid layer consisting of multiple dynamically balanced macromolecules, such as membrane proteins, carbohydrate and lipids, is regarded as a promising platform for various surface engineering strategies. Through different chemical modification routes, we are able to incorporate various artificial materials into the cell surface for biomedical applications in small molecule and cellular therapeutics. In this dissertation, we establish two different cell coating techniques for applications of cell-mediated drug delivery and the localization of cell-based therapies to specific tissues. The first part of this dissertation establishes a membrane-associated hydrogel patch for drug delivery. The crosslinking of a grafted polymeric patch from a mammalian cell membrane is achieved through surface-mediated photolithographic polymerization. With the use of photomask, the formation of nanoparticle-loaded PEGDA hydrogel is controlled to deposit various geometric features on photoinitiator-immobilized surfaces. Through microarray patch patterning, we analyzed the influence of processing parameters on the accuracy of polymer patterning on a microarray. We then optimized the patterning approach for the formation of PEGDA patches on live A549 cells. In the second part of this dissertation, we study the use of tissue-adhesive coatings to improve the retention of therapeutic mesenchymal stem cells (MSCs) in the heart following intramyocardial or intravenous injection. MSCs were coated with antibodies against ICAM1 to adhere to CAM-overexpressed endothelium present in the heart following MI. Through intramyocardial or intravenous delivery, we observe higher number of coated cells retained in the heart over uncoated ones, supporting enhanced affinity for the inflamed endothelium near the infarct. We correlate the detachment force of antigen-interacted MSCs by a parallel laminar flow assay with the density of ICAM on the substrate and the density of anti-ICAM on the MSC surface. MSC retention on CAMmodified surfaces or activated HUVECs was significantly increased on antibody-coated groups (~90%) under physiologically hemodynamic forces (\u3c 30dyne/cm2), compared to uncoated MSCs (~20%). Moreover, a dramatic reduction of immune cell quantity was observed after intravenous injection, indicating the enhanced immunoregulatory efficacy by systemically delivering ICAM-adhesive MSCs to the site of inflammation

Learning Styles of Undergraduate and Graduate Physical Therapy Students in Taiwan

AbstractThe research was conducted to identify the learning styles of undergraduate and graduate physical therapy students in Taiwan and to examine the associations between learning style and academic performance. Basic data and Kolb's Learning Style Inventory were obtained from 52 participants from one university. The most commonly occurring style of learner was assimilator (44%), followed by diverger (23%), accommodator (15%), and converger (17%). There was no significant difference in academic performance among the four different styles of learners. Qualitative analyses provided further understanding of the preferred learning and teaching strategies. The different strategies are recommended to meet students’ learning preferences

Ceftriaxone attenuates hypoxic-ischemic brain injury in neonatal rats

<p>Abstract</p> <p>Background</p> <p>Perinatal brain injury is the leading cause of subsequent neurological disability in both term and preterm baby. Glutamate excitotoxicity is one of the major factors involved in perinatal hypoxic-ischemic encephalopathy (HIE). Glutamate transporter GLT1, expressed mainly in mature astrocytes, is the major glutamate transporter in the brain. HIE induced excessive glutamate release which is not reuptaked by immature astrocytes may induce neuronal damage. Compounds, such as ceftriaxone, that enhance the expression of GLT1 may exert neuroprotective effect in HIE.</p> <p>Methods</p> <p>We used a neonatal rat model of HIE by unilateral ligation of carotid artery and subsequent exposure to 8% oxygen for 2 hrs on postnatal day 7 (P7) rats. Neonatal rats were administered three dosages of an antibiotic, ceftriaxone, 48 hrs prior to experimental HIE. Neurobehavioral tests of treated rats were assessed. Brain sections from P14 rats were examined with Nissl and immunohistochemical stain, and TUNEL assay. GLT1 protein expression was evaluated by Western blot and immunohistochemistry.</p> <p>Results</p> <p>Pre-treatment with 200 mg/kg ceftriaxone significantly reduced the brain injury scores and apoptotic cells in the hippocampus, restored myelination in the external capsule of P14 rats, and improved the hypoxia-ischemia induced learning and memory deficit of P23-24 rats. GLT1 expression was observed in the cortical neurons of ceftriaxone treated rats.</p> <p>Conclusion</p> <p>These results suggest that pre-treatment of infants at risk for HIE with ceftriaxone may reduce subsequent brain injury.</p

Hydrothermal–galvanic couple synthesis of directionally oriented BaTiO3 thin films on TiN-coated substrates

AbstractBaTiO3 films were synthesized on TiN-coated Si substrate below 100°C by a hydrothermal–galvanic couple technique in barium contained alkaline solutions. X-ray diffraction and electron backscatter diffraction results show that the BaTiO3 thin films were directionally oriented grown on the TiN/Si substrates, i.e., (111) BaTiO3 over (111) TiN. The surface morphologies revealed that BaTiO3 nucleated and grew over the TiN surface with a single layer. From kinetic analyses, the growth rates of BaTiO3 films prepared by the hydrothermal–galvanic couple technique were faster than a hydrothermal method. The galvanic effects were confirmed by investigating the induced currents and energies. The galvanic currents were generated and controlled by both the dissolution of TiN and the formation of BaTiO3. The output electric energies increased rapidly with the reaction time and leveled off at the full coverage of BaTiO3

Coatings on Mammalian Cells: Interfacing Cells with Their Environment

The research community is intent on harnessing increasingly complex biological building blocks. At present, cells represent a highly functional component for integration into higher order systems. In this review, we discuss the current application space for cellular coating technologies and emphasize the relationship between the target application and coating design. We also discuss how the cell and the coating interact in common analytical techniques, and where caution must be exercised in the interpretation of results. Finally, we look ahead at emerging application areas that are ideal for innovation in cellular coatings. In all, cellular coatings leverage the machinery unique to specific cell types, and the opportunities derived from these hybrid assemblies have yet to be fully realized

Concurrent image-guided intensity modulated radiotherapy and chemotherapy following neoadjuvant chemotherapy for locally advanced nasopharyngeal carcinoma

<p>Abstract</p> <p>Background</p> <p>To evaluate the experience of induction chemotherapy followed by concurrent chemoradiationwith helical tomotherapy (HT) for nasopharyngeal carcinoma (NPC).</p> <p>Methods</p> <p>Between August 2006 and December 2009, 28 patients with pathological proven nonmetastatic NPC were enrolled. All patients were staged as IIB-IVB. Patients were first treated with 2 to 3 cycles of induction chemotherapy with EP-HDFL (Epirubicin, Cisplatin, 5-FU, and Leucovorin). After induction chemotherapy, weekly based PFL was administered concurrent with HT. Radiation consisted of 70 Gy to the planning target volumes of the primary tumor plus any positive nodal disease using 2 Gy per fraction.</p> <p>Results</p> <p>After completion of induction chemotherapy, the response rates for primary and nodal disease were 96.4% and 80.8%, respectively. With a median follow-up after 33 months (Range, 13-53 months), there have been 2 primary and 1 nodal relapse after completion of radiotherapy. The estimated 3-year progression-free rates for local, regional, locoregional and distant metastasis survival rate were 92.4%, 95.7%, 88.4%, and 78.0%, respectively. The estimated 3-year overall survival was 83.5%. Acute grade 3, 4 toxicities for xerostomia and dermatitis were only 3.6% and 10.7%, respectively.</p> <p>Conclusion</p> <p>HT for locoregionally advanced NPC is feasible and effective in regard to locoregional control with high compliance, even after neoadjuvant chemotherapy. None of out-field or marginal failure noted in the current study confirms the potential benefits of treating NPC patients by image-guided radiation modality. A long-term follow-up study is needed to confirm these preliminary findings.</p

Isokinetic eccentric exercise can induce skeletal muscle injury within the physiologic excursion of muscle-tendon unit: a rabbit model

BACKGROUND AND PURPOSE: Intensive eccentric exercise can cause muscle damage. We simulated an animal model of isokinetic eccentric exercise by repetitively stretching stimulated triceps surae muscle-tendon units to determine if such exercise affects the mechanical properties of the unit within its physiologic excursion. METHODS: Biomechanical parameters of the muscle-tendon unit were monitored during isokinetic eccentric loading in 12 rabbits. In each animal, one limb (control group) was stretched until failure. The other limb (study group) was first subjected to isokinetic and eccentric cyclic loading at the rate of 10.0 cm/min to 112% (group I) or 120% (group II) of its initial length for 1 hour and then stretched to failure. Load-deformation curves and biomechanical parameters were compared between the study and control groups. RESULTS: When the muscle-tendon unit received eccentric cyclic loading to 112%, changes in all biomechanical parameters – except for the slope of the load-deformation curve – were not significant. In contrast, most parameters, including the slope of the load-deformation curve, peak load, deformation at peak load, total energy absorption, and energy absorption before peak load, significantly decreased after isokinetic eccentric cyclic loading to 120%. CONCLUSION: We found a threshold for eccentrically induced injury of the rabbit triceps surae muscle at between 12% and 20% strain, which is within the physiologic excursion of the muscle-tendon units. Our study provided evidence that eccentric exercise may induce changes in the biomechanical properties of skeletal muscles, even within the physiologic range of the excursion of the muscle-tendon unit

Isoflavones prevent bone loss following ovariectomy in young adult rats

Soy protein, a rich source of phytoestrogens, exhibit estrogen-type bioactivity. The purpose of this study was to determine if ingestion of isoflavones before ovariectomy can prevent bone loss following ovariectomy. Twenty-four nulliparous Wistar rats were randomly divided into four groups. In the normal diet groups, a sham operation was performed on Group A, while ovariectomy was performed on Group B. For Groups C and D, all rats were fed with an isoflavone-rich (25 mg/day) diet for one month, then bilateral ovariectomy were performed. In the rats in Group C, a normal diet was begun following the ovariectomy. The rats in Groups D continued to receive the isoflavone-rich diet for two additional months postoperatively. All rats were sacrificed 60 days after surgery. The weight of bone ash of the long bones and whole lumbar spine were determined. A histological study of cancellous bone was done and biochemical indices of skeletal metabolism were performed and analyzed. The markers of bone metabolism exhibited no significant changes. When compared with the sham-operated rats fed a normal diet, the bone mass of ovariectomized rats decreased significantly; pre-ovariectomy ingestion of an isoflavone-rich diet did not prevent bone loss. The bone mass of rats treated with an isoflavone-rich diet for three months was higher than controls two months after ovariectomy

Intensity modulated radiotherapy for elderly bladder cancer patients

<p>Abstract</p> <p>Background</p> <p>To review our experience and evaluate treatment planning using intensity-modulated radiotherapy (IMRT) and helical tomotherapy (HT) for the treatment of elderly patients with bladder cancer.</p> <p>Methods</p> <p>From November 2006 through November 2009, we enrolled 19 elderly patients with histologically confirmed bladder cancer, 9 in the IMRT and 10 in the HT group. The patients received 64.8 Gy to the bladder with or without concurrent chemotherapy. Conventional 4-field "box" pelvic radiation therapy (2DRT) plans were generated for comparison.</p> <p>Results</p> <p>The median patient age was 80 years old (range, 65-90 years old). The median survival was 21 months (5 to 26 months). The actuarial 2-year overall survival (OS) for the IMRT vs. the HT group was 26.3% <it>vs </it>.37.5%, respectively; the corresponding values for disease-free survival were 58.3% <it>vs</it>. 83.3%, respectively; for locoregional progression-free survival (LRPFS), the values were 87.5% <it>vs</it>. 83.3%, respectively; and for metastases-free survival, the values were 66.7% <it>vs</it>. 60.0%, respectively. The 2-year OS rates for T1, 2 <it>vs</it>. T3, 4 were 66.7% <it>vs</it>. 35.4%, respectively (<it>p </it>= 0.046). The 2-year OS rate was poor for those whose RT completion time greater than 8 weeks when compared with the RT completed within 8 wks (37.9% vs. 0%, <it>p </it>= 0.004).</p> <p>Conclusion</p> <p>IMRT and HT provide good LRPFS with tolerable toxicity for elderly patients with invasive bladder cancer. IMRT and HT dosimetry and organ sparing capability were superior to that of 2DRT, and HT provides better sparing ability than IMRT. The T category and the RT completion time influence OS rate.</p