Highly compliant biomimetic scaffolds for small diameter tissue-engineered vascular grafts (TEVGs) produced via melt electrowriting (MEW)

Biofabrication approaches toward the development of tissue-engineered vascular grafts (TEVGs) have been widely investigated. However, successful translation has been limited to large diameter applications, with small diameter grafts frequently failing due to poor mechanical performance, in particular mismatched radial compliance. Herein, melt electrowriting (MEW) of poly(ϵ-caprolactone) has enabled the manufacture of highly porous, biocompatible microfibre scaffolds with physiological anisotropic mechanical properties, as substrates for the biofabrication of small diameter TEVGs. Highly reproducible scaffolds with internal diameter of 4.0 mm were designed with 500 and 250µm pore sizes, demonstrating minimal deviation of less than 4% from the intended architecture, with consistent fibre diameter of 15 ± 2µm across groups. Scaffolds were designed with straight or sinusoidal circumferential microfibre architecture respectively, to investigate the influence of biomimetic fibre straightening on radial compliance. The results demonstrate that scaffolds with wave-like circumferential microfibre laydown patterns mimicking the architectural arrangement of collagen fibres in arteries, exhibit physiological compliance (12.9 ± 0.6% per 100 mmHg), while equivalent control geometries with straight fibres exhibit significantly reduced compliance (5.5 ± 0.1% per 100 mmHg). Further mechanical characterisation revealed the sinusoidal scaffolds designed with 250µm pores exhibited physiologically relevant burst pressures of 1078 ± 236 mmHg, compared to 631 ± 105 mmHg for corresponding 500µm controls. Similar trends were observed for strength and failure, indicating enhanced mechanical performance of scaffolds with reduced pore spacing. Preliminaryin vitroculture of human mesenchymal stem cells validated the MEW scaffolds as suitable substrates for cellular growth and proliferation, with high cell viability (>90%) and coverage (>85%), with subsequent seeding of vascular endothelial cells indicating successful attachment and preliminary endothelialisation of tissue-cultured constructs. These findings support further investigation into long-term tissue culture methodologies for enhanced production of vascular extracellular matrix components, toward the development of the next generation of small diameter TEVGs.

Quality assurance in 3D-printing: A dimensional accuracy study of patient-specific 3D-printed vascular anatomical models

3D printing enables the rapid manufacture of patient-specific anatomical models that substantially improve patient consultation and offer unprecedented opportunities for surgical planning and training. However, the multistep preparation process may inadvertently lead to inaccurate anatomical representations which may impact clinical decision making detrimentally. Here, we investigated the dimensional accuracy of patient-specific vascular anatomical models manufactured via digital anatomical segmentation and Fused-Deposition Modelling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLS), and PolyJet 3D printing, respectively. All printing modalities reliably produced hand-held patient-specific models of high quality. Quantitative assessment revealed an overall dimensional error of 0.20 ± 3.23%, 0.53 ± 3.16%, -0.11 ± 2.81% and -0.72 ± 2.72% for FDM, SLA, PolyJet and SLS printed models, respectively, compared to unmodified Computed Tomography Angiograms (CTAs) data. Comparison of digital 3D models to CTA data revealed an average relative dimensional error of -0.83 ± 2.13% resulting from digital anatomical segmentation and processing. Therefore, dimensional error resulting from the print modality alone were 0.76 ± 2.88%, + 0.90 ± 2.26%, + 1.62 ± 2.20% and +0.88 ± 1.97%, for FDM, SLA, PolyJet and SLS printed models, respectively. Impact on absolute measurements of feature size were minimal and assessment of relative error showed a propensity for models to be marginally underestimated. This study revealed a high level of dimensional accuracy of 3D-printed patient-specific vascular anatomical models, suggesting they meet the requirements to be used as medical devices for clinical applications.

Current intraoperative storage and handling practices of autologous bypass conduit: A survey of the royal australasian college of surgeons

During bypass surgery for peripheral arterial occlusive disease and ischaemic heart disease, autologous graft conduit including great saphenous veins and radial arteries are frequently stored in solution. Endothelial damage adversely affects the performance and patency of autologous bypass grafts, and intraoperative graft storage solutions have been shown to influence this process. The distribution of storage solutions currently used amongst Cardiothoracic and Vascular Surgeons from Australia and New Zealand is not well defined in the literature. The aim of this study was to determine current practices regarding autologous graft storage and handling amongst this cohort of surgeons, and discuss their potential relevance in the context of early graft failure. From this survey, the most frequently used storage solutions were heparinized saline for great saphenous veins, and pH-buffered solutions for radial arteries. Duration of storage was 30–45 min for almost half of respondents, although responses to this question were limited. Further research is required to investigate whether ischaemic endothelial injury generates a prothrombotic state, whether different storage media can alter this state, and whether this is directly associated with clinical outcomes of interest such as early graft failure.

Biofabrication of small diameter tissue-engineered vascular grafts

Current clinical treatment strategies for the bypassing of small diameter (<6 mm) blood vessels in the management of cardiovascular disease frequently fail due to a lack of suitable autologous grafts, as well as infection, thrombosis, and intimal hyperplasia associated with synthetic grafts. The rapid advancement of 3D printing and regenerative medicine technologies enabling the manufacture of biological, tissue-engineered vascular grafts (TEVGs) with the ability to integrate, remodel, and repair in vivo, promises a paradigm shift in cardiovascular disease management. This review comprehensively covers current state-of-the-art biofabrication technologies for the development of biomimetic TEVGs. Various scaffold based additive manufacturing methods used in vascular tissue engineering, including 3D printing, bioprinting, electrospinning and melt electrowriting, are discussed and assessed against the biomechanical and functional requirements of human vasculature, while the efficacy of decellularization protocols currently applied to engineered and native vessels are evaluated. Further, we provide interdisciplinary insight into the outlook of regenerative medicine for the development of vascular grafts, exploring key considerations and perspectives for the successful clinical integration of evolving technologies. It is expected that continued advancements in microscale additive manufacturing, biofabrication, tissue engineering and decellularization will culminate in the development of clinically viable, off-the-shelf TEVGs for small diameter applications in the near future. STATEMENT OF SIGNIFICANCE: Current clinical strategies for the management of cardiovascular disease using small diameter vessel bypassing procedures are inadequate, with up to 75% of synthetic grafts failing within 3 years of implantation. It is this critically important clinical problem that researchers in the field of vascular tissue engineering and regenerative medicine aim to alleviate using biofabrication methods combining additive manufacturing, biomaterials science and advanced cellular biology. While many approaches facilitate the development of bioengineered constructs which mimic the structure and function of native blood vessels, several challenges must still be overcome for clinical translation of the next generation of tissue-engineered vascular grafts.

Impact of g force and timing on the characteristics of platelet-rich fibrin matrices

Recently, new centrifugation protocols for the preparation of platelet-rich fibrin (PRF) have been introduced in an attempt to further improve the beneficial impact of these 2nd generation platelet concentrate membranes. This in-vitro study aimed to compare the biological and physical characteristics of three types of PRF membranes using two different centrifuges with adapted relative centrifugal forces (RCF): leucocyte- and platelet-rich fibrin, advanced platelet-rich fibrin, and advanced platelet-rich fibrin⁺. Release of growth factors, macroscopic dimensions, cellular content and mechanical properties of the respective membranes, prepared from blood of the same individual were explored. Furthermore, the impact of timing (blood draw-centrifugation and centrifugation-membrane preparation) was assessed morphologically as well as by electron microscopy scanning. No statistically significant differences amongst the three PRF modifications could be observed, neither in their release of growth factors or the cellular content, nor in clot/membrane dimensions. The difference between both centrifuges were negligible when the same g-force was used. A lower g-force, however, reduced membrane tensile strength. Timing in the preparation process had a significant impact. Adaptation of RCF only had a minimal impact on the final characteristics of PRF membranes.

Cross-cultural validation of the Portuguese from Portugal version of the test for respiratory and asthma control in kids questionnaire

Summary

Objective. The Test for Respiratory and Asthma Control in Kids (TRACK) is a tool to assess asthma control in preschool children. This study aims to validate the Portuguese from Portugal version of the TRACK questionnaire. Methods. A prospective cohort study was carried out to assess their psychometric characteristics. Caregivers of 141 children under age 5 with asthma symptoms were enrolled. Results. Internal reliability was close to 0.70 (Cronbach's α). The test-retest reliability was 0.87. TRACK scores were different between well, partially, and non-controlled asthma groups (p less than 0.001). Patients rated as having better control showed an increase in TRACK scores. Conclusions. The Portuguese version of the TRACK questionnaire is accurate and reliable for monitoring asthma control. Its use may help to overcome challenges with the management of this age group.

Short and extended provocation tests have similar negative predictive value in non-immediate hypersensitivity to beta-lactams in children

INTRODUCTION AND OBJECTIVES

Drug provocation tests (DPTs) are the gold-standard method to diagnose non-immediate hypersensitivity reactions (NIHSR) to beta-lactam antibiotics (BL) in children. Our aim was to compare the negative predictive value (NPV) of one-day (short) DPT versus 3-7 days (extended) DPT for the diagnosis of NIHSR to BL in paediatric age. A secondary aim was to compare confidence on drug re-exposure after short and extended negative DPTs.

METHODS

The occurrence of HSR on drug re-exposure and drug refusal after negative diagnostic DPTs were evaluated in children/adolescents with a history of NIHSR to BL using a questionnaire performed six months to ten years after DPT. Patients were divided into two groups according to the protocol performed: short DPT vs. extended DPT.

RESULTS

We enrolled 212 children and adolescents (86 females, 126 males, mean age at DPT 5.52 years, p25=3 years, p75=7.25 years): 69 tested with short DPT, and 143 with extended DPT. The NPV of both types of DPT together was 95.2%. The NPV of short DPT was 97.5% and the NPV of extended DPT was 93.8% (p=0.419). After negative DPT, beta-lactams were refused by carers in 14.75% of the children requiring subsequent treatment, 6.98% in the short DPT group and 18.99% in the extended DPT group (p=0.074).

CONCLUSIONS

In our paediatric sample, prolonging drug administration did not increase the NPV of diagnostic DPT for NIHSR to BL or reduce drug refusal. Altogether, the data here reported suggest that, however intuitive, prolonging DPT is not beneficial in the parameters analysed.

Effect of carrier tunneling on the structure of Si nanowires fabricated by metal assisted etching

The metal assisted etching mechanism for Si nanowire fabrication, triggered by doping type and level and coupled with choice of metal catalyst, is still very poorly understood. We explain the different etching rates and porosities of wires we observe based on extensive experimental data, using a new empirical model we have developed. We establish as a key parameter, the tunneling through the space charge region (SCR) which is the result of the reduction of the SCR width by level of the Si wafer doping in the presence of the opposite biases of the p- and n-type wafers. This improved understanding should permit the fabrication of high quality wires with predesigned structural characteristics, which hitherto has not been possible.

Medical Graduates, Tertiary Hospitals, and Burnout: A Longitudinal Cohort Study

BACKGROUND

Burnout among junior doctors can affect patient care. We conducted a longitudinal cohort study designed to explore the incidence of burnout in medical interns and to examine the changes in burnout during the course of the intern year.

METHODS

Interns were recruited at two tertiary hospitals in Brisbane, Australia (n=180). Participants completed surveys at four time points during their internship year. All interns (100%) completed the baseline survey during their orientation. Response rates were 85%, 88%, and 79%, respectively, at 5-week, 6-month, and 12-month follow-up.

RESULTS

Interns reported high levels of personal and work-related burnout throughout the year that peaked at 6 months with mean scores of 42.53 and 41.81, respectively. Increases of 5.1 points (confidence interval [CI] 2.5,7.7; P=0.0001) and 3.5 points (CI 1.3,5.6; P=0.0015) were seen at 6 months for personal and work-related burnout, respectively. The mean score for patient-related burnout at 12 months was 25.57, and this number had increased significantly by 5.8 points (CI 3.2,8.5; P<0.0001) throughout the year. Correlation with demographic variables (age, sex) were found. The total incidence of burnout was 55.9%.

CONCLUSION

Our study showed that burnout is a common problem among interns. The high incidence of burnout demonstrates the need for appropriate strategies to prevent adverse effects on doctors' quality of life and on the quality of care patients receive.

Diffusion induced effects on geometry of Ge nanowires

We report diffusion induced germanium nanowire growth and its dependence on the Ge evaporation flux. The wires show a growth rate (dL/dt) in agreement with the previously reported models, but detection of anomalies in the grown wires may indicate the prevalence of the direct Ge impinging effect on large diameter wires. Additionally, we demonstrate that change in deposition flux could directly affect the diffusion length of the Ge adatoms on the wire sidewalls. This in turn modifies the geometry of the grown wires by introducing a lateral growth starting from the base of the wire. A detailed understanding of the deposition flux effect on the growth and geometry of wires will result in improved knowledge of physical properties of wires.

Ischemic cardiomyopathy: midterm survival and its predictors

BACKGROUND

the aim of the study was to analyze all-cause mortality and predictors of long-term survival after myocardial revascularization for ischemic cardiomyopathy.

METHOD

data of 101 patients (mean age, 63.86 years; age range, 30-85 years; 92% male), operated on with stable coronary artery disease and left ventricular ejection fraction <30% between April 2000 and June 2010, were analyzed.

RESULTS

operative mortality was 1.9% (2/101). There was a significant improvement in left ventricular ejection fraction from 25.99% ± 3.8% preoperatively to 34% ± 12% postoperatively (p <0.0001). The mean duration of follow-up was 56.3 ± 33 months, and it was 97% complete (98/101). There were 18/96 (18.75%) late deaths. Overall actuarial survival at 1, 3, 5, and 10 years was 96%, 89%, 83% and 75%, respectively. Univariate predictors of late death were preoperative arrhythmia, cerebrovascular disease, peripheral vascular disease, and logistic EuroSCORE. Multivariate predictors of late death were cerebrovascular disease and preoperative arrhythmia.

CONCLUSION

our study suggests that myocardial revascularization for ischemic cardiomyopathy improves left ventricular ejection fraction and is associated with favorable long-term survival. Patients with cerebrovascular disease and preoperative arrhythmias had poorer outcomes.

A randomized clinical trial of adjuvant chemotherapy with doxorubicin, ifosfamide, and cisplatin followed by radiotherapy versus radiotherapy alone in patients with localized uterine sarcomas (SARCGYN study). A study of the French Sarcoma Group

BACKGROUND

There is no proven benefit of adjuvant treatment of uterine sarcoma (US). SARCGYN phase III study compared adjuvant polychemotherapy followed by pelvic radiotherapy (RT) (arm A) versus RT alone (arm B) conducted to detect an increase ≥ 20% of 3-year PFS.

METHODS

Patients with FIGO stage ≤ III US, physiological age ≤ 65 years; chemotherapy: four cycles of doxorubicin 50 mg/m&sup2; d1, ifosfamide 3 g/m&sup2;/day d1-2, cisplatin 75 mg/m&sup2; d3, (API) + G-CSF q 3 weeks. Study was stopped because of lack of recruitment.

RESULTS

Eighty-one patients were included: 39 in arm A and 42 in arm B; 52 stage I, 16 stage II, 13 stage III; 53 leiomyosarcomas, 9 undifferenciated sarcomas, 19 carcinosarcomas. Gr 3-4 toxicity during API (/37 patients): thrombopenia (76%), febrile neutropenia (22%) with two toxic deaths; renal gr 3 (1 patient). After a median follow-up of 4.3 years, 41/81 patients recurred, 15 in arm A, 26 in arm B. The 3 years DFS is 55% in arm A, 41% in arm B (P = 0.048). The 3-year overall survival (OS) is 81% in arm A and 69% in arm B (P = 0.41).

CONCLUSION

API adjuvant CT statistically increases the 3 year-DFS of patients with US.

Return to work after coronary artery bypass in patients aged under 50 years

Background: This study was designed to identify factors associated with return to work and quality of life in patients undergoing primary coronary artery bypass at age <50 years.

Methods: 172 patients <50-years old underwent primary coronary artery bypass between January 2000 and December 2006. Predictors of return to work were analysed from variables in a prospectively collected database and on follow-up by the SF-36 questionnaire in 129 (75%) patients.

Results: 136 (79%) patients were working prior to surgery. The educational level was: primary 14.5%, secondary 47%, trade 22%, tertiary 13%, and postgraduate 3%. Type of occupation was blue collar 51%, white collar 41%, pensioner 27%, and unspecfied 8%. The mean follow-up was 86.4 ± 23.4 months. One hundred and twenty-six (69%) patients attended cardiac rehabilitation. Forty (23%) patients experienced recurrence of symptoms; 11 (6%) required reintervention. One hundred and twenty-seven (93%) patients returned to work postoperatively. Univariate predictors of return to work were male sex, blue-collar work, and working prior to surgery. Independent predictors of return to work were working prior to surgery and blue-collar work. Patients who returned to work had significantly higher scores in all 8 domains on the SF36-Questionnaire compared to those who did not return to work.

Conclusions: Preoperative employment and blue collar occupation were associated with a higher rate of return to work after coronary artery bypass in patients of working age. Patients who returned to work had significantly better measured quality of life than those who did not.

Treatment outcomes for ischemic heart disease in dialysis-dependent patients

Objective: To compare outcomes following intervention in dialysis-dependent patients with ischemic heart disease.

Background: Ischemic heart disease is a major cause of mortality in dialysis-dependent patients. Coronary revascularization and medical modification to relieve symptoms is common, however, there is no clear consensus regarding optimal treatment.

Method: Ninety dialysis-dependent patients with ischemic heart disease were prospectively assessed between 1999 and 2009, with a median follow-up of 24 months; 35 received best medical management, 31 had percutaneous coronary angioplasty and stenting, and 24 had coronary artery bypass grafting.

Results: By multivariate analysis, higher body mass index and lower logistic EuroSCORE were associated with having either procedure compared to medical management. Using the time-to-event Kaplan-Meier method, both stenting and coronary bypass grafting had lower risks of an adverse outcome than best medical management. Mortality was 40/90 (44.4%). Multivariate predictors of mortality were smoking and a logistic EuroSCORE of 7–14. Overall mortality was not different among groups, however, the stent group had a survival advantage at 30-days and 1-year compared to the coronary bypass group. Composite median survival was 52.3 months. SF-36 questionnaires showed quality of life after bypass grafting was significantly better than medical management or stenting. Physical function was better after bypass grafting compared to medical management or stenting.

Conclusion: Dialysis-dependent patients with ischemic heart disease have poor survival despite intervention. Coronary artery bypass achieves fewer composite adverse events and better quality of life than stenting. Symptoms and coronary anatomy should dictate treatment decisions in dialysis-dependent patients.