A biomimetic tissue engineering scaffold for repairing the injured spinal cord: proof of concept

Sem resumo disponível.publishe

Electrospinning of bioactive polycaprolactone-gelatin nanofibres with increased pore size for cartilage tissue engineering applications

Polycaprolactone (PCL) electrospun scaffolds have been widely investigated for cartilage repair application. However, their hydrophobicity and small pore size has been known to prevent cell attachment, proliferation and migration. Here, PCL was blended with gelatin (GEL) combining the favorable biological properties of GEL with the good mechanical performance of the former. Also, polyethylene glycol (PEG) particles were introduced during the electrospinning of the polymers blend by simultaneous electrospraying. These particles were subsequently removed resulting in fibrous scaffolds with enlarged pore size. PCL, GEL and PEG scaffolds formulations were developed and extensively structural and biologically characterized. GEL incorporation on the PCL scaffolds led to a considerably improved cell attachment and proliferation. A substantial pore size and interconnectivity increase was obtained, allowing cell infiltration through the porogenic scaffolds. All together these results suggest that this combined approach may provide a potentially clinically viable strategy for cartilage regeneration.publishe

Desenvolvimento de scaffolds anisotrópicos de PCL e gelatina para a regeneração de cartilagem

Um dos maiores desafios da engenharia de tecidos de cartilagem é a dificuldade de imitar o ambiente bioquímico e biomecânico da cartilagem nativa. Até à data, várias estratégias de engenharia de tecidos de cartilagem conseguiram desenvolver cartilagem artificial com propriedades bioquímicas semelhantes às do tecido nativo [1]. No entanto as propriedades mecânicas da cartilagem in-vitro permanecem inferiores às da nativa. Uma das principais limitações da cartilagem artificial é que esta não exibe as variações zonais da cartilagem nativa [2-3]. A organização das fibras de colagénio em forma de arcada ao longo da profundidade da cartilagem nativa é importante e deve ser replicada na cartilagem artificial para tornar se mecanicamente funcional [2-3]. As condições de cultura que têm impacto sobre a síntese de colagénio e sua organização fibrilar incluem os scaffolds e a estimulação mecânica. Alguns investigadores sugerem o uso de scaffolds fibrosos anisotrópicos, a fim de proporcionar um arquétipo para organizar a nova matriz extracelular depositada. A utilização da técnica de eletrofiação para o desenvolvimento de scaffolds fibrosos para a engenharia de tecidos da cartilagem já foi reportada, visto que as matrizes de nanofibras poliméricas alinhadas produzidas mimetizam a topografia da matriz extracelular da cartilagem nativa e funcionam como suporte para organizar a deposição de nova matriz extracelular produzida por células nelas semeadas [4]. Alguns investigadores sugerem que a aplicação de estímulos mecânicos variáveis em profundidade que estimulem de forma diferenciada a síntese de matriz extracelular e logo uma diferente orientação fibrilar em profundidade [5]. A policaprolactona (PCL) é um poliéster sintético, biocompatível e biodegradável que apresenta elevada resistência mecânica e é facilmente processável. As matrizes de nanofibras de PCL mimetizam topograficamente a matriz extracelular no tecido cartilagíneo. No entanto, a hidrofobicidade inerente deste material pode prevenir a adesão, migração, proliferação e diferenciação celular. A combinação de PCL com polímeros naturais tem sido utilizada para obter propriedades mecânicas e biológicas complementares, uma vez que os polímeros naturais possuem uma superfície hidrofílica e recetores reconhecíveis pelas células. A gelatina é um polímero natural derivado do colagénio, que constitui maioritariamente a matriz extracelular da cartilagem [6]. Assim sendo, neste trabalho foi explorada a combinação de estimulação mecânica com a utilização de scaffolds fibrosos anisotrópicos de PCL e gelatina produzidos por electrofiação, envolvidos numa estrutura porosa de óxido de grafeno (GO) e colagénio, para estimular a proliferação celular e produção de matriz extracelular cartilagínea. Várias arquiteturas foram desenvolvidas. As propriedades topográficas, mecânicas e a capacidade de absorção de água dos scaffolds foram analisadas e, posteriormente a biocompatibilidade dos mesmos foi investigada utilizando células progenitoras da cartilagem articular. A estimulação mecânica das células semeadas nos scaffolds por compressão cíclica foi efetuada com recurso um biorreator desenvolvido e patenteado pela equipa [7]. Os resultados obtidos demonstraram que estas estruturas permitem não só a adesão, mas também a proliferação celular. A estimulação mecânica aplicada gerou uma resposta positiva das células, através da produção de elementos da matriz extracelular da cartilagem.publishe

Fabrication of a 3D combinatorial fibrous-porous scaffold for neural tissue engineering applications

The ability of tissue engineered scaffolds to modulate the response of neural stem cells (e.g. adhesion, proliferation and differentiation) is boosting the unlocking of advanced therapeutic strategies capable of attenuating the effects of traumatic pathologies like spinal cord injury [1]. From the wide range of reported scaffolding concepts, it has been consistently demonstrated that nanofibrous networks and graphene-based porous systems are proficient for guiding neurite outgrowth and inducing specific differentiation patterns, respectively [2].publishe

C+L band gain equalization for extended reach WDM-ring PON using hybrid Raman/in line EDFA amplification

“Copyright © [2010] IEEE. Reprinted from ICTON 2010. ISBN 978-1-4244-7798-2. This material is posted here with permission of the IEEE. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.”In this paper, we investigate by simulation the feasibility of gain enlargement and equalization on extended reach WDM-ring PON by means of hybrid Raman/EDFA amplification. The system under analysis is composed by a bidirectional pump at 1480 nm and 16 channels (8 C band + 8 L band). The simulation describes an 80 km WDM ring with 8 nodes in which 2 channels are added/dropped. The results demonstrate gain equalization with a ripple of 2.54 dB over a bandwidth of 50 nm by using a 1480 nm bidirectional pump with 1 W and spans of EDF with a total length of 22 m

Mimicking nature: fabrication of 3D anisotropic electrospun polycaprolactone scaffolds for cartilage tissue engineering applications

There is a growing need to develop strategies capable of engineering the anisotropic cartilaginous fibrous network in vitro and consequently overcome the anatomical and functional restrictions of the standard medical procedures used for cartilage regeneration. In this work, we suggest a fabrication procedure to build 3D anisotropic multi-layered fibrous scaffolds. Polycaprolactone (PCL) was used as bulk material for the different electrospun layers (horizontally, randomly and vertically aligned) that were assembled and then structurally maintained by a biocompatible graphene-oxide-collagen (GO-collagen) microporous network. To validate the resourcefulness of the technique, four PCL-GO-collagen scaffolds with different anisotropic properties were produced and characterized by analysing their depth dependent morphological and mechanical properties.publishe

Microfabrication of a biomimetic arcade-like electrospun scaffold for cartilage tissue engineering applications

Designing and fabricating hierarchical geometries for tissue engineering (TE) applications is the major challenge and also the biggest opportunity of regenerative medicine in recent years, being the in vitro recreation of the arcade-like cartilaginous tissue one of the most critical examples due to the current inefficient standard medical procedures and the lack of fabrication techniques capable of building scaffolds with the required architecture in a cost and time effective way. Taking this into account, we suggest a feasible and accurate methodology that uses a sequential adaptation of an electrospinning-electrospraying set up to construct a system comprising both fibres and sacrificial microparticles. Polycaprolactone (PCL) and polyethylene glycol were respectively used as bulk and sacrificial biomaterials, leading to a bi-layered PCL scaffold which presented not only a depth-dependent fibre orientation similar to natural cartilage, but also mechanical features and porosity compatible with cartilage TE approaches. In fact, cell viability studies confirmed the biocompatibility of the scaffold and its ability to guarantee suitable cell adhesion, proliferation and migration throughout the 3D anisotropic fibrous network. Additionally, likewise the natural anisotropic cartilage, the PCL scaffold was capable of inducing oriented cell-material interactions since the morphology, alignment and density of the chondrocytes changed relatively to the specific topographic cues of each electrospun layer.publishe

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Graphene: The Missing Piece for Cancer Diagnosis?

This paper reviews recent advances in graphene-based biosensors development in order to obtain smaller and more portable devices with better performance for earlier cancer detection. In fact, the potential of Graphene for sensitive detection and chemical/biological free-label applications results from its exceptional physicochemical properties such as high electrical and thermal conductivity, aspect-ratio, optical transparency and remarkable mechanical and chemical stability. Herein we start by providing a general overview of the types of graphene and its derivatives, briefly describing the synthesis procedure and main properties. It follows the reference to different routes to engineer the graphene surface for sensing applications with organic biomolecules and nanoparticles for the development of advanced biosensing platforms able to detect/quantify the characteristic cancer biomolecules in biological fluids or overexpressed on cancerous cells surface with elevated sensitivity, selectivity and stability. We then describe the application of graphene in optical imaging methods such as photoluminescence and Raman imaging, electrochemical sensors for enzymatic biosensing, DNA sensing, and immunosensing. The bioquantification of cancer biomarkers and cells is finally discussed, particularly electrochemical methods such as voltammetry and amperometry which are generally adopted transducing techniques for the development of graphene based sensors for biosensing due to their simplicity, high sensitivity and low-cost. To close, we discuss the major challenges that graphene based biosensors must overcome in order to reach the necessary standards for the early detection of cancer biomarkers by providing reliable information about the patient disease stage

Boosting in vitro cartilage tissue engineering through the fabrication of polycaprolactone-gelatin 3D scaffolds with specific depth-dependent fiber alignments and mechanical stimulation

Due to the limited self-healing ability of natural cartilage, several tissue engineering strategies have been explored to develop functional replacements. Still, most of these approaches do not attempt to recreate in vitro the anisotropic organization of its extracellular matrix, which is essential for a suitable load-bearing function. In this work, different depth-dependent alignments of polycaprolactone-gelatin electrospun fibers were assembled into three-dimensional scaffold architectures to assess variations on chondrocyte response under static, unconfined compressed and perfused culture conditions. The in vitro results confirmed that not only the 3D scaffolds specific depth-dependent fiber alignments potentiated chondrocyte proliferation and migration towards the fibrous systems, but also the mechanical stimulation protocols applied were able to enhance significantly cell metabolic activity and extracellular matrix deposition, respectively.publishe