Kefiran-based Scaffolds For Biomedical Applications

Kefiran is an exopolysaccharide produced by microorganisms present in kefir grains, with several health promoting properties. A optimized protocol was developed for the separation of kefiran from kefir grains, allowing to reach a yield 4÷5 % without using toxic or expensive chemicals. The capability of kefiran to produce scaffold via Thermally Induced Phase Separation (TIPS) technique was investigated and porous scaffolds structure was obtained. Separated kefiran and scaffolds were analyzed via DSC and different thermal properties between purified kefiran and scaffold were revealed. XRD analysis revealed different structure between kefiran and scaffolds. The porous scaffold structure can be…

Human nasoseptal chondrocytes maintain their differentiated phenotype on PLLA scaffolds produced by thermally induced phase separation and supplemented with bioactive glass 1393

Damage of hyaline cartilage such as nasoseptal cartilage requires proper reconstruction, which remains challenging due to its low intrinsic repair capacity. Implantation of autologous chondrocytes in combination with a biomimetic biomaterial represents a promising strategy to support cartilage repair. Despite so far mostly tested for bone tissue engineering, bioactive glass (BG) could exert stimulatory effects on chondrogenesis. The aim of this work was to produce and characterize composite porous poly(L-lactide) (PLLA)/1393BG scaffolds via thermally induced phase separation (TIPS) technique and assess their effects on chondrogenesis of nasoseptal chondrocytes. The PLLA scaffolds without or…

Evidence of Mechanisms Occurring in Thermally Induced Phase Separation of Polymeric Systems

Thermally induced phase separation is a fabrication technique for porous polymeric structures. By means of easy-to-tune processing parameters, such as system composition and demixing temperature, a vast latitude of average pore dimensions, pore size distributions, and morphologies can be obtained. The relation between demixing temperature and morphology was demonstrated via cloud point curve measurement and foams fabrication with controlled thermal protocols, for the model system poly-l-lactide–dioxane–water. The morphologies obtained at a temperature lower than cloud point showed a closed-pore architecture, suggesting a “nucleation-and-growth” separation mechanism, which produced larger po…

PLLA Scaffold with Gradient pore size in microphysiological tissue system bioreactor for Osteochondral regeneration

Cartilage and bone tissues in the joints are intimately linked and form the osteochondral unit. A better understanding of both disease and regenerative processes of bone and cartilage requires the study of both tissues together, as part of the osteochondral unit to account for their mutual interactions. However, the production of scaffolds for osteochondral tissue regeneration is a challenging task, since scaffolds must mimic the differents morphologies of cartilage and bone. Thermally Induced Phase Separation (TIPS) is one of the most adaptable techniques to produce porous scaffold for Tissue Engineering applications. A wide range of morphologies in terms of both pore size and distribution…

A Poly-L-Lactide scaffold with continuous gradient pore size for osteochondral regeneration validated in a microphysiological tissue system bioreactor

A microphysiological tissue system (MPS) bioreactor has been developed to replicate in vitro the in vivo OC physiological conditions. The MPS allows separate control of the chondral and osseous environment while permitting communication between chondrocytes and osteoblasts across the OC junction, similar to the conditions of OC tissue in vivo. We have used here our MPS system to validate the TIPS -generated pore-gradient PLLA scaffold.

Computational modeling and experimental characterization of fluid dynamics in micro-CT scanned scaffolds within a multiple-sample airlift perfusion bioreactor

The perfusion of flow during cell culture induces cell proliferation and enhances cellular activity. Perfusion bioreactors offer a controlled dynamic environment for reliable in vitro applications in the tissue engineering field. In this work, to evaluate the effects of the operating parameters of a custom-made bioreactor, numerical simulations were performed to solve the fluid velocity profile inside the bioreactor containing multi-grid support that allows allocating of multiple seeded scaffolds at the same time. The perfusion system exhibited a uniform distribution of liquid velocities within the regions, suitable for cell growth on seeded scaffolds. The effects of the porous microstructu…

Preparation of polymeric foams with a pore size gradient via Thermally Induced Phase Separation (TIPS)

Abstract Foams with a pore size gradient are promising materials for tissue engineering applications where a complex architecture involving morphological variations in space must be mimicked, e.g. in bone tissue repair. In this paper, a technique to obtain a porous scaffold with a pore size gradient is presented. The preparation procedure is based on Thermally Induced Phase Separation (TIPS), by imposing a different thermal history on the two sides of a polymeric solution. In this way, a gradient in thermal history is produced, which will generate a pore size monotonously varying along scaffold thickness. By controlling some parameters easy to manipulate, such as demixing temperature and/or…

A Continuous Pore Size Gradient PLLA Scaffold For Osteochondral Regeneration

Osteochondral (OC) scaffold-based regenerative approaches in the joint are challenging since the scaffold must provide mechanical strength while also mimicking the local cartilage and bone microenvironments. Thermally Induced Phase Separation (TIPS) can produce scaffolds with a wide range of pore size morphologies/distributions. Here, we produced by TIPS a poly-L-lactide (PLL A) scaffold with a continuous pore size gradient along the sample thickness, from ~70μm diameter on one side to ~200 μm diameter on the opposite surface.

Anisotropic scaffold for Bone Tissue Engineering

Calcium phosphate/polyvinyl acetate coatings on SS304 via galvanic co-deposition for orthopedic implant applications

Abstract In this work, the galvanic deposition method is used to deposit coatings of brushite/hydroxyapatite/polyvinyl acetate on 304 stainless steel. Coatings are obtained at different temperatures and with different sacrificial anodes, consisting of a mixture of brushite and hydroxyapatite. Samples are aged in a simulated body fluid (SBF), where a complete conversion of brushite into hydroxyapatite with a simultaneous change in morphology and wettability occurred. The corrosion tests show that, compared with bare 304, the coating shifts Ecorr to anodic values and reduces icorr Ecorr, and icorr has different values at different aging times due to chemical interactions at the solid/liquid i…

An Innovative Method to Produce Scaffolds with a Pore Size Gradient for Tissue Engineering Applications

Thermally Induced Phase Separation (TIPS) is a technique for the production of porous scaffold for Tissue Engineering applications. A wide range of microporous morphologies, in terms of pore size and distribution, can be obtained by tuning TIPS processing parameters, especially thermal history. The production of scaffolds for bone tissue regeneration is a challenging target: as a matter of fact, scaffolds must mimic the bone morphology, thus requiring a gradient of pore dimension and morphology along one dimension. To attain this goal, an experimental apparatus capable to impose different thermal histories on the two sides of a sample was designed, set up and tested. The sample (35x35 mm su…

Chitosan-Coating Deposition via Galvanic Coupling

A galvanic method to deposit chitosan coatings on stainless steel substrate is reported. Deposition of suitable coatings is desired to improve biocompatibility and corrosion resistance of metallic medical devices to be implanted in human body. In the present work, a thin hydrogel layer of chitosan was deposited on 304SS by a galvanic displacement reaction, which is advantageous first as it does not require external power supply. 304SS was immersed into an aqueous solution of chitosan/lactic acid and electrochemically coupled with magnesium acting as a sacrificial anode. SEM images showed the formation of a uniform layer of chitosan with a thickness controlled by deposition time. Corrosion t…

Deposition and characterization of coatings of Hydroxyapatite, Chitosan, and Hydroxyapatite-Chitosan on 316L for biomedical devices

In the last decades, the scientific community has turned on great interest towards the development of increasingly performing biomedical systems. In the orthopedic field, biomedical devices are made up by metallic materials (mainly steel and titanium alloys), which have low/medium resistance to corrosion and a low osteointegration capacity when implanted inside the human body. This can lead to infection or inflammation that can damage the tissues surrounding the implant. The use of biocompatible coatings allows cancelling or mitigating these phenomena. The coating interposing between aggressive environment and biomedical device inhibits corrosion so limiting the metal ions release into the …

Scaffolds biodegradabili in PLLA con gradiente di porosità per rigenerazione ossea

A Versatile Technique to Produce Porous Polymeric Scaffolds: The Thermally Induced Phase Separation (TIPS) Method

Among the various scaffold fabrication techniques, thermally induced phase separation (TIPS) is one of the most versatile methods to produce porous polymeric scaffold and it has been largely used for its capability to produce highly porous and interconnected scaffolds. The scaffold architecture can be closely controlled by varying the process parameters, including polymer type and concentration, solvent/non-solvent ratio and thermal history. TIPS technique has been widely employed, also, to produce scaffolds with a hierarchical pore structure and composite polymeric matrix/inorganic filler foams.

An Innovative Method to Produce Scaffolds with a Pore Size Gradient for Tissue Engineering

Distributed and Lumped Parameter Models for the Characterization of High Throughput Bioreactors

Next generation bioreactors are being developed to generate multiple human cell-based tissue analogs within the same fluidic system, to better recapitulate the complexity and interconnection of human physiology. The effective development of these devices requires a solid understanding of their interconnected fluidics, to predict the transport of nutrients and waste through the constructs and improve the design accordingly. In this work, we focus on a specific model of bioreactor, with multiple input/outputs, aimed at gen- erating osteochondral constructs, i.e., a biphasic construct in which one side is cartilagi- nous in nature, while the other is osseous. We next develop a general computat…

PLLA scaffolds produced by thermally induced phase separation (TIPS) allow human chondrocyte growth and extracellular matrix formation dependent on pore size

Damage of hyaline cartilage species such as nasoseptal or joint cartilage requires proper reconstruction, which remains challenging due to the low intrinsic repair capacity of this tissue. Implantation of autologous chondrocytes in combination with a biomimetic biomaterial represents a promising strategy to support cartilage repair. The aim of this work was to assess the viability, attachment, morphology, extracellular matrix (ECM) production of human articular and nasoseptal chondrocytes cultured in vitro in porous poly(L-lactic) (PLLA) scaffolds of two selected pore sizes (100 and 200 μm). The PLLA scaffolds with 100 and 200 μm pore sizes were prepared via ternary thermally induced ph…

Ultra-fast-prototyping of PMMA structures for micro-engineering applications: Choosing the right material

Machining of poly(methyl methacrylate) (PMMA) by laser has been extensively studied in engineering research for several applications including microfluidic manufacturing and rapid prototyping. However, very few investigations have taken into consideration the wide range of physico-chemical characteristics of commercially available PMMA that can often affect the quality of the laser-machined structures. These characteristics are often ignored, with many manufacturing publications focusing on a single source of PMMA. To understand the different bonding strengths and laser-cut qualities in the context of our ultra-fast prototyping technique, four types of PMMA have been examined. Molecular wei…

Preparation, characterization and in vitro test of composites poly-lactic acid/hydroxyapatite scaffolds for bone tissue engineering.

Abstract In this work, the possibility to produce composite Poly-L-lactic acid (PLLA)/Hydroxyapatite (HA) porous scaffolds via Thermally Induced Phase Separation (TIPS) for bone tissue engineering applications was investigated. Several PLLA/HA wt/wt ratios (95/5, 90/10, 70/30, 50/50, 34/66) were tested and the as-obtained scaffolds were characterized via Scanning Electron Microscopy, Wide Angle X-Ray Diffraction, Thermogravimetric analysis, Gas Pycnometry, Differential Scanning Calorimetry and mechanical compression test. Morphological analysis revealed an open structure with interconnected pores and HA particles embedded in the polymer matrix. Finally, cell cultures were carried out into t…

Polylactide-based materials science strategies to improve tissue-material interface without the use of growth factors or other biological molecules

In a large number of medical devices, a key feature of a biomaterial is the ability to successfully bond to living tissues by means of engineered mechanisms such as the enhancement of biomineralization on a bone tissue engineering scaffold or the mimicking of the natural structure of the extracellular matrix (ECM). This ability is commonly referred to as "bioactivity". Materials sciences started to grow interest in it since the development of bioactive glasses by Larry Hench five decades ago. As the main goal in applications of biomedical devices and tissue scaffolds is to obtain a seamless tissue-material interface, achieving optimal bioactivity is essential for the success of most biomate…

Improvement of osteogenic differentiation of human mesenchymal stem cells on composite poly l-lactic acid/nano-hydroxyapatite scaffolds for bone defect repair.

Tissue engineering offers new approaches to repair bone defects, which cannot be repaired physiologically, developing scaffolds that mimic bone tissue architecture. Furthermore, biomechanical stimulation induced by bioreactor, provides biomechanical cues that regulate a wide range of cellular events especially required for cellular differentiation and function. The improvement of human mesenchymal stem cells (hMSCs) colonization in poly-L-lactic-acid (PLLA)/nano- hydroxyapatite (nHA) composite scaffold was evaluated in terms of cell proliferation (dsDNA content), bone differen- tiation (gene expression and protein synthesis) and ultrastructural analysis by comparing static (s3D) and dynamic…

Laser Ablation of Poly(lactic acid) Sheets for the Rapid Prototyping of Sustainable, Single-Use, Disposable Medical Microcomponents

The employment of single-use, disposable medical equipment has increased the amount of medical waste produced and the advent of point-of-care diagnostics in lab-on-chip format is likely to add further volume. Current materials used for the manufacture of these devices are derived from petroleum sources and are, therefore, unsustainable. In addition, disposal of these plastics necessitates combustion to reduce infection risk, which has, depending on material composition, an undesirable environmental impact. To address these issues, we have developed a general approach for the rapid prototyping of single-use point-of-care cartridges prepared from poly(lactic acid), a sustainable material whic…

In vitro degradation and bioactivity of composite poly-l-lactic (PLLA)/bioactive glass (BG) scaffolds: comparison of 45S5 and 1393BG compositions

The objective of this study was to compare the effect of two bioglass (BG) compositions 45S5 and 1393 in poly-l-lactic composite scaffolds in terms of morphology, mechanical properties, biodegradation, water uptake and bioactivity. The scaffolds were produced via thermally induced phase separation starting from a ternary polymer solution (polymer/solvent/non-solvent). Furthermore, different BG to polymer ratios have been selected (1, 2.5, 5% wt/wt) to evaluate the effect of the amount of filler on the composite structure. Results show that the addition of 1393BG does not affect the scaffold morphology, whereas the 45S5BG at the highest amount tends to appreciably modify the scaffold archite…

Human nasoseptal chondrocytes maintain their differentiated phenotype on PLLA scaffolds produced by thermally induced phase separation and supplemented with bioactive glass 1393

Damage of hyaline cartilage such as nasoseptal cartilage requires proper reconstruction, which remains challenging due to its low intrinsic repair capacity. Implantation of autologous chondrocytes in combination with a biomimetic biomaterial represents a promising strategy to support cartilage repair. Despite so far mostly tested for bone tissue engineering, bioactive glass (BG) could exert stimulatory effects on chondrogenesis. The aim of this work was to produce and characterize composite porous poly(L-lactide) (PLLA)/1393BG scaffolds via thermally induced phase separation (TIPS) technique and assess their effects on chondrogenesis of nasoseptal chondrocytes. The PLLA scaffolds without or…