Sufficient Mechanical Support Research Articles

3D printing of high-strength bioscaffolds for the synergistic treatment of bone cancer

The challenges in bone tumor therapy are how to repair the large bone defects induced by surgery and kill all possible residual tumor cells. Compared to cancellous bone defect regeneration, cortical bone defect regeneration has a higher demand for bone substitute materials. To the best of our knowledge, there are currently few bifunctional biomaterials with an ultra-high strength for both tumor therapy and cortical bone regeneration. Here, we designed Fe-CaSiO3 composite scaffolds (30CS) via 3D printing technique. First, the 30CS composite scaffolds possessed a high compressive strength that provided sufficient mechanical support in bone cortical defects; second, synergistic photothermal and ROS therapies achieved an enhanced tumor therapeutic effect in vitro and in vivo. Finally, the presence of CaSiO3 in the composite scaffolds improved the degradation performance, stimulated the proliferation and differentiation of rBMSCs, and further promoted bone formation in vivo. Such 30CS scaffolds with a high compressive strength can function as versatile and efficient biomaterials for the future regeneration of cortical bone defects and the treatment of bone cancer.

Structure and physico-mechanical properties of low temperature plasma treated electrospun nanofibrous scaffolds examined with atomic force microscopy

Electrospun nanofibrous scaffolds are willingly used in tissue engineering applications due to their tunable mechanical, chemical and physical properties. Additionally, their complex openworked architecture is similar to the native extracellular matrix of living tissue. After implantation such scaffolds should provide sufficient mechanical support for cells. Moreover, it is of crucial importance to ensure sterility and hydrophilicity of the scaffold. For this purpose, a low temperature surface plasma treatment can be applied.In this paper, we report physico-mechanical evaluation of stiffness and adhesive properties of electrospun mats after their exposition to low temperature plasma. Complex morphological and mechanical studies performed with an atomic force microscope were followed by scanning electron microscope imaging and a wettability assessment. The results suggest that plasma treatment can be a useful method for the modification of the surface of polymeric scaffolds in a desirable manner. Plasma treatment improves wettability of the polymeric mats without changing their morphology.

Removing Carious Tissue: Why and How?

Caries is no longer seen as an infectious disease, and the aim of treating carious lesions is to control their activity, not to remove the lesion itself. Such control can be implemented by sealing off the lesion from the environment, with sealed bacteria being deprived from carbohydrates and thus inactivated. For cavitated lesions, controlling them usually involves the placement of restorations to rebuild the cleansability of the surface. In this case, dental practitioners have traditionally removed carious tissues prior to the restoration. This has historically been for a number of reasons, while today the main reason for restoring a cavity is to maximise restoration longevity. In shallow lesions, dental practitioners should aim to remove as much carious tissue as possible (to allow adequate depth for the restorative material) without unnecessarily removing sound or remineralisable dentine. This means removal to hard dentine around the periphery, to firm dentine centrally for optimising restoration longevity and allowing a tight cavity seal. For deep lesions in teeth with vital pulps (without irreversible pulpitis), maintaining pulp vitality is critical. Dental practitioners should aim to avoid pulp exposure, leaving soft or leathery dentine in pulpoproximal areas. Peripherally, hard tissue is left, again to ensure a tight seal and sufficient mechanical support of the restoration. As an alternative to the selective removal to soft dentine, stepwise removal can be used. With this approach, the soft dentine is temporarily rather than permanently sealed in, and removed in a second step after 6-12 months. Strategies where carious tissue in cavitated lesions is not removed at all, but sealed or managed non-restoratively, are currently restricted to primary teeth.

Silk fibroin-chondroitin sulfate scaffold with immuno-inhibition property for articular cartilage repair.

Severe cartilage defect such as osteoarthritis (OA) is difficult to self-repair because of its avascular, aneural and alymphatic nature. Current scaffolds often focus on providing sufficient mechanical support or bio-mimetic structure to promote cartilage repair. Thus, silk has been adopted and investigated broadly. However, inflammation is one of the most important factors in OA. But few scaffolds for cartilage repair reported anti-inflammation property. Meanwhile, chondroitin sulfate (CS) is a glycosaminoglycan present in the natural cartilage ECM, and has exhibited a number of useful biological properties including anti-inflammatory activity. Thus, we designed this silk-CS scaffold and proved that this scaffold exhibited good anti-inflammatory effects both in vitro and in vivo, promoted the repair of articular cartilage defect in animal model.

Composite elastomeric polyurethane scaffolds incorporating small intestinal submucosa for soft tissue engineering.

Hybrid composites containing synthetic polymers with high mechanical strength and naturally derived components, which create a bio-mimetic environment, are one of the most promising biomaterials. Although synthetic polymer/ECM composites have been previously used for soft tissue repair, their resilience properties were not investigated in sufficient detail, while the development of elastic composites composed of synthetic polymers and ECMs in nontoxic aqueous solutions remains a rather challenging task. In this study, porous PU/SIS composites were fabricated in a non-toxic manner; the obtained materials exhibited sufficient mechanical support, which promote cell growth, angiogenesis, and tissue regeneration. The described method can be adapted for the development of scaffolds with various acellular matrices and subsequently used during the restoration of particular types of tissue.

Fatigue behaviour of NiTi shape memory alloy scaffolds produced by SLM, a unit cell design comparison

Selective laser melting (SLM) is an additive manufacturing technique able to produce complex functional parts via successively melting layers of metal powder. This process grants the freedom to design highly complex scaffold components to allow bone ingrowth and aid mechanical anchorage.This paper investigates the compression fatigue behaviour of three different unit cells (octahedron, cellular gyroid and sheet gyroid) of SLM nitinol scaffolds. It was found that triply periodic minimal surfaces display superior static mechanical properties in comparison to conventional octahedron beam lattice structures at identical volume fractions. Fatigue resistance was also found to be highly geometry dependent due to the effects of AM processing techniques on the surface topography and notch sensitivity. Geometries minimising nodal points and the staircase effect displayed the greatest fatigue resistance when normalized to yield strength. Furthermore oxygen analysis showed a large oxygen uptake during SLM processing which must be altered to meet ASTM medical grade standards and may significantly reduce fatigue life. These achieved fatigue properties indicate that NiTi scaffolds produced via SLM can provide sufficient mechanical support over an implants lifetime within stress range values experienced in real life.

Laser Debonding for 2.5D, 3D and Emerging Advanced Packaging Solutions

In recent years temporary bonding has evolved to a widely used process technology as it is an enabling process for many products relyinnovel solutions are typically assessed on two key criteria which are a broad process window and cost effectiveness. Thus in this paper these criteria will be discussed in more detail for the case of UV laser debonding with respect to wafer level packaging. By temporary bonding the thin or to be thinned device wafer is bonded to a carrier wafer by an adhesive interlayer to provide sufficient mechanical support which is crucial for many downstream processes. In the past several different technologies have been studied and implemented. A major differentiation factor between the offered solutions is the debonding method, including separation processes at room or elevated temperatures. Nowadays a particular focus is on UV laser debonding as it offers several advantages, as the debonding process can be performed at room temperature with fast process times and force free separation. Furthermore crosslinking adhesive materials with high temperature stability can be used. This can be achieved due to the high intensity UV light provided by an excimer laser system which is absorbed by the polymer close to the carrier surface and breaks the chemical bonds. The low debonding temperature in combination with high temperature stability of the adhesives leads to a broad process window for the temporary bonded stack. In addition transparent adhesive materials can be used in combination with the glass carrier to support better visibility of alignment marks within the bond interface. However, for industrial requirement besides the technical advantages the most critical parameters are ease of implementation, throughput and costs. In this paper we will review integration principles for advanced packaging as well as new devices that utilize temporary bonding. Special focus will also be put on upcoming demands for future device concepts. A short discussion will discuss temporary bonding methods and materials, benefits and drawbacks of each one. In the following laser debonding will be discussed as a focus topic for next generation packaging process technology. Laser debonding is already being applied in volume for couple of technologies, focussing on different wavelengths. We will focus on a newly developed technology, using UV solid state laser technology. Here, we will discuss all relevant process parameter, critical process steps along with reliability of different laser debonding material systems.

Morphological effects of porous poly-d,l-lactic acid/hydroxyapatite scaffolds produced by supercritical CO2 foaming on their mechanical performance.

A novel supercritical CO2 foaming technique was used to fabricate scaffolds of controllable morphology and mechanical properties, with the potential to tailor the scaffolds to specific tissue engineering applications. Biodegradable scaffolds are widely used as temporary supportive structures for bone regeneration. The scaffolds must provide a sufficient mechanical support while allowing cell attachment and growth as well as metabolic activities. In this study, supercritical CO2 foaming was used to prepare fully interconnected porous scaffolds of poly-d,l-lactic acid and poly-d,l-lactic acid/hydroxyapatite. The morphological, mechanical and cell behaviours of the scaffolds were measured to examine the effect of hydroxyapatite on these properties. These scaffolds showed an average porosity in the range of 86%-95%, an average pore diameter of 229-347 µm and an average pore interconnection of 103-207 µm. The measured porosity, pore diameter, and interconnection size are suitable for cancellous bone regeneration. Compressive strength and modulus of up to 36.03 ± 5.90 and 37.97 ± 6.84 MPa were measured for the produced porous scaffolds of various compositions. The mechanical properties presented an improvement with the addition of hydroxyapatite to the structure. The relationship between morphological and mechanical properties was investigated. The matrices with different compositions were seeded with bone cells, and all the matrices showed a high cell viability and biocompatibility. The number of cells attached on the matrices slightly increased with the addition of hydroxyapatite indicating that hydroxyapatite improves the biocompatibility and proliferation of the scaffolds. The produced poly-d,l-lactic acid/hydroxyapatite scaffolds in this study showed a potential to be used as bone graft substitutes.

Absorbable scaphoid screw development: a comparative study on biomechanics

BackgroundThe scaphoid is critical for maintaining the stability and movement of the wrist joints. This study aimed to develop a new internal fixator absorbable scaphoid screw (ASS) for fixation of the scaphoid waist after fracture and to test the biomechanical characteristics of ASS.Materials and methodsAn ASS was prepared using polylactic acids and designed based on scaphoid measurements and anatomic features. Twenty fractured scaphoid waist specimens were randomly divided into experimental and control groups (n=10/group). Reduction and internal fixation of the scaphoid were achieved with either Kirschner wires (K-wires) or ASS. A moving target simulator was used to test palmar flexion and dorsal extension, with the range of testing (waist movement) set from 5° of palmar flexion to 25° of dorsal extension. Flexion and extension were repeated 2,000 times for each specimen. Fracture gap displacements were measured with a computerized tomography scanning. Scaphoid tensile and bending strengths were measured by using a hydraulic pressure biomechanical system.ResultsPrior to biomechanical fatigue testing, fracture gap displacements were 0.16±0.02 mm and 0.22±0.02 mm in the ASS and K-wire groups, respectively. After fatigue testing, fracture gap displacements in the ASS and the K-wire groups were 0.21±0.03 mm and 1.52±0.07 mm, respectively. The tensile strengths for the ASS and K-wire groups were 0.95±0.02 MPa and 0.63±0.02 MPa, respectively.ConclusionFixation using an ASS provided sufficient mechanical support for the scaphoid after fracture.

Bio-Adaption between Magnesium Alloy Stent and the Blood Vessel: A Review

Biodegradable magnesium (Mg) alloy stents are the most promising next generation of bio-absorbable stents. In this article, we summarized the progresses on the in vitro studies, animal testing and clinical trials of biodegradable Mg alloy stents in the past decades. These exciting findings led us to propose the importance of the concept "bio-adaption" between the Mg alloy stent and the local tissue microenvironment after implantation. The healing responses of stented blood vessel can be generally described in three overlapping phases: inflammation, granulation and remodeling. The ideal bio-adaption of the Mg alloy stent, once implanted into the blood vessel, needs to be a reasonable function of the time and the space/dimension. First, a very slow degeneration of mechanical support is expected in the initial four months in order to provide sufficient mechanical support to the injured vessels. Although it is still arguable whether full mechanical support in stented lesions is mandatory during the first four months after implantation, it would certainly be a safety design parameter and a benchmark for regulatory evaluations based on the fact that there is insufficient human in vivo data available, especially the vessel wall mechanical properties during the healing/remodeling phase. Second, once the Mg alloy stent being degraded, the void space will be filled by the regenerated blood vessel tissues. The degradation of the Mg alloy stent should be 100% completed with no residues, and the degradation products (e.g., ions and hydrogen) will be helpful for the tissue reconstruction of the blood vessel. Toward this target, some future research perspectives are also discussed.

The Effects of Kinesiotape Applied to the Lateral Aspect of the Ankle: Relevance to Ankle Sprains--A Systematic Review.

ObjectiveTo identify, evaluate and synthesise evidence on the effect of kinesiotape applied to the lateral aspect of the ankle, through a systematic review of quantitative studies.Data SourcesA search for quantitative studies was undertaken using key terms of “kinesiotape” and “ankle” in seven electronic databases, using the maximum date ranges. Databases included: the Cochrane Library, Cumulative Index to Nursing and Allied Health Literature, Medline, Physiotherapy Evidence Database, Scopus, SPORTDiscus and Web of Science.Study SelectionDatabase hits were evaluated against explicit inclusion criteria. From 107 database hits, 8 quantitative studies were included.Data ExtractionTwo independent reviewers appraised the methodological rigour of the studies using the McMaster Critical Review Form for Quantitative Studies. Data were extracted on participant characteristics, kinesiotape parameters, comparison interventions, outcome measures and findings.Data SynthesesMost studies (n=7) had good to very good methodological rigour. Meta-analysis was not possible due to heterogeneity in participants, interventions and outcome measures. No adverse events were reported. Kinesiotape may produce different effects in healthy and injured ankles. In healthy ankles, kinesiotape may increase postural control, whereas in injured ankles it may improve proprioception, plantarflexor endurance and the performance of activities. These trends were identified from a small body of evidence including 276 participants.ConclusionsIt is recommended that kinesiotape may be used in clinical practice to prevent lateral ankle injuries (through its effects on postural control) and manage lateral ankle injuries due to its positive effects on proprioception, muscle endurance and activity performance. It appears that kinesiotape may not provide sufficient mechanical support to improve postural control in unstable ankles. Adverse events associated with kinseiotape are unlikely.

Hip endoprosthetics in osteoarthritis after acetabular fractures

The incidence of post-traumatic osteoarthritis after acetabular fractures is between 26 and 57%. With total hip arthroplasty (THA), affected patients can achieve a clear functional improvement and pain reduction if specific conditions are heeded. Depending on the degree and localisation of bone defects and deformities, scarring and the presence of remaining osteosynthesis material, different treatment strategies are available. This review gives an overview of current treatment strategies. Review of relevant clinical studies, meta-analyses and presentation of our own approach. The best results regarding to implant survival and clinical outcome, comparable with THA in primary osteoarthritis, can be achieved, when cementless acetabular reconstruction with anatomical restoration of the hip's rotational center and sufficient mechanical support is obtained. Pre-operative planing based on a thorough radiographic examination is essential. Althoug the postoperative complication rate is elevated after THA for posttraumatic arthritis after acetabular fractures compared with primary osteoarthritis, the overall functional results and implant survival are comparable.

Stability investigation of micro-configured Pd–Ag membrane modules – Effect of operating temperature and pressure

The long-term stability over a period of up to 50 days has been reported for various designs of microstructured Pd77Ag23 membrane modules for H2 production and purification. Even though microchannels provide sufficient mechanical support for moderate trans-membrane pressure difference and temperatures, i.e., 4–5 bars and 400–450 °C, long-term operation under these operating conditions results in a large deformative settling of the Pd77Ag23 film into the microchannel support. This settling leads to microstructural changes and pore formation on the feed surface of the membrane film that ultimately results in membrane failure. For pressures above approximately 5 bars, the application of microchannel-supported modules is thus not feasible, and for that purpose a continuous porous stainless steel support is introduced that allows for a sufficient stabilisation of the thin Pd77Ag23 films. For such a porous stainless steel supported microchannel module, a hydrogen flux of 195.3 mL cm−2 min−1 is obtained at 450 °C and 5 bars feed pressure, corresponding to a permeability of 3.4·10−8 mol m−1 s−1 Pa−0.5. During the complete operation of 1100 h at 450 °C, the module shows a very good stability up to the highest feed pressure applied of 15 bars. The N2 leakage flux has remained below the detection limit of the equipment, 5 μL cm−2 min−1, resulting in a minimum value for the H2/N2 permselectivity of 39.000 applying the pure H2 flux value obtained at 5 bars.

Stem cell-loaded nanofibrous patch promotes the regeneration of infarcted myocardium with functional improvement in rat model

Myocardial infarction (MI) leads to the loss of cardiomyocytes, followed by left ventricular (LV) remodeling and cardiac dysfunction. The authors hypothesize that an elastic, biodegradable nanofibrous cardiac patch loaded with mesenchymal stem cells (MSC) could restrain LV remodeling and improve cardiac function after MI. Poly(ε-caprolactone)/gelatin (PG) nanofibers were fabricated by electrospinning, and the nanofibers displayed a porous and uniform nanofibrous structure with a diameter of 244±51nm. An MI model was established by ligation of the left anterior descending coronary artery of female Sprague–Dawley rats. The PG nanofibrous patch seeded with MSC, isolated from rat bone marrow, was implanted on the epicardium of the infarcted region of the LV wall of the heart. After transplantation, the PG–cell patch restricted the expansion of the LV wall effectively and reduced the scar size, and the density of the microvessels increased. Cells within the patch were able to migrate towards the scar tissue, and promoted new blood vessel formation at the infarct site. Angiogenesis and the cardiac functions improved significantly after 4weeks of implantation. The MSC-seeded PG nanofibrous patches are demonstrated to provide sufficient mechanical support, to induce angiogenesis and to accelerate cardiac repair in a rat model of MI. The study highlights the positive impact of implantation of an MSC-seeded PG nanofibrous patch as a novel constituent for MI repair.

Microdevice-based cell therapy for age-related macular degeneration.

This chapter reports the application of a micromachined parylene-C device as an artificial Bruch's membrane for the stem cell-based therapy of age-related macular degeneration. The feasibility of parylene-C as a substitute substrate material is demonstrated by evaluating the permeability of membranes of submicron thicknesses. It has been found that parylene-C membranes thinner than 0.3 µm possess similar molecular weight exclusion limit and nutrient diffusion flux to that of the healthy human Bruch's membrane. This conclusion is further validated by the in vitro perfusion cell viability test. Since the submicron parylene-C itself is difficult to handle, we design a mesh-supported submicron parylene membrane (MSPM) to provide sufficient mechanical support. This MSPM can support the growth of retinal pigment epithelial (RPE) cells in a monolayer with well-polarized morphology. Human embryonic stem cell-derived H9-RPE cells are cultured in vitro on the MSPM for one month before the implantation of the MSPM into the rat's retina. To facilitate the surgical implantation, a parylene-C/SU-8 hybrid microfluidic device is designed as an inserter. Histological studies with hematoxylin-eosin staining and immunofluorescence staining show that the implanted RPE cells adhere well to the artificial Bruch's membrane and are able to maintain high viability and normal morphology in vivo.

Enhanced Bone Regeneration of Cortical Segmental Bone Defects Using Porous Titanium Scaffolds Incorporated with Colloidal Gelatin Gels for Time- and Dose-Controlled Delivery of Dual Growth Factors

Porous titanium scaffolds are a promising class of biomaterials for grafting large bone defects, because titanium provides sufficient mechanical support, whereas its porous structure allows bone ingrowth resulting in good osseointegration. To reinforce porous titanium scaffolds with biological cues that enhance and continue bone regeneration, scaffolds can be incorporated with bioactive gels for time- and dose-controlled delivery of multiple growth factors (GFs). In this study, critical femoral bone defects in rats were grafted with porous titanium scaffolds incorporated with nanostructured colloidal gelatin gels. Gels were loaded with bone morphogenetic protein-2 (BMP-2, 3 μg), fibroblast growth factor-2 (FGF-2, 0.6 μg), BMP-2, and FGF-2 (BMP-2/FGF-2, ratio 5:1) or were left unloaded. GF delivery was controlled by fine tuning the crosslinking density of oppositely charged nanospheres. Grafted femurs were evaluated using in vivo and ex vivo micro-CT, histology, and three-point bending tests. All porous titanium scaffolds containing GF-loaded gels accelerated and enhanced bone regeneration: BMP-2 gels gave an early increase (0-4 weeks), and FGF-2 gels gave a late increase (8-12 weeks). Interestingly, stimulatory effects of 0.6 μg FGF-2 were similar to a fivefold higher dose of BMP-2 (3 μg). BMP-2/FGF-2 gels gave more bone outside the porous titanium scaffolds than gels with only BMP-2 or FGF-2, resulted in bridging of most defects and showed superior bone-implant integrity in three-point bending tests. In conclusion, incorporation of nanostructured colloidal gelatin gels capable of time- and dose-controlled delivery of BMP-2 and FGF-2 in porous titanium scaffolds is a promising strategy to enhance and continue bone regeneration of large bone defects.

Properties of commonly used calcium phosphate cements in trauma and orthopaedic surgery

Half of the population sustains at least one fracture during their lifetime [1], and the majority of these fractures heal successfully. Successful fracture healing requires the following five elements; (i) osteogenic cells (e.g., osteoblasts), (ii) osteoinductive stimuli (e.g., bone morphogenetic proteins); (iii) an osteoconductive matrix; (iv) adequate blood and nutrient supply, and (v) sufficient mechanical support [2]. One or more elements can be compromised due to the existence of a bone defect.

Total Reconstruction of the Atrophic Maxilla with Intraoral Bone Grafts and Biomaterials: A Prospective Clinical Study with Cone Beam Computed Tomography Validation

To perform a preliminary validation with cone beam computed tomography (CBCT) of the combined use of intraoral bone blocks and biomaterials for total reconstruction of the atrophic maxilla. Consecutive cases of total edentulism of the maxilla (Cawood and Howell classes IV or V) treated with bilateral sinus floor elevation, mandibular bone block grafts, and biomaterials were evaluated prospectively. Implants were placed 14 to 16 weeks after grafting. Each patient received a CBCT scan preoperatively, immediately after bone augmentation, and at reentry. A three-dimensional reconstruction of the maxilla with volumetric calculations was obtained at each stage. Fourteen patients participated. Successful graft integration occurred in all cases, with no major complications. Mean preoperative volume was 11,312 mm3. Mean postoperative volume was 19,997 mm3 immediately after surgery and 19,042 mm3 before implant insertion. The average percentage volumetric increase between the preoperative condition and the situation at reentry was 71.99%. One hundred eight implants were inserted. Immediate loading was possible with 81 implants in 10 patients. The rehabilitation of the severely resorbed maxilla remains a formidable challenge. The results of this study suggest that the use of mandibular bone blocks in combination with biomaterials is an effective, reliable procedure for the rehabilitation of the severely resorbed maxilla. Significant volume increases and adequate stability of the augmented areas at reentry were found with CBCT analysis. The grafted bone provided sufficient mechanical support to permit provisionalization and immediate loading. This technique enabled the restoration of function and esthetics with a fixed rehabilitation at 4 months.

Mechanical Circulatory Support beyond PCPS

Ventricular assist device (VAD) provides sufficient mechanical circulatory support for acute heart failure patients who are progressively deteriorating under PCPS. However, currently, implantable VAD is only available for heart transplantation (HTx). In this study, we evaluated our temporary VAD strategy for acute cardiogenic shock patients using temporary VAD.

Design and Characterization of a Biocompatible Packaging Concept for Implantable Electronic Devices

A biocompatible packaging process for implantable electronic systems is described, combining biocompatibility and hermeticity with extreme miniaturization. In Phase 1 of the total packaging sequence, all chips are encapsulated in order to realize a bidirectional diffusion barrier, preventing body fluids from leaching into the package, which would cause corrosion, and preventing IC materials such as Cu from diffusing into the body, which would cause various adverse effects. For cost-effectiveness, this hermetic chip sealing is performed as a postprocessing step at the wafer level using modifications of standard clean room (CR) fabrication techniques. Well-known conductive and insulating CR materials are investigated with respect to their biocompatibility, diffusion barrier properties, and sensitivity to corrosion. In Phase 2 of the packaging process, all chips of the final device should be electrically connected, applying a biocompatible metallization scheme using, for example, gold or platinum. For electrodes in direct contact with the tissue after implantation, IrOx metallization is proposed. Phase 3 of device assembly is the final packaging step, during which all system components, such as electronics, passives, a battery, among others, will be interconnected. To provide sufficient mechanical support, all these components are embedded using a biocompatible elastomer such as PDMS.