Changing the Paradigm-Controlling Polymer Morphology during 3D Printing Defines Properties.

Direct digital manufacturing consists of a set of techniques that enable products to be fabricated directly from their digital definition, without the use of complex tooling or moulds. This manufacturing approach streamlines prototyping and small-scale production, as well as the mass customization of parts with complex designs immediately fixed before fabrication. With broad applicability, there are clearly opportunities in the field of medical devices for its use. However, many of the developments of direct digital manufacturing focus on simply specifying the shape or the form of the product, and this limited scope throws away many of the particular advantages of direct digital manufacturing. This work is focused on remedying this situation so that the digital specification of the fabricated product includes the properties as well as the form of the product. We use in situ time-resolving small-angle X-ray scattering measurements performed at the ALBA Synchrotron Light Source in Barcelona to evaluate the control that can be exerted on the morphology of a semi-crystalline polymer during extruder-based 3D printing. We use this as a methodology for printing the patterns of the morphology of the polymer to realise the patterns of properties of the polymeric material, specifically the modulus of the polymer. We give an example of products produced in this manner that contain spatial variation in their properties.

Staff SARS-CoV-2 Seroprevalence and Mental Health as Key Factors in University Response to COVID-19 Pandemic.

Background: In response to rapid global spread of the newly emerged coronavirus disease 2019 (COVID-19), universities transitioned to online learning and telework to decrease risks of inter-person contact. To help administrators respond to the COVID-19 pandemic and better understand its impacts, we surveyed SARS-CoV-2 seroprevalence among NOVA University employees and assessed community mental health. Methods: Data were collected from voluntary participants at six NOVA University locations, in the Lisbon metropolitan area, from June 15-30, 2020. All subjects provided written informed consent. Of 1,627 recruited participants (mean age 42.0 ± 12.3 years), 1,624 were tested. Prior to blood collection, participants completed a questionnaire that assessed: COVID-19 symptoms during the previous 14 days, chronic non-communicable diseases, chronic medication, anxiety, and depression symptoms. SARS-CoV-2 serology tests were then performed, and results communicated approximately 4 days after blood draw. Participants with positive serology tests were contacted to assess COVID-19 symptoms since February. Results: Estimated prevalence of SARS-CoV-2 IgG antibodies was 3.1% (n = 50), of which 43.5% reported symptoms in the previous 4 months. The Medical School had the highest seroprevalence (6.2%). Participants reported having at least one chronic disease (63.7%), depression-like symptoms (2.1%), and anxiety symptoms (8.1%). Rates of depression and anxiety symptoms were significantly higher in women, with sleep hours and occasional alcohol consumption negatively associated with depression. Male gender, older age, and sleep hours negatively associated with anxiety symptoms. School of employment and presence of comorbidities positively associated with anxiety. Conclusion: By measuring seroprevalence of SARS-CoV-2 antibodies among NOVA employees and assessing subjects' mental health, we aim to help administrators at European public universities in urban areas, such as Lisbon, Portugal, better understand the needs of their communities. This study resulted in implementation of a stricter contingency plan in the Medical School, while other schools continued to follow Government mitigation guidelines. These findings may also guide the development of tailored strategies to ensure physical and mental health of the academic community during this pandemic crisis. We conclude that, together with COVID-19 contingency plans, psychological support services and facilities to help people effectively face pandemic-associated challenges and minimise anxiety and depression should be implemented.

Microwave-Assisted Synthesis, Structural Characterization and Assessment of the Antibacterial Activity of Some New Aminopyridine, Pyrrolidine, Piperidine and Morpholine Acetamides.

A series of new acetamide derivatives 22-28 of primary and secondary amines and para-toluene sulphinate sodium salt have been synthesized under microwave irradiation and assessed in vitro for their antibacterial activity against one Gram-positive and two Gram-negative bacterial species such as S. pyogenes, E. coli, and P. mirabilis using the Mueller-Hinton Agar diffusion (well diffusion) method. The synthesized compounds with significant differences in inhibition diameters and MICs were compared with those of amoxicillin, ampicillin, cephalothin, azithromycin and doxycycline. All of the evaluated acetamide derivatives were used with varying inhibition concentrations of 6.25, 12.5, 37.5, 62.5, 87.5, 112.5 and 125 µg/mL. The results show that the most important antibacterial properties were displayed by the synthetic compounds 22 and 24, both of bear a para-chlorophenyl moiety incorporated into the 2-position moiety of acetamide 1. The molecular structures of the new compounds were determined using the FT-IR and 1H-NMR techniques.

Biomaterials for In Situ Tissue Regeneration: A Review.

This review focuses on a somewhat unexplored strand of regenerative medicine, that is in situ tissue engineering. In this approach manufactured scaffolds are implanted in the injured region for regeneration within the patient. The scaffold is designed to attract cells to the required volume of regeneration to subsequently proliferate, differentiate, and as a consequence develop tissue within the scaffold which in time will degrade leaving just the regenerated tissue. This review highlights the wealth of information available from studies of ex-situ tissue engineering about the selection of materials for scaffolds. It is clear that there are great opportunities for the use of additive manufacturing to prepare complex personalized scaffolds and we speculate that by building on this knowledge and technology, the development of in situ tissue engineering could rapidly increase. Ex-situ tissue engineering is handicapped by the need to develop the tissue in a bioreactor where the conditions, however optimized, may not be optimum for accelerated growth and maintenance of the cell function. We identify that in both methodologies the prospect of tissue regeneration has created much promise but delivered little outside the scope of laboratory-based experiments. We propose that the design of the scaffolds and the materials selected remain at the heart of developments in this field and there is a clear need for predictive modelling which can be used in the design and optimization of materials and scaffolds.

Biofabrication for osteochondral tissue regeneration: bioink printability requirements.

Biofabrication allows the formation of 3D scaffolds through a precise spatial control. This is of foremost importance when aiming to mimic heterogeneous and anisotropic architecture, such as that of the osteochondral tissue. Osteochondral defects are a supreme challenge for tissue engineering due to the compositional and structural complexity of stratified architecture and contrasting biomechanical properties of the cartilage-bone interface. This review highlights the advancements and retreats witnessed by using developed bioinks for tissue regeneration, taking osteochondral tissue as a challenging example. Methods, materials and requirements for bioprinting were discussed, highlighting the pre and post-processing factors that researchers should consider towards the development of a clinical treatment.

Comparison of flanged and unflanged acetabular cup design. An experimental study using ceramic and cadaveric acetabuli.

BACKGROUND AND PURPOSE: Adequate depth of cement penetration and cement mantle thickness is important for the durability of cemented cups. A flanged cup, as opposed to unflanged, has been suggested to give a more uniform cement mantle and superior cement pressurization, thus improving the depth of cement penetration. This hypothesis was tested experimentally. MATERIALS AND METHODS: The same cup design with and without flange (both without cement spacers) was investigated regarding intraacetabular pressure, cement mantle thickness, and depth of cement penetration. With machine control, the cups were inserted into open-pore ceramic acetabular models (10 flanged, 10 unflanged) and into paired cadaver acetabuli (10 flanged, 10 unflanged) with prior pressurization of the cement. RESULTS: No differences in intraacetabular pressures during cup insertion were found, but unflanged cups tended to migrate more towards the acetabular pole. Flanged cups resulted in thicker cement mantles because of less bottoming out, whereas no differences in cement penetration into the bone were observed. INTERPRETATION: Flanged cups do not generate higher cementation pressure or better cement penetration than unflanged cups. A possible advantage of the flange, however, may be to protect the cup from bottoming out, and there is possibly better closure of the periphery around the cup, sealing off the cement-bone interface.

Chronic arthritis leads to disturbances in the bone collagen network.

INTRODUCTION: In this study we used a mice model of chronic arthritis to evaluate if bone fragility induced by chronic inflammation is associated with an imbalance in bone turnover and also a disorganization of the bone type I collagen network. METHODS: Serum, vertebrae and femur bones were collected from eight-month-old polyarthritis SKG mice and controls. Strength of the femoral bones was evaluated using three-point bending tests and density was assessed with a pycnometer. Bone turnover markers carboxy-terminal collagen cross-linking telopeptides (CTX-I) and amino-terminal propeptide of type I procollagen (PINP) were measured in serum. The organization and density of bone collagen were analyzed in vertebrae using second-harmonic generation (SHG) imaging with a two-photon microscope and trabecular bone microstructure was assessed by scanning electron microscope (SEM). RESULTS: Femoral bones of SKG mice revealed increased fragility expressed by deterioration of mechanical properties, namely altered stiffness (P = 0.007) and reduced strength (P = 0.006), when compared to controls. Accordingly, inter-trabecular distance and trabecular thickness as observed by SEM were reduced in SKG mice. PINP was significantly higher in arthritic mice (9.18 +/- 3.21 ng/ml) when compared to controls (1.71 +/- 0.53 ng/ml, P < 0.001). Bone resorption marker CTX-I was 9.67 +/- 3.18 ng/ml in arthritic SKG mice compared to 6.23 +/- 4.11 ng/ml in controls (P = 0.176). The forward-to-backward signal ratio measured by SHG was higher in SKG animals, reflecting disorganized matrix and loose collagen structure, compared to controls. CONCLUSIONS: We have shown for the first time that chronic arthritis by itself impairs bone matrix architecture, probably due to disturbed bone remodeling and increased collagen turnover. This effect might predispose patients to bone fragility fractures.

The influence of initial pressurization and cup introduction time on the depth of cement penetration in an acetabular model.

BACKGROUND: Acetabular cementation during total hip arthroplasty is considered difficult mainly due to the appearance and anatomy of the acetabulum. Improved cementation technique has been shown to improve the longevity of acetabular components. METHOD: We designed a ceramic model to investigate the effect of varying the initial cement pressurization and cup introduction times on the depth of cement penetration. 4 groups were prepared, 2 of which involved varying initial cement pressurization and cup introduction times. Group 3 involved initial cement pressurization with no cup introduction, while group 4 involved cup introduction with no prior cement pressurization. RESULTS AND INTERPRETATION: Most cement penetration occurred in the early pressurization phase, and we conclude that a relatively early and longer cement pressurization time and late cup introduction are positive factors for increased cement penetration in the acetabulum model.

Effect of iodixanol particle size on the mechanical properties of a PMMA based bone cement.

Iodixanol (IDX) is a water soluble opacifier widely used in radiographical examinations of blood vessels and neural tissue, and it has been suggested as a potential contrast media in acrylic bone cement. The effect of the iodixanol particle size on the polymerisation process of the bone cement, the molecular weight, and the quasi-static mechanical properties have been investigated in this article. The investigation was performed using radiolucent Palacos powder mixed with 8 wt% of iodixanol with particle sizes ranging from 3 to 20 microm MMD, compared with commercial Palacos R (15 wt% ZrO2) as control. Tensile, compressive and flexural tests showed that smaller particles (groups with 3, 4, and 5 microm particles) resulted in significantly lower mechanical properties than the larger particles (groups with 15, 16, and 20 microm particles). There was no difference in molecular weight between the groups. The thermographical investigation showed that the IDX cements exhibit substantially lower maximum temperatures than Palacos R, with the 4 microm IDX group having the lowest maximum temperature. The isothermal and the constant rate differential scanning calorimetry (DSC) did not show any difference in polymerisation heat (DeltaH) or glass transition temperature (Tg) between radiolucent cement, or cement containing either IDX, or ZrO2. The findings show that the particle size for a bone cement containing iodixanol should be above 8 microm MMD.

Osteolytic potential of triphenyl bismuth as an alternative contrast medium in acrylic bone cement.

Radiopaque cement containing barium sulfate causes significantly more bone resorption in vivo and in vitro than radiolucent cement. The aim of this study was to investigate the osteolytic potential of an alternative radiopaque agent, triphenyl bismuth (TPB). Bone cement particles containing various concentration of TPB (15 and 25 wt %) prepared by two methods, blending and dissolution, were added to monocytes in a bone resorption assay and the extent of lacunar resorption on dentine slices was determined. The results clearly show that cement particles containing TPB cause less bone resorption than cement particles containing barium sulfate. In addition, our results suggest that TPB prepared by dissolution in bone cement induces less osteolytic response than TPB-cement prepared by blending. The osteolysis in response to bone cement wear particles may therefore be reduced with TPB prepared using the blending technique.