Bio-medical materials and engineering最新文献

Photoacoustic technology can non-invasively obtain the temperature and pressure of tissues, holding great promise for applications in the laser thermal ablation of pigmented skin diseases. The coefficient of thermal expansion is the primary source of temperature sensitivity in photoacoustic technology. In this paper, a non-contact full-field strain measurement system based on temperature-variable three-dimensional digital image correlation is used to measure the variation of the thermal expansion coefficient of melanin in the retinal pigment epithelium layer of porcine eyes. It is found that the thermal strain of melanin exhibits non-uniformity and nonlinear increase in radial Angle and circular domain. Before the glass-transition temperature (49°C), the average coefficients of thermal expansion for concentric circular regions and different radial directions are 4.14 × 10^-4 K^-1 and 3.82 × 10^-4 K^-1, respectively. Approximating the thermal expansion coefficient of melanin with that of graphite leads to a large error, with a difference of two orders of magnitude.

Background: Vertically oriented femoral neck fractures are a challenge for orthopedic surgeons, and the complication rates are also high. Recently, several innovative devices have been proposed, such as the proximal femoral bionic nail, InterTAN, and medial buttress plate combined with cannulated screws, to increase the stability of fixation. However, the differences among these innovative devices need to be addressed.

Objective: This study aimed to compare the stability of the proximal femoral bionic nail, InterTAN, and medial buttress plate combined with cannulated screws for vertically oriented femoral neck fractures. Additionally, traditional fixation devices-including three parallel cannulated screws, a compression hip screw system, and a proximal femoral nail-were included for comparison, resulting in a total of six distinct devices evaluated in this study.

Methods: A finite element model of a femoral neck fracture fixed with the six internal fixation devices was created. Furthermore, two different fracture conditions-with and without a 1-mm fracture gap-were considered. The maximum loading during level walking was applied to the model for comparison.

Results: The results indicated that the InterTAN has the best ability to maintain the gap and prevent collapse. Under the fracture gap condition, the peak displacement of the femoral head was smaller in the innovative devices compared to the traditional ones. Specifically, the peak displacements were 1.98 mm for the medial buttress plate combined with cannulated screws, 2.12 mm for the proximal femoral bionic nail, and 1.16 mm for the InterTAN system. The von Mises stress in the medial buttress plate was also the highest among the devices, with values of 1000 MPa with the gap and 1477 MPa without the gap.

Conclusion: Based on the present results, the medial buttress plate combined with cannulated screws, proximal femoral bionic nail, and InterTAN are recommended for cases without a fracture gap, while the InterTAN is recommended for cases with a fracture gap to prevent bone shortening.

Background: Glioblastoma multiforme (GBM) is the most common type of brain tumor and it is considered as one of the most aggressive malignancies (1.5 years of survival rate).

Objective: Determine the antitumor potential of bismuth lipophilic nanoparticles (BisBAL NP) on a human glioblastoma cell-line.

Methods: BisBAL NP were characterized by scanning electron microscopy (SEM). BisBAL NP entry and intracellular distribution on U-87 MG cells were observed by transmission electron microscopy (TEM). The effect of BisBAL NP on tumor cells was evaluated by MTT assay (IC₅₀ value), Calcein AM staining, Live/dead assay, apoptosis quantification, and comet assay.

Results: BisBAL NP-induced cytotoxicity more efficient than temozolomide (TMZ). The IC₅₀ value of BisBAL NP was 12.7 µM. For the first time, direct interaction between BisBAL NP and plasmatic U-87 MG cell membrane was obtained by TEM. Calcein AM assay revealed loss of permeability of tumor cells after 24 h-exposure to 25 µM of BisBAL NP. 25 µM of BisBAL induced 48.5% of apoptosis, while 50 µM of BisBAL induced a higher rate of apoptosis 77.2%.

Conclusion: BisBAL NP inhibited U-87 MG cell growth through membrane attack and loss membrane permeability, apoptosis induction and later promoting genotoxicity among tumor cells.

BackgroundMonopolar Radiofrequency uses high-frequency waves to generate heat for skin tightening and tissue repair. However, individual fat layer thickness variation causes uneven radiofrequency (RF) penetration and heat thresholds, compromising personalized results.ObjectiveThe purpose of this study is to analyze the temperature distribution of tissues with different fat thickness after radio frequency treatment and the experimental temperature distribution and tissue changes of pork tissues in vitro by finite element analysis and in vitro experiment verification, so as to achieve appropriate energy parameters for different individuals.MethodsA two-dimensional bio-thermal model including epidermis, dermis and subcutaneous tissue was developed in COMSOL Multiphysics 6.2. Four fat thicknesses (2, 4, 6, and 8 mm) were simulated to assess their impact on dermal temperature distribution during 6.78 MHz, 120 W radiofrequency exposure. The electromagnetic-thermal coupling effects were validated through in vitro experiments.ResultsExperimental results validate the simulations, demonstrating consistent thermal trends across fat thicknesses (2-8 mm). Post-treatment intratissue temperatures reached 69  °C (2 mm), 60 °C (4 mm), 55 °C (6 mm), and 45 °C (8 mm), all within epidermal safety limits.ConclusionThe results show that the energy parameters need to be adjusted according to the thickness of adipose tissue during radiofrequency therapy, and higher energy or longer treatment time may be needed for the treatment site with thicker adipose tissue to achieve the expected effect.

BackgroundResin composite restorations exhibit dimensional changes in the oral environment due to polymerization reaction and/or water sorption, which generates stresses in the surrounding tooth structures. The state of stress may differ between self-adhesive resin composites (SARCs) and conventional resin composites because only SARCs contain hydrophilic monomers.ObjectiveThe objective of this study was to evaluate the influence of water sorption on polymerization stresses of SARCs.MethodsCracks were introduced near a cylindrical hole in a glass disk, and their lengths were measured. The hole was filled with the composites. The crack lengths were repeatedly measured during 1-week water storage 37°C. Stresses at the composite-glass interface were calculated from the crack lengths and fracture toughness of the glass. Flexural moduli, water sorption and solubility of composites were also measured.ResultsPolymerization stresses of SARCs were equivalent to or less than that of a conventional composite generating relatively little stress. Significant reduction of stress occurred between 1-h and 1-day water storage in all composites. This reduction tended to be more noticeable with a larger decrease in modulus and/or larger water sorption.ConclusionsQuicker and/or larger stress reduction were considered to be beneficial for the longevity of SARC restorations.

BackgroundCardiovascular diseases are the leading cause of mortality worldwide, with coronary artery bypass grafting being the most effective treatment for severe cases. While autografts are preferred, donor veins are often limited. Human umbilical arteries (hUAs) show promise as an alternative. However, to make vascular graft by decellularization, a traditional chemical method can damage tissue structure and function.ObjectiveThis study aims to evaluate the shortening of treatment time and the hUA decellularization efficiency of the perfusion bioreactor systems.MethodshUAs were perfused with 1% Triton X-100 for 6 h, followed by two different concentrations of (0.5% and 1%) SDS for 18 h, and subsequently subjected to a washing procedure. The decellularization process was evaluated using histological staining and DNA quantification, along with tests for cytotoxicity, cell adhesion and proliferation.ResultsThe 0.5% SDS protocol proved most effective, reducing residual DNA to below 50 ng/mg of dry weight while preserving collagen structure. It showed no cytotoxicity to L929 cells, SEM analysis confirmed human umbilical vein endothelial cell (HUVEC) attachment and CCK-8 testing showed promoted HUVECs proliferation.ConclusionThe decellularization protocol of perfusing through 1% TX for 6 h and 0.5% SDS for 18 h through the perfusion bioreactor system is efficient in the intact hUAs tissue. This sets the stage for future in vivo studies and potential clinical applications.

A composite of polyvinyl alcohol (PVA) and beta-tricalcium phosphate (β-TCP) was synthesized as a biomaterial filament for 3D printers and its analytical and chemical evaluation was performed. PVA powder and β-TCP were mixed in the range of 0-20 wt% and hot-melt extruded at 200 °C using a single-screw extruder. Comprehensive material characterization of the synthesized filament was performed by powder X-ray diffraction (XRD), near-infrared spectroscopy (NIR), and scanning electron microscopy (SEM). XRD analysis confirmed that the amorphous nature of PVA and the crystalline nature of β-TCP coexisted and the physical mixture state was well maintained. In near-infrared spectroscopy, concentration-dependent spectral changes were observed by normalization, and principal component analysis showed that the first principal component explained 85.6% of the variance. In machine learning regression analysis, partial least squares regression (PLS), random forest (RF), and support vector machine (SVM) were compared, and SVM achieved the best prediction accuracy (R² = 0.910). SEM observations confirmed streaky structures along the extrusion direction and uniform dispersion of β-TCP particles. This study demonstrated that a combined NIR spectroscopy and machine learning approach is effective as a non-destructive quality evaluation technique for composite filaments for 3D printing. This technique enables real-time composition monitoring and quality control of biomaterial filaments, and is expected to be applied to the manufacturing of patient-specific biomedical devices.

ObjectiveThe popularity of brushite cement (BrC) in bone regeneration is related to its biocompatibility and favorable resorption properties. Nevertheless, it has poor clinical performance due to quick settling, lack of mechanical strength, and anti-bacterial activity. This paper offered the research on the impact of adding chitosan-selenium nanoparticles (CS-SeNPs) into BrC to improve its mechanical, physical, and biological characteristics.MethodsCS-SeNPs were added to BrC at 1 and 2 wt.% concentration. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR) were used to characterize the modified materials. Physical and mechanical properties were evaluated through mass-loss investigations, setting time, and mechanical properties, shear bond strength [SBS], diametral compressive strength [DCS] and biaxial flexural strength [BFS]. The antibacterial activity, and cytocompatibility were also tested.ResultsThe use of CS-SeNPs enhanced BrC crystallinity, mechanical strength and antibacterial activities. SBS, DCS as well as BFS improved considerably with nanoparticles inclusion. The highest mass loss was observed at 1 wt.% CS-SeNP after 48 h and the setting times were longer in comparison with the control. The zone of inhibition and decrease in optical density were seen significant in 1 wt.% group, which indicates superior antibacterial activity. The biocompatibility tests showed moderate cytotoxicity at the higher concentrations.ConclusionThe use of up to 2 wt.% CS-SeNPs increases the structural, mechanical, and antibacterial behavior of brushite cement considerably without deteriorating its fundamental features. This engineered formulations promises to be applied in the regeneration of bones that need a greater mechanical strength and antimicrobial coverage.

BackgroundYttria-stabilized zirconia (YSZ) represents a promising alternative to titanium for dental and orthopedic implants owing to its mechanical strength and esthetics. However, its bioinertness limits osteoconductivity. Although hydroxyapatite (HAp) coatings can enhance osteointegration, uniform deposition of morphology-controlled HAp on YSZ remains challenging to achieve, limiting implant optimization.ObjectivesThis study was aimed at the uniform deposition of morphology-controlled HAp on YSZ using electrostatic layer-by-layer (LBL) assembly to improve biological performance.MethodsPlate-like HAp was hydrothermally synthesized using dodecanedioic acid and surface-modified with poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate). YSZ discs were similarly charge-modified to enable electrostatic adsorption of HAp. Samples were evaluated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and wettability tests. Osteogenic responses were assessed using MC3T3-E1 cells through alkaline phosphatase (ALP) activity and Alizarin Red S staining.ResultsNegatively charged HAp was uniformly deposited on positively charged YSZ, forming a homogeneous coating. Characterization confirmed successful HAp deposition and improved hydrophilicity. HAp/YSZ composites enhanced osteogenic differentiation, exhibiting higher ALP activity and greater calcium deposition than YSZ.ConclusionLBL-mediated deposition of morphology-controlled HAp enables uniform coating and enhanced osteogenic activity on YSZ, facilitating advances in next-generation bioactive zirconia implants.

BackgroundSitting on a chair is an essential part of daily life, however the posture is a heavy burden on the lower back, leading to lower back pain.ObjectiveIn this study, lumbar stress distribution was analyzed when sitting on a chair with different backrest inclination, sitting distance and seat pan inclination in order to visualize the stress on intervertebral discs and sacroiliac joints (SIJs).MethodsBody pressure distribution was measured on backrests and seat pans of six subjects. Each sitting posture on a chair was reproduced using a finite element model of a spine and pelvis, and the stress distribution in the lower back was analyzed based on the results of the body pressure distribution measurements.ResultsWhen the seat pan was tilted forward, the pressure on the backrest decreased, whereas the pressure increased with large sitting distance. Finite element analyses showed that equivalent stresses on the SIJs and intervertebral discs was decreased when sitting on a chair shallowly and with the seat pan tilted forward.ConclusionBoth sitting shallowly and with a forward-tilted seat are postures that increase the trunk-thigh angle, and the load on the lower back was reduced by reducing the moment applied to the sacrum.