Biomechanics and mechanobiology of the bone matrix

The bone matrix plays an indispensable role in the human body,and its unique biomechanical and mechanobiological properties have received much attention.The bone matrix has unique mechanical anisotropy and exhibits both strong toughness and high strength.These mechanical properties are closely associated with human life activities and correspond to the function of bone in the human body.None of the mechanical properties exhibited by the bone matrix is independent of its composition and structure.Studies on the biomechanics of the bone matrix can provide a reference for the preparation of more applicable bone substitute implants,bone biomimetic materials and scaffolds for bone tissue repair in humans,as well as for biomimetic applications in other fields.In providing mechanical support to the human body,bone is constantly exposed to mechanical stimuli.Through the study of the mechanobiology of the bone matrix,the response mechanism of the bone matrix to its surrounding mechanical environment can be elucidated and used for the health maintenance of bone tissue and defect regeneration.This paper summarizes the biomechanical properties of the bone matrix and their biological significance,discusses the compositional and structural basis by which the bone matrix is capable of exhibiting these mechanical properties,and studies the effects of mechanical stimuli,especially fluid shear stress,on the components of the bone matrix,cells and their interactions.The problems that occur with regard to the biomechanics and mechanobiology of the bone matrix and the corresponding challenges that may need to be faced in the future are also described.

Simulation Analysis of Deformation Control for Magnetic Soft Medical Robots

Dear Editor,This letter presents a biocompatible cross-shaped magnetic soft robot and investigates its deformation mode control strategy through COMSOL modeling and simulation.Magnetic soft robots offer novel avenues for precise treatment within intricate regions of the human body.

Functionalized carbon dots for corrosion protection:Recent advances and future perspectives

Metal corrosion causes significant economic losses,safety issues,and environmental pollution.Hence,its prevention is of immense research interest.Carbon dots(CDs)are a new class of zero-dimensional carbon nanomaterials,which have been considered for corrosion protection applications in recent years due to their corrosion inhibition effect,fluorescence,low toxicity,facile chemical modification,and cost-effectiveness.This study provides a comprehensive overview of the synthesis,physical and chemical properties,and anticorrosion mechanisms of functionalized CDs.First,the corrosion inhibition performance of different types of CDs is introduced,followed by discussion on their application in the development of smart protective coatings with self-healing and/or self-reporting properties.The effective barrier formed by CDs in the coatings can inhibit the spread of local damage and achieve self-healing behavior.In addition,diverse functional groups on CDs can interact with Fe^(3+)and H^(+)ions generated during the corrosion process;this interaction changes their fluorescence,thereby demonstrating self-reporting behavior.Moreover,challenges and prospects for the development of CD-based corrosion protection systems are also presented.

Coherent Raman scattering imaging of lipid metabolism in cancer

Cancer cells dysregulate lipid metabolism to accelerate energy production and biomolecule synthesis for rapid growth.Lipid metabolism is highly dynamic and intrinsically heterogeneous at the single cell level.Although°uorescence microscopy has been commonly used for cancer research,bulky°uorescent probes can hardly label small lipid molecules without perturbing their biological activities.Such a challenge can be overcome by coherent Raman scattering(CRS)microscopy,which is capable of chemically selective,highly sensitive,submicron resolution and high-speed imaging of lipid molecules in single live cells without any labeling.Recently developed hyperspectral and multiplex CRS microscopy enables quantitative mapping of various lipid metabolites in situ.Further incorporation of CRS microscopy with Raman tags greatly increases molecular selectivity based on the distinct Raman peaks well separated from the endogenous cellular background.Owing to these unique advantages,CRS microscopy sheds new insights into the role of lipid metabolism in cancer development and progression.This review focuses on the latest applications of CRS microscopy in the study of lipid metabolism in cancer.

In vitro and in vivo evaluation of micro-alloyed magnesium for potential application in alveolar bone fixation screws

Alveolar bone augmentation with fixation screws has difficulties such as non-degradable materials that could lead to secondary surgery and insufficient osseointegration due to the subgingival environment in dental practice.With degradability and a high degree of osteogenesis,Mg alloy is a successful biodegrad-able material for orthopedic applications,and its application in dentistry has made certain progress.How-ever,considering the unique subgingival healing properties of oral implants,there is still a gap between the desired material properties for clinical applications and available materials.Indeed,studies on the use of Mg-based fixation screws for dentistry applications are still rare.In this study,we reported a magnesium alloy with low combined addition of strontium and lanthanum.The mechanical properties,degradation behavior,osteogenesis,and gingival compatibility were systematically investigated for assess-ing its potential application in alveolar bone fixation screws.With the alloying element content restricted to 0.3 wt.%,Mg-Sr-La alloy still exhibited good mechanical properties,with yield tensile and compressive strength twice higher than those of pure Mg.The in vitro degradation rate of this alloy was 0.10 mm y-1,which was slightly slower than high-purity Mg.The indirect and direct cell assay confirmed the elevated osteoblastic differentiation of MC3T3-E1 and migration of HGF-1 cells.Moreover,Mg-Sr-La alloy demon-strated a relatively slow degradation in the maxillary bone of Beagles.A remarkable promotion of the bone-implant contacts and significantly decreased fibrous encapsulation was observed in the subgingival environment,implying superior osseointegration of the experimental alloy than the titanium control.The empirical findings here reveal the great potential of Mg-Sr-La alloy for the application in alveolar bone fixation devices.

Material,design,and fabrication of custom prosthetic liners for lower-extremity amputees:A review

As a physical interface,a prosthetic liner is commonly used as a transition material between the residual limb and the stiff socket.Typically made from a compliant material such as silicone,the main function of a prosthetic liner is to protect the residual limb from injuries induced by load-bearing normal and shear stresses.Compared to conventional liners,custom prosthetic lower-extremity(LE)liners have been shown to better relieve stress concentrations in painful and sensitive regions of the residual limb.Although custom LE liners have been shown to offer clinical benefits,no review article on their design and efficacy has yet been written.To address this shortcoming in the literature,this paper provides a comprehensive survey of custom LE liner materials,design,and fabrication methods.First,custom LE liner materials and components are summarized,including a description of commercial liners and their efficacy.Subsequently,digital methods used to design and fabricate custom LE liners are addressed,including residual limb biomechanical modeling,finite element-based design methods,and 3-D printing techniques.Finally,current evaluation methods of custom/commercial LE liners are presented and discussed.We hope that this review article will inspire further research and development into the design and manufacture of custom LE liners.

MV-mediated biomineralization mechanisms and treatments of biomineralized diseases

As the quality of life improves,people pay more and more attention to health.They are concerned about the causes of diseases,and seek better treatments.The most common diseases are biomineralized diseases,four different kinds of typical examples among which are selected to elaborate their mechanisms and existing treatments.Whether it is tooth and bone in physiological mineralization or cartilage and blood vessel in pathological mineralization,they are all related to matrix vesicle(MV)-mediated biomineralization.MV-mediated biomineralization is the initial stage of biomineralization and the nucleation site mediating collagen mineralization.Definition,composition,biogenesis,and action mechanism of MVs are refined and expounded,especially a novel biomineralization pathway similar to exosome(EX)origin.Four differences are summarized to distinguish MVs and EXs.A series of treatments using MVs to solve biomineralized diseases such as tooth and bone defects,osteoarthritis and atherosclerosis are proposed,and the experimental extraction steps of MVs are summarized.

Composite double-layer microneedle loaded with traditional Chinese medicine for the treatment of androgenic alopecia

Androgenetic alopecia(AGA)is an androgen-mediated alopecia affected by both genes and hormones.Medication is a relatively common treatment.As a new drug delivery method,microneedles(MNs)can effectively break through the stratum corneum barrier,deliver drugs more efficiently,and achieve better therapeutic effects.In this study,we develop a composite double-layer MN through multi-step casting fabrication using a polydimethylsiloxane mold.The needle tip was fabricated by mixed solution of chitosan and polyvinylpyrrolidone which was loaded with Polygonum multiflorum extract,and the base layer was prepared by mixed solution of polyvinyl alcohol and polyvinylpyrrolidone.In vitro mechanical tests showed that the maximum load of a single tip of the drug-loaded MN was about 3.5 N,which met the mechanical requirements of skin puncture(>1 N).The drug release experiment showed that the MN could achieve gradual drug release.In the animal experiment,pigmentation and hair regrowth occurred earlier in the Polygonum multiflorum-MN(Pm-MN)group than in the other groups,and hair growth finally appeared in almost the entire area.Compared with the AGA model mice,mice in the Pm-MN group achieved an increase in the number and diameter of hair follicles.In conclusion,the Pm-MN is scientific and feasible for treating AGA.

The Regulatory Effect of Braided Silk Fiber Skeletons with Differential Porosities on In Vivo Vascular Tissue Regeneration and Long-Term Patency

The development of small-diameter vascular grafts that can meet the long-term patency required for implementation in clinical practice presents a key challenge to the research field.Although techniques such as the braiding of scaffolds can offer a tunable platform for fabricating vascular grafts,the effects of braided silk fiber skeletons on the porosity,remodeling,and patency in vivo have not been thoroughly investigated.

Comparison of stem cell characteristics between perichondral-derived stem cells and periosteal stem cells in postnatal rats

Bone marrow mesenchymal stem cells(BMSCs),periosteal stem cells(PSCs),and other bone stem cells originate from embryonic bone formation,but their function and stem cell characteristics such as proliferation ability and differentiation ability change at different anatomical locations.Perichondral-derived stem cells(PCSCs)are more closely related to PSCs in origin and function,usually used to be studied together with PSCs as one type of stem cell.However,this leads to the ignoration of the PCSCs'characteristics.Since the anatomical locations of these two types of stem cells diverse,PCSCs should have some differences from PSCs.In this study,the PCSCs in the perichondrium surrounding the growth plate cartilage expressed CTSK and CD200 same as PSCs.However,when compared the stem cell characteristics of PCSCs with that of PSCs,PCSCs were more elongated than PSCs in morphology and have stronger self-renewal ability,as well as stronger chondrogenic and adipogenic differentiation potentials.This study revealed the stem cell characteristics of PCSCs distinguished from PSCs,which may indicate PCSCs and PSCs should not be treated as one type of cell to research in the future.

Effect of mechanical stresses on degradation behavior of high-purity magnesium in bone environments

High-purity(HP)magnesium(Mg)has emerged as a promising biomaterial for supporting functional bone tissue.Our previous study found that mechanical stresses and the surrounding fibrotic tissue(subcuta-neous)both play crucial roles in the degradation of HP Mg.However,due to challenges in the degradation and regeneration process in vivo,it remains unclear how stress affects HP Mg degradation in bone en-vironments,limiting its further application.In this study,novel loading devices were designed and the effects of tensile and compressive stresses on HP Mg degradation in vivo and in vitro bone environments were quantitatively analyzed.In addition,bone osteointegration around HP Mg was explored preliminar-ily.Tensile stress increases the degradation rate of HP Mg in vivo and in vitro.HP Mg degradation in vivo is more sensitive to stress factors than in vitro,but the sensitivity decreases with corrosion time.The volume loss rate of HP Mg is multilinear with the applied stress and degradation time.The volume of bone tissue surrounding HP Mg is larger in the no-stress group compared to the stressed groups,which is more pronounced with increasing implantation time.These results provide valuable insights for optimiz-ing the design of HP Mg-based implants considering load conditions.This will help to achieve a balance between the degradation rate of the implant and the regeneration rate of the surrounding bone.

A systematic review of DVT and stent restenosis after stent implantation for iliac vein compression syndrome

Iliac vein compression syndrome(IVCS)is a common venous disease caused by joint compression of the right common iliac artery and the lumbosacral vertebrae.The compression of iliac vein not only causes venous hypertension in the lower extremities,but also induces venous valve dysfunction and superficial varicose veins in lower extremities.Moreover,the compression of iliac vein is an important potential factor for iliofemoral vein thrombosis.Currently,open surgery and stent implantation are the main treatment for IVCS.Due to the advantages of minimally invasive and postoperative patency,stent implantation for IVCS has gradually become the standard treatment.However,when the stent is implanted into the iliac vein to treat IVCS,the complications,such as restenosis,deep vein thrombosis(DVT)appear,which affect the patency of stent and hamper the patient recovery.Up to now,the mechanism how the stent implantation induces the restenosis and DVT is still unclear.In this review,we summarized the clinical symptoms,treatment methods of IVCS and the complications after stent implantation,and analyzed the mechanism of stent restenosis and DVT,and finally discuss the iliac vein stent design specifically for treating IVCS.

Effect of mechanical stretching and substrate stiffness on the morphology,cytoskeleton and nuclear shape of corneal endothelial cells

Due to the limited capacity of corneal endothelial cells(CECs)division,corneal endothelial diseases have become a great challenge.The cornea is subjected to various mechanical stimuli in vivo,which may have a positive or negative influence.Thus,it is significant to gain an insight into the mechanism of mechanobiology of CECs for seeking more possible treatment.The purpose of this study was to determine the impacts of mechanical stretch and substrate stiffness on the morphology and fundamental cell behavior of CECs.Rabbit corneal endothelial cells(RCECs)were subjected to a 5%mechanical stretch or cultured on substrates of different stiffness.The impacts of mechanical stimulus on cell area,aspect ratio,circularity,cell density,nuclear shape,cytoskeleton,and cell viability were investigated.The expressions of the corneal endothelium-related markers ZO-1 and Na^(+)/K^(+) ATPase were also evaluated by confocal immunofluorescence microscopy in the stiffness group.Our results suggested that mechanical stretch promoted the rearrangement of the cytoskeleton while decreasing the cell circularity,nuclear area,and cell density as well as cell viability.RCECs cultured on 10 kPa substrates,which was close to the physiological stiffness of rabbit Descemet's membrane(DM),showed better cell morphology,more stable actin cytoskeleton assembly,and more robust expression of the functional marker compared with other softer or stiffer substrates.In summary,mechanical stretch and substrate stiffness have profound influences on the morphology and function of CECs,which may have implications for the understanding and possible treatment of corneal endothelial diseases.

Design, kinematic modeling and evaluation of a novel soft prosthetic hand with abduction joints

This paper presents a novel tendon-driven soft prosthetic hand with 5 fingers and 9 independent actuators.A special notched structure was used as the finger joint,which brings adequate compliance to grasping.The soft finger has two kinds of vertically arranged joints that can produce flexion/extension and abduction/adduction motions under tension and release,enabling a three-dimensional workspace of the finger and improving the dexterity of the hand.The design and manufacture of the finger and soft hand are described in detail.An openloop kinematic model based on piecewise constant curvature of the finger was established and verified experimentally.The results show that the model could precisely predict finger movement.The slip resistance of the soft hand was tested,and the capacity to grasp objects was evaluated based on power grasp and precision grasp.With abduction joints,the proposed hand can perform various gestures and in-hand manipulations,which indicate high dexterity.This work provides a way to realize high dexterity for soft prosthetic hands.

Experimental and finite element analysis studies of a reduction-force reducing traction method for pelvic fracture surgeries

Pelvic fracture is among the most complicated fractures in traumatic orthopedics,with high mortality and morbidity rates.The main difficulty associated with the reduction surgery is significant muscle resistance.It then becomes necessary to decrease the reduction force against this strong muscle resistance,for improving surgical safety.Here,we propose a novel traction method for decreasing the reduction force during pelvic reduction,and investigate the performance of the elastic traction method on decreasing the reduction force using experimental tests and simulation-based analyses.From the experimental results,the reduction force decreased by 59.2%when 10 kg of elastic traction was applied.We also establish a musculoskeletal model of the pelvic fracture reduction,for analyzing the muscle resistance and the optimal traction force applied in reduction surgeries.The elastic traction method can counteract the muscle resistance increase in the non-traction direction owing to its flexibility.We conclude that the optimal traction force applied should be in the 10–15 kg range,and recommend adopting a dynamic traction strategy rather than continuous traction in clinical settings.Elastic traction is very promising for various surgeries that require traction,including pelvic reduction.It significantly reduces force,which can significantly reduce the physical exertion of the operating surgeon,the possibility of additional injuries to the operated patient,and promotes robot-assisted reduction surgeries.

Effects of Geometrical Characteristics of Suture on Fracture Resistance of Walnut Shell

Nut shells have good impact and fracture resistance,but many kinds of nut shells have suture structures with low bonding strength.Therefore,the mechanism of impact and fracture resistance of nut shells as a whole is important to study,particularly given that sutures maintain low bonding strength.In this study,we investigated the effect of the geometrical characteristics of sutures(morphology,thickness,and number)on the overall fracture resistance of walnuts,based on mechanical tests of C-ring samples,microstructure analysis after cracking,quantitative analysis of suture geometric model,and numerical simulations.We found that the cracking of walnuts was mainly caused by tensile stress,and the bonding strength was approximately 2.48±0.64 MPa.We discovered that the thickness of the suture was 1.55±0.32 times thicker than the shell,which improved the fracture resistance ability by more than 28.4%.The undulating and inclined morphology of the walnut suture also increased the fracture force.Additionally,an appropriate suture number reduced the cracking of walnuts.In conclusion,our study sheds light on the physiological function of walnut sutures from a biomechanical perspective and provides useful references for designing fracture resistance measures in thin shell structures.

In vitro cell stretching devices and their applications:From cardiomyogenic differentiation to tissue engineering

Mechanical stretch plays an important role in the control of cardiomyocyte behavior,as well as in the study of the mechanisms of cardiovascular function and pathology.The complexity involved in biological systems in vivo has created a need for better in vitro techniques,thus a variety of cell stretching devices have been developed for a deeper understanding of cellular responses to strain.In this review,we introduce the design,functionality,and characteristics of multiple types of cell stretching devices from two and three dimensions,then discuss the research progress of promoting cardiomyogenic differentiation of stem cells by external stretching and its application in cardiac tissue engineering.

Sex differences in eye movements and neural oscillations during mental rotation in virtual reality

Virtual reality(VR)has been a promising tool for developing visuospatial tasks.Among visuospatial tasks,mental rotation tasks are widely used in the assessment of visuospatial ability.Males have a distinct advantage in mental rotation ability compared to females,yet it is generally produced by investigations based on two-dimensional(2D)images on a computer screen.Sex differences in mental rotation tasks with three-dimensional(3D)objects in VR were not fully investigated.It is unclear whether the male's advantages in 2D mental rotation tasks are weakened in 3D tasks.The aim of this study was to provide new insights into the understanding of sex differences in mental rotation tasks presented in VR.Here,we developed a VR mental rotation task(VR-MRT)using 3D objects presented by a head-mounted display(HMD)and used VR-based eye tracking and electroencephalography(EEG)to examine eye movements and neural oscillations for males and females.Our results showed that females preferred a piecemeal strategy compared to males,suggesting a significant sex difference in visual strategy.More importantly,we found no significant sex differences in alpha-band and beta-band oscillations related to rotation processes of VR-MRT.These findings indicated that sex differences in the VR-MRT were mainly attributed to the selection of visual strategy rather than the rotation processes.The study helps to comprehensively understand the dominant factors contributing to the sex differences in the VR-MRT.

Effect of 3D anchorage attachment on the alleviating tipping/extrusion of premolars for en-mass distalization of maxillary molars with clear aligners:A finite element study

This study aimed to explore the optimal invisible orthodontic force system during the en-mass distalization of two maxillary molars to minimize the side effect of anchorage loss by changing the direction of the application of the orthodontic force system.A high bio-fidelity 3D finite element model including maxilla,periodontal ligament,dentition,clear aligner,3D anchorage attachment and mini-implant was established.Different lengths of lateral hooks of 3D-printed anchorage attachments and mini-implant positions into the palatal alveolus were considered.A 200 g distal force was applied to the lateral hooks of different horizontal lengths(3.26 mm,6.52 mm and 9.78 mm)with the mini-implant as the application point.Using ABAQUS software,orthodontic tooth movements under 12 different clinical treatment designs were analyzed and calculated.The 3D anchorage attachment enhanced the anchorage of anterior teeth and alleviated the tipping/extrusion of premolars.In contrast to without clear aligners,length of the lateral hook had a negligible effect on both mesial tipping and buccal tipping with clear aligners,which could then be ignored.The change in mesial tipping was less and nearly remained constant despite of the different heights of the mini-implant.The 3D anchorage attachment assisted clear aligner can avoid the side effects of anterior tooth proclination caused by insufficient anchorage.The length of the lateral hook,and height of the mini-implant in this invisible orthodontic force system hardly affects the tooth movement of anchorage units.Clear aligners can effectively control the rotation and tipping of anchorage units caused by 3D anchorage attachment.

Collagen-based bioinks for regenerative medicine: Fabrication, application and prospective

In the field of regenerative medicine,the importance of 3D bioprinting is self-evident and nonnegligible.However,3D bioprinting technology also requires bioink with excellent performance as support material to fabricate a multi-functional bioinspired scaffold.Collagen-based bioink is regarded as an ideal 3D bioprinting ink for its excellent biocompatibility,controllable printability and cell loading property.It is an important breakthrough in regenerative medicine with the progress of collagen-based bioink,which fabricates bioinspired scaffolds with different functions and is applied in different repair scenarios.This review summarizes the different applications of collagen-based bioink and classifies them as soft tissue and hard tissue according to the target region.The applications of target region in soft tissues include skin,cartilage,heart and blood vessels,while in hard tissues include femur,skull,teeth and spine.When the collagen-based bioink is applied in repairing soft tissue,the requirements of function are higher,while the mechanical properties must be further improved in repairing hard tissue.We further summarize the characteristics of collagen-based bioink and point out the most important properties that should be considered in different repair scenarios,which can provide reference for the preparation of bioinks with different functions.Finally,we point out the main challenges faced by collagen-based bioink and prospect the future research directions.