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.

Polar-coordinate line-projection light-curing continuous 3D printing for tubular structures

3D printing techniques offer an effective method in fabricating complex radially multi-material structures.However,it is challenging for complex and delicate radially multi-material model geometries without supporting structures,such as tissue vessels and tubular graft,among others.In this work,we tackle these challenges by developing a polar digital light processing technique which uses a rod as the printing platform.The 3D model fabrication is accomplished through line projection.The rotation and translation of the rod are synchronized to project and illuminate the photosensitive material volume.By controlling the distance between the rod and the printing window,we achieved the printing of tubular structures with a minimum wall thickness as thin as 50 micrometers.By controlling the width of fine slits at the printing window,we achieved the printing of structures with a minimum feature size of 10 micrometers.Our process accomplished the fabrication of thin-walled tubular graft structure with a thickness of only 100 micrometers and lengths of several centimeters within a timeframe of just 100 s.Additionally,it enables the printing of axial multi-material structures,thereby achieving adjustable mechanical strength.This method is conducive to rapid customization of tubular grafts and the manufacturing of tubular components in fields such as dentistry,aerospace,and more.

Relationship between mechanical load and surface erosion degradation of a shape memory elastomer poly(glycerol-dodecanoate)for soft tissue implant

Poly(glycerol-dodecanoate)(PGD)has aroused increasing attention in biomedical engineering for its degradability,shape memory and rubber-like mechanical properties,giving it potential to fabricate intelligent implants for soft tissues.Adjustable degradation is important for biodegradable implants and is affected by various factors.The mechanical load has been shown to play an important role in regulating polymer degradation in vivo.An in-depth investigation of PGD degradation under mechanical load is essential for adjusting its degradation behavior after implantation,further guiding to regulate degradation behavior of soft tissue implants made by PGD.In vitro degradation of PGD under different compressive and tensile load has proceeded in this study and describes the relationships by empirical equations.Based on the equations,a continuum damage model is designed to simulate surface erosion degradation of PGD under stress through finite element analysis,which provides a protocol for PGD implants with different geometric structures at varied mechanical conditions and provides solutions for predicting in vivo degradation processes,stress distribution during degradation and optimization of the loaded drug release.

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.

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.

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.

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.

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.

Responses of osteoblasts under varied tensile stress types induced by stretching basement materials

Osteoblasts are mechanosensitive cells.Tensile stress with different conditions,including loading time,frequency,magnitude,etc.would cause varied responses in osteoblasts.However,it was not clarified that the effect of the loading types on the osteoblasts.In this study,we focused on the effect of varied tensile stress types on osteoblasts,including isotropic stretch,biaxial stretch,and uniaxial stretch with the negative ratio of transverse strain to axial strain(NR)-1,0,and 0.2 respectively.Cell proliferation was determined to be most efficient when stimulated by 6%strain at a frequency of 1 Hz and a negative value of 0 for 1 h/day.The varied strain resulted in a thickening of the F-actin cytoskeleton and a thinning of the nucleus.Nuclear flattening caused Yes-associated protein(YAP)to be transported to the nucleus.It was suggested that the influence of loading types on the mechanobiology responses must be noticed.The mechanism of cell mechanical sensitivity under varied loading types was explored,which would provide good sugges-tions for designing microstructures to control deformation patterns in bone tissue engineering.

The role of primary cilia in mechanical transmission of osteocyte based on a 3D finite element model

The primary cilium,as a mechanical receptor of osteocytes,participates in the regulation of osteocyte mechanosensitivity.However,how the length of osteocyte primary cilia changes with fluid shear stress(FSS)are unclear,and how the mechanical transmission within osteocytes altered by primary cilia is not well understood yet.Therefore,the ciliary length changes of osteocyte under 15dyn/cm2 of FSS were experimentally detected,and then 3D finite element models of osteocyte primary cilia containing the basal body and axoneme were built.The results showed that(1)The ciliary length of the CON group,FSS 1h,and FSS 6h were 3.71±1.34μm,3.79±1.04μm,and 1.24±0.73μm respectively,indicating the different durations of FSS might lead to the adaptive changes of cilium length.The calculations showed(2)when the ciliary length became shorter with the ciliary angle stayed the same,the deformation and stress of the cell membrane and membrane skeleton was increased.However,the deformation and stress of the cilia membrane,basal body,the rotation angles of basal body were decreased,and those of cytoplasm,cytoskeleton,actin cortex and nucleus were also decreased;(3)With the decrease of the ciliary angle,the deformation and stress of the cilia membrane,basal body,as well as the rotation angles of basal body were increased.Those of the cytoplasm,cytoskeleton,actin cortex,and nucleus were also increased except the cell membrane and membrane skeleton.The calculation results suggested the length and angle of the primary cilia,the deformation and stress of intracellular structures in osteocyte were altered with ciliary basal body,indicated the connection between the basal body and cytoskeleton may be a key factor that affected the mechanical transport in osteocytes across the cell membrane.This finally promoted the adaptive change of ciliary length under FSS.

Wireless measurement of orthodontic forces in invisible aligners

Invisible orthodontic treatment is an effective form of malocclusion treatment favored in recent years.The magnitude of its orthodontic force has a crucial impact on the outcome of the treatment and has gained a high level of clinical interest.However,there are very few explorations of in vivo measurements of orthodontic force,and existing studies are limited to a large number of couplings,which are inconvenient for clinical use.In this work,we developed a wireless flexible measurement system that allows quantitative measurement of the orthodontic force of an invisible aligner on a dental model.The system is wireless,tiny,flexible,fast responding,and has a range suitable for the range of orthodontic forces.We show the difference in the orthodontic force applied to different tooth positions and the difference in the orthodontic force applied to different positions of the same tooth.In addition,the system can evaluate the mechanical differences between aligners of different brands and materials as well as the deviation of fabrication results.This system provides a test tool and evaluation method for future real-time assessment of clinical orthodontic forces.

A bio-feedback-mimicking electrode combining real-time monitoring and drug delivery

Effective disease management based on real-time physiological changes presents a significant clinical challenge.A flexible electrode system integrating diagnosis and treatment can overcome the uncertainties associated with treatment progress during localized interventions.In this study,we develop a system featuring a biomimetic feedback regulation mechanism for drug delivery and real-time monitoring.To prevent drug leakage,the system incorporates a magnesium(Mg)valve in the outer layer,ensuring zero leakage when drug release is not required.