Research perspective and prospective of additive manufacturing of biodegradable magnesium-based materials

Biodegradable metals such as magnesium(Mg)and its alloys have attracted extensive attention in biomedical research due to their excellent mechanical properties and biodegradability.However,traditional casting,extrusion,and commercial processing have limitations in manufacturing components with a complex shape/structure,and these processes may produce defects such as cavities and gas pores which can degrade the properties and usefulness of the products.Compared to conventional techniques,additive manufacturing(AM)can be used to precisely control the geometry of workpieces made of different Mg-based materials with multiple geometric scales and produce desirable medical products for orthopedics,dentistry,and other fields.However,a detailed and thorough understanding of the raw materials,manufacturing processes,properties,and applications is required to foster the production of commercial Mg-based biomedical components by AM.This review summarizes recent advances and important issues pertaining to AM of Mg-based biomedical products and discusses future development and application trends.

High plastic Zr–Cu–Fe–Al–Nb bulk metallic glasses for biomedical applications

Four Zr–Cu–Fe–Al-based bulk metallic glasses（BMGs） with Zr contents greater than 65at% and minor additions of Nb were designed and prepared. The glass forming abilities, thermal stabilities, mechanical properties, and corrosion resistance properties of the prepared BMGs were investigated. These BMGs exhibit moderate glass forming abilities along with superior fracture and yield strengths compared to previously reported Zr–Cu–Fe–Al BMGs. Specifically, the addition of Nb into this quaternary system remarkably increases the plastic strain to 27.5%, which is related to the high Poisson＇s ratio and low Young＇s and shear moduli. The Nb-bearing BMGs also exhibit a lower corrosion current density by about one order of magnitude and a wider passive region than 316 L steel in phosphate buffer solution（PBS, pH 7.4）. The combination of the optimized composition with high deformation ability, low Young＇s modulus, and excellent corrosion resistance properties indicates that this kind of BMG is promising for biomedical applications.

Effects of different simulated fluids on anticorrosion biometallic materials

The corrosion behaviors of SUS316L stainless steel, Co Cr alloy and Ti 6Al 4V alloy in Ringer’s, PBS(-) and Hank’s solutions have been investigated. The results indicate that the corrosion of Ringer’s solution is the strongest, then followed by PBS(-) and Hank’s solution. The presence of HPO 2- 4, H 2PO - 4, SO 2- 4 and glucose in the PBS(-)and Hank’s solution probably reduces the corrosion inhibitor and corrosion current. The decrease of the solution’s pH significantly increases the corrosion rate and susceptibility to localized corrosion of SUS316L SS and Co Cr alloy. However, Ti 6Al 4V alloy exhibits an exceptional stability and has only a slight increase of corrosion rate with decreasing pH.

Biomanufacturing in Japan:frontier research from 2018 to 2023

Biomanufacturing(BM)is a multidisciplinary area incorporating the characteristics of living organisms and engineering principles to create valuable products for various sectors,including medicine,energy,and the environment.BM has undergone a remarkable transformation in the last two decades,entering the era of BM4.0 and becoming a pivotal driver of the sustainable revolution.Notably,Japan has made significant advances in BM,contributing to its development through the creation of innovative materials,advanced processes,and interdisciplinary applications.However,because of certain development policies,this research has not been widely recognized on an international level.This paper provides a comprehensive summary of the research progress made by renowned Japanese laboratories and researchers in biomedical materials,bio-three-dimensional(3D)printing,and biomedical applications in the last five years.Their unique contributions are introduced and analyzed,illuminating the distinctive approaches and breakthroughs within each domain.Additionally,this review highlights the current challenges and prospects of BM.The viewpoints presented in this paper are intended to serve as a valuable reference for scholars studying BM in Japan.

As-cast microstructure and properties of non-equal atomic ratio TiZrTaNbSn high-entropy alloys

High-entropy alloys have been proved to be potential candidate materials in the biomedical field due to their balanced mechanical properties and excellent biocompatibility.The effects of atomic ratios on the as-cast microstructural evolution,mechanical properties,and electrochemical property of TiZrTaNbSn high-entropy alloys were studied systematically.The crystal structure of TiZrTaNbSn high-entropy alloys is single BCC phase,and the microstructural evolution is based on atomic ratio.The dendric structure,peritectic structure,pseudo eutectic and equiaxed grain,which are associated with element segregation,can be obtained by non-equal atomic ratio.Ti_(30)Zr_(20)Ta_(20)Nb_(20)Sn_(10)alloy demonstrates a high compressive strength and fracture strain,which are 2,571.8 MPa and 12%,respectively,and the fracture behavior is quasicleavage faults.The Ti_(45)Zr_(35)Ta_(5)Nb_(5)Sn_(10),Ti_(30)Zr_(20)Ta_(20)Nb_(20)Sn_(10)and Ti_(35)Zr_(25)Ta_(15)Nb_(15)Sn_(10)alloys show excellent corrosion resistance according to Nyquist diagram,polarization curves and corrosion morphology.Compared with TiZrTaNbSn alloy,the corrosion rate of Ti_(45)Zr_(35)Ta_(5)Nb_(5)Sn_(10) alloy increases by about 98.9%.It can be concluded that non-equal atomic ratios are effective for microstructure control and performance optimization.

Electrochemical behaviour of commercially pure titanium and Co-Cr alloy in Ringer's solution

The electrochemical behaviors of commercially pure titanium (CP Ti) and Co-Cralloy in Ringer's solution have been investigated. The results indicate that the electric potentialof passive region for CP Ti is up to 3000 mV, and its passive current density is 3.078 μA/cm^2.The excellent corrosion resistance of CP Ti can be attributed to the formation of TiO_2 oxide film.The passive region of Co-Cr alloy is 770 mV, which is narrower than that of CP Ti. However, nohysteresis loops are found in the reverse scanning curves of Cu-Cr alloy. A complex oxide film ofCo_3O_4, Co_2O_3, and Cr_2O_3 formed on the surface provides Co-Cr alloy with a stableelectrochemistry property. The corrosion rates of the crevice samples increase with the pH value ofmedium decreasing. The electron probe microanalyzer (EPMA) analysis indicates that Ti in CP Ti andCo, Cr in Co-Cr alloy dissolve in crevice area due to the Sealed-Cell effect.

Tribological behaviour of biomedical Ti–Zr-based shape memory alloys

The tribological behaviour of Ti-30Zr, Ti-20Zr-10Nb and Ti-19Zr-10Nb-1Fe alloys was investigated using reciprocating friction and wear tests. X-ray diffraction（XRD） results indicate that Ti-30Zr, Ti-20Zr-10Nb and Ti-19Zr-10Nb-1Fe alloys are composed of hexagonal a＇-martensite, orthorhombic a＇＇-martensite and bcc β phases,respectively. Ti-30Zr alloy has the highest hardness of HV（273.1 ± 9.3）, while Ti-20Zr-10Nb alloy exhibits the lowest hardness of HV（235.2 ± 20.4） among all the alloys.The tribological results indicate that Ti-30Zr alloy shows the best wear resistance among these alloys, corresponding to the minimum average friction coefficient of 0.052 and the lowest wear rate of 6.4x10^-4mm3·N^-1·m^-1. Ti-20Zr-10Nb alloy displays better wear resistance than Ti-19Zr-10Nb-1Fe alloy, because the iron oxide is easy to fall off and less Nb2O5 films form on the worn surface of the latter.Delamination and abrasive wear in association with adhesive wear are the main wear mechanism of these alloys.

Zr-Ti-Al-Fe-Cu bulk metallic glasses for biomedical device application

A series of Zr_(63.5-x)Ti_(x)Al_(9)Fe_(4.5)Cu_(23)(x=0,1.5,3.0,4.5,6.0;at%) bulk metallic glasses(BMGs) were designed and produced by means of copper mold suction casting.The effect of Ti addition on the glass-forming ability(GFA) and mechanical properties of Zr_(63.5-x)Ti_(x)Al_(9)Fe_(4.5)Cu_(23) alloys was first investigated.The glassforming ability and room-temperature plasticity of BMGs increase first and then reduced with Ti content increasing.At x=3.0,the Zr_(60.5)Ti_(3)Al_(9)Fe_(4.5)Cu_(23) BMG showed a critical glass formation diameter of 10 mm and excellent room-temperature compressive plasticity(εP=4.7%) by using the samples with dimensions of Φ3 mm × 6 mm.Meanwhile,the BMG also showed better biocompatibility and biocorrosion resistance compared with Ti6 A14 V alloy.Under the imitated human body condition,the corrosion current density(Icorr) of BMG was 6.61 × 10^(-10) A·cm^(-2),which is two orders of magnitude lower than that of conventional Ti6Al4V alloy.Moreover,the CCD-986 sk cell viabilities are,respectively,65.4% and 46.6% on the BMG and Ti6 A14 V alloy,indicating better biocompatibility of BMG.The Zr_(60.5)Ti_(3)Al_(9)Fe_(4.5)Cu_(23) BMG with larger GFA,excellent mechanical properties,biocompatibility and biocorrosion resistance is considered as a potential material in biomedical device fields.

BIOMEDICAL MATERIAL FOR SUTURELESS ESOPHAGOGASTROSTOMY ANALYSIS OF 31 CASES

The results of 31 cases of sutureless esophagogastrostomy by intraluminal elastic circular ligation (IECL) with the biodegradable supporting tube were reported. The fate of the supporting tube could be tracked satisfactorily by X-ray, The tube-dislodge time was 15.03 +/- 2.23 days and unaffected by the size of supporting tube or the site of anastomosis, The supporting tube could be safely absorbed or partially discharged through the alimentary tract. IECL, with the merits of saving time, anastomosing tightly and leaving no suture materials in the anastomotic site, can be expected to further reduce the incidence of anastomotic leakage and provide references for other gastrointestinal anastomosis.

Influences of Reaction Parameters and Ce Contents on Structure and Properties of Nano-scale Ce-HA Powders

Ce-incorporated apatite（Ce-HA） nano-scale particles with different Ce percentage contents（atomic ratio of Ce to Ce ＋ Ca is 5%,10%and 20%,respectively） were synthesized via a simple wet chemical method in this study.The crystal structure,chemical groups,thermal stability,crystal morphologies and crystal sizes of the Ce-HA nano-particles were characterized by X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,and transmission electron microscopy（TEM）.The influences of reaction temperature,reaction time,pH value,and the atomic ratio of Ce to Ce ＋ Ca on the structure and performance of Ce-HA particles were studied.The results show that the lattice constants,particle sizes,crystallinity and thermal stability of Ce-HA vary with the doped Ce contents.With the increase of Ce content,the lattice constants of the Ce-HA nano-particles remarkably increase but the particle size,crystallinity and thermal stability gradually decrease.The reaction temperature as well as the reaction time has no significant effect on the properties of the final products,while the pH value has a direct relationship with their final chemical composition.The obtained Ce-HA nanosize particles possess potential application in preparing artificial bone implants,bone tissue engineering scaffold and other bioactive coatings.

Improving the fretting biocorrosion of Ti6Al4V alloy bone screw by decorating structure optimised TiO2 nanotubes layer

TiO2 nanotubes(NT)has been demonstrated its potential in orthopaedic applications due to its enhanced surface wettability and bio-osteointegration.However,the fretting biocorrosion is the main concern that limited its successfully application in orthopaedic application.In this study,a structure optimised thin TiO2 nanotube(SONT)layer was successfully created on Ti6Al4V bone screw,and its fretting corrosion performance was investigated and compared to the pristine Ti6Al4V bone screws and NT decorated screw in a bone-screw fretting simulation rig.The results have shown that the debonding TiO2 nanotube from the bone screw reduced significantly,as a result of structure optimisation.The SONT layer also exhibited enhanced bio-corrosion resistance compared pristine bone screw and conventionally NT modified bone screw.It is postulated that interfacial layer between TiO2 nanotube and Ti6Al4V substrate,generated during structure optimisation process,enhanced bonding of TiO2 nanotube layer to the Ti6Al4V bone screws that leading to the improvement in fretting corrosion resistance.The results highlighted the potential SONT in orthopaedic application as bone fracture fixation devices.

Synthesis and Characterization of Tb-incorporated Apatite Nano-scale Powders

Nano-scale Tb-incorporated apatite （nano-Tb-AP） particles with different Tb contents （Tb/（Tb＋Ca）） of 0%, 5%, 10% and 20% were synthesized through a simple wet chemical method in this study. The crystal structure, thermal stabilities, chemical groups, crystal morphologies and crystal sizes of the nano--Tb-AP particles were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, and transmission electron microscopy （TEM）, respectively. It was found that lattice constants, particle sizes, crystalline and thermal stability varied with the doped Tb contents. With the increasing of Tb content, the lattice constants, particle size, length/diameter ratio, crystalline and thermal stability of nano-Tb-AP gradually decrease. Especially, almost all the 20%Tb-AP nano particles had been decomposed at 1200 ℃ while only a few of the decomposed products （β-TCP） were detected in the Tb-free nano apatite powders： This kind of nano-scale Tb-incorporated apatite exhibits an extremely potential clinic application because it integrates both the excellent biological functions of Tb element and apatite in human body.

Zrs5.8Al19.4（CO1-xCux）24.8 （x = 0-0.8 at.%） bulk metallic glasses for surgical devices applications

Zr-Al-Co-Cu bulk metallic glasses （BMGs） are promising surgical materials. By using the electron concentration criterion for BMG composition design, a series of Zr55.8Al19.a（Co1-xCux）24.8 （x = 0-0.8 at.%） alloys were produced, of which BMG rod samples with different diameters were made by copper mold casting. Among these alloys, the Zr55.8A119.4Co17.36Cu7.44 BMG exhibited a centimeter-scale glass formation size （dmax = 12 mm）, an ultrahigh strength （δy = 2.04 GPa）, a large room-temperature plasticity （εp = 4.0%）, and a fracture toughness （KQ = 120 MPa m^l/2）, as well as good corrosion resistance in phosphate-buffered solution. The attAlnment of the combination of properties as large glass-forming ability with excellent mechanical and corrosion stability would suit the surgical devices applications.

Circular Dichroism Analysis of the Effect of Metalic Ions on Structure of Colagen Molecules

Circular dichroism spectroscopy was used to study the effect of metallic ions such as Fe 3+ , Al 3+ and Ca 2+ on the structure of collagen molecules. The results showed the effect of the ions was similar to that of thermal denaturation but not as strong. On the basis of the obtained results,the mechanism used by the metallic ions to protect the biovalves from calcification may be explained as follows. Collagen is the dominant component of the biovalves. Pretreating the biovalves with glutaraldehyde caused many amino acid residues in collagen molecules to cross link. This leads to a decrease in the total positive charge in the collagen molecules and a relative surplus of free carboxyl groups. The trivalent metallic ions such as Fe 3+ preferentially bound with negatively charged carboxyl groups of collagen molecules, which caused the superhelix of the collagen to be loose and random. This improved the mechanical properties of the biovalve and neutralized surplus free carboxyl groups caused by the glutaraldehyde treatment, closed the sites where the Ca 2+ was bound. Also, it effectively protected the biovalves from calcification.