a bioresorbable cardiovascular stent prepared from l-lactide, trimethylene carbonate and glycolide terpolymers.

by:Qingyu     2020-03-05
Introduction with the dramatic increase in cardiovascular events, due to its minimal trauma, and the development of vascular coronary intervention such as stent has been developed.
Patient Treatment [1,2]
Although cardiovascular intervention using a metal stent has become the standard care for narrow blood vessels, the lifetime duration of the metal stent in the arteries may result in a long period of time
Eventually lead to hyperplasia of the new endometrium [3, 4]
The biodegradable stent is expected to reduce the thrombosis in the advanced stent and shorten the treatment time of double anti-platelet. And it is conducive to the recovery of the integrity of the natural blood vessels, because in the event of delayed or incomplete internal skin, no foreign substances will eventually be exposed to the blood.
As a result, more and more people are concerned about the use of biodegradable and biodegradable polymers in the manufacture of cardiovascular stent to reduce re-stenosis [5-8].
Several polymer bio-regulatory brackets for various applications have been reported.
Aglaval and Clark investigated a poly (L-lactide)(PLLA)
Supports designed based on slotted polymer fibers can withstand up to 1000mm Hg pressure [9], The Igaki-
Tamai bracket, coilstent made of PLLA monofilament (
Molecular Weight 183)
The Azigzag spiral design has a radial force of 11, 9%/0.
006 MPa and isFirst for human coronary artery [10].
Recently, ivimo
Vascular Stent absorption [TM]
CE labeling approval for treatment of coronary artery disease has been obtained. ABSORB[TM]
Made from PLLA, is the first bioadjustable scaffold with clinical and imaging results similar to metal drugs
2 years of eluted stent implantation but with potential advantages of Complete Stent absorption [11].
As a biodegradable and biodegradable material, Poly-C Ester (PLA)
It has been widely used in the fields of suture, drug administration system, surgical implants, cardiovascular stent, etc [12, 13].
Optical purePLLA has sufficient tensile strength, but its high rigidity and crystalline, slow degradation and acidic degradation products are the main obstacles to limiting the application of the scaffold [14,15].
PLLA and gathering (1,3-
Turtle salt in Sanya)(PTMC)
It is a means to regulate the performance of polymer.
PTMC is a kind-12[degrees]C.
High molecular weight PTMC has good mechanical properties including high elasticity and high tensile strength [16].
The degradation of pure hydrolysis is extremely slow. 1, 17, 18].
In contrast, in vivo degradation of PTMC occurs rapidly through surface erosion and may involve enzymes [17, 19].
The degradation of PTMC produces neutral products, I . E. e.
Carbon dioxide.
Various polymers of la and TMC are reported19-23].
These polymers with excellent flexibility have been studied as guidelines for cardiac structure and nerve regeneration [19, 20]
Cartilage implants and wound dressings [21]
Sustained drug release carrier [22]
, Bracket cover [23].
In our previous work, all kinds of PLLA-
The TMC polymer was obtained by changing the chemical composition and chain structure [24-26].
The thermal properties, degradation behavior and mechanical properties of the polymer were considered.
It seems thePLLA-
The TMC polymer has relatively high tensile strength and crystalline degree, but the degradation speed is slow.
In contrast, low crystals may cause loss of tensile strength due to low content.
In fact, the use of the cardiovascular stent requires high mechanical strength to withstand the pressure of the blood vessels, excellent flexibility for in situ expansion, and appropriate degradation rates. Hence, PLLA-
The TMC polymer does not seem to meet all the requirements of the cardiovascular stent.
Similar to PLLA, Poly B ester (PGA)
It is also a highly crystalline polymer that can be degraded (45-
55% crystalline degree)
The greenhouse temperature is ~ 35 [degrees]
Melting temperature between C and 220 to 225 [degrees]C [27].
PGA is a fast degradation polymer with high tensile strength and low breaking elongation.
At the same time, GA monomer showed higher reactivity than la and tmc monomer [18, 28].
Therefore, the GA unit is incorporated into plla-
The TMC chain should be a promising way to regulate thermal, physical and mechanical properties as well as degradation rates.
Ternary polymers of la, TMC and GA with a relatively low molecular weight range of 2. 46 X [10. sup. 4]to 5. 39 X [10. sup. 4]g[mol. sup. -1]
Zini and others reported for the first time. [29]
These trimers have glass transitions close to the temperature of the human body and show shape memory properties.
However, in the glass position area, the elastic modulus suddenly dropped by about three orders of magnitude, so they were unable to withstand the pressure of the vessel at the body temperature.
A similar trimer is also used as a monofilament suture [30, 31].
It is well known that the thermal and degradation behavior of the polymer depends directly on the composition and molecular weight of the monomer.
High molecular weight is essential to ensure good mechanical performance.
In this work, high molecular weight ternary polymers based on la, TMC and GA were synthesized, covering a wide range of compositions and characterized to evaluate their presence in cardiovascular stent
The effects of composition on thermal and mechanical properties were studied.
Corresponding PLLA-
For comparison, TMC polymers as well as PLLA and PTMC homopolymers were synthesized. Plasma-treated poly[(L-lactide)-co-glycolide](PLGA)
Terpolymer matrix is reinforced with fiber with excellent mechanical strength.
Using a single-made a micro pipe
It is then processed by CNC engraving machine to form a heart vascular bracket.
Experimental material L-
Lactic acid, zinc powder, acetic acid, antimony 3-
Ding diol, carbonated Diester, sodium metal, dibutyl disulfur tin, and sub-tin ocate ([SnOct. sub. 2])
From the car (China)
Same as received.
The solvent has an analytical grade and can be used without further purification.
The Beijing Textile Research Institute provided pla fiber kindly.
The fibers are made by melting and spinning from pla random polymer with a la/GA ratio of 10/90.
Synthesis of Xinluo by L-polymerization method
Decomposition and synthesis of lactic acid.
Under similar conditions, GA was prepared with ethanol acid.
These two kinds of monomer are obtained with five recrystals.
TMC is written using a program reported in the literature [18].
In short, 1-3 of 1 mpropanediol,1.
2 M carbonate Diester, 1/1000 M dibutyl disulfur tin, 0.
8g sodium metal remelted at 140 [degrees]C for 6 h.
Distillation removes ethanol and residual Diester carbonate.
1/1000A/about/SnOct. sub. 2]was then added.
Nearly 200 grams of crude products were obtained by thermal decomposition at 180 [degrees]C for 12 h.
Five purification was carried out by re-crystalline fromacetone/acetate (v/v = 1/3)
Before aggregation.
After 72 hours of vacuum drying at room temperature, la, GA and tmc.
C-fat, PTMC, PLLA-TMC, and PLLA-TMC-GA homo-
Through the ring-
Use [to open the polymerization of the appropriate monomer feedSnOct. sub. 2]as catalyst. The monomers/[SnOct. sub. 2]
The Moore ratio remains at 2000/1.
The monomer and catalyst are charged in an Asian polymerization tube.
After degassing, seal the tube under vacuum and aggregate at 130 [degrees]C for 72 h.
The resulting polymer is recovered by dissolving in and settling in methanol in the chloride, and then vacuum-dried at room temperature until the weight remains the same.
The infrared spectrum measured is the record of Nigo Magna.
IR 560 spectral instrument for A 4 [cm. sup. -1]resolution. [sup. 1]
H nmr spectra were performed on aBruker DMX500 spectrometer at 400 MHz.
Tritium generation of methane (CD[Cl. sub. 3])
Used as a solvent.
Chemistry class ([delta])
About four silicone is given (TMS). [sup. 13]
Nuclear magnetic resonance profiles were recorded using BRUKER AMX400 spectrometer and cd [125 MHz]Cl. sub. 3]as solvent.
Gel penetration chromatography (GPC)
The measurement was carried out on the Shimadzu instrument equipped with the refraction index (RI)
With Melamine (THF)
Ata flow rate of As solvent 1. 0 mL [min. sup. -1]. Nearly 60 [micro]L of 1.
0 w/v % solution was injected into each analysis.
Calibration was completed with polystyrene standard. X-
Ray diffraction (XRD)
Recording the spectrum with a Philips diffraction instrument composed of Cu K [alpha]([lambda]= 1. 54 [Angstrom])
Light Source, quartz monochrome device and test plate.
The contact point was determined on the solvent
Cast the film using the Kruss tension meter K100 at room temperature.
Repeat three times each measurement.
DSC with TA Q2000 instrument.
Use nearly 5 mg samples for each analysis.
All samples are first heated at 10 [degrees]C [min. sup. -1]
The temperature is much higher than the glass transition temperature ([T. sub. g])
Or melting temperature ([T. sub. m])
Clear the Heat history and then cool quickly at [50 °c]degrees]C [min. sup. -1].
Finally, a second heating scan was implemented at 10 [degrees]C [min. sup. -1].
Unless otherwise stated ,[T. sub. m]
Enthalpy of melting ([DELTA][H. sub. m])
It was confirmed from the first run, and [T. sub. g]
From the second run.
Through thermal weight analysis (TGA, TA Q500)
From room temperature to 450 [degrees]
C The heating rate is 10 [degrees]C[min. sup. -1]
Under the atmosphere of nitrogen (
40 ml [traffic]min. sup. -1]).
The tensile test film was prepared by solution casting for tensile test.
All kinds of people
At a concentration of 10 w/v %, the polymer was dissolved in acetone.
Pour the solution into a petri dish.
Air drying overnight and then vacuum drying at room temperature to constant weight at 80 [vacuum drying]degrees]C for 72 h. Dumbbell-
Shape sample size ASTM D882-02 standard (4 X 75 X 0. 3 [mm. sup. 3])
We finally cut it out of the movie.
In order to prepare the composite film, plasma treatment of pla fiber was first performed as previously reported [25].
To put it simply, pla fibers are treated in a family
Ion injection machine.
Plasma treatment was performed using a beam voltage of AC 12 kV, an electrode power of 70 W, and a plasma chamber pressure of 0. 5 Pa.
The surface of the fiber was modified in an oxygen gas atmosphere with a frequency of 13.
The scheduled time period is 6 MHz.
A predetermined amount of fiber with an average diameter of 11. 7 [micro]
The average length is 0. 3-0.
6mm is then introduced into the polymer solution.
To ensure uniform dispersion, the mixed solution is stirred into fewhours.
The composite film and corresponding tensile samples are then prepared under the same conditions, as in the case of neat polymers.
Tensile test at room temperature (20-23[degrees]C)
On the DXLL10000 Universal Tensile testing machine, run at the cross speed of 10mm [min. sup. -1]and a grip-to-
Gripseparation 25mm.
Calculation of tensile strength, fracture strain and elastic modulus based on stressstrain curves.
All data shows an average of at least four repeated measurements.
The three-element polymer is selected to manufacture the bracket.
First of all, the wall thickness of the acylindrical tube, the inner and the die of the outsidediameters being squeezed, singlescrew extruder(Diameter of screws]PHI]
= 15mm, L/D-ratio of length to diameter-22).
The unit speed is maintained at 40 rpm and the barrel temperature is from 150 to 170 [degrees]C.
Then use the CNCengraving machine to make tubes (518 JIG)
A cardiovascular stent is produced according to the previously reported pattern of coronary stent design [32]
The final size of the bracket is 5.
Diameter 0mm, 0.
Wall thickness is 22mm and length is 10mm.
Results and discussion the development of synthetic and characterizing cardiovascular stent requires a material with a strictly defined feature in terms of thermal properties, wetting properties, mechanical properties, and degradation behavior.
A series of gay
Polymers based on la, TMC and GA were synthesized for the manufacture of cardiovascular stent, which is expected to support the diseased vessels during healing.
Synthesis by bulk ring-
Open polymerization of circulating monomer, using [SnOct. sub. 2]as catalyst (Scheme 1). [SnOct. sub. 2]
Has been selected for the synthesis of highly efficient and commonly used biomedical application polymers [33]. Five PLLA-TMC-
GA Ternary Polymer and corresponding PLLA-
By changing the feeding rate, different components of TMCcopolymers were obtained.
For clarity, various initials acronyms are introduced to specify the polymer (Table 1).
For example, PLT95/5 specifies PLLA-
The feeding ratio of 95/5, PLTG95/5 means PLLA-TMC-
The ratio of GAwith la/TMC/GA material is 95/5.
PLLA and PTMC homopolymers were also synthesized for comparison.
All the samples obtained a high yield rate of more than 80%. [
Non-reproducible formula in ASCII]
Figure 1 shows the FT-
Infrared spectrum of PLLA-TMC and PLLA-TMC-
GAcopolymers are homopolymers with PLLA and PTMC.
PLLA presents the ribbon at 1757 and 1184 [cm. sup. -1]
The carbon-based ether bond is assigned separately.
Similarly, the ketone and ether bonds of PTMC were detected at [1741 and 1244]cm. sup. -1]. On the FT-
Infrared spectrum of PLLA-TMC copolymer (PLT75/25)
The vibration of the ether bond splits into two bands at 1190 and 1267 [cm. sup. -1]
And only one carbon adsorption band was detected at 1752 [cm. sup. -1].
These findings suggest that co-polymerization occurs between la and TMC monomer.
In the case of PLLATMCGA terpolymer (PLTG90/10/15)
Feature absorption-C[H. sub. 2]
Observation of PGA group is about 1423 [cm. sup. -1].
The composition of the polymer was determined from [sup. 1]H NMRspectra.
Figure 2 shows [sup. 1]
Nuclear magnetic resonance profiles of PLLA, PLT95/5 and pltg95/5 in CD [Cl. sub. 3].
PLLA shows a double material at 1. 4-1. 7 ppm (peak4)
And a five-point quartet. 0-5. 2 ppm (peak 1)
This is due to theC [H. sub. 3]
And CH protons.
On the spectrum of PLT95/5, signals of la and TMC components were detected. The middleC[H. sub. 2]
The proton of the TMC component appears in 2. 03 ppm (peak 3). Twolateral C[H. sub. 2]
The proton appears at 4. 24 ppm (peak 2)[30, 34]
Interestingly, the signal is 5. 0-5.
The 2 ppm area can be divided into two groups: the lower wild group of about 5.
2 ppm belongs to the main chain LLAunits, and the upfield group is around 5.
Assign 0 ppm to the la unit linked to the TMC unit.
Terpolymer PLTG95/5 shows the signal for all three components.
Multiple of C [H. sub. 2]
The gambling proton was detected at 4. 6-5. 0 ppm (peak 5)
Shows the existence of many TMCor LLA-
Due to the low content of the GA unit, it has a higher reactivity compared to la and TMC [so connect it18, 28].
These findings confirm PLLA-TMC-
GA Ternary Polymer was successfully obtained.
The composition of Terpolymers is calculated based on the integral of the 4-point signal. 1-4.
3 ppm of the TMC unit, at 5. 0-5.
For the Xinluo unit and 4 points, 2 ppm. 6-5.
The GA unit is 0ppm.
As shown in Table 1, the composition of the polymer is very close to the feed ratio, which is consistent with the good conversion rate of the monomer.
Detailed analysis]sup. 13]
C nmr Spectra enable us to have an in-depth understanding of the chain structure of the polymer as we have previously reported [30]. The [sup. 13]
MRI of typical PLLA-TMC-GAterpolymer (PLTG95/5/5)
As shown in the figure. 3.
Carbon in the carbonyl mc, GA and la sections was observed at 154. 3, 166. 5, and 169.
5 ppm respectively.
The CH carbon in the La Part appears between 69. 0 and 71. 4ppm, and C [H. sub. 3]
The group was detected at 16. 6 ppm. The middleC[H. sub. 2]
Carbon in the TMC portion was observed at 27.
9 ppm and the other two C [H. sub. 2]
Carbon is between 61. 8 and 65. 0 ppm. TheC[H. sub. 2]
The carbon of the GA part was detected between 60. 6 and 60. 9 ppm. The enlarged [sup. 13]
The c nmr region of PLTG95/5 is also shown in the figure. 3.
A wild quilt ([delta]= 69. 10, 69. 19, 69. 24, and 69. 29ppm)is detected.
At the same time, multiple signals are clearly splitH. sub. 2]
The region of GA is also observed, which indicates that PLLA-TMC-GA terpolymers.
Average molecular weight and number ([[bar. M]. sub. w]and [[bar. M]. sub. n], respectively)
More dispersed ([[bar. M]. sub. w]/[[bar. M]. sub. n]
As shown in Table 1, one of the various polymers is determined by prediction. All the homo-
Polymer with high molecular weight and [[bar. M]. sub. n]
More than 100,000, except for a little lower PTMC.
The multi-dispersion value of all polymers is from 1. 9to 2. 6.
This is an important feature because the support material should be able to be in the initial 3-
Implant for 6 months 【10].
As we all know, the mechanical properties will deteriorate as the molecular weight decreases.
An average molecular weight of about 25,000 has been proposed as the limit value for the loss of tensile properties [16].
At the same time, the melting extrusion process will also cause the phenomenon of broken chain. 35, 36].
Therefore, the initial molecular weight of the polymer should be high enough to ensure good mechanical properties after processing.
Humidity is one of the important criteria for evaluating the surface properties of biological materials [37]
, The results of the contact angle measurement are shown in Table 1.
Water contact point for PLLAis 85. 2[degrees].
In the case of polymer, the contact angle value changes in the range of 80. 6[degrees]to 83. 8[degrees]
, Consistent with the hydrophobic properties of various polymers [38, 39].
Crystal structure of the selected solution-
X-check the show
Ray diffraction, as shown in the figure. 4.
The film of PLLA, PLT95/5 and PLT95/5 showed semi-crystalline, and the diffraction peak was theta = 8. 3[degrees], 9. 5[degrees], and 11. 2[degrees]
The crystal structure corresponding to PLLA is respectively.
Ptmc is known to be an amorphous elastic material.
The diffraction peaks of the PGA were not observed, indicating that the PGA block did not crystallize for long enough.
Different peak intensity was observed.
PLLA is more crystalline than polymer, which is consistent with different PLLA contents.
Thermal performance of PLLA-TMC-
Thermal Properties of GA Ternary Polymer
As shown in the figure, the polymer-based polymer can be adjusted to a large extent by adjusting the single feed ratio5 and Table 2.
All polymers show only one glass through temperature ([T. sub. g]). The [T. sub. g]
PLLA and PTMC were observed at 61. 1[degrees]C and -12. 3[degrees]C, respectively. PLLA-
Under \"TMC aggregation]T. sub. g]
Due to the presence of TMC components, than PLLA.
The higher the TMC content, the lower [T. sub. g].
As we all know ,[T. sub. g]
About 36 PGA homopolymers [degrees]C [27]
, Below PLT75/25 (44. 4[degrees]C).
Therefore, using the same la/TMC localization, reduce [T. sub. g]
It was for PLLA-TMC-
GA Ternary Polymer compared to PLLA-
TMC polymer with increased GA content. Allthe PLLA-TMC-
GA Ternary PolymerT. sub. g]above 50[degrees]C.
In order to reasonably explain the change of glass transition temperature with composition in Ternary Polymer, well-
The known Fox equation is modified to explain three-
The composition system is as follows: 1 /[T. sub. g]= [w. sub. 1]/[T. sub. g1]+ [w. sub. 2]/[T. sub. g2]+[w. sub. 3]/[T. sub. g3](1)where [w. sub. 1]; [w. sub. 2], and [w. sub. 3]
Refer to the weight score of the three components and [T. sub. g], [T. sub. g2]and[T. sub. g3]refer to the [T. sub. g]
The corresponding Olympic athletes.
The results obtained from the Fox equation are very close to the experimental data shown in Table 2, indicating that all components are not separated.
PLLA is an essentially semi-crystalline polymer with peaks at 176. 1[degrees]
C has the enthalpy of melting ([DELTA][H. sub. m])of 38. 4 J [g. sup. -1]
In sharp contrast to PTMC, PTMC is amorphous. PLLA-
The TMC polymer is semi-crystalline at a content of more than 85 mol %.
A decrease in La content leads to a decrease in melting temperature [T. sub. m]
And the reduction of heat.
In the case of PLLA
Only the TMCGA polymer of PLTG95/5 presented a very weak melting peak at 157. 2[degrees]
C and the corresponding [DELTA][H. sub. m]of 0. 3 J [g. sup. -1].
The ability of these Xinluo crystals
The base polymer is strongly influenced by the Xinluo content and the average sequence length.
PLTG95/5 is higher than plt85/15 but slightly lower [T. sub. m]and [DELTA][H. sub. m]values.
This finding suggests that the Ternary Polymer has a shorter luminous length and a more random chain structure.
As we all know, crystal fragments formed during degradation may cause unexpected late inflammatory reactions and have a negative impact on tissue growth [40].
Therefore, given the use of these polymers in biomedical applications, the smallest crystals are better.
In order to determine the decomposition temperature of the polymer, the thermal weight analysis of the polymer was carried out.
TGA shows that in the range of room temperature to 200 [degrees]
C. All the polymers studied were very stable with a maximum observed weight loss of 1%.
All polymers degrade in one decomposition step.
The thermal stability of PLLA and PTMC homopolymers is the best, and the temperature at the maximum weight loss rate ([T. sub. d max])
About 357 and 363 【degrees]C,respectively. The [T. sub. d max]of the PLLA-TMC and PLLA-TMC-
Change of GAcopolymers between 337 and 355 [degrees]C (Table 2).
It shows that polymers such as PLT95/5 and pltg95/5 with very high la content exhibit more TMC and ga monomer than they have due to more regular chain structure
PLLA for mechanical properties-TMC-
The mechanical properties of GA Ternary Polymer and composite materials are critical for the application of the support. Grabow et al.
Biodegradable plastics that can withstand compression pressures of up to 1 have been developed.
Equivalent to 3 pieces of ordinary metal stainless steelsteel stents[32]
Therefore, the mechanical properties of the polymer were evaluated compared to PLLA.
Tensile strength ([
Partial derivative])
Strain when broken ([[epsilon]. sub. break])
, And Young\'s modulus (E)
Listed in Table 3. The [T. sub. m]and [DELTA][H. sub. m]ofthe solution-
Considering that the mechanical properties of the polymer are strongly dependent on the crystal, a cast film is also given.
The polymer with different molar ratios was observed to have significantly different mechanical properties.
PLLA has the British properties of tensile strength ,[[epsilon]. sub. break]
And the model value of 61. 3 MPa, 8.
9% and 2039 MPa, respectively.
PTMC exhibits elastic behavior [[epsilon]. sub. break]
The value of the previous report is 719% [34].
Therefore, with the increase of TMC content, the tensile strength and elastic modulus of the polymer are reduced, while [[epsilon]. sub. break]
In line with our previous work, [gradually]34]
, PTL75/25 shows the lowest strength (14. 1 MPa)andmodulus (941 MPa)
Values in all selected PLLA-
TMC samples, but the highest strain at the time of fracture (453%).
These findings can be explained by the crystal loss of PLLA-TMC copolymers.
In the case of PLLATMC-
GA Ternary Polymer, with the introduction of 5 mol % GA portion to PLLA-, the tensile strength decreased slightlyTMCcopolymers. Surprisingly, [[epsilon]. sub. break]
Greatly improved.
Typical pressure
Figure 1 shows the strain behavior.
For example 6, takingPLT95/5 and PLTG95/5.
The tensile strength of PLTG95/5 is 52. 3 MPa, i. e.
Slightly lower than PLT95/5 (54. 7 MPa).
Instead ,[[epsilon]. sub. break]of PLTG95/5/5 (249%)
It is nearly 9 times that of PLT95/5 (28. 5%).
On the other hand, the tensile strength and elastic modulus gradually decreased with the increase of ga content.
So all PLLA-TMC-
GA polymer with high [[epsilon]. sub. break]
However, the tensile strength is slightly lower than that of PLLA.
These can be assigned to PLLA-TMC-
GA Ternary Polymer as mentioned above.
So a series of plla-TMC-
Compared with PLLA homopolymers, GA ternary polymers with sufficient tensile strength and better flexibility were obtained.
According to Venkatraman, the collapse pressure is about 2.
For PLLA made of tensile strength over 50 MPa [5 bars can be obtained41]
, The compression strength of the micro-hole tube holder prepared by the PLLA/PCL mixture is 5581mm Hg, and the tensile strength of the mixture film is 9 MPa [42]
, Gathered by PLLA (4-Dingone)
Blendwith with a tensile strength of 36 MPa presents a collapse pressure of 1. 1bars [43]
GA ternary polymers should have sufficient collapse strength when processed into a stent, which makes them promising to be a candidate for the development of cardiovascular stent.
To further improve the tensile strength of PLLA-TMC-
The GA Ternary Polymer, pla fiber with a LA/GA ratio of 10/90 was selected to enhance the ternary polymer matrix.
In fact, under the trademark of Vicryl [the pla fiber is commonly used biologically adjustable stitching]R].
The monofilament is the basic unit of pla Multifilament, and its tensile strength depends on the number of monofilament.
In this work, the tensile strength of the monofilament is used to demonstrate the mechanical properties of the multi-filament staple fiber used to enhance.
As mentioned earlier [25]
Tensile strength of 172.
5 MPa much higher than PLLA-TMC-GA terpolymers.
PLTG95/5 was selected as a material due to its excellent mechanical properties and a series of short pla fiber composites with different contents were prepared (
The average length is 0. 3-0. 6 mm).
The pla fiber prepared is Plasma-
Treatment for 15 minutes to improve affinity with matrix [j]25]
, As shown in Table 3, the strength of the composite increases strongly with the increase of pla fiber content.
The tensile strength of the 8wt % fiber composite increased from the original 52. 3-69.
1 MPa, from the initial 1877-2855 MPa. But the [[epsilon]. sub. break]
It dropped sharply from the initial 249 to 4%.
The poor toughness of the composite is considered to be the cause of the poor affinity between the fiber and The Matrix, although the pla fiber is Plasma-treated.
According to our previous study, the degradation rate of composite materials with 5wt % plgafiber is higher than that of PLLA-
TMC Neat polymer and PLLAbecause accelerate the degradation of pla fiber to matrix by self-catalytic action [26]
At the same time, the composite with 5wt % fiber has almost the same tensile strength and flexibility as PLLA, but has a higher modulus.
Pla fiber has low solubility in organic solvent and melting temperature is as high as 204 [degrees]
About 50 [C]degrees]
C is higher than PLTG95/5, which should allow the solution or heat treatment of the composite.
Gater polymer enhanced with pla fiber is also a considerable candidate for scaffold applications.
The bracket is made of PLTG95/5 Ternary Polymer with relatively high tensile strength and excellent toughness. Mini-
Tube with outer diameter of 5.
0mm, wall thickness 0.
22mm is manufactured by a single
Get the screw extruder using the CNC engraving machine and then get the bracket.
Figure 7 shows a stand prototype with a length of 10mm.
It is worth noting that chain cutting occurred during extrusion processing. [bar. [M. sub. n]]and[bar. [M. sub. w]]
The strength of PLTG95/5 is from the initial 2. 36 X[10. sup. 5]and 5. 16 X [10. sup. 5]g [mol. sup. -1]to 1. 84 X [10. sup. 5]and3. 80 X [10. sup. 5]g [mol. sup. -1]
Despite the large amount of vacuum drying of the polymer before processing.
This finding illustrates the need to use high molecular weight polymers to ensure good mechanical properties after heat treatment.
Therefore, for the first time, the cardiovascular stent was made with PLLATMC-
GA terpolymers using CNC engraving machine.
In order to determine the mechanical properties, degradation behavior and biological compatibility of the scaffold, further studies are under way.
Conclusion This study aims to design a suitable polymer system for the preparation of cardiovascular stent.
A variety of ternary polymers based on la, TMC and GA were studied, covering a wide range of components and with the corresponding PLLA-
As well as PLLA and ptmc homopolymers.
All polymers have high molecular weight, which is critical for the mechanical properties of the material.
The thermal and mechanical properties of the polymer are closely related to the composition.
Only one glass transition temperature of the polymer was observed. PLLA-
TMC polymer is the atTMC content of semi-crystalline under 25 mol %, but the degree of crystal is lower than plla.
The addition of the GA unit further reduces the plla-TMC-
GA Ternary Polymer due to more random microstructure.
At the same time, the toughness of ternary polymer has been greatly improved, but the tensile strength has decreased slightly. Plasma-
The treated pla fiber is used to enhance the PLLA-TMC-GA terpolymers.
The tensile strength of the 8wt % fiber composite is much higher, while the toughness is greatly reduced.
Using the CNC engraving machine, the bracket prototype was successfully manufactured from aterpolymer, thus demonstrating the potential of Ternary Polymer with good mechanical properties in the development of cardiovascular stent.
Further studies are under way to investigate the mechanical properties of the scaffold and the degradation behavior in vivo. REFERENCES [1. ]Z. Zhang, R. Kuijer, S. K. Bulstra, D. W. Grijpma, and J.
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Dong Jianting ,(1)Lan Liao, (1)Li Shi, (1)Zaishang Tan, (1)Fan Zhongyong ,(1)Suming Li, (2)Zhiqian Lu (3)(1)
Department of Materials Science, Fudan University, Shanghai 200433, China (2)
Interface, physical chemistry and polymer system of umr enscm European Film Institute-UM2-
CNRS 5635, 34095, 5 Montpellier cedex, France 2, Eugene batalong square University (3)
The Sixth People\'s Hospital of Shanghai Jiaotong University, Shanghai 200233, China; e-
Email: zyfan @ Fudanedu. cn orSuming Li; e-mail: suming. li@iemm. univ-montp2.
National Natural Science Foundation: fr
Contract award number: 51073041;
Signing unit: Shanghai Municipal Science and Technology Commission;
Contract Number: 12441903103;
Contracted funding unit: key technology research on strategic emerging industry projects in Guangdong province. DOI 10. 1002/pen.
23662 online release in the Wiley Online Library (
Wileyonlinelibrary. com).
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