CN101254137A - Preparation of micro-nano structure bionics valve, surface congeal-resistance and drag reduction testing method thereof - Google Patents

Abstract

The invention relates to a medical graft, which is applied to various artificial prosthesis cardiac valves. A fine structure form on the surface of an artificial cardiac valve is designed through determining the structural geometric parameters that are a, b, and h according to a biological prototype of the cardiac valve, the apparent contact angle calculation formula of the surface which is denoted by the geometric parameters is deduced, the proper fine structural geometric parameters are determined according to the calculation formula to lead the apparent contact angle on the cardiac valve surface to be larger than 150 degrees, so as to gain a more ideal super-hydrophobic surface; then a template which is provided with a fine structure surface is processed by utilizing the technology of femtosecond laser machining, and is washed, dried and processed through the silanization treatment; a PDMS valve surface which has the same fine structure with the template is copied by using a soft lithography method. The valve surface structure made by the invention is stable, has obvious characteristics of anticoagulation resistance and drag-reduction, effectively prevents the thrombosis, is hard to be damaged when being used for a long time, and is reusable without damage and deformation. Therefore, the mass production can be completed. In addition, the test method is simple and reliable.

Description

The making of the bionical valve of micro-nano structure and surperficial anticoagulant and drag reduction testing method

Technical field

The present invention relates to the medical science graft, the manufacture method of refering in particular to the bionical valve of a kind of micro-nano structure with and the method for surperficial anticoagulant and resistance reducing performance test, applicable to all kinds of artificial prosthesis cardiac valve.

Background technology

The human heart valve can be treated by the cardiac surgery operation replacement prosthetic valve owing to the organic disease that the various causes of disease form.Portland cardiac surgeon Albert Starr at first successfully carries out the first routine cardiac valve replacement so far from the early sixties U.S., and the development of Cardiac valve prosthesis reaches its maturity, and is just more and more used in cardiac surgery operation.

Cardiac valve prosthesis commonly used both at home and abroad at present has bioprosthetic valve and mechanical prosthetic valve by the material branch.Natural valvular shape and the flow pattern of biovalve simulation by biological organization material is made so its blood compatibility is good, is difficult for producing blood coagulation, haemolysis, and valve need not or only need the short-term anticoagulant after implanting.But because the easy calcification of biomaterial or decay, so its life-span is shorter, the patient often needs expensive additional big surgical operation just can change.By comparison, mechanical prosthetic valve is the most widely used in the world at present Cardiac valve prosthesis, special circumstances do not take place after the implantation can be used throughout one's life, but because its anticoagulant property, blood compatibility, blood smoothness and mechanical property are all not ideal enough, so need lifelong anticoagulant therapy after implanting.Conventional mechanical valve prosthesis makes blood produce stasis in the lobate part of valve; form local thrombus (a kind of gathering of blood factor thus; mainly be holding back of platelet and fibrin and cell component; usually can form the obstruction that the position causes blood vessel at it) so that finally cause thromboembolism (the unexpected obstruction of blood delivery tube).Therefore under the situation of using conventional mechanical valve prosthesis, thromboembolism accident and the death that takes place subsequently all may interrelate with valve prosthesis directly or indirectly.Therefore the blood compatibility that improves valve surface is important research in present cardiac valve design and the many research topics made.The cold auspicious forever people of grade adopts ion beam technology to cover the TiO2/TiN bilayer film to improve (the 1. pyrolytic carbon Cardiac valve prosthesis material surface modifying research of its blood compatibility at pyrolytic carbon valve surface titanium deposition sull and at the Ti alloy surface, biomedical engineering's magazine, 1999,16 (2): 127-131; 2.The microstructureand mechanical properties of TiN and TiO2/TiN duplex films synthesized by plasmaimmersion ion implantation and deposition on artificial heart valve, Surface ﹠amp; Coating Technology, 2006,201:1012-1016).E.M.E.Kristensen etc. use the heparin coating to improve its blood compatibility by the Cardiac valve prosthesis surface.(Heparin?coating?durability?on?artificialheart?valves?studied?by?XPS?and?antithrom?bin?binding?capacity，Colloids?andSurfaces?B：Biointerfaces，2006，49：1-7)。Taking a broad view of these researchs can find, Cardiac valve prosthesis is carried out surface treatment can improve its blood compatibility, but come off from valve surface easily with thin film or the coating that said method is made, thereby influence its serviceability.The present invention improves its blood compatibility by making up fine structure in valve surface on the basis of super-hydrophobic theory.

Summary of the invention

The objective of the invention is to according to super-hydrophobic theory, the Cardiac valve prosthesis manufacture method that a kind of surface has fine structure and the method for anticoagulant and resistance reducing performance test thereof are provided, to overcome the shortcoming and defect of mechanical valve prosthesis in the past, a kind of good blood compatibility that has is provided, be difficult for forming thrombosis, do not need lifelong anticoagulant, the Cardiac valve prosthesis of long service life.

The shape of the fine structure of the cyclic array on cardiac valve of the present invention surface can be square column, paraboloid of revolution, tip-like, truncated rectangular pyramids or optical grating construction etc.

The present invention realizes as follows:

1. according to valvular biological prototype, on super-hydrophobic theoretical basis, design the fine structure form on Cardiac valve prosthesis surface, promptly determine geometrical parameters a, b, h, as for optical grating construction, a, b, h are respectively that the ridge of grating is wide, groove width and ridge are dark; For the square column structure, a is that the square column length of side, b are that square column spacing, h are square column height (that is depth of groove), and derive the apparent contact angle computing formula on this surface that characterizes with geometric parameter, determine suitable fine structure geometric parameter according to this formula again, make the apparent contact angle of valve surface greater than 150 °, in the hope of obtaining comparatively desirable super hydrophobic surface.

2. utilize the femtosecond laser process technology to process template, carry out silanization behind the cleaning, drying and handle, so that the PDMS valve after the replica can separate with template easily with superfine structure surface.

3. copy with template with soft etching method and have identical fine structure PDMS valve surface.

4. after the fine structure valve that replica obtained cleans and soaks with buffer, place the platelet blood plasma that makes by fresh anticoagulant human blood, and the platelet that does not adsorb on the flush away surface after hatching in water bath with thermostatic control, again valve fixed, dewatered, drying and metal spraying, and the quantity by observing fine structure valve surface platelet adhesion and the form anticoagulation function that characterizes valve.

5. utilize flow graph to carry out the test of fine structure valve surface resistance reducing performance, under identical shear rate, identical gap, measure the moment of torsion of same blood on smooth surface and fine structure valve surface and Peltier board respectively, calculate drag reducing efficiency, characterize the property of reduction drag of fine structure valve surface thus.

The present invention has the following advantages:

1. the valve surface Stability Analysis of Structures that makes of the present invention, life-time service is not fragile yet.

2. reusable and do not have the distortion of damaging after the valve surface one-shot forming that makes, so can be mass-produced, can effectively reduce production costs.

3. the valve that makes of the present invention has tangible anticoagulant, property of reduction drag, can prevent the formation of tampon effectively.

4. the method for testing of the anticoagulant of valve provided by the invention, property of reduction drag is simple, reliable.

Description of drawings

The square microtrabeculae structure of Fig. 1 structural parameters sketch map (a) optical grating construction (b)

SEM figure (a) vertical view (b) cross-sectional view of Fig. 2 optical grating construction

The square microtrabeculae structure of Fig. 3 silicon template surface SEM figure

The SEM of parallel grating body structure surface figure after Fig. 4 replica

PDMS pit SEM relative with the silicon template after replica of Fig. 5 schemes

The SEM figure of the square microtrabeculae structure of the PDMS of Fig. 6 double replica

The specific embodiment

Below be specifying to Cardiac valve prosthesis surface design and making and anticoagulant thereof, resistance reducing performance test implementation situation:

Embodiment 1: the optical grating construction Cardiac valve prosthesis

1. the design of valve surface fine structure

Grating structural parameter is shown in Fig. 1 (a), and a, b are respectively the wide and groove width of ridge of grating, and h is that ridge is dark.Formula according to Wenzel theory and Cassie theory in the classical moistening theory $\cos {\mathrm{\θ}}_r^w=r\cos {\mathrm{\θ}}_e,$ $\cos {\mathrm{\θ}}_r^C=-1+f(\cos {\mathrm{\θ}}_e+1)$ Can determine that the geometric parameter of valve surface of grating fine structure and the pass of apparent contact angle are

$\cos {\mathrm{\θ}}_r^W=[1+\frac{2h}{a+b}]\cos {\mathrm{\θ}}_e$

$\cos {\mathrm{\θ}}_r^C=-1+\frac{1}{1+b/a}(\cos {\mathrm{\θ}}_e+1)$

Because the real area of rough surface is S _a=(a+b) l+2hl, its projected area is S _p=(a+b) l, the projected area of columnar protrusions is S _s=al (wherein l is a grating length) can determine surface roughness factor r=S thus _a/ S _p=1+2h/ (a+b), the area fraction f that surperficial square body projection is shared ₁=S _s/ S _p=a/ (a+b).

Thus, can determine suitable geometric parameter a, b, h, make the apparent contact angle of valve surface, promptly have super-hydrophobicity greater than 150 °.

2. template processing and surface treatment

Utilize femtosecond laser to go out grating micro structure template in the sheet Surface Machining, Fig. 2 is the SEM figure of optical grating construction, and wherein (a) is vertical view, (b) is cross-sectional view.The template that processes is put into ultrasonic washing unit, and vibration is 10 minutes in acetone and dehydrated alcohol mixed liquor, washes 3 times with deionized water then, then with 17 fluorine decyltrichlorosilanes template is carried out silanization in vacuum desiccator and handles.

3. soft etching method is made grating micro structure valve surface

With the PDMS prepolymer---firming agent (Curing angent) is pressed accurate weighing of mass ratio in 1: 10 and mix homogeneously with silicones (Sylgard 184 Basesilicone elastomer), after putting into depurator degasification 60min it is cast on the template, put into vacuum drying oven, in vacuum degasification 1h once more under the condition of 0.06MPa, behind 100 ℃ of baking 1h, PDMS film after solidifying is stripped down from the silicon template, just can obtain having the valve of fine structure, as shown in Figure 4.Simultaneously can also repeat replica as template, thereby make valve surface fast and in large quantities with grating fine structure with the PDMS that obtains.

4. valve surface anticoagulant performance test

(1) grating micro structure valve is placed on deionized water for ultrasonic and cleans three times after, reuse PBS buffer soaks 2h.Get fresh anticoagulant human blood, 1000rpm centrifugalize 10min, preparation platelet blood plasma.

(2) draw the upper strata platelet rich plasma, grating micro structure valve is placed in one, in 37 ℃ of waters bath with thermostatic control, hatch 2h.

(3) inhale and to remove platelet rich plasma, clean three times with the PBS that has diluted 10 times is careful, the platelet that does not adsorb on the flush away surface, the glutaraldehyde of reuse 2.5% is fixing 2h at room temperature.

(4) clean up with PBS earlier after sample takes out, reuse 30%, 50%, 70%, 90%, 100% ethanol/water solution is dewatered in succession, each 30min.

(5) CO in critical exsiccator ₂Behind the critical point drying, metal spraying is observed, is taken pictures platelet with scanning electron microscope, choose 8～10 at random * 1000 visual field photo do platelet count and statistical analysis.

The final anticoagulation function that characterizes valve according to the quantity and the form of grating micro structure valve surface platelet adhesion.

5. valve surface resistance reducing performance test

Measure moment of torsion M, M ', the M of blood on smooth surface and grating micro structure valve surface and Peltier board with flow graph ₀After, calculate the drag reducing efficiency of grating micro structure valve surface by following drag reducing efficiency formula, weigh its property of reduction drag with this.

$r=\frac{\frac{1}{M^{\′}}-\frac{1}{M}}{\frac{1}{M^{\′}}-\frac{1}{M_0}}\×100\%$

The temperature of Peltier board is 20 ± 0.1 ℃ during test, selects the plate jig of 40mm for use, and the gap is 500 μ m between anchor clamps and valve, and shear rate is 10～1001/s.

Embodiment 2: square microtrabeculae structure artificial cardiac valve

1. the design of valve surface fine structure

Periodic regular is arranged square microtrabeculae structural parameters shown in Fig. 1 (b), and a is that the square column length of side, b are that square column spacing, h are square column height (that is depth of groove).According to the Wenzel formula $\cos {\mathrm{\θ}}_r^w=r\cos {\mathrm{\θ}}_e$ With the Cassie formula, $\cos {\mathrm{\θ}}_r^C=-1+f(\cos {\mathrm{\θ}}_e+1)$ Can determine that the geometric parameter of valve surface of square microtrabeculae structure and the pass of apparent contact angle are:

$\cos {\mathrm{\θ}}_r^W=[1+\frac{4V_{\mathrm{AR}}}{{(1+V_{\mathrm{PS}})}^2}]\cos {\mathrm{\θ}}_e$

$\cos {\mathrm{\θ}}_r^C=-1+\frac{1}{{(1+V_{\mathrm{PS}})}^2}(\cos {\mathrm{\θ}}_e+1)$

V wherein _PS=b/a (period pitch), V _AR=h/a (depth-to-width ratio)

Because the real area of rough surface is S _a=(a+b) ²+ 4ah, its projected area is S _p=(a+b) ², the projected area of columnar protrusions is S _s=a ²So, roughness factor r=S _a/ S _p=1+4ah/ (a+b) ², the area fraction f that surperficial square body projection is shared ₁=S _s/ S _p=a ²/ (a+b) ²

Thus, can determine suitable geometric parameter a, b, h, make the apparent contact angle of valve surface, promptly have super-hydrophobicity greater than 150 °.

2. template processing and surface treatment

Arrange square microtrabeculae structure with light lithographic method processing and fabricating periodic regular on polished silicon slice, Fig. 3 is the SEM figure of the template after the processing.Its surface treatment process is identical with the surface treatment process of case 1.

3. soft etching method is made the square microtrabeculae structure of light positive valve surface

Its concrete operating procedure is with the soft etching method operating procedure of case study on implementation 1, obtains SEM photo such as Fig. 5 of the PDMS pit relative with silicon template microtrabeculae structure after replica.The PDMS film that obtains with replica carries out just can obtaining PDMS square microtrabeculae structure after the double replica with identical method as template, and its SEM figure sees Fig. 6.

4. the drag reduction of valve surface is identical with the method for testing and the step of anticoagulant performance test methods and step and embodiment 1.

Claims (2)

1. the manufacture method of the bionical valve of micro-nano structure is characterized in that:

(1) according to valvular biological prototype, based on super-hydrophobic theory, design the fine structure form on Cardiac valve prosthesis surface, promptly determine geometrical parameters a, b, h, promptly for optical grating construction, a, b, h are respectively that the ridge of grating is wide, groove width and ridge are dark; For the square column structure, a is that the square column length of side, b are that square column spacing, h are the square column height, and derive the apparent contact angle computing formula on this surface that characterizes with geometric parameter, and determine the fine structure geometric parameter according to this formula again, make the apparent contact angle of valve surface greater than 150 °;

(2) utilize the femtosecond laser process technology to process template, carry out silanization behind the cleaning, drying and handle with superfine structure surface;

(3) copy with template with soft etching method and have identical fine structure PDMS valve surface.

2. the anticoagulant of the bionical valve of micro-nano structure according to claim 1 and resistance reducing performance method of testing, after it is characterized in that fine structure valve that replica is obtained cleans and soaking with buffer, place the platelet blood plasma that makes by fresh anticoagulant human blood, and the platelet that does not adsorb on the flush away surface after hatching in water bath with thermostatic control, again valve fixed, dewatered, drying and metal spraying, and the quantity by observing fine structure valve surface platelet adhesion and the form anticoagulation function that characterizes valve;

Utilize flow graph to carry out the test of fine structure valve surface resistance reducing performance, under identical shear rate, identical gap, measure the moment of torsion of same blood on smooth surface and fine structure valve surface and Peltier board respectively, calculate drag reducing efficiency, characterize the property of reduction drag of fine structure valve surface thus.

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