METHOD FOR EVALUATING RHEOLOGICAL PROPERTIES OF A GEL

Abstract

A method for evaluating the rheological properties of at least one gel, consisting in determining the extent of the plastic domain in stress ζ.sub.c−ζ.sub.p, and in strain γ.sub.c−γ.sub.p, the determination being carried out according to the steps: subjecting at least one sample of at least one gel to oscillating mechanical stresses at a fixed frequency, determining and plotting curves of the elastic modulus G′ and the viscous modulus G″ as a function of the strain and stress, determining ζ.sub.c and ζ.sub.p at the point of intersection X.sub.c of the curves of G′ and G″ under stress and strain, determining ζ.sub.p and γ.sub.p by fixing an arbitrary value of G′ (G′x) that is defined as the entry value into the plastic domain, and calculating ζ.sub.c−ζ.sub.p and γ.sub.c−γ.sub.p.

Claims

1. A method for evaluating the rheological properties of at least one gel, consisting in determining the extent of the plastic domain in stress ζ.sub.c−ζ.sub.p and in strain γ.sub.c−γ.sub.p, the determination being carried out according to the steps of: subjecting at least one sample of at least one gel to oscillatory mechanical stresses at a fixed frequency, determining and plotting the curves of the elastic modulus G′ and of the viscous modulus G″ as a function of the strain and of the stress, determining ζ.sub.c and ζ.sub.p at the point of intersection X.sub.c of the curves of G′ and G″ under stress and strain, determining ζ.sub.p and γ.sub.p by fixing an arbitrary value of G′ (G′x) that is defined as the entry value into the plastic domain, and calculating ζ.sub.c−ζ.sub.p and γ.sub.c−γ.sub.p.

2. The method as set forth in claim 1, wherein the oscillatory mechanical stresses are implemented by means of an amplitude sweep.

3. The method as set forth in claim 2, wherein the amplitude sweep is a strain and/or stress sweep.

4. The method as set forth in claim 1, wherein the arbitrary value of G′ is defined as the value for which the elastic modulus G′ has decreased by at most 15% compared to the value of G′ at the plateau of the linear domain.

5. The method as set forth in claim 1, wherein the fixed frequency is between 0.1 and 10 Hz.

6. The method as set forth in claim 1, wherein the fixed frequency is equal to 1 Hz.

7. The method as set forth in claim 1, wherein it is implemented through the use of a rheometer connected a control unit for carrying out the measurements and the calculations.

8. The method as set forth in claim 1, wherein the gel is a hydrogel.

9. The method as set forth in claim 1, wherein the hydrogel consists of at least one polysaccharide selected from the group comprising: hyaluronic acid, heparosan, keratan, heparin, cellulose, cellulose derivatives, alginic acid, xanthan, carrageenan, chitosan, chondroitin, heparosan, and biologically acceptable salts thereof, alone or as a mixture.

10. The method as set forth in claim 1, wherein the gel consists of hyaluronic acid.

11. The method as set forth in claim 1, wherein the gel is an injectable gel.

12. A method for comparing and differentiating gels, comprising the steps of: determining, according to the method of claim 1, the resistance range of gels, the resistance range being defined by the difference ζ.sub.c−ζ.sub.p, i.e., the extent of the plastic domain in stress, determining, according to the method of claim 1, the malleability of gels, the malleability range being defined by the difference γ.sub.c−γ.sub.p, i.e., the extent of the plastic domain in strain, using the parameters defined above in order to compare and differentiate the gels.

Description

FIGURES

[0138] FIG. 1 is a schematic representation of the evolution of the viscous and elastic moduli of a gel sample subjected to a strain and/or stress sweep and of the linearity domains denoted LI, plastic domains denoted PL, and spread domains denoted ET.

[0139] FIG. 2 and FIG. 3 are representations of the extent of the plastic domain in stress of different formulas with abscissa ζ in Pa and ordinates F0.

[0140] FIG. 4 and FIG. 5 are representations of the extent of the plastic domain in strain of different formulas with abscissa γ in (%) and ordinate F0.

[0141] FIG. 7, FIG. 10, and FIG. 13 are representations of the extent of the plastic domain in stress of different formulas with abscissa ζ in Pa and ordinates for the different gels studied.

[0142] FIG. 8, FIG. 11, and FIG. 14 are representations of the extent of the plastic domain in strain of different formulas with abscissa γ in (%) and ordinate for the different gels studied.

[0143] FIG. 6, FIG. 9, and FIG. 12 are representations of the elastic moduli G′ in Pa at 1 Hz of different products.

[0144] FIG. 15 is a representation of the differences between the method disclosed in patent application WO2016/150974 or in patent EP3274685B1 and the method according to the present invention.

EXAMPLES

[0145] The measurements are performed on the DHR-2 rotational shear rheometer (TA Instruments) using a 2° 40 mm cone-plane geometry at 25° C.

[0146] The viscoelastic parameters are evaluated by means of a strain sweep performed from 0.1 to 1000% strain at a frequency of 1 Hz. The value of the elastic and viscous moduli G′ and G″ at frequency 1 Hz corresponds to that of the elastic and viscous moduli in the linear domain.

[0147] For all of the examples, G′p is the value of G″ for which the elastic modulus has decreased by 10% relative to the value of G′ at the plateau of the linear domain.

Example 1

[0148] Table 1 below shows the rheological parameters of a non-crosslinked hyaluronic acid gel measured according to the method of the invention.

TABLE-US-00001 TABLE 1 G′ G″ @ 1 @ 1 tanδ Hz Hz @ γ.sub.p ζ.sub.p γ.sub.c ζ.sub.c γ.sub.c − γ.sub.p ζ.sub.c − ζ.sub.p Product (Pa) (Pa) 1 Hz (%) (Pa) (%) (Pa) (%) (Pa) A 1100 319 0.29 36 375 192 813 156 439 B 788 344 0.44 40 322 230 863 190 541

[0149] This non-crosslinked hyaluronic acid gel was prepared by dissolving sodium hyaluronate with a molecular mass of 3 MDa in PBS buffer at a concentration of 30 mg/mL.

[0150] The method according to the invention made it possible to evaluate the rheological parameters of the gel before and after the step of sterilizing the gel.

[0151] In the context of this example, the gel before the sterilization step is denoted A, and the gel after the sterilization step is denoted B.

[0152] In the above table, a variation in the rheological parameters is observed during the hyaluronic acid gel sterilization step.

There is an increase in the malleability range and a decrease in the resistance range during this sterilization step.

Example 2

[0153] The table below presents the rheological parameters of a KartilageCross® gel (intra-articular injection) sold by Laboratoires Vivacy and measured according to the method of the invention.

TABLE-US-00002 TABLE 2 G′ @ 1 G″ @ 1 tanδ @ γ.sub.p ζ.sub.p γ.sub.c ζ.sub.c γ.sub.c − γ.sub.p ζ.sub.c − ζ.sub.p Product Hz (Pa) Hz (Pa) 1 Hz (%) (Pa) (%) (Pa) (%) (Pa) C 169.3 26.9 0.159 40 63 253 182 213 119

[0154] In the context of this example, the KartilageCross gel marketed by Laboratoires VIVACY is denoted C.

[0155] The method according to the invention made it possible to measure and evaluate the conventional rheological parameters of gel C such as the elastic modulus and the viscous modulus.

[0156] In addition, the method according to the invention made it possible to measure rheological parameters such as the malleability range and the resistance range of gel C.

[0157] These parameters make it possible, in particular, to complete the study of the behavior of gel C.

Example 3

[0158] Table 3 below presents the rheological parameters of two formulations of gel measured according to the method of the invention.

TABLE-US-00003 TABLE 3 G′ @ G″ @ Steam 1 Hz 1 Hz γ.sub.p ζ.sub.p γ.sub.c ζ.sub.c γ.sub.c − γ.sub.p ζ.sub.c − ζ.sub.p sterilization Product (Pa) (Pa) (%) (Pa) (%) (Pa) (%) (Pa) No D 367 43 54 183 417 540 363 358 E 379 39 51 176 384 511 333 334 F.sub.0 = D 311 44 57 164 494 542 436 378 9 min E 284 40 64 167 508 529 444 362 F.sub.0 = D 282 42 64 167 538 544 474 377 20.5 min E 238 37 64 140 595 527 531 387 F.sub.0 = D 242 41 64 143 619 559 555 415 46.5 min E 171 31 64 101 766 560 703 458

[0159] The first is a formulation produced according to the method described in patent EP231108 with incorporation of mannitol (denoted D in the table above).

[0160] The second is a formulation produced according to the method in patent EP231108 without incorporation of mannitol (denoted E in the table above).

[0161] The method according to the invention made it possible to evaluate the rheological parameters of these two formulations at different sterilization values F.sub.0=9 min; F.sub.0=20.5 min; and F.sub.0=46.5 min.

[0162] As a reminder, the sterilization value is expressed in units of time and makes it possible to quantify the effect of a sterilizing treatment.

[0163] In the table above, it can be seen that the elastic modulus of formulations D and E decreases during the sterilization step.

[0164] In contrast, as is shown in FIG. 2 and FIG. 3, the resistance range parameter increases upon sterilization of formulations D and E.

[0165] As shown in FIG. 4 and FIG. 5, the extent of the malleability range increases significantly during the process of the sterilization of formulations D and E.

Example 4

[0166] The table below presents the rheological parameters of two different gels measured according to the method of the invention.

TABLE-US-00004 TABLE 4 G′ @ G″ @ tanδ 1 Hz 1 Hz @ γ.sub.p ζ.sub.p γ.sub.c ζ.sub.c γ.sub.c − γ.sub.p ζ.sub.c − ζ.sub.p Product (Pa) (Pa) 1 Hz (%) (Pa) (%) (Pa) (%) (Pa) F 213 25 0.12 16 31 128 112 112 81 H 204 33 0.16 51 95 309 253 258 158

[0167] The first is the product Juvederm Volbella (with lidocaine) marketed by the company Allergan. In the context of this example, the product Volbella is denoted F.

[0168] The second is the product Special Lips from the Stylage range marketed by Laboratoires Vivacy. In the context of this example, the product Special Lips is denoted H.

[0169] As illustrated in FIG. 6, gels F and H have similar elastic moduli G′.

[0170] They also have similar viscous moduli G″.

[0171] On the other hand, the extent of the resistance range and the malleability range distinguish the two products.

[0172] As shown in FIG. 7, the resistance range of product H is twice as extensive as that of product F, and it is also shifted translationally to higher values of ζ such that there is practically no overlap of the resistance ranges.

[0173] Also in FIG. 8, it can be seen that the malleability range of product H is twice as extensive as that of product F, and it is also shifted translationally toward higher values of ζ, but significant overlap of the resistance ranges is preserved.

[0174] In conclusion, the method according to the invention made it possible to differentiate between two gels with similar elastic and viscous moduli.

Example 5

[0175] The table below shows the rheological parameters of three different Restylane gels measured according to the method of the invention.

TABLE-US-00005 TABLE 5 G′ @ G″ @ Tanδ 1 Hz 1 Hz @ γ.sub.p ζ.sub.p γ.sub.c ζ.sub.c ζ.sub.c − ζ.sub.p γ.sub.c − γ.sub.p Product (Pa) (Pa) 1 Hz (%) (Pa) (%) (Pa) (Pa) (%) I 262.5 26.01 0.099 32 77 631 664 587 599 J 160 25 0.16 64 94 942 679 585 878 K 168 25 0.15 64 98 874 660 562 810

[0176] The first is the product Restylane Defyne marketed by the company Galderma. In the context of this example, the product Restylane Defyne is denoted I.

[0177] The second is the product Restylane Volyme marketed by the company Galderma. In the context of this example, the product Restylane Volyme is denoted 3.

[0178] The third is the product Restylane Kysse marketed by the Galderma company. In the context of this example, the Restylane Kysse product is denoted K.

[0179] As illustrated in FIG. 9, gels J and K have similar elastic moduli G′, whereas the elastic modulus of gel I is different.

[0180] On the other hand, gels I, J, and K exhibit similar viscous moduli G″.

[0181] As shown in FIG. 10, the resistance range of gels I and J is almost identical and is of the same order of magnitude for gel K.

[0182] As shown in FIG. 11, it is observed that the malleability range differs depending on the nature of products I, J, and K.

[0183] In the context of this example, the method according to the invention made it possible to differentiate between two gels with similar elastic and viscous moduli (J and K).

[0184] In conclusion, the method according to the invention made it possible to evaluate the rheological parameters of commercial gels and to differentiate between two gels with similar elastic and viscous moduli.

Example 6

[0185] The table below presents the rheological parameters of two different gels measured according to the method of the invention.

TABLE-US-00006 TABLE 6 G′ @ 1 G″ @ 1 γ.sub.p ζ.sub.p γ.sub.c ζ.sub.c γ.sub.c − γ.sub.p ζ.sub.c − ζ.sub.p Hz (Pa) Hz (Pa) (%) (Pa) (%) (Pa) (%) (Pa) L 50 4 101 46 346 90 245 44 M 71 5 90 58 442 158 352 100

[0186] The non-sterile 2% bovine gelatin solution, denoted L, was obtained from “high bloom”-type gelatin after dissolution in purified water, homogenization by vortexing, and heating at 37° C. for 15 minutes, followed by further homogenization and, finally, cooling to room temperature.

[0187] The non-sterile 2% porcine gelatin solution, denoted M, was obtained from “high bloom”-type gelatin after dissolution in purified water, homogenization by vortexing, and heating at 37° C. for 15 minutes, followed by further homogenization and, finally, cooling to room temperature.

[0188] As illustrated in FIG. 12, the gels L and M have similar elastic moduli G′.

[0189] They also exhibit similar viscous moduli G″.

[0190] As illustrated in FIG. 13, the resistance range of product M is twice as extensive as that of product L and it is also shifted translationally toward higher values of ζ, but significant overlap of the resistance ranges is preserved.

[0191] Also in FIG. 14, we see that the malleability range of product M is more extensive than that of product L.

[0192] These parameters make it possible, in particular, to complete the study of the behavior of gels L and M.

[0193] In conclusion, the method according to the invention has made it possible to evaluate and compare the rheological parameters of gelatin gels such as gels L and M.