Dual functional hydroxyapatite powder with ultraviolet absorption and antibacterial properties

Abstract

This invention provides a bifunctional hydroxyapatite powder with both ultraviolet absorption and antibacterial properties. The structural feature of this bifunctional hydroxyapatite powder is that a portion of the Ca atoms in the hydroxyapatite lattice... 2+ Ce 3+ Ag + Zn 2+ The components are respectively substituted, and their general formula is [Ca 10‑x‑y‑z Ce x Ag y Zn z The compound is (PO4)6(OH)2, wherein 0.1≤x≤1, 0.1≤y≤0.3, 0.1≤z≤0.5, and the molar ratio of the metal element to phosphorus element is (Ca+Ce+Ag+Zn) / P=1.67. The bifunctional hydroxyapatite powder with ultraviolet absorption and antibacterial properties has high phase purity and stable structure. It exhibits strong absorption of light with wavelengths of 220-400nm, good antibacterial effects against Staphylococcus aureus and Escherichia coli, and also possesses thickening and moisturizing effects. It can be used as a functional additive in cosmetics, clothing, and sun umbrellas with sun protection functions.

Description

TECHNICAL FIELD

[0001] The present application provides a bifunctional hydroxyapatite powder with ultraviolet absorption and antibacterial properties, which belongs to the field of bacteriostatic sunscreen functional powders. BACKGROUND

[0002] Ultraviolet rays in sunlight are one of its important components, and its wavelength can be divided into three bands: UVA (320-400 nm), UVB (280-320 nm), and UVC (200-280 nm). Among them, UVA and part of UVB can reach the earth's surface, and part of UVC is blocked by the stratosphere and ozone layer around the planet. However, due to the depletion of the ozone layer, even part of the UVC can reach the earth's surface, causing damage to the skin. UVA can penetrate the skin with ultraviolet radiation, and DNA, lipids, and proteins will absorb ultraviolet energy, triggering the loss of collagen, leading to skin problems such as aging and laxity. Excessive exposure to UVB can cause skin pigmentation, stimulate the production of melanocytes, lead to the formation of melanin, and produce sunspots and age spots. It can also penetrate the dermis and denature proteins or nucleic acids within the cells, triggering a series of skin problems. According to reports, three main types of skin cancer, including basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma, are caused by ultraviolet radiation. Sunscreen as a common and effective sunscreen method can shield ultraviolet rays and protect the skin.

[0003] Current sunscreens are divided into two categories: one is chemical sunscreen, which mainly absorbs ultraviolet rays through chemical excitation, transfers the absorbed energy to electrons, and dissipates the energy at a longer wavelength when the electrons return to the ground state; the other is physical sunscreen, which mainly absorbs and scatters ultraviolet rays to achieve the purpose of sun protection. Many chemical sunscreens can penetrate the skin, causing photoallergic, phototoxic reactions, and skin irritation, and the sunscreen effect will decay with chemical reactions. For these reasons, physical sunscreens are currently a better choice, and common physical sunscreens include titanium dioxide and zinc oxide. However, when using products containing these ingredients, their high refractive index (titanium dioxide refractive index 2.62, zinc oxide refractive index 2.029) can make the skin look unnatural white. In addition, their high photocatalytic activity easily promotes the production of reactive oxygen species, which can oxidize and degrade other ingredients in the product, posing a safety hazard. At the same time, nanoscale titanium dioxide has "genetic toxicity", which can cause genetic damage to cells. Therefore, the development of other alternative materials has gradually become a hot topic in the sunscreen field.

[0004] Hydroxyapatite (HA) has a chemical composition of Ca 10 (PO4)6(OH)2, density 3.16 g / cm 3, refractive index 1.64, is the main inorganic component of human and animal bone, has biocompatibility, non-toxicity and non-inflammatory. The calcium ions in hydroxyapatite can be replaced by a variety of metal ions through ion exchange reaction, so that the corresponding functional design can be carried out by ion doping, so that the modified hydroxyapatite powder has more functions, so as to obtain more extensive application. Patent CN114681615 A prepared a kind of iron ion doped hydroxyapatite, which has good osteogenesis and antibacterial function; Patent CN112062114 A provides a kind of trivalent manganese ion doped hydroxyapatite, which endows hydroxyapatite with high efficient catalytic and antibacterial properties, but the above materials do not consider the absorption capacity of ultraviolet. Paduraru A V et al. by co-precipitation method with Ce 3+ and Ce 4+ substitute Ca 2+ (Paduraru A V, Musuc AM, Oprea O C, et al. Synthesis and Characterization of Photoluminescent Ce(III) and Ce(IV) Substituted Hydroxyapatite Nanomaterials by Co-Precipitation Method: Cytotoxicity and Biocompatibility Evaluation [J]. Nanomaterials, 2021, 11(8): 15.) significantly improves the ultraviolet absorption function of hydroxyapatite, but does not consider the antibacterial function of the material. Yasukawa A et al. synthesized titanium-cerium-calcium hydroxyapatite (Ti-Ce-Ca-HA) solid solution particles by precipitation method (Yasukawa A, Tamura J. Preparation and structure of titanium-cerium-calcium hydroxyapatite particles and their ultraviolet protecting ability [J]. Colloids and Surfaces a-Physicochemical and Engineering Aspects, 2021, 609: 6.), which shows strong absorption capacity under 400 nm wavelength ultraviolet, but also does not reflect the antibacterial function.

[0005] The above materials cannot make the modified hydroxyapatite have ultraviolet absorption and antibacterial function. Therefore, we provide a kind of dual functional hydroxyapatite powder with ultraviolet absorption and antibacterial function, which is prepared by precipitation method with Ce 3+ , Ag+ Zn 2+ Partial Ca replacement in hydroxyapatite 2+ This allows for its widespread application in the sunscreen field. Firstly, the proper matching of the three ionic components is key to ensuring the material possesses efficient UV absorption and antibacterial properties. The effects of the three doped ions in this invention are manifested in: Ce... 3+ Hydroxyapatite possesses primary UV absorption properties and also exhibits some antibacterial activity; Ag + Hydroxyapatite possesses the main antibacterial properties; Zn 2+ This endows hydroxyapatite with certain UV absorption and antibacterial properties, and also stabilizes its structure, ensuring a higher Ce content. 3+ and Ag + The doping of the three ions does not destroy the crystal structure, but promotes crystal formation and suppresses impurity phases. Secondly, the appropriate doping amount of the three ions is another key to ensuring the dual functionality of the material. If the doping amount is too low, it is difficult for the material to achieve the corresponding functionalization; if the doping amount is too high, it may destroy the crystal structure of the material and produce impurity phases. In addition, different elements are doped with different levels of difficulty. Too high or too low doping of one element will affect the doping amount of other elements and will produce interactions that change the grain size, topology, chemical composition, crystallinity and surface charge of the material, thereby achieving a deep-level modification effect.

[0006] Therefore, the present invention relates to [Ca 10-x-y-z Ce x Ag y Zn z The composition and proportion of (PO4)6(OH)2 have been rationally optimized to ensure high material phase purity, structural stability, and good safety, while also possessing efficient UV absorption and antibacterial functions. Furthermore, it retains the inherent thickening and moisturizing effects of hydroxyapatite, making it suitable as a functional additive for cosmetics, clothing, and sun umbrellas with sun protection functions. Summary of the Invention

[0007] This invention provides a bifunctional hydroxyapatite powder with ultraviolet absorption and antibacterial properties. This material is prepared by a simple precipitation method, exhibiting high phase purity, stable structure, a band gap of 4.4 eV, and a grain size between 20-50 nm. It has strong absorption of light with wavelengths of 220-400 nm, good antibacterial effects against Staphylococcus aureus and Escherichia coli, and also possesses thickening and moisturizing properties, making it suitable as a functional additive for sunscreen cosmetics, clothing, and sun umbrellas.

[0008] Partial Ca in the lattice of the bifunctional hydroxyapatite powder with ultraviolet absorption and antibacterial properties 2+ Ce 3+ Ag + Zn 2+ The components are respectively substituted, and their general formula is [Ca10-x-y-z Ce x Ag y Zn z ](PO4)6(OH)2, wherein 0.1≤x≤1, 0.1≤y≤0.3, 0.1≤z≤0.5, and the molar ratio of metal elements to phosphorus elements is (Ca+Ce+Ag+Zn) / P=1.67.

[0009] The preparation method of the dual-function hydroxyapatite powder with ultraviolet absorption and antibacterial property is as follows:

[0010] (1) 0.2171-2.1711g of Ce(NO3)3·6H2O, 0.0849-0.2547g of AgNO3, and 0.1487-0.7437g of Zn(NO3)2·6H2O are respectively weighed, 82-97mL of 0.5M Ca(NO3)2 solution is added, and ultrasonic treatment is performed for 20min, stirring is performed at 90℃ for 1h, 100mL of 0.3M NH4H2PO4 solution is added, the pH value is adjusted to 10-11 by dropping NH3·H2O, and stirring is continuously performed at room temperature for 1h to obtain a mixed solution A.

[0011] (2) The mixed solution A is sealed under normal pressure to keep water from evaporating, and is aged at 20-30℃ for 24h.

[0012] (3) The precipitate is obtained by filtration separation, is washed and centrifugally separated alternately with 50mL of anhydrous ethanol and 50mL of deionized water for 3 times, is dried at 80℃ for 24h, and is calcined at 200℃ for 1h (heating rate 5℃ / min) to obtain the dual-function hydroxyapatite powder with ultraviolet absorption and antibacterial property.

[0013] The present application has the following beneficial effects:

[0014] The dual-function hydroxyapatite powder with ultraviolet absorption and antibacterial property provided by the present application has high purity, stable structure, strong absorption effect on light with a wavelength of 220-400nm, good bacteriostatic effect on Staphylococcus aureus and Escherichia coli, and the functions of thickening and moisturizing. The material has the advantages of wide raw material source, low price, simple process, long-term preservation of the material, etc. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Fig. 1 is an XRD spectrum of the dual-function hydroxyapatite powder with ultraviolet absorption and antibacterial property prepared by the present application.

[0016] Figure 2 Fig. 2 is a SEM photo of the dual-function hydroxyapatite powder with ultraviolet absorption and antibacterial property prepared by the present application.

[0017] Figure 3is the UV-DRS spectrum of the ultraviolet absorption and antibacterial bifunctional hydroxyapatite powder prepared by the present application.

[0018] Figure 4 is the inhibition zone photograph of the ultraviolet absorption and antibacterial bifunctional hydroxyapatite powder prepared by the present application. Specific implementation method

[0019] The present application is further illustrated below in conjunction with the accompanying drawings and examples. The above description is only examples of the present application, and does not limit the patent scope of the present application, and any equivalent transformation or direct or indirect application in other related technical fields by using the content of the present application specification and drawings is also included in the patent protection scope of the present application.

[0020] Example 1

[0021] [Ca 9.7 Ce 0.1 Ag 0.1 Zn 0.1 ](PO4)6(OH)2hydroxyapatite powder

[0022] 0.2171g of Ce(NO3)3·6H2O, 0.0849g of AgNO3, and 0.1487g of Zn(NO3)2·6H2O were weighed out and added to 97mL of 0.5M Ca(NO3)2solution and ultrasonically treated for 20min, and then stirred at 90℃ for 1h, and then 100mL of 0.3M NH4H2PO4solution was added, and the pH value was adjusted to 10-11 by dropwise adding NH3·H2O, and then the stirring was continued at room temperature for 1h to obtain a mixed solution A. The mixed solution A was sealed under normal pressure to keep the water from evaporating, and then aged at 20-30℃ for 24h. The precipitate was separated by filtration, and then washed and centrifuged alternately with 50mL of anhydrous ethanol and 50mL of deionized water for 3 times, and then dried at 80℃ for 24h, and then calcined at 200℃ for 1h (heating rate 5℃ / min) to obtain the ultraviolet absorption and antibacterial bifunctional hydroxyapatite powder.

[0023] Example 2

[0024] [Ca 9.3 Ce 0.1 Ag 0.3 Zn 0.3 ](PO4)6(OH)2hydroxyapatite powder

[0025] Weigh 0.2171g Ce(NO3)3·6H2O, 0.2547g AgNO3, and 0.4462g Zn(NO3)2·6H2O, add them to 93mL of 0.5M Ca(NO3)2 solution, sonicate for 20min, stir at 90℃ for 1h, then add 100mL of 0.3M NH4H2PO4 solution, adjust the pH to 10-11 by adding NH3·H2O dropwise, and continue stirring at room temperature for 1h to obtain mixture A. Seal mixture A under normal pressure to prevent moisture evaporation and age at 20-30℃ for 24h. Filter to separate the precipitate, wash alternately with 50mL anhydrous ethanol and 50mL deionized water, centrifuge, repeat the washing cycle 3 times, dry at 80℃ for 24h, and then calcine at 200℃ for 1h (heating rate 5℃ / min) to obtain bifunctional hydroxyapatite powder with UV absorption and antibacterial properties.

[0026] Example 3

[0027] [Ca 9.1 Ce 0.1 Ag 0.3 Zn 0.5 ](PO4)6(OH)2 Hydroxyapatite powder

[0028] Weigh 0.2171g Ce(NO3)3·6H2O, 0.2547g AgNO3, and 0.7437g Zn(NO3)2·6H2O, add them to 91mL of 0.5M Ca(NO3)2 solution, sonicate for 20min, stir at 90℃ for 1h, then add 100mL of 0.3M NH4H2PO4 solution, adjust the pH to 10-11 by adding NH3·H2O dropwise, and continue stirring at room temperature for 1h to obtain mixture A. Seal mixture A under normal pressure to prevent moisture evaporation, and age at 20-30℃ for 24h. Filter to separate the precipitate, wash alternately with 50mL anhydrous ethanol and 50mL deionized water, centrifuge, repeat the washing cycle 3 times, dry at 80℃ for 24h, and then calcine at 200℃ for 1h (heating rate 5℃ / min) to obtain bifunctional hydroxyapatite powder with UV absorption and antibacterial properties.

[0029] Example 4

[0030] [Ca 9.5 Ce 0.3 Ag 0.1 Zn 0.1 ](PO4)6(OH)2 Hydroxyapatite powder

[0031] Weigh 0.6513g Ce(NO3)3·6H2O, 0.0849g AgNO3, and 0.1487g Zn(NO3)2·6H2O, add them to 95mL of 0.5M Ca(NO3)2 solution, sonicate for 20min, stir at 90℃ for 1h, then add 100mL of 0.3M NH4H2PO4 solution, adjust the pH to 10-11 by adding NH3·H2O dropwise, and continue stirring at room temperature for 1h to obtain mixture A. Seal mixture A under normal pressure to prevent moisture evaporation, and age at 20-30℃ for 24h. Filter to separate the precipitate, wash alternately with 50mL anhydrous ethanol and 50mL deionized water, centrifuge, repeat the washing cycle 3 times, dry at 80℃ for 24h, and then calcine at 200℃ for 1h (heating rate 5℃ / min) to obtain bifunctional hydroxyapatite powder with UV absorption and antibacterial properties.

[0032] Example 5

[0033] [Ca 9.1 Ce 0.3 Ag 0.3 Zn 0.3 ](PO4)6(OH)2 Hydroxyapatite powder

[0034] Weigh 0.6513g Ce(NO3)3·6H2O, 0.2547g AgNO3, and 0.4462g Zn(NO3)2·6H2O, add them to 91mL of 0.5M Ca(NO3)2 solution, sonicate for 20min, stir at 90℃ for 1h, then add 100mL of 0.3M NH4H2PO4 solution, adjust the pH to 10-11 by adding NH3·H2O dropwise, and continue stirring at room temperature for 1h to obtain mixture A. Seal mixture A under normal pressure to prevent moisture evaporation, and age at 20-30℃ for 24h. Filter to separate the precipitate, wash alternately with 50mL anhydrous ethanol and 50mL deionized water, centrifuge, repeat the washing cycle 3 times, dry at 80℃ for 24h, and then calcine at 200℃ for 1h (heating rate 5℃ / min) to obtain bifunctional hydroxyapatite powder with UV absorption and antibacterial properties.

[0035] Example 6

[0036] [Ca 8.9 Ce 0.3 Ag 0.3 Zn 0.5 ](PO4)6(OH)2 Hydroxyapatite powder

[0037] Example 1

[0038] Example 2

[0039] [Ca 9.3 Ce 0.5 Ag 0.1 Zn 0.1 ](PO4)6(OH)2hydroxyapatite powder

[0040] Example 3

[0041] Example 4

[0042] [Ca 8.9 Ce 0.5 Ag 0.3 Zn 0.3 ](PO4)6(OH)2hydroxyapatite powder

[0043] Weigh 1.0856g Ce(NO3)3·6H2O, 0.2547g AgNO3, and 0.4462g Zn(NO3)2·6H2O, add them to 89mL of 0.5M Ca(NO3)2 solution, sonicate for 20min, stir at 90℃ for 1h, then add 100mL of 0.3M NH4H2PO4 solution, adjust the pH to 10-11 by adding NH3·H2O dropwise, and continue stirring at room temperature for 1h to obtain mixture A. Seal mixture A under normal pressure to prevent moisture evaporation and age at 20-30℃ for 24h. Filter to separate the precipitate, wash alternately with 50mL anhydrous ethanol and 50mL deionized water, centrifuge, repeat the washing cycle 3 times, dry at 80℃ for 24h, and then calcine at 200℃ for 1h (heating rate 5℃ / min) to obtain bifunctional hydroxyapatite powder with UV absorption and antibacterial properties.

[0044] Example 9

[0045] [Ca 8.7 Ce 0.5 Ag 0.3 Zn 0.5 ](PO4)6(OH)2 Hydroxyapatite powder

[0046] Weigh 1.0856g Ce(NO3)3·6H2O, 0.2547g AgNO3, and 0.7437g Zn(NO3)2·6H2O, add them to 87mL of 0.5M Ca(NO3)2 solution, sonicate for 20min, stir at 90℃ for 1h, then add 100mL of 0.3M NH4H2PO4 solution, adjust the pH to 10-11 by adding NH3·H2O dropwise, and continue stirring at room temperature for 1h to obtain mixture A. Seal mixture A under normal pressure to prevent moisture evaporation, and age at 20-30℃ for 24h. Filter to separate the precipitate, wash alternately with 50mL anhydrous ethanol and 50mL deionized water, centrifuge, repeat the washing cycle 3 times, dry at 80℃ for 24h, and then calcine at 200℃ for 1h (heating rate 5℃ / min) to obtain bifunctional hydroxyapatite powder with UV absorption and antibacterial properties.

[0047] Example 10

[0048] [Ca 8.8 CeAg 0.1 Zn 0.1 ](PO4)6(OH)2 Hydroxyapatite powder

[0049] Take 2.1711 g Ce(N03)3-6H20, 0.0849 g AgN03, 0.1487 g Zn(N03)2-6H20, add 88 mL 0.5M Ca(N03)2solution, ultrasonic treatment for 20 min, stirring at 90°C for 1 h, then add 100 mL 0.3M NH4H2P04solution, adjust pH value to 10-11 by dropping NH3-H20, continue stirring at room temperature for 1 h, to obtain mixed solution A. The mixed solution A is sealed under normal pressure to keep water from evaporating, and is aged at 20-30°C for 24 h. The precipitate is separated by filtration, washed and centrifuged alternately with 50 mL anhydrous ethanol and 50 mL deionized water, and the alternately washing is repeated for 3 times, dried at 80°C for 24 h, and then calcined at 200°C for 1 h (heating rate 5°C / min), to obtain the dual-functional hydroxyapatite powder with ultraviolet absorption and antibacterial property.

[0050] Example 11

[0051] [Ca 8.4 CeAg 0.3 Zn 0.3 ](P04)6(OH)2hydroxyapatite powder

[0052] Take 2.1711 g Ce(N03)3-6H20, 0.0849 g AgN03, 0.1487 g Zn(N03)2-6H20, add 88 mL 0.5M Ca(N03)2solution, ultrasonic treatment for 20 min, stirring at 90°C for 1 h, then add 100 mL 0.3M NH4H2P04solution, adjust pH value to 10-11 by dropping NH3-H20, continue stirring at room temperature for 1 h, to obtain mixed solution A. The mixed solution A is sealed under normal pressure to keep water from evaporating, and is aged at 20-30°C for 24 h. The precipitate is separated by filtration, washed and centrifuged alternately with 50 mL anhydrous ethanol and 50 mL deionized water, and the alternately washing is repeated for 3 times, dried at 80°C for 24 h, and then calcined at 200°C for 1 h (heating rate 5°C / min), to obtain the dual-functional hydroxyapatite powder with ultraviolet absorption and antibacterial property.

[0053] Example 12

[0054] [Ca 8.2 CeAg 0.3 Zn 0.5 ](P04)6(OH)2hydroxyapatite powder

[0055] Take 2.1711 g Ce(NO3)3·6H2O, 0.2547 g AgNO3, 0.7437 g Zn(NO3)2·6H2O, add 82 mL 0.5M Ca(NO3)2 solution, ultrasonic treatment for 20 min, stirring at 90℃ for 1 h, then add 100 mL 0.3M NH4H2PO4 solution, adjust pH to 10-11 by dropping NH3·H2O, continue stirring at room temperature for 1 h, to obtain mixed solution A. The mixed solution A is sealed under normal pressure to keep water from evaporating, and is aged at 20-30℃ for 24 h. The precipitate is separated by filtration, washed with 50 mL anhydrous ethanol and 50 mL deionized water alternately, and centrifuged, the washing and centrifugation are repeated for 3 times, dried at 80℃ for 24 h, and then calcined at 200℃ for 1 h (heating rate 5℃ / min), to obtain the dual-functional hydroxyapatite powder with ultraviolet absorption and antibacterial effect.

[0056] For example, the example 12, Figure 1 For the XRD spectrum of the sample, it can be seen that the material is consistent with the characteristic peaks of hydroxyapatite (PDF # 09-0432), which indicates that the [Ca 8.2 CeAg 0.3 Zn 0.5 The (PO4)6(OH)2 powder has the crystal structure characteristics of hydroxyapatite.

[0057] Figure 2 For the SEM photo of the sample, it can be seen that the grain morphology is microspherical, the size is between 20-50 nm, and several or dozens of microspheres are aggregated into microsphere clusters, and most of the microspheres are elliptical.

[0058] Figure 3 For the UV-DRS spectrum of the sample, it can be seen that the material has strong absorption effect on the light with wavelength of 220-400 nm.

[0059] Figure 4 For the bacteriostatic ring photo of the sample, it can be seen that the material has good bacteriostatic effect on Staphylococcus aureus and Escherichia coli.

Claims

1. A bifunctional hydroxyapatite powder having both ultraviolet absorption and antibacterial properties, characterized by: The structural feature of the bifunctional hydroxyapatite powder with ultraviolet absorption and antibacterial property is that part of Ca 2+ is replaced by Ce 3+ , Ag + , and Zn 2+ respectively, and the composition general formula is [Ca 10-x-y-z Ce x Ag y Zn z ](PO4)6(OH)2, wherein 0.1≤x≤1, 0.1≤y≤0.3, 0.1≤z≤0.5, and the molar ratio of metal elements to phosphorus elements is (Ca+Ce+Ag+Zn) / P=1.

67.

2. The bifunctional ultraviolet absorbing and antibacterial hydroxyapatite powder according to claim 1, characterized in that, The chemical composition is x=1, y=0.3, and z=0.5, the light with a wavelength of 220-400 nm is strongly absorbed, and the staphylococcus aureus and escherichia coli are well inhibited.

3. The bifunctional ultraviolet absorbing and antibacterial hydroxyapatite powder according to claim 1, characterized by, The preparation method is as follows: (1) 0.2171-2.1711 g of Ce(NO3)3·6H2O, 0.0849-0.2547 g of AgNO3, and 0.1487-0.7437 g of Zn(NO3)2·6H2O are respectively weighed, 82-97 mL of 0.5 M Ca(NO3)2 solution is added and ultrasonic treatment is performed for 20 min, stirring is performed at 90 ℃ for 1 h, 100 mL of 0.3 M NH4H2PO4 solution is added, the pH value is adjusted to 10-11 by dropwise adding NH3·H2O, and stirring is continuously performed at room temperature for 1 h, to obtain a mixed solution A; (2) the mixed solution A is sealed under normal pressure to keep water from evaporating, and is aged at 20-30 ℃ for 24 h; (3) the precipitate is obtained by filtration separation, is washed and centrifugally separated alternately with 50 mL of anhydrous ethanol and 50 mL of deionized water, the alternately washing is repeated for 3 times, is dried at 80 ℃ for 24 h, and is calcined at 200 ℃ for 1 h (heating rate 5 ℃ / min), to obtain the dual-functional hydroxylapatite powder with ultraviolet absorption and antibacterial effect.

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