Invented by Xueqing Qiu, Yong Qian, Ying Li, Dongjie Yang, Hongming Lou, Shiping Zhu, Weifeng Liu, South China University of Technology SCUT
The South China University of Technology SCUT invention works as followsThe present invention is a chemical sun-screening agents preparation that discloses the preparation of a lignin/chemical sunscreen agent microcapsule with high ultraviolet absorption using lignin for its wall. The present invention includes the following steps: 1) dissolving lignin at a concentration of 1-20 parts per 100-200 parts of aqueous solutions with pH 12; 2) adjusting pH to 7-10 and removing any insoluble substances through filtration. 3) mixing 10-50 parts of this lignin-based solution with 1-10 part of a chemical sunscreen agent and applying ultrasonic power between 200-1500 watts for 10 seconds to 25 minutes to produce a microcapsule emulsion. The lignin/chemical sunscreen agent microcapsules of the present invention have excellent ultraviolet absorption properties, can prevent photodegradation, and are stable. They also effectively prevent the chemical sunscreening agents from directly contacting the skin and causing harm.
Background for Microcapsules containing a chemical sun-screening agent and lignin with high ultraviolet absorption, and a method for their preparation
Sun exposure is a major factor in skin aging. Skin cancer may be caused by intense ultraviolet radiation. The UVB band (290 – 320 nm), which is responsible for skin erythema and DNA damage, has been shown to pass through the epidermis and stratum corneum. UVA rays (320-400nm) are able to reach the dermis, which is a major factor in melanoma. Sun protection is therefore essential. Sunscreens can absorb or scatter UVB and UVA rays, and they are classified into two main categories: chemical and physical. Physical sun-screening particles such as zinc oxide, titanium dioxide, and other inorganic materials can scatter or reflect ultraviolet radiation. However, they have poor affinity for the skin and are uncomfortable. This limits their practical application. The active ingredients of sun-screening products are mostly chemical sun-screening substances.
The sun-screening skincare based on chemical sun-screening agent has a more delicate texture and has a wider sun-screening range. They also have a stronger sun-screening capability. This is why they are generally well received by consumers. The chemical sun-screening agents themselves can absorb ultraviolet radiation, have photochemical or physical activity and undergo photodegradation. This results in a reduction in the sun-screening ability, as well as an increase in skin irritation and allergies caused by degradation products.
The chemical sunblocks are also micromolecular substances that can penetrate the skin and trigger DNA variations. They are easily broken down under illumination, resulting in highly active free radicals which can damage biological macromolecules, various cells, and lead to skin cancer.
Researchers from home and abroad developed liposomes, gels, and other substrate systems to coat chemical sun-screening agents. The chemical sunscreening agents coated with liposomes and gels are more stable, while the agents can be separated from the skin to reduce the side effects. Liu Shuangxi, Song Chunjin and others developed a method for coating a chemical sunscreen agent with chitosan as a wall. The chemical sunscreening agent, gelatin and an emulsifier were emulsified with high speed. A mixed solution of chitosan, acetic and calcium chloride was then added to the primary mixture, followed by reagglomeration and curing using glutaraldehyde to form the embedded body. (CN 1709219[P]). Zhang Wanping & Niu Wenxia successfully coated the octyl-methoxycinnamate sun-screening chemical agent with solid lipids nanoparticles. They also inhibited penetration of the sun-screening chemical agent into the skin through controlling the particle size in the coating carrier. Deng et al. The multi-step synthesis of polylactic acid and polyglycerol was used to embed a chemical sunscreen agent. Polyglycerol was then hydroformylated in order to produce microcapsules containing the polymer/chemical agent with bioadsorption characteristics (Nature Materials 2015, 14:1278-1285). It is not enough to embed the chemical sunscreen agent in chitosan, liposomes, or polylactic-polyglycerol through chemical crosslinking. Other additives, such as emulsifiers and crosslinking agents, are required. These additives increase the cost for preparation and separation and also cause harm to the skin and body. “We still need to evaluate the embedding properties and retention of the above-wall materials for the chemical sunscreen agent.
Lignin, a polymer compound found in plant cell walls, is a natural substance. The lignin molecule contains many functional groups, including a benzene group, a double-bond, a carbonyl and a phenolic group. This lignin molecule is a natural UV absorber and antioxidant. Qian, et.al. found that lignin has excellent UV and oxidation resistant and good dispersibility. The alkali-lignin mixture was tested with a hand-cream without sun-screening effects. When the lignin concentration was 10%, it had a sun-screening index of 5.72. This indicates that lignin has both broad-spectrum UV protection properties and synergizes well with sun-screening chemicals in sun-screening products (Green Chemistry 2015, 17: 322-324).
After purification, studies have shown that industrial lignin has a good compatibility with the human body. These studies have eliminated the safety concerns about lignin, both in the cosmetic skincare and medical fields (Bioresources Technology 2008, 99(14), 6683-6687). “Whether it is in terms or theory, experimentation, ecology, or safety, lignin has been developed into a natural anti-UV polymer wall material that can be used to embed chemical sunscreen agents in order to prepare composite microcapsules and used in the sun-screening skincare field.
Contents of the Invention
The present invention aims to overcome these shortcomings and disadvantages by providing a lignin/chemical sunscreening agent microcapsule with high ultraviolet absorption using lignin wall material. The lignin/chemical sunscreen agent microcapsules of the present invention have an amphiphilic, spherical shape, which has a better ultraviolet absorption than the chemical and lignin. It can also avoid photodegradation and is stable.
The present invention also aims to provide a microcapsule containing the lignin/chemical sunscreen agent.
Lignin is characterized by a number of conjugated structural elements, such as the benzene group and carbonyl group. It also contains reactive functional groups that are highly absorbent to ultraviolet light. These include a phenolic-hydroxyl group and methoxyl group. The large number phenolic groups in lignin molecules can produce phenolic radicals when exposed to ultrasonic waves. This promotes the intermolecular polymerization. The present invention is a combination of a chemical sunscreen agent and a solution of lignin, which prepares a microcapsule containing lignin/chemical Sun-screening agents by emulsion-crosslinking using ultrasonic energy in a single step. This method is easy to prepare, low-cost, environmentally-friendly, does not require an emulsifier, or cross-linking agents, and has a simple, straightforward preparation process.
The following technical solution is used to achieve the objects of this invention:
The following steps are included in a method for the preparation of a microcapsule containing lignin/chemical sunscreening agents:
(1) Dissolving 1-20 parts of lignin by weight in 100-200 part of an aqueous aqueous with a pH 12 and adjusting the pH to 7-10 and then removing the insoluble substances through filtration, to obtain a solution of lignin;
(2) mixing 10-50 part by weight of the solution of lignin in step (1) with a chemical sunscreening agent and applying ultrasonic radiation at a power between 200-1500 W from 10 s up to 25 minutes to obtain a microcapsule emulsion of lignin/chemical sunscreening agent.
The lignin can be a solvent-based lignin or an enzymatic, alkali, or lignosulfonate lignin.
Alkali-lignin is a mixture of wood pulp, bamboo pulp, wheat straw, reed, bagasse, alfalfa, cotton, and alfalfa.
The lignosulfonate is composed of bamboo pulp, wheat straw, bagasse, alfalfa, cotton, and reed.
Industrial lignins come primarily from steamed or boiling wastewater in the paper pulping industries. The physical and chemical characteristics of industrial lignins vary widely depending on the raw fiber materials, pulping processes and extraction methods. This makes their applications very diverse. Industrial lignins can be divided into four main categories. Alkali-lignin is derived from the waste liquids of alkaline pulping processes such as the sulfate and alkaloid methods. Lignosulfonate, derived from waste liquids of sulfite-based pulping methods with good water solubility. It has a wide range of applications. Other lignins include enzymatic, solvent-based and other lignins.
The chemical sunblocking agent can be isooctylmethoxycinnamate (or avobenzone), homosalate or other sunblocking chemicals.
The pH of the solution should be adjusted to between 8.5 and 9.5 in order to achieve the further objectives of the invention.
To further achieve the objectives of the invention, it is preferred to adjust the pH of solution at step (1) using a diluted acid solution. More preferably, this solution should be a diluted hydrochloric solution.Click here to view the patent on Google Patents.