Photoprotection in changing times – UV filter efficacy and safety,sensitization processes and regulatory aspects

As excessive sun exposure is tightly associated with different pathological changes of the skin, for example premature skin ageing or the development of skin cancer, an appropriate protection of the skin against UV radiation is of particular importance. Sun protection products and UV filter substances have evolved continuously in the past few decades. New developments and improved technical conditions of production have led to increasingly effective and efficient products with broadband protection ability. Accordingly, legal requirements have also changed and expanded. Although certain trends exist to harmonize the regulation of sunscreens at a global level, there are still large differences how UV absorbers are approved, which testing methods are prescribed, and which general requirements sun protection products must fulfil. Modern UV filters provide efficient protection against UVA and UVB radiation, are heat and photostable, user‐friendly, cost‐effective, water resistant and non‐toxic. As inorganic and organic UV filters are topically applied to the skin in relatively high concentrations (up to 25%), especially the assessment of their (photo)sensitization potential is of particular importance. Accordingly, skin sensitization is a key endpoint for the legally required safety assessment of cosmetic ingredients in Europe and many other countries. This review will summarize the current regulatory status of different approved UV filters, will describe their beneficial and adverse properties and will give an overview of how the efficacy of sunscreens can be evaluated. Finally, an insight into the basic mechanism of (photo)allergic reactions and existing skin sensitization test methods will be provided.     

Delivery by Design (DbD): A Standardized Approach to the Development of Efficacious Nanoparticle‐ and Microparticle‐Based Delivery Systems

The design and development of nanoparticle‐ and microparticle‐based delivery systems for the encapsulation, protection, and controlled release of active agents has grown considerably in the agrochemical, cosmetic, food, personal care, and pharmaceutical industries. These colloidal delivery systems can be utilized to overcome problems such as poor solubility, low activity, and chemical instability of active agents, as well as to create novel functional attributes such as controlled or targeted delivery. The purpose of this article is to develop a systematic approach, referred to as “delivery‐by‐design” (DbD), to make the design and fabrication process more efficient and effective. Initially, a brief review of some of the challenges associated with incorporating active agents into commercial products is given, and then an overview of different kinds of simple and complex colloidal delivery systems is given. The DbD approach is then presented as a series of stages: (1) definition of the molecular and physicochemical properties of the active agent; (2) definition of the required physicochemical, sensory, and functional attributes of the end‐product; (3) specification of the required attributes of the colloidal delivery system; (4) specification of particle properties and delivery system selection; (5) optimization of delivery system manufacturing process; (6) establishment and implementation of delivery system testing protocol; and (7) optimization of delivery system performance. Utilization of the DbD approach may lead to more rapid design of efficacious and economically viable colloidal delivery systems for commercial applications.     

First-derivative spectroscopic determination of sunscreens in cosmetic formulations

Nowadays, cosmetic as well as pharmaceutical forms must undergo many controls, i.e. in-process controls on the finished product and stability testing. The authors suggest using first derivative spectroscopy for active ingredients assay presenting an ultra-violet absorption. It offers the advantage of a direct assay through simple dilution and without active ingredient extraction.
Tests were made on classic mixtures of the sunscreens benzimidazol and cinnamate derivative (pair 1), and a mixture of two benzophenones (pair 2). The studied forms were solutions in propylene glycol and commercialized W/O and O/W creams.
After analytical method validation for each sunscreen by precision, reproducibility and repeatability studies, the percentages of error of the various assays have been reported in various preparations (solutions or creams).
A comparative study between HPLC assay (traditionally used) and the proposed method was carried out. The results show that a highly significant linear correlation exists between the two methods for the four sunscreens (R > 0.992). The speed and simplicity of the first derivative spectrometric method should find applications in routine control or in development of cosmetic or pharmaceutical preparations.     

Evaluation of skin cancer chemoprevention potential of sunscreen agents using the Epstein–Barr virus early antigen activation in vitro assay

In our continuing search for novel cancer chemopreventive compounds of natural and synthetic origin, we have evaluated 14 commonly used ultraviolet (UV) sunscreen agents (designated UV‐1 to UV‐14) for their skin cancer chemoprevention potential. They belong to 8 different chemical categories: aminobenzoate (UV‐5, UV‐7, UV‐8 and UV‐14), benzophenone (UV‐1, UV‐2, UV‐3 and UV‐13), benzotriazole (UV‐10), benzyloxyphenol (UV‐9), cinnamate (UV‐6), quinolone (UV‐4), salicylate (UV‐11) and xanthone (UV‐12). In the in vitro assay employed, the sunscreens were assessed by their inhibition of the Epstein–Barr virus early antigen (EBV‐EA) activation induced by the tumour promoter 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in human lymphoblastoid Raji cells. All sunscreens tested were found to exhibit anti‐tumour promoting activity: listed in decreasing order, moderate (UV‐11, UV‐2, UV‐7, UV‐12, UV‐3, UV‐9 and UV‐14) to weak (UV‐1, UV‐6, UV‐8, UV‐16, UV‐5, UV‐4 and UV‐10) with octyl salicylate (UV‐11) as the most potent and drometrizole (UV‐10) as the least potent among the compounds evaluated. A plausible relationship between the antioxidant property of sunscreens and their ability to promote anti‐tumour activity was noted. The results call for a comprehensive analysis of skin cancer chemoprevention potential of currently used UV sunscreen agents around the globe to identify those with the best clinical profile.     

Formulation of sunscreens with enhancement sun protection factor response based on solid lipid nanoparticles

Solid lipid nanoparticle (SLN) was regarded as new topical delivery systems for pharmaceutical and cosmetic active ingredients. The purpose of this study is to develop carrier systems for organic and inorganic sunscreens based on a matrix composed of carnauba wax and decyl oleate. Formulae (F1–F7) were prepared using butyl methoxydibenzoylmethane and octyl methoxycinnamate as organic components, and titanium dioxide (TiO₂) was used as inorganic component. Both types of sunscreens were incorporated into SLN formulations using classical method of preparation. To evaluate the effect of the pigments on the nanoparticles, particle size was measured using Mastersizer particle size analyser. UV‐protection abilities of formulations were investigated by the in vitro sun protection factor test (SPF). Further parameters determined were spreadability as well as viscosity. The rheological behaviour of the formulations was also carried out. From the plot of log of shear stress vs. log of shear rate, the slope of the plot representing flow index and ontology of the y‐intercept indicating consistency index was calculated. The formulae showed a flow index of 0.2074–0.4005 indicating pseudoplastic flow behaviour. Significant increases in SPF values up to about 50 were reported after the encapsulation by using organic and inorganic filters in Canada wax and decyl oleate. So, SLN could be appropriate vehicles to carry organic and inorganic sunscreens. The rational combination of cinnamates, titanium dioxide and Zinc oxide has shown a synergistic effect to improve the SPF of cosmetic preparations.     

Beyond sun protection factor testing

Ultraviolet radiation in sunlight produces a range of acute and chronic adverse effects on the skin including sunburn, photosensitivity rashes, immunosuppression, photoageing and carcinogenesis. Sunscreens aim to provide protection, but standard testing procedures primarily involve assessment of ability to protect against acute erythema, as evidenced by the sun protection factor (SPF). The SPF may correlate poorly with other aspects of protection, particularly since ultraviolet A is weakly erythemogenic compared with ultraviolet B, yet may make a greater contribution to certain other skin effects of sunlight. Nevertheless, there is an increasing tendency for the sunscreen industry to make claims for their products beyond the SPF data. There is a need to develop systems for clinical testing of sunscreens against other endpoints caused by ultraviolet exposure of skin, including immunosuppression and photosensitivity rashes. In particular, there is a largely unrecognized need for testing of sunscreens against the condition known as polymorphic light eruption, a photosensitivity disorder estimated to affect a staggering 10-20% of the population in the northern hemisphere. Ultimately, protection of the skin by sunscreens can only be as effective as their adequacy of application to the skin surface in the everyday setting permits. Optimal sunscreen formulation, and public and patient education in appropriate application technique, both make vital contributions to efficacy of sunscreen protection. This article focuses on the need for extended clinical testing of sunscreens, with particular reference to the photosensitivity disorders, and for improvements in sunscreen formulation and in the adequacy of sunscreen application to the skin surface.     

Soybean extract showed modulation of retinoic acid‐related gene expression of skin and photo‐protective effects in keratinocytes

Soy extracts are well known as medicinal and nutritional ingredients, and exhibit benefits towards human skin including depigmenting or anti‐ageing effects. Despite the wrinkle decreasing effects of retinoids on skin as an anti‐ageing ingredient, retinoid application can causes photo‐sensitive responses such as skin irritation. Thus, their daytime usage is not recommended. The aim of this study is the investigation into the activities of soybean extract as an anti‐ageing ingredient and their comparison to retinoids in this respect. Soybean extract decreased the relative ratio of MMP‐1/TIMP‐1 mRNA to the same degree as retinoic acid in normal human fibroblasts. It also affected mRNA levels of HAS2 and CRABP2 in normal human keratinocytes. Furthermore, we investigated its effect on mRNA expression of histidase, an enzyme that converts histidine into urocanic acid, the main UV light absorption factor of the stratum corneum. Unlike the complete inhibition of histidase exhibited by the mRNA expression of retinoic acid, the effect of soybean extract on histidase gene expression was weaker in normal human keratinocytes. Also, soybean extract pretreatment inhibited UVB‐induced cyclobutane pyrimidine dimer formation dose‐dependently in normal human keratinocytes. In this study, we found that soybean extract modulated retinoic acid‐related genes and showed photo‐protective effects. Our findings suggest that soybean extract could be an anti‐ageing ingredient that can be safely used under the sunlight.     

Vitamin A palmitate photostability and stability over time

Vitamin A palmitate photostability in relation to ultravoilet A (UVA) and ultravoilet B (UVB) was tested in hydroxy ethyl cellulose hydrogels at pH 4.0, 5.6, 7.0, and 8.0, alone and with the addition of sunscreens (3,4‐methylbenzilidencamphor or butyl methoxy dibenzoylmethane) or an antioxidant (butylated hydroxy toluene). The photostability of vitamin A palmitate was also tested in encapsulated systems (Tagravit_A1 microcapsules, Lipotec_liposomes, phosphatidylcholine liposomes, and Lipotec_nanocapsules) dispersed in gels at pH 5.6 and 7.0. The stability of retinyl palmitate over time in hydroxy ethyl cellulose hydrogels at pH 5.6 and 7.0 (stored 1 month at 25 or 40 °C), alone or with butylated hydroxy toluene, was also tested. The stability of retinyl palmitate over time in encapsulated systems, dispersed in gels at pH 5.6 and 7.0, was also studied. O/W emulsions were also prepared to compare the stability of vitamin A palmitate introduced in a lipophilic/hydrophilic medium (O/W emulsions) and a hydrophilic medium (hydrogels). HPLC analysis showed that encapsulated systems such as Lipotec_nanocapsules, Tagravit_A1 microcapsules, phosphatidylcholine liposomes, and Lipotec_liposomes protect the vitamin A ester over time from hydrolysis and from oxidation to retinaldeide and retinoic acid, and that Lipotec_nanocapsules and phosphatidylcholine liposomes also improve the vitamin's photostability. A change in pH (5.6–7.0) of the gels did not influence the vitamin ester's stability. pH levels of 4.0 and 8.0 determined a decrease in the stability of retinyl palmitate in the gels. A high concentration of sunscreens improved the photostability of retinyl palmitate in the gels at pH 5.6 and 7.0. Butylated hydroxy toluene protected retinyl palmitate from degradation induced by light at all the pH levels studied and by heat at pH 5.6 and 7.0, as can be seen from the study of the photostability of vitamin A palmitate under UVB and UVA and of stability over time. Rheological studies showed a slight decrease in the viscosity of the gels after UVB–UVA irradiation and a higher decrease in the viscosity of the gels and the emulsions after storage at 25 and 40°C. This decrease can be attributed to a partial degradation of hydroxy ethyl cellulose and of emulsifier, as can be seen from the decrease in shear stress versus shear rate values under these conditions of storage, denoting a depolymerization of the rheological modifier.     

The adverse consequences of not using sunscreens

The adverse effects of solar ultraviolet radiation (UVR) on normal skin are well established, especially in those with poorly melanized skin. Clinically, these effects may be classified as acute, such as erythema or chronic such as keratinocyte and melanocyte skin cancers. Apart from skin type genetics, clinical responses to solar UVR are dependent on geophysical (e.g., solar intensity) and behavioural factors. The latter are especially important because they may result in ‘solar overload’ with unwanted clinical consequences and ever greater burdens to healthcare systems. Correctly used, sunscreens can mitigate the acute and chronic effects of solar UVR exposure. Laboratory studies also show that sunscreens can inhibit the initial molecular and cellular events that are responsible for clinical outcomes. Despite public health campaigns, global trends continue to show increasing incidence of all types of skin cancer. Large-scale epidemiological studies have shown the benefits of sunscreen use in preventing skin cancer, though it is likely that sunscreen use has not been optimal in such studies. It is evident that without substantial changes in sun-seeking behaviour, sunscreen use is a very important part of the defence against the acute and chronic effects of solar exposure. Ideally, sunscreens should be able to provide the level of protection that reduces the risk of skin cancer in susceptible skin types to that observed in heavily melanized skin.     

Plant-based active photoprotectants for sunscreens

Excessive exposure to the sun's radiation is the major exogenous mediator of skin damage, which accelerates skin ageing and increases the risk of developing skin cancer. Compounds with photoprotectant activity are extremely useful for decreasing the effect of ultraviolet (UV) radiation on the skin; however, numerous sun filters, especially organic sunscreens, are allergenic. Therefore, the development of formulations containing plant extracts, which may be potentially safer, is extensively being explored. Plant-based cosmetics are commonly used to avoid skin ageing because they contain antioxidant agents that minimize free radical activity, and numerous studies have investigated the skin-protectant effects of related plant species. In addition to their antioxidant properties, plant-based cosmetics protect the skin against solar radiation because they contain polyphenols such as flavonoids and carotenoids. Therefore, this study aims to present a review of plant species commonly used in sunscreens to protect the skin against damage due to sunlight exposure.     

Monitoring of the microcapsule/liposome application on textile fabrics

In recent years, new technologies have led to the production of biofunctional textiles. These biofunctional textiles contain microscopic capsules of ingredients that break as the fabric rubs the skin, releasing the active agents. Absorption and desorption behaviour of active agents embedded into the different biofunctional textiles should be taken into account when determining the amount of active agents incorporated into these textiles and when following the delivery mechanism as the fabric comes in contact with the skin. In this work, an encapsulated active agent (a sun filter, ethyl hexyl methoxycinnamate [EHMC] into microcapsules or liposomes) was applied by foulard onto different fabrics. The amount of capsules and active agents embedded into the fibres were quantified by (1) weight difference between untreated and treated fabrics, (2) extraction with isopropanol in an ultrasound bath, or (3) extraction with isopropanol/water 50/50 in a soxhlet device. Sun filter detection of the extraction baths was followed by HPLC and by UV spectrophotometry. The results show that the real amount of the EHMC present in different textile substrates depends on the way that the active agent is trapped, the ionic character of the fibres and on the vehicles used.     

Natural Antimicrobial Edible Coatings for Microbial Safety and Food Quality Enhancement

Natural antimicrobial agents have been investigated as alternatives to synthetic ones for ensuring food safety and quality. However, the practical use of these preservatives in the food industry is limited due to their negative impact on the odor and taste of food products, as well as the early loss of functionality due to their rapid diffusion and interaction with food components. The incorporation of natural antimicrobial agents into edible coatings has been investigated to control diffusion of active compounds and maintain their concentrations at a critical level on a food surface. Recently, nanoencapsulating and multilayered/nanolaminate delivery systems have emerged as promising tools to enhance the functionality of edible coatings. This review highlights the potential use of polymeric edible coatings for the incorporation of natural antimicrobial agents and the improvement of their controlled release in food systems. The methods used to assess the antimicrobial activity of encapsulated natural antimicrobial agents and the most recent findings regarding the application of nanoencapsulating and multilayered/nanolaminate delivery systems in food products are also discussed.     

Emulsion microgel particles: Novel encapsulation strategy for lipophilic molecules

BackgroundLipophilic molecules such as flavours, essential oils, vitamins and fatty acids are difficult to deliver in food matrices owing to their limited solubility, rapid oxidation and degradation during physiological transit. Among the technologies available to deliver lipophilic molecules, emulsion microgel particles are a relatively new class of soft solid particles of discrete size, shape, and interesting release properties.Scope and approachRelevant literature concerning the processing of emulsion gels and emulsion microgel particles has been reviewed. Factors affecting the mechanical properties of protein-stabilised emulsion gels with key emphasis on the role of “active” and “inactive fillers” are discussed. Technologies for creation of emulsion gel particles using top-down and bottom-up approaches has been covered. Special attention was dedicated to the release mechanisms from emulsion microgel particles via swelling and erosion.Key findings and conclusionsEmulsion gels with “active fillers” offer the potential to create emulsion microgel particles using top-down approach. Polymer extrusion, multiple emulsion templating, fluid gels are few routes for creating emulsion microgel particles using bottom-up approaches. Although whey protein has been well researched, modified starch, plant proteins need to be investigated for design of new emulsion microgel particles that can act as surfactant and bulk gelling agents in their own right through intelligent tuning of processing conditions. If designed carefully with an end goal of “controlled delivery” in mind, responsiveness to oral temperature, gastric enzymes, intestinal pH etc, can be built into emulsion microgel particles so that they may find novel applications in food, pharmaceutical and personal care industries.     

A novel in vitro technique for measuring the water resistance of sunscreens

A novel in vitro technique has been used to assess the water resistance of topical sunscreens. The technique is based upon transmission spectrometry using excised human epidermis as the substrate. The sun protection factors (SPFs) of four sunscreens obtained prior to water immersion and after two immersions were compared with in vivo data determined using human volunteers. In every case there was close agreement between the SPFs obtained on dry skin and on skin that had been immersed in water. Not only does the technique provide a less expensive and less time consuming alternative to in vivo testing, it also offers the possibility to study the effect that water immersion may have on the absorption spectrum of products which cannot be determined in vivo. This can give valuable information on which, if any, of the active ingredients present in sunscreens are being preferentially removed by water. In addition, the method can be easily adapted to study the effects on sunscreen substantivity of other factors such as water temperature, salinity and turbulence.     

Targeted delivery of salicylic acid from acne treatment products into and through skin: role of solution and ingredient properties and relationships to irritation

Salicylic acid (SA) is a beta‐hydroxy acid and has multifunctional uses in the treatment of various diseases in skin such as acne, psoriasis, and photoaging. One problem often cited as associated with salicylic acid is that it can be quite irritating at pH 3–4, where it exhibits the highest activity in the treatment of skin diseases. We have identified strategies to control the irritation potential of salicylic acid formulations and have focused on hydroalcoholic solutions used in acne wipes. One strategy is to control the penetration of SA into the skin. Penetration of the drug into various layers of skin, i.e. epidermis, dermis, and receptor fluid, was measured using a modified Franz in vitro diffusion method after various exposure times up to 24 h. A polyurethane polymer (polyolprepolymer‐15) was found to be an effective agent in controlling delivery of SA. In a dose‐dependent fashion it targeted delivery of more SA to the epidermis as compared to penetration through the skin into the receptor fluid. It also reduced the rapid rate of permeation of a large dose of SA through the skin in the first few hours of exposure. A second strategy that proved successful was incorporation of known mild nonionic surfactants like isoceteth‐20. These surfactants cleanse the skin, yet due to their inherent mildness (because of their reduced critical micelle concentration and monomer concentration), keep the barrier intact. Also, they reduce the rate of salicylic acid penetration, presumably through micellar entrapment (either in solution or on the skin surface after the alcohol evaporates). Cumulative irritation studies showed that targeting delivery of SA to the epidermis and reducing the rapid early rate of penetration of large amounts of drug through the skin resulted in a reduced irritation potential. In vivo irritation studies also showed that the surfactant system is the most important factor controlling irritancy. SA delivery is secondary, as formulations with less SA content reduced the rate of delivery to the receptor and yet were some of the most irritating formulations tested, presumably due to the action of the specific anionic surfactant on the barrier. Alcohol content also did not appreciably affect irritation and SA delivery; formulations with considerably low alcohol content but containing anionic versus nonionic surfactant systems exhibited considerably higher irritancy. Thus the surfactant type was again the predominant factor in those studies, although arguably alcohol plays some role (solubilization of SA). Results showed that both polymers and mild surfactants work in concert to provide the optimal formulation benefits of targeted delivery and reduced irritation. Synergistic relationships among hydroalcoholic formulation components will be discussed along with the mechanisms likely involved in controlling delivery of SA to skin.     

基于环糊精及其衍生物的递送体系在食品领域的研究进展

利用环糊精及其衍生物无毒害、无气味等特性,包埋水溶性差、且对光照、温度、pH等敏感的活性成分,起到提高水溶性、增强稳定性、掩蔽不良气味等作用,并且可以达到靶向释放活性成分的目的。本文综述了近几年国内外关于环糊精包埋活性成分递送体系的研究,首先介绍了几种基于环糊精及其衍生物的递送体系,包括包合物、水凝胶和Pickering乳液,其中重点讨论了包合物的常用制备方法,即共沉淀法、超声法、研磨法、冷冻干燥法和喷雾干燥法的优缺点及适用范围;然后总结了环糊精及其衍生物递送体系对食品领域中抗菌剂、抗氧化剂、以及维生素、蛋白质等活性成分的保护和递送;最后,对环糊精递送体系在食品领域的研究和应用进行展望,为后续研究提供参考资料。     

The effect of rheological properties of experimental moisturizing creams/lotions on their efficacy and perceptual attributes

Although anecdotal evidence suggests that the rheology of creams and lotions might affect their moisturizing efficacy and perceptual qualities, to date no systematic investigation of these effects has been carried out. We prepared 12 prototype moisturizing creams that had identical overall formulae but differed in as far as they contained three different polymers (Carbopol 981, Carbopol 5984 and Permulen TR.-2) each at four concentration levels. Using these creams, we carried out two series of experiments. In the first series, we applied pre-determined quantities of creams to defined areas of skin on the forearms of eight panelists and then measured the subsequent changes in Transepidermal Water Loss (TEWL) and Skin Capacitance (SC) values as a function of time. In the second series, the panelists were asked to spread and rub over their entire two hands as much of the creams as they deemed necessary for achieving satisfactory perceived moisturization. In this latter series, we also weighed the amounts of cream used and measured the TEWL and SC values at several skin sites as a function of time subsequent to the cream application. The panelists also scored 14 skin attributes for each of the 12 creams used. The same procedures were also carried out with a commercial skin moisturizing cream (Keri(R)) that was used as a control. In separate laboratory experiments, the rheological properties (i.e. the elastic and viscous moduli) of the various creams at a number of frequencies were measured. The analysis of the experimental results suggested that the overall rheology of creams had little direct effect on both, the moisturizing efficacy and the perceived perceptual attributes. Neither did the overall viscoelasticity or the esthetic attributes of the preparations seem to affect the amounts of creams/lotions that the panelists judged to be necessary for achieving satisfactory perceived hand moisturization. Although all preparations contained the same occlusive material (oil) at identical concentration, nevertheless some of the preparations appeared to show different efficacies depending on the nature and the levels of the polymeric ingredient present.     

Lipoprotein creams: utilization of multifunctional ingredients for the preparation of cosmetic emulsions with excellent skin compatibility

Lipoproteins are plant-derived surface-active biopolymers, which act as emulsifying as well as viscosity-enhancing agents in oil-in-water emulsions. Depending on the degree of hydrolization, lipoproteins are dispersible or even soluble in water. In the presence of low to medium polar oils, lipoproteins are adsorbed and align at the oil-water interface, whereas in mixtures with high polar oils the lipoproteins are repelled from the oil-water interface. The water-dispersible lipoproteins show higher interfacial activity than the hydrolysates. Lipoproteins bear a negative electric charge in aqueous dispersions at pH 6.5, which is probably the reason for the stabilization of oil droplets against coalescence. Lipoprotein creams were characterized in terms of particle size, rheology, and emulsion stability against sedimentation, which was evaluated by a near-infrared sedimentometer. After topical application, emulsion stability breaks down and an emulsion film is formed on the skin surface. Lipoprotein creams cause a distinct increase in skin pliability and skin moisture and show excellent skin compatibility. In a home use test the panelists appreciated the cosmetic and caring properties of the lipoprotein cream.     

复配海藻酸盐凝胶作为传递体系的研究进展

海藻酸钠是传递体系中应用最广泛的聚合物多糖之一,以其为原料制备的凝胶常被用作生物活性化合物和药物等物质的运输载体,在食品和药品领域具有较大的应用潜力.目前复配凝胶法已被用于改善单一海藻酸盐凝胶的机械性能和应用缺陷,并且应用形式多样.本文综述了海藻酸钠的结构与基本性质,重点介绍了近年来海藻酸钠复配凝胶的研究状况,包括与多...     

Progress in microencapsulation of probiotics: A review

The potential health benefits of probiotics may not be realized because of the substantial reduction in their viability during food storage and gastrointestinal transit. Microencapsulation can be used to enhance the resistance of probiotics to unfavorable conditions. A range of oral delivery systems has been developed to increase the level of probiotics reaching the colon including embedding and coating systems. This review introduces emerging strategies for the microencapsulation of probiotics and highlights the key mechanisms of their stress–tolerance properties. Recent in vitro and in vivo models for evaluation of the efficiency of probiotic delivery systems are also reviewed. Encapsulation technologies are required to maintain the viability of probiotics during storage and within the human gut so as to increase their ability to colonize the colon. These technologies work by protecting the probiotics from harsh environmental conditions, as well as increasing their mucoadhesive properties. Typically, the probiotics are either embedded inside or coated with food‐grade materials such as biopolymers or lipids. In some cases, additional components may be coencapsulated to enhance their viability such as nutrients or protective agents. The importance of having suitable in vitro and in vivo models to evaluate the efficiency of probiotic delivery systems is also emphasized.