4.1. Functional Foods
Functional food, in general terms, may be defined as a natural or processed food, which contains an identified component, in qualitative and quantitative amounts, with a proven and documented health benefit [
136,
137]. This concept was created in recent decades, opening a new research field that is in constant expansion due to consumers’ increasing awareness of the close correlation between diet and health. Beyond providing nutrients required for the bodily metabolism, it is well-known that food may play a key role in the prevention and treatment of certain diseases, along with the improvement of physical and mental well-being [
138,
139]. Following this trend, safety issues regarding the consumption of processed foods have also become a concern. National authorities, such as the Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA), have restricted the use of many synthetic additives in food, e.g., synthetic dyes, due to a growth in cancer development or allergic reactions [
6,
51].
Accordingly, there is a great interest in the investigation of natural resources and biologically active compounds with high nutritional value and functionality to be used as a food ingredient in the development of novel functional foods [
140]. Among these, microalgae are emerging as a valuable and economically viable alternative, as they represent a rich source of food-grade compounds and almost an unlimited field of exploration due to their abundant taxonomic diversity [
140,
141]. A variety of microalgae biomass has already been successfully applied in the fortification of assorted food products, such as cookies, bread, pasta, and some dairy goods [
142].
On the other hand, the incorporation of nutraceutical compounds into food is more of a challenging approach. The effectiveness of a bioactive as a health-promoting substance within the food matrix depends on keeping its functionality intact during food processing and storage; conserving the characteristics (taste, texture, colour, smell, etc.) and acceptability of the original food; and lastly, assuring the bioavailability of the active ingredients, which includes sustaining sufficient time of gastric residence without degradation and appropriate gut permeability [
95]. Due to the inherent instability of most bioactive compounds present in microalgae, the efficacy of this process may be compromised. Consequently, their incorporation into encapsulation systems seems to be a promising strategy to deliver microalgae health benefits at boosted levels through functional foods [
96].
One of the most explored microalgae concerning encapsulation systems for food applications is the species
Haematococcus pluvialis. Several research groups have investigated the encapsulation of its extract obtained by different methods or purified compounds, essentially the carotenoid astaxanthin. A resume of the systems reported in the literature and their main findings are described in
Table 1.
Astaxanthin, which possesses a singular and recognized antioxidant potential, is present in a considerable amount in the
H. pluvialis cyst cells formed under adverse environmental conditions. Nevertheless, the pure addition of the whole cells into food may not be applicable; during the cyst phase, the bioactive compounds are surrounded by a thick cell wall, which could hinder proper release and bioavailability. Therefore, an extraction method is normally required to achieve cell wall disruption and obtain the compounds of interest [
170]. When the extraction process is concluded, highly sensitive substances, such as astaxanthin, once protected by the cell wall, are now susceptible to the effects of light, oxygen and high temperatures, among others, which explains the high number of studies applying encapsulation for this compound [
171].
In
Table 1, it is possible to observe that all the studies have used as core substance the already disrupted
H. pluvialis cell; purified astaxanthin, as powder or oleoresin; or an astaxanthin-rich extract, always obtained through green techniques. The coating materials selected for those encapsulation systems were majoritarian natural polymers, mainly chitosan, alginate, whey protein, maltodextrin, and Arabic gum, as they are food-grade and widely used as food additives. Regarding the encapsulation techniques applied for
H. pluvialis and its compounds, the diversity reported in the studies is clear, including both top-down and bottom-up approaches. Among them, spray drying, extrusion, and emulsification were preferred by half of the authors for the encapsulation processes.
Despite all the differences found for astaxanthin encapsulation, the protective potential of this strategy over such a compound is unquestionable. The coating layer was reported to promote stability improvement under storage at adverse conditions, such as high temperatures, oxygen exposure, or extreme pH values, while preserving its antioxidant potential. Nonetheless, greater stability was usually detected when the encapsulation system was stored at low temperatures. Moreover, the enhancement in astaxanthin bioaccessibility and bioavailability was also investigated, obtaining positive results in in vitro studies.
The development of an encapsulation system is a complex process; as such, understanding the influence of the type and concentration of the coating material or the applied technique, on the particle physicochemical properties is also a significant step to guarantee its functionality when added into a food matrix. Anarjan and Tan [
167], for instance, investigated the emulsification and stabilization ability of four different polysaccharides, namely Arabic gum, xanthan gum, pectin, and methylcellulose, in the preparation of water-dispersible astaxanthin nanoparticles. The authors reported that the physicochemical characteristics of the prepared nanodispersions were significantly influenced by the type and chemical structures of the polysaccharide used as the coating material, with the one produced with Arabic gum showing the smallest average particle diameter and highest physical stability. However, they observed a considerable astaxanthin degradation after 30 days of storage for all samples, which allowed them to conclude that, generally, the nanodispersions produced with polysaccharides have a larger average particle size and less physicochemical stability than those obtained with proteins and small molecule emulsifiers.
The encapsulation of bioactives from the marine microalga Phaeodactylum tricornutum for food applications was described in two different studies, both using the electrospray/electrospinning technique. This species is considered a significant source of the carotenoid fucoxanthin and PUFAs, which have been associated with several health-promoting properties. Nevertheless, the rough algal extract is not suitable for food fortification due to its distinctive odour, consistency, and low bioactive concentration. Additionally, such lipophilic bioactives possess an inherent sensitivity to many adverse environmental conditions, low water solubility, compromised bioavailability, and potential degradation during digestion.
Seeking to overcome these issues, Koo et al. [
172] researched the development of a fucoxanthin-enriched fraction from
P. tricornutum-loaded nanoparticles to improve the application of this carotenoid into the food industry. The nanoparticles were prepared through homogenization followed by an electrospray system, firstly using only casein as the coating material, then followed by an extra layer of chitosan. In vitro simulated digestion studies have demonstrated a better bioaccessibility of the nanoparticles over the
P. tricornutum powder. Such a result was also corroborated by the in vivo pharmacokinetic assay, where the casein-chitosan nanoparticles exhibited superior bioavailability, possibly due to increased retention or adsorption to the mucin by the presence of chitosan. In another study, Papadaki et al. [
51] recovered a lipid fraction from
P. tricornutum through ultrasound-assisted extraction using coconut oil as a solvent. Subsequently, the extract was emulsified and encapsulated in ulvan:pullulan nanofibers by electrospinning. The encapsulation process showed an entrapment efficiency of 90%, for both carotenoids and PUFAs, in food-grade water-based polysaccharides; thus, representing a promising strategy for incorporation of lipophilic bioactives from the microalga
P. tricornutum into food matrices.
The cultivation and bioactive extraction optimization of the microalga
Dunaliella salina are topics constantly researched in the literature. As the richest natural source of the carotenoid β-carotene, the encapsulation of this species is also a trending area when it concerns functional foods. Techniques that were already investigated comprise calcium alginate beads followed by fluidized bed drying [
173] and spray-drying using a mixture of maltodextrin:Arabic gum [
174] or different combinations of gelatine, maltodextrin and Arabic gum, as coating materials [
175]. All the researchers concluded that encapsulation was able to promote stability improvement in the β-carotene content naturally present in
D. salina; however, they also reinforced that better results can be achieved through the utilization of lower temperatures in the drying process, with the absence of light and high temperatures during storage.
The encapsulation of microalgae of the genus
Chlorella has been widely investigated for environmental monitoring, but its use in the food industry has not been fully explored yet. Differing from what has been published about other microalgae species,
Chlorella was considered as a possible coating material in the encapsulation system of other bioactives.
Chlorella vulgaris cells were investigated as a carrier for the polyphenol curcumin [
176] and
C. pyrenoidosa cells as a carrier for the carotenoid lycopene [
177], aiming at protecting the core substance while developing an innovative nutraceutical complex. The encapsulation process in both studies was performed by adsorption. Results demonstrated an increase in the photostability of curcumin by about 2.5-fold, and an improvement in the thermal and storage stability of lycopene when loaded into
Chlorella cells. Moreover, the
Chlorella–lycopene complex presented higher antioxidant activity when compared to the same amount of free lycopene at room temperature for 25 days, which might be partly due to the carrier protection, and partly due to the endogenous antioxidants present in
C. pyrenoidosa cells.
The species
Chlorella pyrenoidosa was also chosen as the object of study of Wang and Zhang [
178], where they evaluated the extraction and antitumor activity of a polypeptide obtained from this microalga to further encapsulate through two different techniques, namely complex coacervation and ionotropic gelation. The antitumor activity was confirmed to have inhibitory activity on human liver cancer HepG2 cells and encapsulation was carried out as a solution to avoid stomach degradation, followed by a proper release in the intestinal environment. The in vitro release assay revealed that the encapsulated
C. pyrenoidosa polypeptide was well preserved against gastric enzymatic degradation, increasing its bioavailability at least two-fold when compared to the non-encapsulated bioactive.
Another microalga that has been investigated for food purposes is the species
Phormidium valderianum. Chatterjee et al. [
179] reported the encapsulation process by spray-drying of an antioxidant-rich fraction of
P. valderianum obtained through supercritical carbon dioxide extraction, aiming at enhancing the storage stability of the extracted compounds. A mixture of maltodextrin:Arabic gum was selected as wall material and the optimization of the microencapsulation process parameters was performed to achieve the best yield and biological properties, which were examined by antioxidant capacity, phenolic content and reducing power. The condition that provided the best response combination of the analysed parameters was spray-drying at an inlet temperature of 130 °C, with wall material composition of maltodextrin:Arabic gum (70:30). Additionally, a stability study was also carried out for 60 days, comparing the IC
50 values of the DPPH (2,2-diphenyl-1-picrylhydrazyl) antioxidant assay of non-encapsulated and encapsulated microalgal extract. As a result, it was confirmed that the encapsulation process was able to protect the antioxidant compounds for a longer period, enhancing the antioxidant activity shelf-life by eight-fold.
Similarly, Bonilla-Ahumada et al. [
180] investigated the microencapsulation of fresh biomass from the microalga
Tetraselmi chuii by spray-drying, along with the effect of the wall material (maltodextrin:Arabic gum (60:40), chitosan 3% or gelatine 2%) and processing conditions (inlet temperature 110, 130, and 150 °C) on the preservation of β-carotene and other antioxidant compounds present in this species. The work reported preservation of 80–92% of β-carotene and 46–81% of the phenolic compounds in freshly microencapsulated microalga, even after three months of storage in the dark,at 25 °C, when coated with maltodextrin and spray-dried at 130 °C. Moreover, the authors emphasized the advantage of using spray-drying regarding algal biomass, as it is capable of protecting unstable metabolites, as well as facilitating the transport and further incorporation into food products.
The encapsulation process is also widely employed for microalgae of the genus
Arthrospira, focusing on improving several challenges involved in the incorporation of its biomass/powder, extracts, or compounds into functional foods. A compilation of published studies can be found in
Table 2. The species
A. platensis, the main representative of this group, is acknowledged as a pronounced protein source and rich in many essential nutrients for the human diet. The fortification of different food products with whole
A. platensis biomass has already been explored by many authors seeking to increase their nutritional content and functionality, i.e., antioxidant potential [
181,
182,
183]. However, encapsulation may provide not only a protective layer for stability enhancement over processing and storage conditions, but the possibility to achieve more uniform distribution in the food matrix.
The addition of microencapsulated
A. platensis powder obtained through spray drying into yoghurt was investigated by Da Silva et al. [
189] and compared to a formulation containing the free microalga. The authors reported that microencapsulation was able to promote higher thermal stability, showing better anti-inflammatory activity without exerting cytotoxicity. Moreover, the yoghurts incorporated with encapsulated
A. platensis exhibited a more homogeneous appearance, lighter green colour, and noticeable decrease in the strong odour, whilst, at the same time, maintaining yoghurt’s nutritional profile and an improved antioxidant activity throughout the storage time. Recently, Zen et al. [
192] developed a functional pasta fortified with
A. platensis biomass-loaded alginate microparticles also through spray-drying. Even though the pasta properties were affected by the addition of microparticles, the overall acceptability index was not influenced according to sensorial studies. Most importantly, microencapsulation was able to protect 37.8% of the biomass antioxidant potential from the pasta cooking conditions.
On the other hand, the addition of
A. platensis extracts and the protein-pigment phycocyanin—its main antioxidant compound—into food suffers from the limitations previously described for food fortification with natural bioactives. The extract composition obtained from this microalga is highly dependent on the extraction technique and, mostly, on the type of solvent used. Aqueous-based extracts are essentially rich in phycocyanin, phenolic compounds, and other polar substances, while organic-based extracts are rich in chlorophyll, carotenoids, and other lipophilic compounds [
197].
Among all the studies, the encapsulation of isolated phycocyanin was investigated by a considerable number of authors using different techniques, such as spray drying, extrusion, and electrospraying. The particles’ properties were analysed and optimized to achieve the best coating material concentration or composition of two distinct types, with the highest entrapment efficiency, particle size consistency, and stability. Some authors also explored the stability of encapsulated phycocyanin, describing thermal stability improvement and resistance to the acidic environment when alginate and chitosan were used together as coating materials [
184] and thermal resistance up to 216 °C with full preservation of its antioxidant activity when encapsulated with PVA [
194]. Concerning the encapsulation of
A. platensis extract, phenolic-rich, carotenoid-rich, aqueous-based, and a commercial powder extract were evaluated as the core of four different encapsulation systems. The beneficial effects of encapsulation were confirmed through different outcomes, comprising gastric protection of the phenolic extracts, high stability of the carotenoids, antioxidant potential over storage, and preservation of colour stability and antioxidant potential of the encapsulated aqueous-based extract.
4.2. Pharmaceutical
Naturally derived products have served as a vital source of drugs since ancient times. Nowadays, approximately one-third of the top-selling pharmaceuticals are of natural origins or their derivatives. Plants and microorganisms represent a practically unlimited source of biochemical molecules, which may have promising pharmacological activities and therapeutic benefits in the treatment of diverse diseases [
198]. In particular, microalgae have shown their importance in the discovery of new therapeutic molecules, as well as in the isolation and characterization of already acknowledged ones [
199].
As previously mentioned, the application of natural compounds in therapeutics faces significant shortcomings and developmental challenges, highlighting their usually poor aqueous solubility, inherent instability, and low bioavailability [
200]. The use of micro/nanoencapsulation has been shown as a solution by the pharmaceutical industry to address the issues associated with these drawbacks, where the therapeutic value of biologically active compounds can be drastically improved [
198]. Microalgae, as a rich and valuable universe of natural products with proven pharmacological properties, are assumed to benefit from this strategy. However, the application of these microorganisms in drug delivery systems for pharmaceutical purposes is still a field to be explored.
Similar to what has been reported for microalgae encapsulation in food applications, the species
H. pluvialis, particularly its main bioactive compound astaxanthin, is the most researched one regarding disease treatment. There is a vast number of biological activities associated with this carotenoid; however, studies involving encapsulation strategies only consist of a few examples (
Table 3). As can be observed in
Table 3, liposomes and nanoemulsion were the encapsulation techniques chosen by most of the authors, aiming to improve the biopharmaceutical properties of astaxanthin. Through the results, it was possible to confirm that most of the astaxanthin’s biological activities are due to its unique antioxidant potential, which is able to protect against diverse deleterious effects of oxidative stress.
The use of encapsulation, nonetheless, significantly boosted the outcomes. The anti-aging activity of astaxanthin-rich extract loaded nanofibers was investigated by Nootem et al. [
201] and not only was a strong potential against oxidative stress reported, but the nanofibers also promoted a slower in vitro release profile and increased the stability of the core compounds in comparison with the free extract. In another study, Chiu et al. [
202] proposed that astaxanthin-loaded liposomes could be beneficial to lipopolysaccharide (LPS)-induced acute hepatotoxicity, which is expressively related to oxidative stress. The results indicate that, in fact, encapsulated astaxanthin had its bioavailability and liver cell uptake enhanced, and that the developed drug delivery demonstrated in-vivo hepatoprotective and acute anti-inflammatory effects, with even superior results than the one found for the positive control N-acetylcysteine. Overall, astaxanthin therapeutic properties may profit deeply from drug delivery systems, presenting enhanced effects without cytotoxicity when compared to the free molecule.
Likewise, bioactive compounds from microalgae of the genus
Arthrospira were also considered as the core substance of encapsulation systems focusing on pharmaceutical applications. The protein C-phycocyanin was the compound with a major interest in this regard; however, phenolic and free fatty acid-rich extracts were equally investigated. A resume of a literature review comprising the encapsulation of
Arthrospira bioactives as drug delivery systems can be found in
Table 4. According to these studies, the encapsulation of these microalgae compounds for skin delivery has been particularly explored. Phycocyanin is correlated with several biological properties, whose therapeutic applications may be challenged by its molecular features (instability and high molecular weight) and the gastrointestinal acidic environment. Aiming to overcome these issues, Hardiningtyas et al. [
203] studied the possible transdermal permeation of phycocyanin in a solid-in-oil nanodispersion, which was successfully achieved; the developed encapsulation system was able to facilitate the accumulation of phycocyanin in the
stratum corneum, followed by its permeation into deeper skin layers.
Concerning the treatment of cutaneous diseases, the anti-inflammatory potential of phycocyanin-loaded liposomes [
213] and the anti-biofilm growth activity of
A. platensis fatty acid-loaded coper-alginate nanocarriers [
214] were investigated, exhibiting positive effects due to the combination of the bioactives and encapsulation systems. In the first work, liposomes improved phycocyanin accumulation in the whole skin, as well as the anti-inflammatory response, which was confirmed by its superior results when compared to the free phycocyanin gel; while in the second study, the encapsulated fatty acids were able to inhibit half of the film formation with a very low dosage in 24 h.
The process of encapsulating an active compound also represents a possibility of enhancing its time of residence in the body; thus, increasing the cell uptake; or promoting an active targeting, which could be achieved through particle surface functionalization. In this context, Yang et al. [
216] hypothesized that polysaccharides from
A. platensis could be used as a surface decorator of nanomaterials to prevent plasma protein adsorption, maximize circulation time, and improve their cell-penetrating abilities, more specifically cancer-targeting ability. Selenium nanoparticles were then prepared and functionalized with purified
A. platensis polysaccharides and its cell uptake, cytotoxicity, and in vitro anticancer activity were evaluated. Results show that the polysaccharides’ surface significantly enhanced the cell-penetrating and apoptosis-inducing abilities of the selenium nanoparticles towards several human cell lines; especially in A375 human melanoma cells, where they were found to be extremely susceptible to the functionalized particle (IC
50 of 7.94 µM). Accordingly,
A. platensis polysaccharides were suggested as a potential enhancer of the anticancer activity of nanomaterials.
Equally focusing on anticancer targeting, the microalgae
Chlorella protothecoides and
Nannochloropsis oculata had their lipid extract incorporated into two different encapsulation systems in the study performed by Karakas et al. [
217], aiming at bioactive protection and assessment of the in vitro cytotoxicity activity in human cancer cells. The nano-microparticles were obtained by electrospray and microemulsification techniques, using PVA:chitosan or PVA:sodium alginate, and calcium alginate, respectively. Based on the MTT test (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), it was possible to confirm that the encapsulated microalgae extract exhibited cytotoxicity in the cancer cell lines from brain glioblastoma and colon colorectal carcinoma, while no effect was observed in healthy cells.
Finally, the encapsulation of
Dunaliella salina extract was carried out by Zamani et al. [
218], seeking to develop an oral drug delivery system for gastric protection and release control of the microalga compounds. Arabic gum-coated magnetic nanoparticles were selected as the encapsulation system for the extracts obtained at the logarithmic and stationary growth phases; and their properties, such as release profile, antioxidant and anticancer capacity, were assessed. The authors reported that both formulations promoted a sustained release of
D. salina extract in PBS at pH 4.5 and 7.2, with final relative release values of 72.41 and 43.51% for logarithmic and stationary phases over 48 h, respectively. Moreover, the antioxidant and cytotoxic activity of the free and nanoparticulated extract on MCF-7 and HeLa cells indicated that both phases presented strong antioxidant and anticancer effects in a time and dose-dependent manner. Therefore, it was concluded that the oral delivery of encapsulated
D. salina extract seems to be an effective approach to reduce adverse gastric effects and maintain the functionality of its compounds.
4.3. Cosmetics
Cosmetics are a class of products aimed at improving the structure, morphology, and appearance of skin or external parts of the body. A large section of this segment comprises skin topical formulations, which are composed of excipients and one or more active ingredients. Following the current global trend for products derived from natural sources, there is a demand for the development of environmentally sustainable cosmetic products, with less chemical compounds, which could act as cosmeceuticals [
219].
The interest in microalgae regarding cosmetics application is relatively recent; these microorganisms produce metabolites in response to changes in the environment, whose main function is linked to the cell’s ability to regenerate and self-protect against external adverse conditions. In this context, it is assumed these compounds could instigate the equivalent effect when applied on the skin. Among the bioactives extracted from microalgae that can be potentially used in cosmetics formulation are the ones with pronounced antioxidant activity, such as astaxanthin and C-phycocyanin [
220,
221].
The skin is the outer organ of the body and therefore acts as the primary barrier against the loss of endogenous substances, as well as the penetration of external agents into the human body. As it constitutes an interface with the environment, the skin is considered a target of several exogenous factors, such as UV radiation, pathogens, pollution, and other toxic compounds. Such factors are usually associated with excessive production of reactive oxygen species and other free radicals, which are pro-inflammatory mediators and may induce many deleterious effects, including DNA damage, oxidative stress, photoaging, and carcinogenesis [
221,
222]. As such, microalgae bioactives could play an advantageous role in maintaining the skin health status and in the treatment of some dermatological issues, such as hyperpigmentation, dehydration, photo-oxidation, photoaging, as well as protection against skin cancer [
219,
223].
However, the topical application of natural bioactives may be limited not only by their chemical instability in terms of product development, but by their poor water solubility, which might restrain the skin absorption and lead to low bioavailability. Additionally, some bioactives also possess a high molecular weight, which makes their permeation through the first skin layer, the
stratum corneum, impracticable [
224,
225]. Given these conditions, it is imperative to develop an appropriate and efficient delivery system for microalgae bioactives onto the skin, which have already been described by a few authors. The encapsulation of
H. pluvialis in liposomes was performed by Hama et al. [
226], and its protective effect on ultraviolet-induced skin damage through topical application was investigated. Firstly, the authors analysed and confirmed the powerful in vitro antioxidant activity of astaxanthin-loaded liposomes, which was followed by an in vivo assay. The topical application of the developed encapsulation system was then capable of inhibiting UV-induced skin damage, collagen degradation, and melanin production; hence, showing its potential as a protective formulation against UV-induced skin disorders.
In another study, Sun et al. [
224] developed an astaxanthin non-aqueous nanoemulsion through a high-pressure homogenization method for topical application, to combine the advantages of an encapsulation system and non-aqueous emulsions. Results show that the system was able to avoid astaxanthin degradation, keeping its stability for over 4 weeks at 25 °C. Additionally, when compared to traditional water-based emulsions, the non-aqueous type could effectively improve astaxanthin chemical stability against light and high temperatures. In vitro cell assays revealed that the non-aqueous nanoemulsion had low toxicity and protected the cells against oxidative stress. Moreover, in vitro permeation studies and skin section histological analyses exhibited the enhanced permeation of astaxanthin with low systemic absorption and unchanged epidermis, which proved the efficacy and safety of the astaxanthin-loaded non-aqueous nanoemulsion for topical application of that carotenoid. Likewise, Hu et al. [
223] prepared and optimized astaxanthin-loaded PLGA nanoparticles through the emulsification-solvent evaporation technique and investigated its cellular uptake, cytotoxicity, and photodamage protective effect in human keratinocyte (HaCaT) cells. According to the in vitro study, the optimized nanoparticles exhibited excellent cell viability and cell uptake, as well as low cytotoxicity. Additionally, the photodamage assay demonstrated that the nanoparticles presented higher antioxidant activity compared to pure astaxanthin after exposure to UVB radiation and were able to resist photodamage in the cells by reducing ROS levels and restoring mitochondrial membrane potential.
The encapsulation of the microalga
Arthrospira sp. for cosmetic purposes was interestingly explored by Byeon et al. [
227]. The study aimed at the development of an
Arthrospira sp. extract-impregnated nanofiber patch in a double-layer form, which was supported by a PCL nanofibrous cover matrix; both prepared through the electrospinning technique. The mechanical stability, cytotoxicity, water absorption, and extract release profile were assessed by the authors. As result, the patch was found to be non-cytotoxic in human cell-based tests and it presented more moisture and better adhesiveness than the patch prepared with only alginate nanofibers, which indicates the
Arthrospira sp. extract enhanced those properties, in addition to its biological effects on the skin. Furthermore, the dry patch promoted the release of most of the extract onto the skin within 30 min, suggesting its potential to be an innovative skincare product.
The bioactive phycocyanin for food and pharmaceutical applications reported in this review was commonly derived from the microalga
Arthrospira sp. However, the species
Aphanizomenon flos-aquae is also a rich source of this compound and was the object of study of Castangia et al. [
225] for cosmetic purposes. The authors encapsulated phycocyanin in hyalurosomes, a type of phospholipid vesicle immobilized with hyaluronan sodium, or alternatively in PEG hyalurosomes, due to the high molecular weight and consequent low bioavailability of this compound. The skin delivery and the protective potential against oxidative stress damage of these encapsulation systems were assessed through in vitro cell-based permeability, biocompatibility, and antioxidant activity assays. The permeation studies demonstrated that hyalurosomes favoured phycocyanin deposition in the deeper skin layers, mainly when the permeation promoter PEG was added to the particle surface. Results also show that the phycocyanin-loaded hyalurosomes were highly biocompatible, with improved phycocyanin antioxidant activity on stressed human keratinocytes when compared to the free compound, also promoting control in inflammation and a stimulus in keratinocyte proliferation.