Fast-Dissolving, Prolonged Release, and Antibacterial Cyclodextrin/Limonene-Inclusion Complex Nanofibrous Webs via Polymer-Free Electrospinning

Enrofloxacin Pharmaceutical Formulations through the Polymer-Free Electrospinning of β-Cyclodextrin-oligolactide Derivatives

Enrofloxacin (ENR), a member of the fluoroquinolone class of antibiotics, is widely used in veterinary medicine to treat bacterial infections. Like many antibiotics, ENR has limited water solubility and low bioavailability. To address these challenges, drug formulations using solid dispersions, nanosuspensions, surfactants, cocrystal/salt formation, and inclusion complexes with cyclodextrins may be employed. The approach described herein proposes the development of ENR formulations by co-electrospinning ENR with custom-prepared cyclodextrin-oligolactide (CDLA) derivatives. This method benefits from the high solubility of these derivatives, enabling polymer-free electrospinning. The electrospinning parameters were optimized to incorporate significant amounts of ENR into the CDLA nanofibrous webs, reaching up to 15.6% by weight. The obtained formulations were characterized by FTIR and NMR spectroscopy methods and evaluated for their antibacterial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. This study indicates that the presence of CDLA derivative does not inhibit the antibacterial activity of ENR, recommending these formulations for further development.

Synthesis of Nanosized γ-Cyclodextrin Metal-Organic Frameworks as Carriers of Limonene for Fresh-Cut Fruit Preservation Based on Polycaprolactone Nanofibers

To address the issue of bacterial growth on fresh-cut fruits, this paper reports the synthesis of nanosized γ-cyclodextrin metal-organic frameworks (CD-MOFs) using an ultrasound-assisted method and their application as carriers of limonene for antibacterial active packaging. The effects of the processing parameters on the morphology and crystallinity of the CD-MOFs are investigated, and the results prove that the addition of methanol is the key to producing nanosized CD-MOFs. The limonene loading content of the nanosized CD-MOFs can reach approximately 170 mg g-1. The sustained-release behaviors of limonene in the CD-MOFs are evaluated. Molecular docking simulations reveal the distribution and binding sites of limonene in the CD-MOFs. CD-MOFs are deposited on the surfaces of polycaprolactone (PCL) nanofibers via an immersion method, and limonene-loaded CD-MOF@PCL nanofibers are prepared. The morphology, crystallinity, thermal stability, mechanical properties, and antibacterial activity of the nanofibers are also studied. The nanofiber film effectively inhibits bacterial growth and prolongs the shelf life of fresh-cut apples. This study provides a novel strategy for developing antibacterial active packaging materials based on CD-MOFs and PCL nanofibers.

Covalent modification of γ-cyclodextrin with geraniol: An antibacterial agent with good thermal stability, solubility and biocompatibility

Geraniol (Ger) is an essential oil molecule with excellent biological activity. High hydrophobicity and volatility limit its practical application. Cyclodextrins (CDs) are water-soluble cyclic oligosaccharides with hydrophobic cavities. Physical encapsulation of CDs to improve the solubility and stability of essential oil molecules is not satisfactory. Therefore, this study synthesized the γ-CD derivative (γ-CD-Ger) by grafting Ger onto γ-CD using a bromide-mediated method. Compared to the inclusion complexes (γ-CD/Ger) formed by both, the derivatives exhibit better solubility and thermal stability. The derivative has better antibacterial activity when the ratio of γ-CD to Ger was 1:2. In addition, the derivatives did not exhibit cytotoxic and hemolytic properties. These results indicate that this research provides a water-soluble antibacterial agent with a wide range of promising applications and offers new ideas for the application of alcohol hydrophobic molecules in aqueous systems.

Advancements in application of chitosan and cyclodextrins in biomedicine and pharmaceutics: recent progress and future trends

The global community is faced with numerous health concerns such as cancer, cardiovascular and neurological diseases, diabetes, joint pain, osteoporosis, among others. With the advancement of research in the fields of materials chemistry and medicine, pharmaceutical technology and biomedical analysis have entered a new stage of development. The utilization of natural oligosaccharides and polysaccharides in pharmaceutical/biomedical studies has gained significant attention. Over the past decade, several studies have shown that chitosan and cyclodextrin have promising biomedical implications in background analysis, ongoing development, and critical applications in biomedical and pharmaceutical research fields. This review introduces different types of saccharides/natural biopolymers such as chitosan and cyclodextrin and discusses their wide-ranging applications in the biomedical/pharmaceutical research area. Recent research advances in pharmaceutics and drug delivery based on cyclodextrin, and their response to smart stimuli, as well as the biological functions of cyclodextrin and chitosan, such as the immunomodulatory effects, antioxidant, and antibacterial properties, have also been discussed, along with their applications in tissue engineering, wound dressing, and drug delivery systems. Finally, the innovative applications of chitosan and cyclodextrin in the pharmaceutical/biomedicine were reviewed, and current challenges, research/technological gaps, and future development opportunities were surveyed.

Multifunctionality of cyclodextrin-based polymeric nanoparticulate delivery systems for chemotherapeutics, combination therapy, and theranostics

As cancer being the most difficult disease to treat, different kinds of medications and therapeutic approaches have been prominently developed by scientists. For certain families of drugs, such as immuno-therapeutics or antibody-drug conjugates, efficient delivery systems are required during administration to protect the drugs from chemical degradation or biological inactivation. Delivery systems with the ability to carry different therapeutics or diagnostic agents or both, hold promising potential to tackle the abnormalities behind cancer. In this context, this review provides updated insights on how cyclodextrin-based polymeric nanosystems have become an effective treatment approach against cancer. Cyclodextrins (CDs) are natural oligosaccharides that are famously exploited in pharmaceutical research due to their exceptional quality of entrapping water-insoluble molecules inside their hydrophobic core and providing enhanced solubility with the help of their hydrophilic exterior. Combining the properties of CDs with polymeric nanoparticles (PNPs) brings out excellent versatile and tunable profiles, thanks to the submicron-sized PNPs. By introducing the significance of CD as a delivery system, a collective discussion on different binding approaches and release mechanisms of CD-drug complexation, followed by their characterization studies has been done in this review. Further, in light of recent studies, the article majorly focuses on conveying how promoting CD to a polymeric and nanoscale elevates the multifunctional advantages against cancer that can be successfully applied in combination therapy and theranostics. Moreover, CD-based delivery systems including CALAA-01, CRLX101, and CRLX301, have demonstrated improved tumor targeting, reduced side effects, and prolonged drug release in preclinical studies and clinical trials.

Preparation of aromatic β-cyclodextrin nano/microcapsules and corresponding aromatic textiles: A review

Fragrance finishing of textiles is receiving substantial interest, with aromatherapy being one of the most popular aspects of personal health care. However, the longevity of aroma on textiles and presence after subsequent launderings are major concerns for aromatic textiles directly loaded with essential oils. These drawbacks can be weakened by incorporating essential oil-complexed β-cyclodextrins (β-CDs) onto various textiles. This article reviews various preparation methods of aromatic β-cyclodextrin nano/microcapsules, as well as a wide variety of methods for the preparation of aromatic textiles based on them before and after forming, proposing future trends in preparation processes. The review also covers the complexation of β-CDs with essential oils, and the application of aromatic textiles based on β-CD nano/microcapsules. Systematic research on the preparation of aromatic textiles facilitates the realization of green and simple industrialized large-scale production, providing needed application potential in the fields of various functional materials.

High hydrostatic pressure (HHP) reinforces solid encapsulation of d-limonene into V-type starch and its application in strawberry storage

The formation of inclusion complexes (ICs) between V-type starch and flavors is traditionally conducted in an aqueous system. In this study, limonene was solid encapsulated into V6-starch under ambient pressure (AP) and high hydrostatic pressure (HHP). The maximum loading capacity reached 639.0 mg/g after HHP treatment, and the highest encapsulation efficiency was 79.9 %. X-ray Diffraction (XRD) results showed that the ordered structure of V6-starch was ameliorated with limonene, which avoided the reduction of the space between adjacent helices within V6-starch generated by HHP treatment. Notably, HHP treatment may force molecular permeation of limonene from amorphous regions into inter-crystalline amorphous regions and crystalline regions as the Small-angle X-ray scattering (SAXS) patterns indicated, leading to better controlled-release behavior. Thermogravimetry analysis (TGA) revealed that the solid encapsulation of V-type starch improved the thermal stability of limonene. Further, the release kinetics study showed that a complex prepared with a mass ratio of 2:1 under HHP treatment sustainably released limonene over 96 h and exhibited a preferable antimicrobial effect, which could extend the shelf life of strawberries.

Exploring inclusion complex of an anti-cancer drug (6-MP) with β-cyclodextrin and its binding with CT-DNA for innovative applications in anti-bacterial activity and photostability optimized by computational study

The co-evaporation approach was used to examine the host-guest interaction and to explore the cytotoxic and antibacterial properties of an important anti-cancer medication, 6-mercaptopurine monohydrate (6-MP) with β-cyclodextrin (β-CD). The UV-Vis investigation confirmed the inclusion complex's (IC) 1 : 1 stoichiometry and was also utilized to oversee the viability of this inclusion process. FTIR, NMR, and XRD, among other spectrometric techniques, revealed the mechanism of molecular interactions between β-CD and 6-MP which was further hypothesized by DFT to verify tentative outcomes. TGA and DSC studies revealed that 6-MP's thermal stability increased after encapsulation. Because of the protection of drug 6-MP by β-CD, the formed IC was found to have higher photostability. This work also predicts the release behavior of 6-MP in the presence of CT-DNA without any chemical changes. An evaluation of the complex's antibacterial activity in vitro revealed that it was more effective than pure 6-MP. The in vitro cytotoxic activity against the human kidney cancer cell line (ACHN) was also found to be significant for the IC (IC50 = 4.18 μM) compared to that of pure 6-MP (IC50 = 5.49 μM). These findings suggest that 6-MP incorporation via β-CD may result in 6-MP stability and effective presentation of its solubility, cytotoxic and antibacterial properties.

Studies on the Phytochemical Profile of Ocimum basilicum var. minimum (L.) Alef. Essential Oil, Its Larvicidal Activity and In Silico Interaction with Acetylcholinesterase against Aedes aegypti (Diptera: Culicidae)

Aedes aegypti L. (Diptera: Culicidae) is an important transmitter of diseases in tropical countries and controlling the larvae of this mosquito helps to reduce cases of diseases such as dengue, zika and chikungunya. Thus, the present study aimed to evaluate the larvicidal potential of the essential oil (EO) of Ocimum basilicum var. minimum (L.) Alef. The EO was extracted by stem distillation and the chemical composition was characterized by gas chromatography coupled with mass spectrometry (GC/MS and GC-FID). The larvicidal activity of EO was evaluated against third instar Ae. aegypti following World Health Organization (WHO) standard protocol and the interaction of the major compounds with the acetylcholinesterase (AChE) was evaluated by molecular docking. The predominant class was oxygenated monoterpenes with a concentration of 81.69% and the major compounds were limonene (9.5%), 1,8-cineole (14.23%), linalool (24.51%) and methyl chavicol (37.41%). The O. basilicum var. minimum EO showed unprecedented activity against third instar Ae. aegypti larvae at a dose-dependent relationship with LC50 of 69.91 (µg/mL) and LC90 of 200.62 (µg/mL), and the major compounds were able to interact with AChE in the Molecular Docking assay, indicating an ecological alternative for mosquito larvae control.

Encapsulation of Essential Oils in Nanocarriers for Active Food Packaging

Active packaging improves a packaging system's effectiveness by actively integrating additional components into the packaging material or the headspace around the packaging. Consumer demand and awareness have grown enough to replace chemical agents with natural active agents. Essential oils (EOs) are extensively distributed throughout nature but at low levels and sometimes with poor recovery yields, which poses an issue with their application in food. Due to the instability of EOs when added directly into a food product, they require encapsulation before being added to a packaging matrix such as liposomes, solid-lipid nanoparticles, nano-emulsions, cyclodextrins, and nanostructured lipid nano-carriers. This article is focused on the encapsulation of EOs in different types of nanocarriers. Nanocarriers can improve the efficiency of active substances by providing protection, stability, and controlled and targeted release. The advantages of the many types of nanocarriers that contain active substances that can be used to make antibacterial and antioxidant biopolymeric-based active packaging are discussed. A nanocarrier-encapsulated EO enables the controlled release of oil, stabilizing the packaging for a longer duration.

Electrospun pullulan nanofiber loading zanthoxylum bungeanum essential oil/β-cyclodextrin inclusion complexes for active packaging

In this study, zanthoxylum bungeanum essential oil/β-cyclodextrin inclusion complexes (ZBEO/β-CD-ICs) were first prepared by precipitation method. When the addition of ZBEO was 1 g, the reaction time was 4 h and the reaction temperature was 55 °C, the recovery (73.88%) and loading content (9.53%) reached the highest value. The characterization results showed inclusion complexation changed the crystalline structure, enhanced interaction among molecules and increased the thermal stability. Then, nanofiber films containing ZBEO/β-CD-ICs were prepared by electrospinning. When the total polymer concentration was constant at 20%, with the increase of ZBEO/β-CD-IC content, the diameter of nanofiber and mechanical strength decreased, but the temperature corresponding to the maximum rate of weight loss increased. X-ray diffraction analysis proved that the addition of ZBEO/β-CD-IC increased the crystallinity degree of film. The Fourier transform infrared spectra indicated hydrogen bond interactions among molecules. Releasing behavior of ZBEO indicated that increase of temperature and relative humidity accelerated the releasing speed. Antibacterial and antioxidant activity results demonstrated the increase of ZBEO content enhanced antibacterial and antioxidant efficiency, Z40P10 nanofibers had the maximum antibacterial rate of 62.02% against S. aureus and the maximum antioxidant activity of 60.18%.

Development of PVA-Psyllium Husk Meshes via Emulsion Electrospinning: Preparation, Characterization, and Antibacterial Activity

In this study, polyvinyl alcohol (PVA) and psyllium husk (PSH)/D-limonene electrospun meshes were produced by emulsion electrospinning for use as substrates to prevent the growth of bacteria. D-limonene and modified microcrystalline cellulose (mMCC) were preferred as antibacterial agents. SEM micrographs showed that PVA–PSH electrospun mesh with a 4% amount of D-limonene has the best average fiber distribution with 298.38 ± 62.8 nm. Moreover, the fiber morphology disrupts with the addition of 6% D-limonene. FT-IR spectroscopy was used to analyze the chemical structure between matrix–antibacterial agents (mMCC and D-limonene). Although there were some partial physical interactions in the FT-IR spectrum, no chemical reactions were seen between the matrixes and the antibacterial agents. The thermal properties of the meshes were determined using thermal gravimetric analysis (TGA). The thermal stability of the samples increased with the addition of mMCC. Further, the PVA–PSH–mMCC mesh had the highest value of contact angle (81° ± 4.05). The antibacterial activity of functional meshes against Gram (−) (Escherichia coli, Pseudomonas aeruginosa) and Gram (+) bacteria (Staphylococcus aureus) was specified based on a zone inhibition test. PPMD6 meshes had the highest antibacterial results with 21 mm, 16 mm, and 15 mm against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, respectively. While increasing the amount of D-limonene enhanced the antibacterial activity, it significantly decreased the amount of release in cases of excess D-limonene amount. Due to good fiber morphology, the highest D-limonene release value (83.1%) was observed in PPMD4 functional meshes. The developed functional meshes can be utilized as wound dressing material based on our data.

Cyclodextrins inclusion complex: Preparation methods, analytical techniques and food industry applications

This review offers a vision of the chemical behaviour of natural ingredients, synthetic drugs and other related compounds complexed using cyclodextrins. The review takes care of different sections related to i) the inclusion complexes formation with cyclodextrins, ii) the determination of the inclusion formation constant, iii) the most used methods to prepare host inclusion in the non-polar cavity of cyclodextrins and iv) the analytical techniques to evidence host inclusion. The review provides different literature that shows the application of cyclodextrins to improve physical, chemical, and biological characteristics of food compounds including solubility, stability and their elimination/masking. Moreover, the review also offers examples of commercial food/supplement products of cyclodextrins to indicate that cyclodextrins can be used to generate biotechnological substances with innovative properties and improve the development of food products.

Enzyme- and Relative Humidity-Responsive Antimicrobial Fibers for Active Food Packaging

Active food packaging materials that are sustainable, biodegradable, and capable of precise delivery of antimicrobial active ingredients (AIs) are in high demand. Here, we report the development of novel enzyme- and relative humidity (RH)-responsive antimicrobial fibers with an average diameter of 225 ± 50 nm, which can be deposited as a functional layer for packaging materials. Cellulose nanocrystals (CNCs), zein (protein), and starch were electrospun to form multistimuli-responsive fibers that incorporated a cocktail of both free nature-derived antimicrobials such as thyme oil, citric acid, and nisin and cyclodextrin-inclusion complexes (CD-ICs) of thyme oil, sorbic acid, and nisin. The multistimuli-responsive fibers were designed to release the free AIs and CD-ICs of AIs in response to enzyme and RH triggers, respectively. Enzyme-responsive release of free AIs is achieved due to the degradation of selected polymers, forming the backbone of the fibers. For instance, protease enzyme can degrade zein polymer, further accelerating the release of AIs from the fibers. Similarly, RH-responsive release is obtained due to the unique chemical nature of CD-ICs, enabling the release of AIs from the cavity at high RH. The successful synthesis of CD-ICs of AIs and incorporation of antimicrobials in the structure of the multistimuli-responsive fibers were confirmed by X-ray diffraction and Fourier transform infrared spectrometry. Fibers were capable of releasing free AIs when triggered by microorganism-exudated enzymes in a dose-dependent manner and releasing CD-IC form of AIs in response to high relative humidity (95% RH). With 24 h of exposure, stimuli-responsive fibers significantly reduced the populations of foodborne pathogenic bacterial surrogates Escherichia coli (by ∼5 log unit) and Listeria innocua (by ∼5 log unit), as well as fungi Aspergillus fumigatus (by >1 log unit). More importantly, the fibers released more AIs at 95% RH than at 50% RH, which resulted in a higher population reduction of E. coli at 95% RH. Such biodegradable, nontoxic, and multistimuli-responsive antimicrobial fibers have great potential for broad applications as active and smart packaging systems.

Journey of Limonene as an Antimicrobial Agent

Injudicious consumption of antibiotics in the past few decades has arisen the problem of resistance in pathogenic organisms against most antibiotics and antimicrobial agents. Scenarios of treatment failure are becoming more common in hospitals. This situation demands the frequent need for new antimicrobial compounds which may have other mechanisms of action from those which are in current use. Limonene can be utilized as one of the solutions to the problem of antimicrobial resistance. Limonene is a naturally occurring monoterpene with a lemon-like odor, which mainly present in the peels of citrus plants like lemon, orange, grapefruit, etc. The study aimed to enlighten the antimicrobial properties of limonene as per previous literature. Advantageous contributions have been made by various research groups in the study of the antimicrobial properties of limonene. Previous studies have shown that limonene not only inhibits disease-causing pathogenic microbes, however, it also protects various food products from potential contaminants. This review article contains information about the effectiveness of limonene as an antimicrobial agent. Apart from antimicrobial property, some other uses of limonene are also discussed such as its role as fragrance and flavor additive, as in the formation of nonalcoholic beverages, as solvent and cleaner in the petroleum industry, and as a pesticide. Antibacterial, antifungal, antiviral, and anti-biofilm properties of limonene may help it to be used in the future as a potential antimicrobial agent with minimal adverse effects. Some of the recent studies also showed the action of limonene against COVID-19 (Coronavirus). However, additional studies are requisite to scrutinize the possible mechanism of antimicrobial action of limonene.

Polymer-free cyclodextrin and natural polymer-cyclodextrin electrospun nanofibers: A comprehensive review on current applications and future perspectives

The present review discusses the use of cyclodextrins and their derivatives to prepare electrospun nanofibers with specific features. Cyclodextrins, owing to their unique capability to form inclusion complexes with hydrophobic and volatile molecules, can indeed facilitate the encapsulation of bioactive compounds in electrospun nanofibers allowing fast-dissolving products for food, biomedical, and pharmaceutical purposes, filtering materials for wastewater and air purification, as well as a variety of other technological applications. Additionally, cyclodextrins can improve the processability of naturally occurring biopolymers helping the fabrication of "green" materials with a strong industrial relevance. Hence, this review provides a comprehensive state-of-the-art of different cyclodextrins-based nanofibers including those made of pure cyclodextrins, of polycyclodextrins, and those made of natural biopolymer functionalized with cyclodextrins. To this end, the advantages and disadvantages of such approaches and their possible applications are investigated along with the current limitations in the exploitation of electrospinning at the industrial level.

Electrospun nanofibers food packaging: trends and applications in food systems

Food safety is a bottleneck problem. In order to provide information about advanced and unique food packaging technique, this study summarized the advancements of electrospinning technique. Food packaging is a multidisciplinary area involving food science, food engineering, food chemistry, and food microbiology, and the interest in maintaining the freshness and quality of foods has grown considerably. For this purpose, electrospinning technology has gained much attention due to its unique functions and superior processing. Sudden advancements of electrospinning have been rapidly incorporated into research. This review summarized some latest information about food packaging and different materials used for the packaging of various foods such as fruits, vegetables, meat, and processed items. Also, the use of electrospinning and materials used for the formation of nanofibers are discussed in detail. However, in food industry, the application of electrospun nanofibers is still in its infancy. In this study, different parameters, structures of nanofibers, features and fundamental properties are described briefly, while polymers fabricated through electrospinning with advances in food packaging films are described in detail. Moreover, this comprehensive review focuses on the polymers used for the electrospinning of nanofibers as packaging films and their applications for variety of foods. This will be a valuable source of information for researchers studying various polymers for electrospinning for application in the food packaging industry.

Production of d-limonene-loaded Pickering emulsions stabilized by chitosan nanoparticles

Recently, Pickering emulsions have been considered as an efficient method to maintain and protect the functional properties of essential oils against the harsh conditions. In this research, the encapsulation of d-limonene, as an aromatic component with several distinct properties, was conducted through optimizing the production of Pickering emulsions stabilized by chitosan nanoparticles (CSNPs) and using the response surface methodology; independent variables were different concentrations of CSNPs (0.43, 0.25, and 0.07% w/v) and ratio of d-limonene to Pickering emulsions (5, 15, and 25%). The stability of the emulsions increased at higher contents of the CSNPs. By increasing the concentration of CSNPs and ratio of d-limonene to Pickering emulsion, viscosity of Pickering emulsions was considerably increased. Considering the chemical interactions, thermal behaviors, and crystallinity of samples, CSNPs can be used as an appropriate stabilizer for d-limonene-loaded emulsions and a food grade delivery carrier for the bioactive compounds.

Encapsulation of Flavours and Fragrances into Polymeric Capsules and Cyclodextrins Inclusion Complexes: An Update

Flavours and fragrances are volatile compounds of large interest for different applications. Due to their high tendency of evaporation and, in most cases, poor chemical stability, these compounds need to be encapsulated for handling and industrial processing. Encapsulation, indeed, resulted in being effective at overcoming the main concerns related to volatile compound manipulation, and several industrial products contain flavours and fragrances in an encapsulated form for the final usage of customers. Although several organic or inorganic materials have been investigated for the production of coated micro- or nanosystems intended for the encapsulation of fragrances and flavours, polymeric coating, leading to the formation of micro- or nanocapsules with a core-shell architecture, as well as a molecular inclusion complexation with cyclodextrins, are still the most used. The present review aims to summarise the recent literature about the encapsulation of fragrances and flavours into polymeric micro- or nanocapsules or inclusion complexes with cyclodextrins, with a focus on methods for micro/nanoencapsulation and applications in the different technological fields, including the textile, cosmetic, food and paper industries.

Progress in the design and development of "fast-dissolving" electrospun nanofibers based drug delivery systems - A systematic review

Electrospinning has emerged as most viable approach for the fabrication of nanofibers with several beneficial features that are essential to various applications ranging from environment to biomedicine. The electrospun nanofiber based drug delivery systems have shown tremendous advancements over the controlled and sustained release complemented from their high surface area, tunable porosity, mechanical endurance, offer compatible environment for drug encapsulation, biocompatibility, high drug loading and tailorable release characteristics. The dosage formulation of poorly water-soluble drugs often faces several challenges including complete dissolution with maximum therapeutic efficiency over a short period of time especially through oral administration. In this context, challenges associated with the dosage formulation of poorly-water soluble drugs can be addressed through combining the beneficial features of electrospun nanofibers. This review describes major developments progressed in the preparation of electrospun nanofibers based "fast dissolving" drug delivery systems by employing variety of polymers, drug molecules and encapsulation approaches with primary focus on oral delivery. Furthermore, the review also highlights current scientific challenges and provide an outlook with regard to future prospectus.

Urea-Based Low-Molecular-Weight Pseudopeptidic Organogelators for the Encapsulation and Slow Release of (R)-Limonene

Low-molecular-weight compounds containing alkylurea fragments attached to the amino end of different miminalistic pseudopeptidic structures have been shown to be excellent organogelators in a variety of organic solvents and liquid organic compounds of different nature. The formation of gels in this work is defined through rheological measurements for those cases where G' > G''. Both the topology and the symmetry of the corresponding urea compounds play a role in defining their organogelator behavior. This can also be tuned by the presence of additional supramolecular guests, as is the case for suberic acid. These compounds also achieve the gelation of relevant active substances such as terpene natural oils and complex mixtures of flavors and fragrances. This provides a simple and mass-efficient supramolecular system for the quantitative encapsulation of active substances, without the need for any additional solvent or complex processes, and their consequent controlled release.

Complexation of methyl salicylate with β-cyclodextrin and its release characteristics for active food packaging

A series of methyl salicylate (MeSA)/β-cyclodextrin (β-CD) inclusion complexes (ICs) were prepared at different MeSA concentrations by the co-precipitation method using methyl salicylate for maintaining the quality of fresh produce. The formation of IC was confirmed through FTIR, ¹H NMR, TGA, and SEM measurements. Among the grades applied, IC with 1:1 grade showed the highest MeSA entrapment efficiency (59%). The release rate of MeSA from an IC was greater at higher temperature and higher relative humidity. In addition, the MeSA release from ICs of all grades followed a diffusive nature and first-order kinetics at 25 °C under all RH conditions, except at 7 °C. These results indicate that the use of a MeSA/β-CD IC in active packaging applications can effective maintain the quality of fresh produce.

Encapsulation of essential oil components with methyl-β-cyclodextrin using ultrasonication: Solubility, characterization, DPPH and antibacterial assay

Essential oils derived from medicinal plants are prosperous sources of active components having high biological potential. Cuminaldehye and isoeugenol, are hydrophobic essential oil components (EOC), are showing drastic limitations in their applications by low water solubility and the respective volatility. Methyl-β-cyclodextrin inclusion complexes (MβCD-ICs) were prepared in aqueous solution and in solid state with the EOC via the ultrasonication method, an energy saving, high efficiency and eco-friend technique, aim to extend their aqueous solubility and biological properties. UV-Vis absorption, fluorescence, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), proton nuclear magnetic resonance (¹H NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD) and computational simulations confirmed the formation of EOC/MβCD-ICs. Result of solubility studies proved the enhanced solubilization of EOC in the presence of MβCD in aqueous and double reciprocal profiles substantiated the guest/host stoichiometry of 1:1. TGA and DSC studies indicated the improved stability of EOC in MβCD-ICs. The efficiency of ICs in terms of the antioxidant activity was verified and the IC displayed higher antioxidant activity compared to that of free EOC, as determined by free radical scavenging assay. Finally, the antibacterial effect of EOC/MβCD-ICs against gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacteria was demonstrated. Overall results not only revealed the potential of MβCD on the bioavailability, solubility and stability, but also that the intensification caused by the IC may be greater that the antioxidant and antibacterial effects of the selected EOC for this study.

Antimicrobial-loaded nanocarriers for food packaging applications

Increasing the demands of consumers for organic and safer foods has led to applying new technologies for food preservation. Active packaging (AP) containing natural antimicrobial agents is a good candidate for promoting the shelf life of food products. The efficiency of AP has been enhanced through nanoencapsulation methods, in which antimicrobial-loaded nanocarriers could provide a controlled release of antimicrobial active packaging for keeping the quality of foods during storage. The main objective of this review is to introduce common methods for designing novel encapsulation delivery systems offering controlled release of antimicrobials in the AP systems. The common nanocarriers for enveloping antimicrobial agents are described and the current state of art in the application of nanoencapsulated antimicrobials in development of antimicrobial APs have been summarized and tabulated. Incorporation of a carrier loaded with natural antimicrobial agents is the most effective method for developing AP in the food packaging sector which has become possible by using nanoencapsulated antimicrobials in films or coating structures, instead of using their free form. Nanoencapsulation approaches provide many advantages including protection against environmental stresses, release control, and improving the solubility and absorption of natural antimicrobials in AP, which are the main achievements overcoming the barriers for using natural antimicrobials in food packaging.

Essential Oils-Loaded Electrospun Biopolymers: A Future Perspective for Active Food Packaging

The growth of global food demand combined with the increased appeal to access different foods from every corner of the globe is forcing the food industry to look for alternative technologies to increase the shelf life. Essential oils (EOs) as naturally occurring functional ingredients have shown great prospects in active food packaging. EOs can inhibit the growth of superficial food pathogens, modify nutritious values without affecting the sensory qualities of food, and prolong the shelf life when used in food packaging as an active ingredient. Since 2016, various reports have demonstrated that combinations of electrospun fibers and encapsulated EOs could offer promising results when used as food packaging. Such electrospun platforms have encapsulated either pure EOs or their complexation with other antibacterial agents to prolong the shelf life of food products through sustained release of active ingredients. This paper presents a comprehensive review of the essential oil-loaded electrospun fibers that have been applied as active food packaging material.

Encapsulation and Stabilization of α-Lipoic Acid in Cyclodextrin Inclusion Complex Electrospun Nanofibers: Antioxidant and Fast-Dissolving α-Lipoic Acid/Cyclodextrin Nanofibrous Webs

In this study, electrospinning of nanofibers from alpha-lipoic acid/cyclodextrin inclusion complex systems was successfully performed without having any polymeric matrix. Alpha-lipoic acid (α-LA) is a natural antioxidant compound which is widely used as a food supplement. However, it has limited water solubility and poor thermal and oxidative stability. Nevertheless, it is possible to enhance its water solubility and thermal stability by inclusion complexation with cyclodextrins. Here, hydroxypropyl-beta-cyclodextrin (HP-β-CyD) and hydroxypropyl-gamma-cyclodextrin (HP-γ-CyD) were chosen as host molecules for forming inclusion complexation with α-LA. Accordingly, α-LA was inclusion complexed with HP-β-CyD and HP-γ-CyD by using very high concentrated aqueous solutions of CyD (200%, w/v) having 1/1 and 2/1 molar ratio of α-LA/CyD. Except α-LA/HP-β-CyD (1/1) solution, other α-LA/CyD solutions were turbid indicating the presence of some noncomplexed α-LA whereas α-LA/HP-β-CyD (1/1) solution was very homogeneous signifying that α-LA was fully complexed with HP-β-CyD. Even so, electrospinning was performed for all of the α-LA/HP-β-CyD (1/1 and 2/1) and α-LA/HP-γ-CyD (1/1 and 2/1) aqueous solutions, and defect-free bead-less and uniform nanofibers were successfully obtained for all of the α-LA/CyD solutions. However, the electrospinning process for α-LA/CyD (1/1) systems was much more efficient than the α-LA/CyD (2/1) systems, and we were able to produce self-standing and flexible nanofibrous webs from α-LA/CyD (1/1) systems. α-LA was efficiently preserved during the electrospinning process of α-LA/CyD (1/1) systems and the resulting electrospun α-LA/HP-β-CyD and α-LA/HP-γ-CyD nanofibers were produced with the molar ratios of ∼1/1 and ∼0.85/1 (α-LA/CyD), respectively. The better encapsulation efficiency of α-LA in α-LA/HP-β-CyD nanofibers was due to higher solubility increase and higher binding strength between α-LA and HP-β-CyD as revealed by the phase solubility test. α-LA was in the amorphous state in α-LA/CyD nanofibers and both α-LA/HP-β-CyD and α-LA/HP-γ-CyD nanofibers were dissolved very quickly in water and also when they wetted with artificial saliva. Additionally, the antioxidant activity of pure α-LA and α-LA/CyD nanofibers was comparatively evaluated using ABTS radical cation assay. α-LA/CyD nanofibers have shown significantly higher antioxidant performance compared to pure α-LA owing to improved water solubility by CyD inclusion complexation. The thermal stability enhancement of α-LA in α-LA/CyD nanofibers was achieved compared to pure α-LA under heat treatment (100 °C for 24 h). These promising results support that antioxidant α-LA/CyD nanofibers may have potential applications as orally fast-dissolving food supplements.

β-Cyclodextrin based air filter for high-efficiency filtration of pollution sources

Airborne particulate matter (PM) pollution has become a serious environmental problem. Thus, there is a need for the development of air filters with satisfactory overall performance. In this paper, we develop a kind of β-cyclodextrin (β-CD) based air filter with high strength, which has not only high filtration efficiency (about 99%) but also good air permeability (the pressure drop is only 45Pa). Especially after long-term application, the pression drop of β-cyclodextrin based was less than half of the commercial air-filter. Additionally, the material can capture the toxic gasous chemicals (e.g. formaldehyde and SO₂). The introduction of β-CD is supposed to be the key factor for improvement of air filter.

Fabrication, characterization and adsorption properties of cucurbit[7]uril-functionalized polycaprolactone electrospun nanofibrous membranes

The fabrication of electrospun nanofibers comprising cucurbit[7]uril (CB[7]) and poly(ε-caprolactone) (PCL) is reported. Various techniques such as SEM, FTIR, XRD, DSC and TG were utilized to characterize the morphology, composition and properties of the nanofibers. Uniform bead-free electrospun nanofibers were obtained from PCL/CB[7] mixed solutions and the average fiber diameter of the nanofibers increases with the increase of CB[7] content. The nanofibers are composed of a physical mixture of PCL and CB[7], and CB[7] itself is present in the PCL fiber matrix in an uncomplexed state. The static adsorption behavior of the PCL/CB[7] nanofibers towards methylene blue (MB) was also preliminary investigated. The results indicate that the adsorption of MB onto the nanofibrous membranes fits the second-order kinetic model and Langmuir isotherm model.

Construction of a water-soluble and photostable rubropunctatin/β-cyclodextrin drug carrier

The purpose of the current study was to construct a β-cyclodextrin drug carrier for rubropunctatin to improve its water solubility and light stability for future cytotoxicity studies. The inclusion complexation behavior of rubropunctatin with β-cyclodextrin was investigated using FESEM, FT-IR and XRD. A molecular docking study was performed to elucidate the most probable inclusion structure. The inclusion complex could be completely dispersed in water and had a small size of 121.87 ± 2.13 nm (n = 3), a good PDI (0.320 ± 0.017), and an acceptable potential value of -27.7 ± 0.32 mV (n = 3). Furthermore, the stability of the rubropunctatin in water under light irradiation was found to be greatly enhanced after being encapsulated in cyclodextrin, and it exhibited a retention rate of over 70% vs. 10.17%. In addition, the cytotoxicity of the inclusion complex was evaluated by MTT assay and Annexin V-FITC/PI detection using cervical adenocarcinoma HeLa cells. The results showed that the inclusion complex had comparable toxicity compared to rubropunctatin solubilized with 0.4% DMSO. More importantly, the formation of the inclusion complex contributed greatly to the intensification of the bioavailability of rubropunctatin because the use of organic solvent was avoided.

Influence of Hydrogen-Bonding Additives on Electrospinning of Cyclodextrin Nanofibers

The electrospinning of highly concentrated solutions of cyclodextrin (CD) leads to bead-free nanofibers without the need of a polymeric carrier. The occurrence of numerous hydrogen bonds among CD molecules is the main driving force for their electrospinning, and hence, additives with hydrogen-bonding potential can disturb the aggregation of CD molecules and affect their electrospinning. In this study, we systematically investigated the influence of five different hydrogen-bonding additives, i.e., methylamine (MA), ethylenediamine (ED), urea, 2,2,2-trifluoroethanol (TFE), and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), on the solution behavior of hydroxypropyl-β-CD (HP-β-CD) by rheology, conductivity, and NMR analyses, and the morphology of the electrospun HP-β-CD nanofibers by scanning electron microscopy. The 1H NMR chemical shifts of the HP-β-CD protons in D2O were observed with the incorporation of hydrogen-bonding molecules due to the occurrence of intermolecular associations between HP-β-CD and additives. Dynamic light scattering measurements revealed a clear decrease in the aggregate size with the introduction of additives. Unlike other additives, which showed a general decreasing trend in viscosity with increasing additive content, the addition of MA led to a significant increase in the viscosity with increasing concentration and gave rise to HP-β-CD nanofibers at lower concentrations. The addition of low concentrations of ED, urea, TFE, and HFIP led to thinner nanofibers due to the lower viscosity of the respective solutions. Increasing additive content deteriorated the electrospinnability of HP-β-CD solutions, resulting in beaded fibers. A systematic relationship was found between the solution viscosity and morphology of the respective electrospun fibers. Overall, this study, for the first time, reports the influence of hydrogen bonding on the polymer-free electrospinning of CD molecules and shows a correlation between solution properties and morphology of their electrospun nanofibers.

Electrospinning of Cyclodextrin Functional Nanofibers for Drug Delivery Applications

Electrospun nanofibers have sparked tremendous attention in drug delivery since they can offer high specific surface area, tailored release of drugs, controlled surface chemistry for preferred protein adsorption, and tunable porosity. Several functional motifs were incorporated into electrospun nanofibers to greatly expand their drug loading capacity or to provide the sustained release of the embedded drug molecules. In this regard, cyclodextrins (CyD) are considered as ideal drug carrier molecules as they are natural, edible, and biocompatible compounds with a truncated cone-shape with a relatively hydrophobic cavity interior for complexation with hydrophobic drugs and a hydrophilic exterior to increase the water-solubility of drugs. Further, the formation of CyD-drug inclusion complexes can protect drug molecules from physiological degradation, or elimination and thus increases the stability and bioavailability of drugs, of which the release takes place with time, accompanied by fiber degradation. In this review, we summarize studies related to CyD-functional electrospun nanofibers for drug delivery applications. The review begins with an introductory description of electrospinning; the structure, properties, and toxicology of CyD; and CyD-drug complexation. Thereafter, the release of various drug molecules from CyD-functional electrospun nanofibers is provided in subsequent sections. The review concludes with a summary and outlook on material strategies.

Efficient Encapsulation of Citral in Fast-Dissolving Polymer-Free Electrospun Nanofibers of Cyclodextrin Inclusion Complexes: High Thermal Stability, Longer Shelf-Life, and Enhanced Water Solubility of Citral

Here, we report a facile production of citral/cyclodextrin (CD) inclusion complex (IC) nanofibers (NFs) from three types of CDs (hydroxypropyl-beta-cyclodextrin (HPβCD), hydroxypropyl-gamma-cyclodextrin (HPγCD), and methylated-beta-cyclodextrin (MβCD)) by an electrospinning technique without the need of any polymeric carrier matrix. Self-standing nanofibrous webs of citral/CD-IC nanofibers (citral/CD-IC-NF) with uniform fiber morphology have been successfully electrospun from aqueous solutions of citral/CD-IC. Thanks to the inclusion complex formed with CDs, the efficient preservation of citral (up to ~80%) in citral/CD-IC-NFs was observed. In addition, the citral/CD-IC-NFs have shown ~50% preservation of citral for 15 days at room temperature even though citral has a highly volatile nature. The enhanced thermal stability of citral (~100–300°C) in citral/CD-IC-NFs compared to pure citral (~50–165°C) has been observed. Moreover, citral/CD-IC-NFs tended to disintegrate in water very quickly. To summarize, citral was efficiently encapsulated in citral/CD-IC-NFs, and these citral/CD-IC-NFs have been shown to be fast dissolving. In citral/CD-IC-NFs, citral/CD-ICs have enhanced water solubility of citral along with high-temperature stability and a longer shelf-life.

Electrospun Nanomaterials Implementing Antibacterial Inorganic Nanophases

Electrospinning is a versatile, simple, and low cost process for the controlled production of fibers. In recent years, its application to the development of multifunctional materials has encountered increasing success. In this paper, we briefly overview the general aspects of electrospinning and then we focus on the implementation of inorganic nanoantimicrobials, e.g., nanosized antimicrobial agents in electrospun fibers. The most relevant characteristics sought in nanoantimicrobials supported on (or dispersed into) polymeric materials are concisely discussed as well. The interesting literature issued in the last decade in the field of antimicrobial electrospun nanomaterials is critically described. A classification of the most relevant studies as a function of the different approaches chosen for incorporating nanoantimicrobials in the final material is also provided.