Encapsulation of 4-terpineol with ß-cyclodextrin: Inclusion mechanism, characterization and relative humidity-triggered release.

4-Terpineol (4-TA), a typical monocyclic monoterpene essential oil compound with important biological activities, poor stability and solubility severely hamper its biological activities. To date, ß-cyclodextrin (ß-CD) encapsulating essential oil to form inclusion complexes (ICs) is considered as a satisfactory treatment. Nevertheless, the detailed inclusion mechanism of ß-CD for 4-TA especially the behavior of 4-TA during inclusion formation have not available yet. Herein, 4-TA/ß-CD ICs were successfully synthesized by the co-precipitation method, and hydrogen bonds and hydrophobic interactions played a key role in the formation of ICs, and the isopropyl of 4-TA entered the cavity through the wide rim of ß-CD. Moreover, the release profile demonstrated that high RH (85 % and 99 %) triggered the release of TA from ICs. This study suggests the great potential of cyclodextrin inclusion strategy for improving the stability and sustained release of 4-TA in food preservation application.

Electrospun polyvinyl alcohol/chitosan nanofibers incorporated with 1,8-cineole/cyclodextrin inclusion complexes: Characterization, release kinetics and application in strawberry preservation.

Development of food packaging systems containing essential oils (EOs) has gained increased attention recently. However, the instability of EOs restricts their application. Therefore, effective encapsulation of EOs is demanded for their protection and controlled release. In this work, 1,8-cineole, the major component in Eucalyptus globulus essential oil, was encapsulated into hydroxypropyl-ß-cyclodextrin to form an inclusion complex, which was then incorporated into polyvinyl alcohol and chitosan composite polymer to fabricate nanofibrous film via electrospinning. The film with 40% (w/w) of inclusion complexes showed enhanced barrier and mechanical properties, and the release of 1,8-cineole from the film was sustained and dominated by the non-Fick diffusion. Moreover, this film could extend the shelf life of strawberries to 6 days at 25 ℃. This work suggested dual encapsulation of EOs by cyclodextrin and electrospun nanofibers is an ideal strategy to improve the availability of EOs, and the produced film is promising for food preservation.

Leaf-stomata-inspired packaging nanofibers with humidity-triggered thymol release based on thymol/EVOH coaxial electrospinning.

Active packaging systems that are sustainable and capable of delivering antimicrobial agents intelligently are in demand in food industry. In this work, an extremely simple strategy inspired by leaf stomata was introduced to smartly trigger thymol release at different relative humidity using EVOH as the "stomata". Thymol was encapsulated into ethylene vinyl alcohol copolymer (EVOH) to form core-shell nanofibers (thymol/EVOH) via coaxial electrospinning. The core-shell structure of the nanofiber was confirmed by transmission electron microscopy. Thymol release could be triggered by the relative humidity (RH), and nanofibers released more thymol at 90% RH than at 30% RH. In addition, this functionalized nanofibers showed excellent antibacterial activity in vitro against Escherichia coli and Staphylococcus aureus and performed good biocompatibility. The nanofiber film was also applied to fruit preservation, and was found to extend the strawberries shelf-life. Sensory analysis also showed that the strawberries flavor treated by thymol/EVOH nanofibers presented high acceptability. The work will provide an innovative approach to design packaging film.

Rational Design of Intelligent and Multifunctional Dressing to Promote Acute/Chronic Wound Healing.

Currently, the clinic's treatment of acute/chronic wounds is still unsatisfactory due to the lack of functional and appropriate wound dressings. Intelligent and multifunctional dressings are considered the most advanced wound treatment modalities. It is essential to design and develop wound dressings with required functions according to the wound microenvironment in the clinical treatment. This work summarizes microenvironment characteristics of various common wounds, such as acute wound, diabetic wound, burns wound, scalded wound, mucosal wound, and ulcers wound. Furthermore, the factors of transformation from acute wounds to chronic wounds were analyzed. Then we focused on summarizing how researchers fully and thoroughly combined the complex microenvironment with modern advanced technology to ensure the usability and value of the dressing, such as photothermal-sensitive dressings, microenvironment dressing (pH-sensitive dressings, ROS-sensitive dressings, and osmotic pressure dressings), hemostatic dressing, guiding tissue regeneration dressing, microneedle dressings, and 3D/4D printing dressings. Finally, the revolutionary development of wound dressings and how to transform the existing advanced functional dressings into clinical needs as soon as possible have carried out a reasonable and meaningful outlook.

Enzyme-responsive food packaging system based on pectin-coated poly (lactic acid) nanofiber films for controlled release of thymol.

Foodborne diseases caused by foodborne pathogens lead to serious harm to food safety and human health. This work fabricated an enzyme-responsive packaging film based on porous poly (lactic acid) (PLA) nanofibers modified by positively charged polyethyleneimine (PEI) and further to adsorb negatively charged pectin coating, which loaded with thymol (THY) for protecting fruits from microbial infection. The porous PLA nanofibers were fabricated by combining "Breath Figure" principle and electrospinning technique. The XPS and FTIR characterizations showed that PLA nanofiber membrane was successfully modified by PEI. The prepared nanofiber membrane significantly inhibited the growth of E. coli, S. aureus and Bacillus subtilis (＞95%), especially showed excellent antifungal activity against Aspergillus niger. The release of THY from pectin-coated porous nanofiber membrane (THY@PLA-PEI-Pectin) was triggered by pectinase, which was secreted by microorganisms from food contamination. Besides, the biocompatible THY@PLA-PEI-Pectin nanofiber membrane prolonged the shelf life of citrus. Therefore, this pectinase-responsive nanofiber membrane has desirable application prospects in the development of active or smart packaging systems.

Polydopamine-modified chitin conduits with sustained release of bioactive peptides enhance peripheral nerve regeneration in rats.

The introduction of neurotrophic factors into injured peripheral nerve sites is beneficial to peripheral nerve regeneration. However, neurotrophic factors are rapidly degraded in vivo and obstruct axonal regeneration when used at a supraphysiological dose, which limits their clinical benefits. Bioactive mimetic peptides have been developed to be used in place of neurotrophic factors because they have a similar mode of action to the original growth factors and can activate the equivalent receptors but have simplified sequences and structures. In this study, we created polydopamine-modified chitin conduits loaded with brain-derived neurotrophic factor mimetic peptides and vascular endothelial growth factor mimetic peptides (Chi/PDA-Ps). We found that the Chi/PDA-Ps conduits were less cytotoxic in vitro than chitin conduits alone and provided sustained release of functional peptides. In this study, we evaluated the biocompatibility of the Chi/PDA-Ps conduits. Brain-derived neurotrophic factor mimetic peptide and vascular endothelial growth factor mimetic peptide synergistically promoted proliferation of Schwann cells and secretion of neurotrophic factors by Schwann cells and attachment and migration of endothelial cells in vitro. The Chi/PDA-Ps conduits were used to bridge a 2 mm gap between the nerve stumps in rat models of sciatic nerve injury. We found that the application of Chi/PDA-Ps conduits could improve the motor function of rats and reduce gastrocnemius atrophy. The electrophysiological results and the microstructure of regenerative nerves showed that the nerve conduction function and remyelination was further restored. These findings suggest that the Chi/PDA-Ps conduits have great potential in peripheral nerve injury repair.

Electrospun functional polymeric nanofibers for active food packaging: A review.

With the increasing demand for food quality and food safety, it is urgent to develop efficient packaging strategies for prolonging the shelf life of food. Functional polymeric nanofibers have emerged as promising packaging materials and made tremendous breakthrough in food packaging field. Electrospinning technique is recognized as a versatile and high-efficiency method to produce nanofibers with multifunctional properties and adjustable structures. This review focus on electrospinning types and structural construction of nanofibers (uniaxial, core-shell and porous structures) as well as highlighted the advanced functionality of polymeric nanofibers in active packaging. Moreover, the emerging stimuli-responsive nanofibers for controlled release of active compounds were introduced in this review. Ultimately, the existing challenges, future prospects and development directions of nanofiber-based packaging materials were also discussed, which will facilitate the utilization of electrospinning nanotechnology in food industry.

Chitin conduits modified with DNA-peptide coating promote the peripheral nerve regeneration.

Peripheral nerve injury (PNI) is one of the common clinical injuries which needs to be addressed. Previous studies demonstrated the effectiveness of using biodegradable chitin (CT) conduits small gap tubulization technology as a substitute for traditional epineurial neurorrhaphy. Aiming to improve the effectiveness of CT conduits in repairing PNI, we modified their surface with a DNA-peptide coating. The coating consisted of single strand DNA (ssDNA) and its complementary DNA'-peptide mimics. First, we immobilize ssDNA (DNA1 + 2) on CT conduits by carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) method to construct CT/DNA conduits. EDC/NHS was used to activate carboxyl groups of modified ssDNA for direct reaction with primary amines on the CT via amide bond formation. Then, DNA1'-BDNF + DNA2'-VEGF mimic peptide (RGI + KLT) were bonded to CT/DNA conduits by complementary base pairing principle at room temperature to form CT/RGI + KLT conduits. When the surrounding environment rose to a certain point (37 °C), the CT/RGI + KLT conduits achieved sustainable release of DNA'-peptide.In vitro, the CT conduits modified with the DNA-peptide coating promoted the proliferation and secretion of Schwann cells by maintaining their repair state. It also promoted the proliferation of human umbilical vein vessel endothelial cells and axon outgrowth of dorsal root ganglion explants.In vivo, CT/RGI + KLT conduits promoted regeneration of injured nerves and functional recovery of target muscles, which was facilitated by the synergistic contribution of angiogenesis and neurogenesis. Our research brings DNA and DNA-peptide hybrids into the realm of tissue engineering to repair PNI.

Electrospun pullulan/PVA nanofibers integrated with thymol-loaded porphyrin metal-organic framework for antibacterial food packaging.

Pathogenic microorganisms posed perniciousness for postharvest fruits and vegetables, as well as brought potential risks for human health. In this work, pullulan/polyvinyl alcohol (PUL/PVA) nanofibers incorporated with thymol-loaded porphyrin metal-organic framework nanoparticles (THY@PCN-224 NPs) were developed for antibacterial food packaging. PCN-224 MOFs not only act as thymol loading carriers but also highly produce singlet oxygen (1O2) with bactericidal activity. PUL/PVA nanofiber was a promising sustainable substrate because of its good flexibility, biocompatibility and biodegradability. The loading capacity of PCN-224 for thymol was about 20%. The THY@PCN/PUL/PVA nanofibers exhibited synergistic antibacterial activities against E. coli (~99%) and S. aureus (~98%) under light irradiation. The cell viability assays and fruit preservation study demonstrated good biosafety of the polymeric film. The results suggested that this novel nanofiber has potential application prospects for food packaging.

Distance-Based Biosensor for Ultrasensitive Detection of Uracil-DNA Glycosylase Using Membrane Filtration of DNA Hydrogel.

In the deoxyribonucleic acid (DNA) repair pathways, DNA repair enzymes have great significance for genomic integrity. As one important initiator of the base-excision repair pathway, the aberrant activity of uracil-DNA glycosylase (UDG) is closely associated with many diseases. Herein, we developed a simple distance-based device for visual detection of UDG activity using a load-free DNA hydrogel. The DNA hydrogel consists of polyacrylamide-DNA chains being bridged by a single-stranded DNA crosslinker containing a responsive uracil base site. UDG can recognize and remove the uracil, resulting in the cleavage effect of the DNA crosslinker strand with the assistance of endonuclease IV (Endo IV). Plugging one end of the capillary tube, the DNA hydrogel acting as a filter membrane separator would control molecules to flow into the tube. The integrity of the DNA hydrogel networks is affected by the excision of UDG. Therefore, taking full advantage of membrane filtration of the DNA hydrogel, the activity of UDG can be quantitatively detected via reading the distance of the red indicator solution in the capillary tube. Without any instruments and complicated procedures, this method realizes high sensitivity and specificity for the detection of UDG as low as 0.02 mU/mL and can even measure UDG in complex cell samples. Additionally, this method is simple, universal, and can be used to screen inhibitors, which shows great potential for point-of-care testing, clinical diagnosis, and drug discovery.

Highly efficient antifogging and antibacterial food packaging film fabricated by novel quaternary ammonium chitosan composite.

In this work, a multifunctional food packaging composite coating with transparent, biodegradable, antifogging and antibacterial properties was designed and fabricated by quaternary ammonium salt modified chitosan (HACC) and poly (vinyl alcohol) (PVA) via a facile and environment-friendly solution casting method. A simple quaternization modification enabled the coating simultaneously to achieve excellent antifogging and antibacterial functions. The excellent antifogging property of the HACC/PVA composite coating was attributed to the strong water absorbency of quaternary ammonium chitosan and PVA. A nearly 98% transmittance ratio of coated glasses was achieved during antifogging test. In addition, the inhibition rate of the HACC/PVA composite coating kill against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Botrytis cinerea were up to ~99%. The antibacterial effect was demonstrated by each group of strawberries after storage for 1, 3, 5 days. The multifunctional coating has broad prospects in the application of fruit and vegetable packaging.

Microencapsulation of Thymol in Poly(lactide-co-glycolide) (PLGA): Physical and Antibacterial Properties.

Thymol has been shown to be a safe and effective broad-spectrum antimicrobial agent that can be used as a food preservative. However, its volatile characteristics and strong odor limit its use in food products. The microencapsulation of this essential oil in biopolymers could overcome these disadvantages. In this work, thymol-loaded poly(lactide-co-glycolide) (PLGA) microparticles were successfully prepared and the optimal encapsulation efficiency was obtained at 20% (w/w) thymol. Microparticles containing thymol presented a spherical shape and smooth surface. Microencapsulation significantly improved the thermal and storage stability of thymol. In vitro release profiles demonstrated an initial fast release followed by a slow and sustained release. Thymol-loaded microparticles had strong antibacterial activity against Escherichia coli and Staphylococcus aureus, and the effectiveness of their antibacterial properties was confirmed in a milk test. Therefore, the thymol-loaded microparticles show great potential for use as an antimicrobial and as preservation additives in food.