Recycling and high-value utilization of polyethylene terephthalate wastes: A review.

Polyethelene terephthalate (PET) is a well-known thermoplastic, and recycling PET waste is important for the natural environment and human health. This study provides a comprehensive overview of the recycling and reuse of PET waste through energy recovery and physical, chemical, and biological recycling. This article summarizes the recycling methods and the high-value products derived from PET waste, specifically detailing the research progress on regenerated PET prepared by the mechanical recycling of fiber/yarn, fabric, and composite materials, and introduces the application of PET nanofibers recycled by physical dissolution and electrospinning in fields such as filtration, adsorption, electronics, and antibacterial materials. This article explains the energy recovery of PET through thermal decomposition and comprehensively discusses various chemical recycling methods, including the reaction mechanisms, catalysts, conversion efficiencies, and reaction products, with a brief introduction to PET biodegradation using hydrolytic enzymes provided. The analysis and comparison of various recycling methods indicated that the mechanical recycling method yielded PET products with a wide range of applications in composite materials. Electrospinning is a highly promising recycling strategy for fabricating recycled PET nanofibers. Compared to other methods, physical recycling has advantages such as low cost, low energy consumption, high value, simple processing, and environmental friendliness, making it the preferred choice for the recycling and high-value utilization of waste PET.

Bacterial Cellulose: A Robust Platform for Design of Three Dimensional Carbon-Based Functional Nanomaterials.

Three dimensional (3D) carbon nanomaterials exhibit great application potential in environmental protection, electrochemical energy storage and conversion, catalysis, polymer science, and advanced sensors fields. Current methods for preparing 3D carbon nanomaterials, for example, carbonization of organogels, chemical vapor deposition, and self-assembly of nanocarbon building blocks, inevitably involve some drawbacks, such as expensive and toxic precursors, complex equipment and technological requirements, and low production ability. From the viewpoint of practical application, it is highly desirable to develop a simple, cheap, and environmentally friendly way for fabricating 3D carbon nanomaterials in large scale. On the other hand, in order to extend the application scope and improve the performance of 3D carbon nanomaterials, we should explore efficient strategies to prepare diverse functional nanomaterials based on their 3D carbon structure. Recently, many researchers tend to fabricate high-performance 3D carbon-based nanomaterials from biomass, which is low cost, easy to obtain, and nontoxic to humans. Bacterial cellulose (BC), a typical biomass material, has long been used as the raw material of nata-de-coco (an indigenous dessert food of the Philippines). It consists of a polysaccharide with a ß-1,4-glycosidic linkage and has a interconnected 3D porous network structure. Interestingly, the network is made up of a random assembly of cellulose nanofibers, which have a high aspect ratio with a diameter of 20-100 nm. As a result, BC has a high specific surface area. Additionally, BC hydrogels can be produced on an industrial scale via a microbial fermentation process at a very low price. Thus, it can be an ideal platform for design of 3D carbon-based functional nanomaterials. Before our work, no systematic work and summary on this topic had been reported. This Account presents the concepts and strategies of our studies on BC in the past few years, that is, converting cheap biomass into high value-added 3D carbon nanomaterials and designing diverse functional materials on 3D carbon structure. We first briefly introduce the history, constituent, and microstructure features of BC and discuss its advantages as a raw material for preparing the CNF aerogels. Then, we summarize the methods and strategies for preparing various 3D carbon-based nanomaterials from BC. In addition, the potential applications of the developed CNF aerogel based functional materials are also highlighted in this Account, including stretchable conductors, oxygen reduction reaction catalysts, supercapacitors, lithium-ion battery, and oil cleanup. Finally, we give some prospects on the future challenges in this emerging research area of designing CNF aerogel based functional nanomaterials from BC.

Synergistic large segmental bone repair by 3D printed bionic scaffolds and engineered ADSC nanovesicles: Towards an optimized regenerative microenvironment.

Achieving sufficient bone regeneration in large segmental defects is challenging, with the structure of bone repair scaffolds and their loaded bioactive substances crucial for modulating the local osteogenic microenvironment. This study utilized digital laser processing (DLP)-based 3D printing technology to successfully fabricate high-precision methacryloylated polycaprolactone (PCLMA) bionic bone scaffold structures. Adipose-derived stem cell-engineered nanovesicles (ADSC-ENs) were uniformly and stably modified onto the bionic scaffold surface using a perfusion device, constructing a conducive microenvironment for tissue regeneration and long bone defect repair through the scaffold's structural design and the vesicles' biological functions. Scanning electron microscopy (SEM) examination of the scaffold surface confirmed the efficient loading of ADSC-ENs. The material group loaded with vesicles (PCLMA-BAS-ENs) demonstrated good cell compatibility and osteogenic potential when analyzed for the adhesion and osteogenesis of primary rabbit bone marrow mesenchymal stem cells (BMSCs) on the material surface. Tested in a 15 mm critical rabbit radial defect model, the PCLMA-BAS-ENs scaffold facilitated near-complete bone defect repair after 12 weeks. Immunofluorescence and proteomic results indicated that the PCLMA-BAS-ENs scaffold significantly improved the osteogenic microenvironment at the defect site in vivo, promoted angiogenesis, and enhanced the polarization of macrophages towards M2 phenotype, and facilitated the recruitment of BMSCs. Thus, the PCLMA-BAS-ENs scaffold was proven to significantly promote the repair of large segmental bone defects. Overall, this strategy of combining engineered vesicles with highly biomimetic scaffolds to promote large-segment bone tissue regeneration holds great potential in orthopedic and other regenerative medicine applications.

Clay Sculpture-Inspired 3D Printed Microcage Module Using Bioadhesion Assembly for Specific-Shaped Tissue Vascularization and Regeneration.

3D bioprinting techniques have enabled the fabrication of irregular large-sized tissue engineering scaffolds. However, complicated customized designs increase the medical burden. Meanwhile, the integrated printing process hinders the cellular uniform distribution and local angiogenesis. A novel approach is introduced to the construction of sizable tissue engineering grafts by employing hydrogel 3D printing for modular bioadhesion assembly, and a poly (ethylene glycol) diacrylate (PEGDA)-gelatin-dopamine (PGD) hydrogel, photosensitive and adhesive, enabling fine microcage module fabrication via DLP 3D printing is developed. The PGD hydrogel printed micocages are flexible, allowing various shapes and cell/tissue fillings for repairing diverse irregular tissue defects. In vivo experiments demonstrate robust vascularization and superior graft survival in nude mice. This assembly strategy based on scalable 3D printed hydrogel microcage module could simplify the construction of tissue with large volume and complex components, offering promise for diverse large tissue defect repairs.

Reconfigurable Magnetic Liquid Building Blocks for Constructing Artificial Spinal Column Tissues.

All-liquid molding can be used to transform a liquid into free-form solid constructs, while maintaining internal fluidity. Traditional biological scaffolds, such as cured pre-gels, are normally processed in solid state, sacrificing flowability and permeability. However, it is essential to maintain the fluidity of the scaffold to truly mimic the complexity and heterogeneity of natural human tissues. Here, this work molds an aqueous biomaterial ink into liquid building blocks with rigid shapes while preserving internal fluidity. The molded ink blocks for bone-like vertebrae and cartilaginous-intervertebral-disc shapes, are magnetically manipulated to assemble into hierarchical structures as a scaffold for subsequent spinal column tissue growth. It is also possible to join separate ink blocks by interfacial coalescence, different from bridging solid blocks by interfacial fixation. Generally, aqueous biomaterial inks are molded into shapes with high fidelity by the interfacial jamming of alginate surfactants. The molded liquid blocks can be reconfigured using induced magnetic dipoles, that dictated the magnetic assembly behavior of liquid blocks. The implanted spinal column tissue exhibits a biocompatibility based on in vitro seeding and in vivo cultivating results, showing potential physiological function such as bending of the spinal column.

Individualized treatment of craniovertebral junction malformation guided by intraoperative computed tomography.

STUDY DESIGN: This study was designed to report our preliminary experience of intraoperative computed tomography (iCT) using a mobile scanner with integrated neuronavigation system (NNS). OBJECTIVE: The objective of this study was to assess the feasibility and potential utility of iCT with integrated NNS in individualized treatment of craniovertebral junction malformation (CVJM). SUMMARY OF BACKGROUND DATA: The surgical management of congenital craniovertebral anomalies is complex due to the relative difficulty in accessing the region, critical relationships of neurovascular structures, and the intricate biomechanical issues involved. METHODS: We reported our first 19 complex CVJM cases including 11 male and 8 female patients from January, 2009 to June, 2009 (mean age, 33.9 y; age range, 13 to 58 y). A sliding gantry 40-slice CT scanner was installed in a preexisting operating room. Image data was transferred directly from the scanner into the NNS using an automated registration system. We applied this technology to transoral odontoidectomy in 17 patients. Moreover, with the extra help of iCT integrated with NNS, odontoidectomy through posterior midline approach, and transoral atlantal lateral mass resection were, for the first time, performed for treatment of complex CVJM. RESULTS: NNS was found to correlate well with the intraoperative findings, and the recalibration was uneven in all cases with an accuracy of 1.6 mm (1.6: 1.2 to 2.0). All patients were clinically evaluated by Nurick grade criteria, and neurological deficits were monitored after 3 months of surgery. Fifteen patients (79%) were improved by at least 1 Nurick grade, whereas the grade did not change in 4 patients (21%). CONCLUSIONS: iCT scanning with integrated NNS was both feasible and beneficial for the surgical management of complex CVJM. In this unusual patient population, the technique seemed to be valuable in negotiating complex anatomy and achieving a safe and predictable decompression.

Multi-Layered Polyamide/Collagen Scaffolds with Topical Sustained Release of N-Acetylcysteine for Promoting Wound Healing.

BACKGROUND: Impaired wound healing might be associated with many issues, especially overactive of reactive oxygen species (ROS), deficiency of blood vessels and immature of epidermis. N-acetylcysteine (NAC), as an antioxidant, could solve these problems by inhibiting overreactive of ROS, promoting revascularization and accelerating re-epithelialization. How to deliver NAC in situ with a controllable releasing speed still remain a challenge. MATERIALS AND METHODS: In this study, we combined collagen (Col) with N-acetylcysteine to perform the characteristics of sustained release and chemically crosslinked Col/NAC composite with polyamide (PA) nanofibers to enhance the mechanical property of collagen and fabricated this multi-layered scaffold (PA-Col/NAC scaffold). The physical properties of the scaffolds such as surface characteristics, water absorption and tensile modulus were tested. Meanwhile, the ability to promote wound healing in vitro and in vivo were investigated. RESULTS: These scaffolds were porous and performed great water absorption. The PA-Col/NAC scaffold could sustainably release NAC for at least 14 days. After cell implantation, PA-Col/NAC scaffold showed better cell proliferation and cell migration than the other groups. In vivo, PA-Col/NAC scaffolds could promote wound healing best among all the groups. CONCLUSION: The multi-layered scaffolds could obviously accelerate the process of wound healing and exert better and prolonged effects.

A biocompatible vascularized graphene oxide (GO)-collagen chamber with osteoinductive and anti-fibrosis effects promotes bone regeneration in vivo.

The survival of transplanted cells and tissues in bone regeneration requires a microenvironment with a vibrant vascular network. A tissue engineering chamber can provide this in vivo. However, the commonly used silicone chamber is biologically inert and can cause rejection reactions and fibrous capsule. Studies have revealed that collagen is highly biocompatible and graphene oxide (GO) could regulate osteogenic activity in vivo. Besides, GO can be cross-linked with natural biodegradable polymers to construct scaffolds. Methods: A vascularized GO-collagen chamber model was built by placing vessels traversing through the embedded tissue-engineered grafts (osteogenic-induced bone mesenchymal stem cells -gelatin) in the rat groin area. Osteogenic activity and inflammatory reactions were assessed using different methods including micro-CT scanning, Alizarin red staining, and immunohistochemical staining. Results: After one month, in vivo results showed that bone mineralization and inflammatory responses were significantly pronounced in the silicone model or no chamber (control) groups. Vascular perfusion analysis confirmed that the GO-collagen chamber improved the angiogenic processes. Cells labeled with EdU revealed that the GO-collagen chamber promoted the survival and osteogenic differentiation of bone mesenchymal stem cells. Conclusion: Overall, the novel biocompatible GO-collagen chamber exhibited osteoinductive and anti-fibrosis effects which improved bone regeneration in vivo. It can, therefore, be applied to other fields of regenerative medicine.

Self-Assembled Human Adipose-Derived Stem Cell-Derived Extracellular Vesicle-Functionalized Biotin-Doped Polypyrrole Titanium with Long-Term Stability and Potential Osteoinductive Ability.

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs), containing proteins or microRNAs (miRNAs), possessing various biological activity and low immunogenicity, are considered promising for surface modification of bone grafts. However, the modification efficiency is not satisfied yet, resulting in compromised therapy effects. Here, we report a novel immobilized method by self-assembling biotinylated MSC-EVs onto the surface of biotin-doped polypyrrole titanium (Bio-Ppy-Ti) to improve its biofunctions in vitro and in vivo. Using this method, the amount of human adipose-derived stem cell-EVs (hASC-EVs) anchored onto the Bio-Ppy-Ti surface was 185-fold higher than that of pure Ti after ultrasonic concussion for 30 s and it remained stable on the Bio-Ppy-Ti surface for 14 days at 4 °C. Compared to pristine Ti, EV-Bio-Ppy-Ti exhibited enhanced cell compatibility and osteoinductivity for osteoblasts in vitro and anti-apoptosis ability in the ectopic bone formation mode. Gene chip analysis further demonstrated that several osteoinductive miRNAs were encapsulated in hASC-EVs, which may explain the high bone regeneration ability of EV-Bio-Ppy-Ti. Thus, this MSC-EV biotin-immobilized method appears to be highly efficient and long-term stable for bone graft bioactive modification, demonstrating its potential for clinical metal implants.

Sustained release of N-acetylcysteine by sandwich structured polycaprolactone/collagen scaffolds for wound healing.

PCL (poly-caprolactone) nanofibers have good biocompatibility and high porosity, which are usually utilized for application in wound dressings. However, wound healing could be hindered by the overproduction of reactive oxygen species (ROS) and different factors. Pure nanofibers cannot satisfy these requirements of wound healing. N-acetylcysteine (NAC), as an antioxidant, meets the requirements for wound healing by resisting the overproduction of ROS and by promoting angiogenesis and maturation of the epidermis. In this study, we prepared a sandwich structured PCL-Col/NAC scaffold using the molding method, which consisted of PCL nanofibers at the core and NAC-loaded collagen on both sides. The hydroscopicity and tensile modulus of PCL-Col/NAC scaffolds showed best performance of these properties among groups. Meanwhile, the drug release profiles of PCL-Col/NAC scaffolds were investigated using the HPLC method and the results suggested a sustained drug release of NAC for PCL-Col/NAC scaffolds. In addition, PCL-Col/NAC scaffolds presented better properties than the control groups in cell migration and proliferation. The in vivo wound healing therapy effect was studied using an oval (2 × 1 cm) full-thickness skin defect wound model for SD rats. After 21 days, gross view and histological analysis showed a favorable beneficial therapeutic effect as well as better epidermal maturation compared with the control groups. CD31 immunohistology results revealed relatively more new vessels in the PCL-Col/NAC group than the control groups. This study developed novel PCL-Col/NAC scaffolds with an excellent hydroscopicity, tensile modulus and the ability to promote epidermal maturation and angiogenesis, demonstrating its promising potential in wound healing treatment. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Bacterial-cellulose-derived carbon nanofiber@MnO2 and nitrogen-doped carbon nanofiber electrode materials: an asymmetric supercapacitor with high energy and power density.

A new kind of high-performance asymmetric supercapacitor is designed with pyrolyzed bacterial cellulose (p-BC)-coated MnO2 as a positive electrode material and nitrogen-doped p-BC as a negative electrode material via an easy, efficient, large-scale, and green fabrication approach. The optimal asymmetric device possesses an excellent supercapacitive behavior with quite high energy and power density.

Drying of colloidal droplets on superhydrophobic surfaces.

Recent research on the flow patterns during the drying of droplets of solutions or suspensions has revealed a characteristic flow of dissolved or suspended material to the droplet periphery to produce the 'coffee ring' phenomenon. This effect was used to make ceramic well-plates by spontaneous manufacturing. Here we demonstrate that when a colloidal droplet dries on a superhydrophobic surface, the effect is rather different. Evaporation from the region adjacent to the three phase line becomes so restricted that the interior flows, and hence the final destination of particles, changes and the characteristic bowl-shape becomes inverted.

Prenatal diagnosis of trisomy 18p and distal 21q22.3 deletion.

OBJECTIVES: To present the perinatal findings and molecular cytogenetic analysis of concomitant trisomy 18p (18p11.2-->pter) and distal 21q22.3 deletion. CASE AND METHODS: A 29-year-old woman, gravida 2 para 1, underwent amniocentesis at 17 weeks' gestation because she was a carrier of a balanced reciprocal translocation, 46,XX,t(18;21)(p11.2;q22.3). Cytogenetic analysis of the cultured amniocytes revealed a karyotype of 46,XX,der(21)t(18;21)(p11.2;q22.3). The fetus had a derivative chromosome 21 with an extra short arm of chromosome 18 attached to the terminal region of the long arm of chromosome 21. Level II sonograms did not find prominent structural anomalies. The pregnancy was terminated subsequently. At autopsy, the proband displayed a mild phenotype of hypertelorism, a small mouth, micrognathia, a narrowly arched palate, low-set ears, and clinodactyly. The brain and other organs were unremarkable. Genetic marker analysis showed a distal deletion at 21q22.3 and a breakpoint between D21S53 (present) and D21S212 (absent), centromeric to the known holoprosencephaly (HPE) minimal critical region D21S113-21qter. CONCLUSION: Genetic marker analysis helps in delineating the region of deletion in prenatally detected unbalanced cryptic translocation. Fetuses with concomitant trisomy 18p and distal 21q22.3 deletion may manifest inapparent phenotypic abnormalities in utero. Haploinsufficiency of the HPE critical region at 21q22.3 may not cause an HPE phenotype.