Carbon nanotube (CNT) and nanofibrillated cellulose (NFC) reinforcement effect on thermoplastic polyurethane (TPU) scaffolds fabricated via phase separation using dimethyl sulfoxide (DMSO) as solvent

Recent perspective of synthesis and modification strategies of cellulose nanocrystals and cellulose nanofibrils and their beneficial impact in scaffold-based tissue engineering: A review

Outstanding properties of nanocellulose provide opportunities for novel applications in various fields, particularly tissue engineering. Despite of numerous useful characteristics of nanocellulose, its production methods suffer from the lack of control of morphology, high cost, and the use of organic solvents. On the other hand, hydrophilicity of nanocellulose is a significant challenge for its dispersion as a reinforcement in hydrophobic polymers matrix. Therefore, sustainable production methods and well-tuning interfacial characteristics of nanocellulose have been identified as critical steps in their development. This review article discusses the numerous preparation methods and surface modification strategies of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) to help nanocellulose users obtain the appropriate material for their desired application. We also cover various polymer/nanocellulose scaffolds that are reported in the literature and investigate the effect of CNC and CNF on their mechanical, thermal and biological properties. Moreover, we provide several scientific figures and tables for a better understanding of the explored topics. Finally, we evaluate the opportunities and challenges of nanocellulose industrialization in the field of tissue engineering. Overall, this review guides researchers towards a deeper understanding of nanocellulose production processes, changing their properties using surface modification methods, and subsequently their performance in scaffold-based tissue engineering.

Novel shish-kebab structured nanofibrous decorating chitosan unidirectional scaffolds to mimic extracellular matrix for tissue engineering

Electrospun nanofibrous scaffolds are renowned for their ability to mimic the microstructure of the extracellular matrix (ECM). However, they often fail to replicate the geometry of target tissues, and the biocompatibility of these scaffolds those made from synthetic polymers is always limited due to the lack of cell binding sites. To address these issues, we proposed an innovative approach that combined unidirectional freeze-drying and electrospinning. During this process, electrospun polycaprolactone (PCL) nanofibers were chopped into nanofibrils, which range in size up to several hundred micrometers, and were incorporated into the chitosan scaffolds via unidirectional freeze-drying. In these scaffolds, the chitosan phase was responsible for maintaining the structural integrity at the macroscale, while the embedded nanofibers enhanced the surface topography at the microscale. The resulting scaffolds exhibited a high porosity of 90% and an impressive water uptake capacity of 2500%. Furthermore, 3T3 fibroblast cells showed strong interactions with the scaffolds, characterized by high rates of cell proliferation and viability. The cells also displayed significant orientation along the direction of the pores, suggesting that the scaffolds effectively guided cellular growth.

Effects of Degreasing Pretreatment on Immunohistochemistry and Molecular Analysis of Gastrointestinal and Breast Cancer Samples

Lymph node status is a key factor in determining stage, treatment, and prognosis in cancers. Small lymph nodes in fat-rich gastrointestinal and breast cancer specimens are easily missed in conventional sampling methods. This study examined the effectiveness of the degreasing pretreatment with dimethyl sulfoxide (DMSO) in lymph node detection and its impact on the analysis of clinical treatment-related proteins and molecules. Thirty-three cases of gastrointestinal cancer specimens from radical gastrectomy and 63 cases of breast cancer specimens from modified radical mastectomy were included. After routine sampling of lymph nodes, the specimens were immersed in DMSO for 30 minutes for defatting. We assessed changes in the number of detected lymph nodes and pN staging in 33 gastrointestinal cancer specimens and 37 breast cancer specimens. In addition, we analyzed histologic characteristics, Masson trichrome special staining, and immunohistochemistry (gastrointestinal cancer: MMR, HER2, and PD-L1; breast cancer: ER, PR, AR, HER2, Ki-67, and PD-L1). Molecular status was evaluated for colorectal cancer (KRAS, NRAS, BRAF, and microsatellite instability) and breast cancer (HER2) in gastrointestinal cancer specimens and the remaining 26 breast cancer specimens. Compared with conventional sampling, DMSO pretreatment increased the detection rate of small lymph nodes (gastrointestinal cancer: P < .001; breast cancer: P < .001) and improved pN staging in 1 case each of gastric cancer, colon cancer, and rectal cancer (3/33; 9.1%). No significant difference in the morphology, special staining, protein, and molecular status of cancer tissue after DMSO treatment was found. Based on these results and our institutional experience, we recommend incorporating DMSO degreasing pretreatment into clinical pathologic sampling practices.

Multifunctional and Washable Carbon Nanotube-Wrapped Textile Yarns for Wearable E-Textiles

Carbon nanotube (CNT) yarns are promising for wearable electronic applications due to their excellent electromechanical and thermal properties and structural flexibility. A spinning system was customized to produce CNT-wrapped textile yarns for wearable applications. By adjusting the spinning parameters and core yarn, a highly tailored hybrid CNT yarn could be produced for textile processing, e.g., knitting and weaving. The electrical resistance and mechanical properties of the yarn are influenced by the core yarn. The high flexibility of the yarn enabled state-of-the-art three-dimensional (3D) knitting of the CNT-wrapped yarn for the first time. Using the 3D knitted technology, CNT-wrapped textile yarns were seamlessly integrated into a wrist band and the index finger of a glove. The knitted structure exhibited a large resistance change under strain and precisely recorded the signal under the different movements of the finger and wrist. When the knitted fabric was connected to a power source, rapid heating above skin temperature was observed at a low voltage. This work presents a novel hybrid yarn for the first time, which sustained 30 washing cycles without performance degradation. By changing the core yarn, a highly stretchable and multimodal sensing system could be developed for wearable applications.

Poly(ethylene glycol)-b-poly(1,3-trimethylene carbonate) Amphiphilic Copolymers for Long-Acting Injectables: Synthesis, Non-Acylating Performance and In Vivo Degradation

This article presents the evaluation of diblock and triblock poly(ethylene glycol)-b-poly(1,3-trimethylene carbonate) amphiphilic copolymers (PEG-PTMCs) as excipients for the formulation of long-acting injectables (LAIs). Copolymers were successfully synthesised through bulk ring-opening polymerisation. The concomitant formation of PTMC homopolymer could not be avoided irrespective of the catalyst amount, but the by-product could easily be removed by gel chromatography. Pure PEG-PTMCs undergo faster erosion in vivo than their corresponding homopolymer. Furthermore, these copolymers show outstanding stability compared to their polyester analogues when formulated with amine-containing reactive drugs, which makes them particularly suitable as LAIs for the sustained release of drugs susceptible to acylation.

Nanofibrous Foams of Poly(3-hydroxybutyrate)/Cellulose Nanocrystal Composite Fabricated Using Nonsolvent-Induced Phase Separation

In this study, we fabricated nanofibrous foams of neat poly(3-hydroxybutyrate) (PHB) and PHB/cellulose nanocrystal (CNC) nanocomposite using nonsolvent-induced phase separation (NIPS) followed by solvent extraction. Two different nonsolvents, tetrahydrofuran (THF) and 1,4-dioxane (Diox), in combination with the solvent, chloroform (CF), were used for NIPS. The parameters of NIPS-derived crystallization kinetics were calculated using Avrami analysis of time-dependent infrared spectral measurements. The lower viscosity and poorer PHB affinity of THF than those of Diox resulted in rapid crystallization and gelation rate, which in turn resulted in higher strength of the foam. The mechanical reinforcement by the incorporation of CNCs was achieved for the composite foam prepared in Diox/CF but not in THF/CF, owing to the relatively better dispersion of the CNCs in Diox than that in THF. A rapid rate of NIPS-derived crystallization and gelation was achieved in THF/CF with the incorporation of CNCs, indicating the effective crystal nucleation of CNCs. However, the presence of CNCs deaccelerated the crystallization in Diox/CF, indicating that the inhibition effect of PHB mobility became more dominant than the nucleation effect of CNCs; this was because the CNC dispersion became more homogeneous in Diox/CF. In vitro cell viability assays exhibited excellent cytocompatibility of the foams, thereby showing potential for use in biomedical applications.

CNT and rGO reinforced PMMA based bone cement for fixation of load bearing implants: Mechanical property and biological response

Polymethyl methacrylate (PMMA) bone cements (BCs) have some drawbacks, including limited bioactivity and bone formation, as well as inferior mechanical properties, which may result in failure of the BC. To deal with the mentioned issues, novel bioactive polymethyl methacrylate-hardystonite (PMMA-HT) bone cement (BC) reinforced with 0.25 and 0.5 wt% of carbon nanotube (CNT) and reduced graphene oxide (rGO) was synthesized. In this context, the obtained bone cements were evaluated in terms of their mechanical and biological characteristics. The rGO reinforced bone cement exhibited better mechanical properties to the extent that the addition of 0.5 wt% of rGO where its compressive and tensile strength of bioactive PMMA-HT/rGO cement escalated from 92.07 ± 0.72 MPa, and 40.02 ± 0.71 MPa to 187.48 ± 5.79 MPa and 64.92 ± 0.75 MPa, respectively. Besides, the mechanisms of toughening, apatite formation, and cell interaction in CNT and rGO encapsulated PMMA have been studied. Results showed that the existence of CNT and rGO in BCs led to increase of MG63 osteoblast viability, and proliferation. However, rGO reinforced bone cement was more successful in supporting MG63 cell attachment compared to the CNT counterpart due to its wrinkled surface, which made a suitable substrate for cell adhesion. Based on the results, PMMA-HT/rGO can be a proper bone cement for the fixation of load-bearing implants.

Highly Permeable Gelatin/Poly(lactic acid) Fibrous Scaffolds with a Three-Dimensional Spatial Structure for Efficient Cell Infiltration, Mineralization and Bone Regeneration

Three-dimensional (3D) fibrous scaffolds allowing sufficient cell infiltration are urgently needed for bone tissue engineering. In this study, a highly permeable 3D interconnected scaffold was fabricated by surface bonding of cotton-like nonwoven fibers with micro- and nanoscale architecture using gaseous chloroform. The results of physiochemical characterization indicated that bonding for 90 min with a fiber density of 0.15 g/cm³ could facilitate satisfactory porosity, supportive mechanical properties, and a 3D spatial microstructure for cell ingrowth. Coating with gelatin on the fibers induced highly efficient in vitro mineralization and in vivo bone formation as indicated by mineral deposition and repair of rabbit radius bone defect. The findings from this work demonstrated that these biofunctionalized fibrous scaffolds could bionically represent topographic nanofeatures and biological composition for cell binding affinities similar to those of the natural extracellular matrix (ECM). It can be concluded that the facile fabrication and modification strategy of 3D fibrous scaffolds exhibit promising prospect to fulfill the progressive needs in bone tissue engineering.

A. M. N, Halim AS, Kumar USU, Bairwan R, Suriani AB. A Review on Micro- to Nanocellulose Biopolymer Scaffold Forming for Tissue Engineering Applications

Biopolymers have been used as a replacement material for synthetic polymers in scaffold forming due to its biocompatibility and nontoxic properties. Production of scaffold for tissue repair is a major part of tissue engineering. Tissue engineering techniques for scaffold forming with cellulose-based material is at the forefront of present-day research. Micro- and nanocellulose-based materials are at the forefront of scientific development in the areas of biomedical engineering. Cellulose in scaffold forming has attracted a lot of attention because of its availability and toxicity properties. The discovery of nanocellulose has further improved the usability of cellulose as a reinforcement in biopolymers intended for scaffold fabrication. Its unique physical, chemical, mechanical, and biological properties offer some important advantages over synthetic polymer materials. This review presents a critical overview of micro- and nanoscale cellulose-based materials used for scaffold preparation. It also analyses the relationship between the method of fabrication and properties of the fabricated scaffold. The review concludes with future potential research on cellulose micro- and nano-based scaffolds. The review provides an up-to-date summary of the status and future prospective applications of micro- and nanocellulose-based scaffolds for tissue engineering.

Highly porous composite aerogel based triboelectric nanogenerators for high performance energy generation and versatile self-powered sensing

Boosting power generation performance while employing economical and biocompatible materials is an ongoing direction in the field of triboelectric nanogenerators (TENGs). Here, highly porous, biocompatible, cellulose nanofibril (CNF) composite-based TENGs are developed through an environmentally friendly freeze-drying approach. High tribopositivity materials, including silica fiber, human hair, and rabbit fur, are used as fillers in composite TENG fabrication for the first time to enhance the triboelectric output performance. Among them, a CNF/rabbit fur composite aerogel-based TENG offers the optimum energy generation ability with a high power density of 3.4 W m-2 achieved on a 4.7 MΩ load at a pressure of 30 kPa. Owing to the high output, the porous composite TENG exhibits an excellent energy harvesting performance and high sensitivity in detecting ultralight forces and monitoring human motion when used as a self-powered sensor. This work introduces a new class of highly porous composite TENGs that integrate biocompatibility, low cost, flexibility, high energy generation performance, and sensing sensitivity, as well as providing new strategies for high performance TENG design and fabrication.

Nano-silver-incorporated biomimetic polydopamine coating on a thermoplastic polyurethane porous nanocomposite as an efficient antibacterial wound dressing

Background

Developing an ideal wound dressing that meets the multiple demands of good biocompatibility, an appropriate porous structure, superior mechanical property and excellent antibacterial activity against drug-resistant bacteria is highly desirable for clinical wound care. Biocompatible thermoplastic polyurethane (TPU) membranes are promising candidates as a scaffold; however, their lack of a suitable porous structure and antibacterial activity has limited their application. Antibiotics are generally used for preventing bacterial infections, but the global emergence of drug-resistant bacteria continues to cause social concerns.

Results

Consequently, we prepared a flexible dressing based on a TPU membrane with a specific porous structure and then modified it with a biomimetic polydopamine coating to prepare in situ a nano-silver (NS)-based composite via a facile and eco-friendly approach. SEM images showed that the TPU/NS membranes were characterized by an ideal porous structure (pore size: ~ 85 μm, porosity: ~ 65%) that was decorated with nano-silver particles. ATR-FITR and XRD spectroscopy further confirmed the stepwise deposition of polydopamine and nano-silver. Water contact angle measurement indicated improved surface hydrophilicity after coating with polydopamine. Tensile testing demonstrated that the TPU/NS membranes had an acceptable mechanical strength and excellent flexibility. Subsequently, bacterial suspension assay, plate counting methods and Live/Dead staining assays demonstrated that the optimized TPU/NS2.5 membranes possessed excellent antibacterial activity against P. aeruginosa, E. coli, S. aureus and MRSA bacteria, while CCK8 testing, SEM observations and cell apoptosis assays demonstrated that they had no measurable cytotoxicity toward mammalian cells. Moreover, a steady and safe silver-releasing profile recorded by ICP-MS confirmed these results. Finally, by using a bacteria-infected (MRSA or P. aeruginosa) murine wound model, we found that TPU/NS2.5 membranes could prevent in vivo bacterial infections and promote wound healing via accelerating the re-epithelialization process, and these membranes had no obvious toxicity toward normal tissues.

Conclusion

Based on these results, the TPU/NS2.5 nanocomposite has great potential for the management of wounds, particularly for wounds caused by drug-resistant bacteria.

Human Knee Meniscus Regeneration Strategies: a Review on Recent Advances

PURPOSE OF REVIEW

Lack of vascularity in the human knee meniscus often leads to surgical removal (total or partial meniscectomy) in the case of severe meniscal damage. However, complete recovery is in question after such removal as the meniscus plays an important role in knee stability. Thus, meniscus tissue regeneration strategies are of intense research interest in recent years.

RECENT FINDINGS

The structural complexity and inhomogeneity of the meniscus have been addressed with processing technologies for precisely controlled three dimensional (3D) complex porous scaffold architectures, the use of biomolecules and nanomaterials. The regeneration and replacement of the total meniscus have been studied by the orthopedic and scientific communities via successful pre-clinical trials towards mimicking the biomechanical properties of the human knee meniscus. Researchers have attempted different regeneration strategies which contribute to in vitro regeneration and are capable of repairing meniscal tears to some extent. This review discusses the present state of the art of these meniscus tissue engineering aspects.

Biomimetic polyurethane/TiO2 nanocomposite scaffolds capable of promoting biomineralization and mesenchymal stem cell proliferation

Scaffolds with extracellular matrix-like fibrous morphology, suitable mechanical properties, biomineralization capability, and excellent cytocompatibility are desired for bone regeneration. In this work, fibrous and degradable poly(ester urethane)urea (PEUU) scaffolds reinforced with titanium dioxide nanoparticles (nTiO2) were fabricated to possess these properties. To increase the interfacial interaction between PEUU and nTiO2, poly(ester urethane) (PEU) was grafted onto the nTiO2. The scaffolds were fabricated by electrospinning and exhibited fiber diameter of <1μm. SEM and EDX mapping results demonstrated that the PEU modified nTiO2 was homogeneously distributed in the fibers. In contrast, severe agglomeration was found in the scaffolds with unmodified nTiO2. PEU modified nTiO2 significantly increased Young's modulus and tensile stress of the PEUU scaffolds while unmodified nTiO2 significantly decreased Young's modulus and tensile stress. The greatest reinforcement effect was observed for the scaffold with 1:1 ratio of PEUU and PEU modified nTiO2. When incubating in the simulated body fluid over an 8-week period, biomineralization was occurred on the fibers. The scaffolds with PEU modified nTiO2 showed the highest Ca and P deposition than pure PEUU scaffold and PEUU scaffold with unmodified nTiO2. To examine scaffold cytocompatibility, bone marrow-derived mesenchymal stem cells were cultured on the scaffold. The PEUU scaffold with PEU modified nTiO2 demonstrated significantly higher cell proliferation compared to pure PEUU scaffold and PEUU scaffold with unmodified nTiO2. The above results demonstrate that the developed fibrous nanocomposite scaffolds have potential for bone tissue regeneration.

A simple model for constant storage modulus of poly (lactic acid)/poly (ethylene oxide)/carbon nanotubes nanocomposites at low frequencies assuming the properties of interphase regions and networks

The networks of nanoparticles in nanocomposites cause solid-like behavior demonstrating a constant storage modulus at low frequencies. This study examines the storage modulus of poly (lactic acid)/poly (ethylene oxide)/carbon nanotubes (CNT) nanocomposites. The experimental data of the storage modulus in the plateau regions are obtained by a frequency sweep test. In addition, a simple model is developed to predict the constant storage modulus assuming the properties of the interphase regions and the CNT networks. The model calculations are compared with the experimental results, and the parametric analyses are applied to validate the predictability of the developed model. The calculations properly agree with the experimental data at all polymer and CNT concentrations. Moreover, all parameters acceptably modulate the constant storage modulus. The percentage of the networked CNT, the modulus of networks, and the thickness and modulus of the interphase regions directly govern the storage modulus of nanocomposites. The outputs reveal the important roles of the interphase properties in the storage modulus.

Biomimetic thermoplastic polyurethane porous membrane with hierarchical structure accelerates wound healing by enhancing granulation tissue formation and angiogenesis

Wound dressing with hierarchical structure enhances wound healing.