Chitosan-based electroconductive inks without chemical reaction for cost-effective and versatile 3D printing for electromagnetic interference (EMI) shielding and strain-sensing applications.

The burgeoning interest in biopolymer 3D printing arises from its capacity to meticulously engineer tailored, intricate structures, driven by the intrinsic benefits of biopolymers-renewability, chemical functionality, and biosafety. Nevertheless, the accessibility of economical and versatile 3D-printable biopolymer-based inks remains highly constrained. This study introduces an electroconductive ink for direct-ink-writing (DIW) 3D printing, distinguished by its straightforward preparation and commendable printability and material properties. The ink relies on chitosan as a binder, carbon fibers (CF) a low-cost electroactive filler, and silk fibroin (SF) a structural stabilizer. Freeform 3D printing manifests designated patterns of electroconductive strips embedded in an elastomer, actualizing effective strain sensors. The ink's high printability is demonstrated by printing complex geometries with porous, hollow, and overhanging structures without chemical or photoinitiated reactions or support baths. The composite is lightweight (density 0.29 ± 0.01 g/cm3), electroconductive (2.64 ± 0.06 S/cm), and inexpensive (20 USD/kg), with tensile strength of 20.77 ± 0.60 MPa and Young's modulus of 3.92 ± 0.06 GPa. 3D-printed structures exhibited outstanding electromagnetic interference (EMI) shielding effectiveness of 30-31 dB, with shielding of >99.9 % incident electromagnetic waves, showcasing significant electronic application potential. Thus, this study presents a novel, easily prepared, and highly effective biopolymer-based ink poised to advance the landscape of 3D printing technologies.

Mechanical and frictional properties of coconut husk powder reinforced polymer immersed in a simulated acidic medium for oil/gas applications.

Polymeric materials are constantly exposed to aggressive environments, negatively impacting their mechanical and chemical properties. In salt, acid, or alkaline solutions, polymer materials degrade due to surface flaws, microcracks, or other irregularities. For the first time, this study considers the behaviour of coconut powder/coir-reinforced synthetic LDPE hybrid composite immersed in an aggressive (acidic) medium for 15, 30 and 45 days. The structural, mechanical, and frictional behaviour of the developed coir/coconut husk powder/LDPE hybrid composites were measured after ageing in hydrochloric acid (HCl) as potential materials for oil and gas applications. From the XRD patterns, the prominent reflections in the control samples increased with the acid ageing days, while less prominent reflections characterized the hybrid composites. The hardness of the reinforced samples immersed for 30 and 45 days (30B and 45A) showed the highest values of 0.28 Hv, while the control samples immersed for 15 days had the least hardness. The reinforced samples immersed for 15 and 30 days (15B and 30B) showed the lowest and highest fracture toughness, respectively. The control samples were observed to absorb little water after immersion for 144 h. The result showed that although the reinforced hybrid composites showed better mechanical properties, with an increase in the days of immersion in an aggressive medium, the properties became compromised compared to the un-reinforced samples. Hence, the applications of the produced reinforced polymers in the oil and gas industries may be limited.

Freeform Liquid 3D Printing of Soft Functional Components for Soft Robotics.

Freeform liquid three-dimensional printing (FL-3DP) is a promising new additive manufacturing process that uses a yield stress gel as a temporary support, enabling the processing of a broader class of inks into complex geometries, including those with low viscosities or long solidification kinetics that were previously not processable. However, the full exploitation of these advantages for the fabrication of complex multilateral structures has been hindered by difficulties in controlling the interfaces between inks and supports. In this work, an in-depth study of the rheological properties and interfacial stabilities between a nanoclay-modified support and silicone-based inks enabled a better understanding of the impact printing parameters have on the extruded filament morphology, and thus on printing resolutions. With these improvements, the fabrication of functional multimaterial pneumatic components applied to soft robotics could be demonstrated, exhibiting superior capabilities compared to casting or traditional extrusion-based additive manufacturing in terms of geometric freedom (overhanging and multimaterial structures), tunability of the component's functionality, and robustness between different phases. Overall, the full exploitation of FL-3DP advantages enables a broader design space for features and functionalities in soft robotic components that require complex and robust combinations of materials.

Genome-Wide Assessment of Population Structure and Genetic Diversity of the Global Finger Millet Germplasm Panel Conserved at the ICRISAT Genebank.

Finger millet [Eleusine coracana (L.) Gaertn.] is an important climate-resilient nutrient-dense crop grown as a staple food grain in Asia and Africa. Utilizing the full potential of the crop mainly depends on an in-depth exploration of the vast diversity in its germplasm. In this study, the global finger millet germplasm diversity panel of 314 accessions was genotyped, using the DArTseq approach to assess genetic diversity and population structure. We obtained 33,884 high-quality single nucleotide polymorphism (SNP) markers on 306 accessions after filtering. Finger millet germplasm showed considerable genetic diversity, and the mean polymorphic information content, gene diversity, and Shannon Index were 0.110, 0.114, and 0.194, respectively. The average genetic distance of the entire set was 0.301 (range 0.040 - 0.450). The accessions of the race elongata (0.326) showed the highest average genetic distance, and the least was in the race plana (0.275); and higher genetic divergence was observed between elongata and vulgaris (0.320), while the least was between compacta and plana (0.281). An average, landrace accessions had higher gene diversity (0.144) and genetic distance (0.299) than the breeding lines (0.117 and 0.267, respectively). A similar average gene diversity was observed in the accessions of Asia (0.132) and Africa (0.129), but Asia had slightly higher genetic distance (0.286) than African accessions (0.276), and the distance between these two regions was 0.327. This was also confirmed by a model-based STRUCTURE analysis, genetic distance-based clustering, and principal coordinate analysis, which revealed two major populations representing Asia and Africa. Analysis of molecular variance suggests that the significant population differentiation was mainly due to within individuals between regions or between populations while races had a negligible impact on population structure. Finger millet diversity is structured based on a geographical region of origin, while the racial structure made negligible contribution to population structure. The information generated from this study can provide greater insights into the population structure and genetic diversity within and among regions and races, and an understanding of genomic-assisted finger millet improvement.

Comparative study of perioperative and survival outcomes after video endoscopic inguinal lymphadenectomy (VEIL) and open inguinal lymph node dissection (O-ILND) in the management of inguinal lymph nodes in carcinoma of the penis.

Open inguinal lymph node dissection (O-ILND) is the gold standard in the management of lymph nodes in carcinoma penis; however, video endoscopic inguinal lymphadenectomy (VEIL) is performed in some centers. Our primary objective is to compare perioperative and survival outcomes in patients undergoing VEIL with O-ILND, as very few studies have reported long-term survival outcomes till date. We analyzed patients who underwent O-ILND and VEIL (laparoscopic or robot-assisted) from January 2009 to January 2020 in our institute for carcinoma of the penis. Patient details, perioperative complications, and survival outcomes were analyzed. Perioperative outcomes were analyzed by logistic regression and survival outcomes by log-rank and Cox regression methods. We analyzed 79 patients (32 O-ILND, 47 VEIL) with a median follow-up of 51 (IQR 25.5-75.5) and 42 months (IQR 21-62). Wound complications were common in O-ILND group (65.6%) compared to VEIL group (27.7%) (p = 0.001), predominantly skin flap necrosis in 14 groins (23.73%) after O-ILND and none after VEIL. Median overall survival was 80 and 88 months (p = 0.840) with five-year survival of 65% and 66.8% (p = 0.636) and five-year DSS of 76.6% and 73.9% (p = 0.96) in O-ILND and VEIL, respectively. Multivariate analysis showed that grade and pathological node status were significant (HR-2.650, p = 0.040; HR-3.218, p = 0.024) factors for survival. The retrospective nature of the study design is the limitation. Management of inguinal lymph nodes in carcinoma penis by VEIL is safe, associated with lesser wound-related complications, and equivalent survival outcomes compared to O-ILND. It should be considered as an alternative option for inguinal lymph node dissection.

Biomimetic Janus chitin nanofiber membrane for potential guided bone regeneration application.

Biopolymer-based membranes are at the forefront of the guided bone regeneration (GBR) in orthopaedics and dentistry, which prevent fast-growing soft tissue migration to the defected alveolar ridge or implants and allow the bone regeneration. In this study, we fabricated a novel Janus -two-faced, GBR membrane composed of a chitin nanofiber face for bone regeneration and a cell membrane mimetic antifouling 2-Methacryloyloxyethyl phosphorylcholine (MPC) polymeric face for suppressing the migration of the soft tissue. In vitro cell study showed a higher cell proliferation rate of osteoblast cells on the chitin nanofiber surface and a lower proliferation rate of fibroblasts cells on the antifouling MPC side. An increased of Alkaline Phosphatase (ALP) rate was observed in the chitin nanofiber face, indicating the ability to maintain proliferation and differentiation of osteogenic cells. These results suggest the biomimetic Janus chitin membrane may have the potential to develop as an advance GBR membrane.

In Situ Zirconia: A Superior Reinforcing Filler for High-Performance Nitrile Rubber Composites.

Zirconia particles are generated into a nitrile rubber (NBR) matrix via a solution sol-gel method in a controlled manner. Formation of zirconia particles from their precursor (zirconium(IV) propoxide) occurs under optimized reaction conditions. As a result, the nanoparticles are embedded and well dispersed in the NBR matrix that results in a remarkable improvement in mechanical and thermal properties of the composite. Such reinforcement is not realized when the composites are prepared following the conventional technique of filler loading by physical mixing, although the filler content remains the same. Use of a surface active coupling agent TESPT (bis-(3-triethoxysilylpropyl) tetrasulfide) in the reactive sol-gel system is found to further boost the mechanical performance of the composites. In order to ensure the practical application of the developed composites, a series of studies have been performed that consist of dynamic performance, swelling, thermal degradation, and resistance to oil, ozone, and abrasion. Analysis of the results reveals that in situ zirconia could be an excellent filler for the NBR composites to withstand in a harsh and adverse environment.

Circular manufacturing of chitinous bio-composites via bioconversion of urban refuse.

Bioinspired manufacturing, in the sense of replicating the way nature fabricates, may hold great potential for supporting a socioeconomic transformation towards a sustainable society. Use of unmodified ubiquitous biological components suggests for a fundamentally sustainable manufacturing paradigm where materials are produced, transformed into products and degraded in closed regional systems with limited requirements for transport. However, adoption is currently limited by the fact that despite their ubiquitous nature, these biopolymers are predominantly harvested as industrial and agricultural products. In this study, we overcome this limitation by developing a link between bioinspired manufacturing and urban waste bioconversion. This result is paramount for the development of circular economic models, effectively connecting the organic by-products of civilization to locally decentralized, general-purpose manufacturing.

Stimuli-responsive injectable cellulose thixogel for cell encapsulation.

Herein, we present the synthesis of surface-oxidized cellulose nanofiber (CNF) hydrogel and characterization with various physicochemical analyses and spectroscopic tools as well as its suitability for cellular encapsulation and delivery. The structure-property relationship as shear thinning, thixotropy, creep-recovery and stimuli responsiveness are explored. The CNF hydrogel is capable to inject possessing shear thinning behavior at shear rate (~10 s-1) range in the normal injecting process. In time-dependent thixotropy, the hydrogel showed rapid transform from flowable fluid back to structured hydrogel fully recovering in less than 60 s. The presence of cell-culture media did not alter shear thinning behavior of CNF hydrogel and showed increased thixotropicity with respect to the control gel. The CNF hydrogel forms 3D structures, without any crosslinker, with a wide range of tunable moduli (~36-1000 Pa) based on concentration and external stimuli. The biological characteristics of the thixotropic gels are studied for human breast cancer cells and mouse embryonic stem cells and indicated high cell viability, long-term survival, and spherical morphology.

Tunichrome-inspired pyrogallol functionalized chitosan for tissue adhesion and hemostasis.

The nature-inspired fabrication of tissue adhesive and hemostatic hydrogels holds great potential for restoring damaged internal tissue in regenerative medicine. However, feeble adhesion, multifaceted systems, prohibitive costs, and toxicity impede their applications in the medical field. In order to solve this problem, we fabricated chitosan-based wet tissue adhesive with hemostatic functions inspired by the self-healing mechanism of the tunicate. In order to introduce pyrogallol moiety, gallic acids, which are broadly distributed in nature, were incorporated into chitosan backbone, a key residue for the self-healing process of tunichrome in tunicates. The in vitro adhesion test results of the tunicate-inspired hydrogel exhibited two-fold greater adhesion ability in wet condition than did fibrin glue, a commercially available surgical glue. Further, the tunicate-inspired hydrogel exhibited significantly more platelet adhesion and blood clotting ability than the parent polymer. We also demonstrated the ability of the derivative to completely mimic the tunicate's fibrous structure by fabricating an electrospun mat. The hemostatic function vis-à-vis the wet adhesiveness of the synthesized chitosan-based material may be useful for facilitating the shortcomings of the restorative tissue medicine. Additionally, the electrospinning capability will enable the modulate of the structure-property relationship and a three-dimensional design for its application site.

Large-scale additive manufacturing with bioinspired cellulosic materials.

Cellulose is the most abundant and broadly distributed organic compound and industrial by-product on Earth. However, despite decades of extensive research, the bottom-up use of cellulose to fabricate 3D objects is still plagued with problems that restrict its practical applications: derivatives with vast polluting effects, use in combination with plastics, lack of scalability and high production cost. Here we demonstrate the general use of cellulose to manufacture large 3D objects. Our approach diverges from the common association of cellulose with green plants and it is inspired by the wall of the fungus-like oomycetes, which is reproduced introducing small amounts of chitin between cellulose fibers. The resulting fungal-like adhesive material(s) (FLAM) are strong, lightweight and inexpensive, and can be molded or processed using woodworking techniques. We believe this first large-scale additive manufacture with ubiquitous biological polymers will be the catalyst for the transition to environmentally benign and circular manufacturing models.

Tunicate-Inspired Gallic Acid/Metal Ion Complex for Instant and Efficient Treatment of Dentin Hypersensitivity.

Dentin hypersensitivity is sharp and unpleasant pains caused by exposed dentinal tubules when enamel outside of the tooth wears away. The occlusion of dentinal tubules via in situ remineralization of hydroxyapatite is the best method to alleviate the symptoms caused by dentin hypersensitivity. Commercially available dental desensitizers are generally effective only on a specific area and are relatively toxic, and their performance usually depends on the skill of the clinician. Here, a facile and efficient dentin hypersensitivity treatment with remarkable aesthetic improvement inspired by the tunicate-self-healing process is reported. As pyrogallol groups in tunicate proteins conjugate with metal ions to heal the torn body armor of a tunicate, the ingenious mechanism by introducing gallic acid (GA) as a cheap, abundant, and edible alternative to the pyrogallol groups of the tunicate combined with a varied daily intake of metal ion sources is mimicked. In particular, the GA/Fe(3+) complex exhibits the most promising results, to the instant ≈52% blockage in tubules within 4 min and ≈87% after 7 d of immersion in artificial saliva. Overall, the GA/metal ion complex-mediated coating is facile, instant, and effective, and is suggested as an aesthetic solution for treating dentin hypersensitivity.

Mussel-Inspired Anisotropic Nanocellulose and Silver Nanoparticle Composite with Improved Mechanical Properties, Electrical Conductivity and Antibacterial Activity.

Materials for wearable devices, tissue engineering and bio-sensing applications require both antibacterial activity to prevent bacterial infection and biofilm formation, and electrical conductivity to electric signals inside and outside of the human body. Recently, cellulose nanofibers have been utilized for various applications but cellulose itself has neither antibacterial activity nor conductivity. Here, an antibacterial and electrically conductive composite was formed by generating catechol mediated silver nanoparticles (AgNPs) on the surface of cellulose nanofibers. The chemically immobilized catechol moiety on the nanofibrous cellulose network reduced Ag⁺ to form AgNPs on the cellulose nanofiber. The AgNPs cellulose composite showed excellent antibacterial efficacy against both Gram-positive and Gram-negative bacteria. In addition, the catechol conjugation and the addition of AgNP induced anisotropic self-alignment of the cellulose nanofibers which enhances electrical and mechanical properties of the composite. Therefore, the composite containing AgNPs and anisotropic aligned the cellulose nanofiber may be useful for biomedical applications.

Chemical studies on the polysaccharides of Salicornia brachiata.

A group of 12 polysaccharide extracts were prepared from the tips, stem and roots of an Indian halophyte Salicornia brachiata Roxb. obtained by sequential extractions with cold water (CW), hot water (HW), aqueous ammonium oxalate (OX) and aqueous sodium hydroxide (ALK) solutions. Monosaccharide composition analysis revealed that all the polysaccharide extract samples consisted primarily of rhamnose, arabinose, mannose, galactose, glucose, whereas ribose and xylose were present only in some of the extracts. All the extracts exhibited low apparent viscosity (1.47-2.02 cP) and sulphate and contained no prominent toxic metal ions. Fucose was detected only in OX extract of the roots. These polysaccharides were found to be heterogeneous and highly branched (glycoside linkage analysis, size-exclusion chromatography, (13)C-NMR, FT-IR, circular dichroism and optical rotation data). Physico-chemical analyses of these polysaccharides including uronic acid, sulphate and protein contents were also carried out. This constitutes the first report on the profiling of Salicornia polysaccharides.

Facile synthesis of a new fluorogenic metal scavenging interpolymeric diamide based on cellulose and alginic acids.

A microwave assisted synthesis of a water soluble fluorogenic interpolymeric diamide has been described involving alginic acid and polyglucuronic acid (PGA) amide of ethylenediamine (EDA), through a monoamide of PGA and EDA, in good yields (>80wt% in each step). PGA was prepared by TEMPO (2,2,6,6-tetramethyl piperidine-1-oxyl radical) mediated oxidation of cellulose of the halophytic plant Salicornia brachiata. The amides were characterized by spectral analyses. The fluorescence emission of the PGA amide was 7-fold greater than that of the interpolymeric diamide. PGA monoamide exhibited superior heavy metal ions [Pb(II) and Hg(II)] uptake properties to the diamide, the former showing optimum adsorptions of ions 398.8 and 282.8mg/g, respectively. These materials may be of utility as potential sensors harnessing their fluorogenic and metal scavenging properties.

Cellulose contents of some abundant Indian seaweed species.

Crude cellulose as well as alpha- and beta-celluloses were estimated in thirty-four seaweed species of fifteen orders of Chlorophyta, Phaeophyta and Rhodophyta of Indian waters. The greatest yields of crude cellulose and a-cellulose were obtained from Chaetomorpha aerea (approx. 20.0% and 18.5%, respectively), and of beta-cellulose (approx. 3.1%) from Caulerpa imbricata. The lowest crude cellulose, and alpha-and beta-contents were recorded for the calcareous red alga Liagora indica (approx. 0.90%, 0.70% and 0.10%, respectively). There was little variation in cellulose content among the brown algae, while wide variations in the yields were found in the green and red algae. The present work contributes to the repertoire of 67 Indian seaweed species studied to now for their cellulose contents in our laboratory. The combined studies highlight that Chaetomorpha aerea, Acrosiphonia orientalis, Caulerpa taxifolia, Sargassum tenerrimum, Hydroclathrus clathratus and Gelidiella acerosa possess relatively high (> 10%) cellulose contents, which could be of potential utility.

Genome scale transcriptional response diversity among ten ecotypes of Arabidopsis thaliana during heat stress.

In the scenario of global warming and climate change, heat stress is a serious threat to crop production worldwide. Being sessile, plants cannot escape from heat. Plants have developed various adaptive mechanisms to survive heat stress. Several studies have focused on diversity of heat tolerance levels in divergent Arabidopsis thaliana (A. thaliana) ecotypes, but comprehensive genome scale understanding of heat stress response in plants is still lacking. Here we report the genome scale transcript responses to heat stress of 10 A. thaliana ecotypes (Col, Ler, C24, Cvi, Kas1, An1, Sha, Kyo2, Eri, and Kond) originated from different geographical locations. During the experiment, A. thaliana plants were subjected to heat stress (38°C) and transcript responses were monitored using Arabidopsis NimbleGen ATH6 microarrays. The responses of A. thaliana ecotypes exhibited considerable variation in the transcript abundance levels. In total, 3644 transcripts were significantly heat regulated (p < 0.01) in the 10 ecotypes, including 244 transcription factors and 203 transposable elements. By employing a systems genetics approach- Network Component Analysis (NCA), we have constructed an in silico transcript regulatory network model for 35 heat responsive transcription factors during cellular responses to heat stress in A. thaliana. The computed activities of the 35 transcription factors showed ecotype specific responses to the heat treatment.

Cellulose of Salicornia brachiata.

Cellulose was extracted from the roots, stems and stem tips of Salicornia brachiata Roxb. Each crude cellulose sample obtained was fractionated into alpha- and beta-celluloses. The yields of crude cellulose from the stems and stem tips were greatest and lowest, respectively, while the yields of alpha- and beta-celluloses were in the order, roots > stems > stem tips. The cellulose samples were characterized by Fourier transform infrared spectroscopy (FT-IR), solid state cross polarisation magic angle spinning carbon-13 nuclear magnetic resonance spectroscopy (CP/MAS 13C NMR), X-ray diffraction pattern (XRD), thermo gravimetric analysis (TGA) and scanning electron microscopy (SEM). The data were compared with those of the celluloses (predominantly alpha-cellulose) isolated from Whatman filter paper No. 4 (WFP).

Profiling of cellulose content in Indian seaweed species.

Cellulose contents were estimated in 12 seaweed samples belonging to different families e.g. red, brown and green, growing in Indian waters. Each cellulose sample was fractionated to yield alpha (alpha) and beta (beta) celluloses. Characterization was done using various analytical tools and results were validated by comparison with those of the cellulose obtained from Whatman filter paper No. 4. The greatest yields of cellulose (crude), alpha- and beta-cellulose were obtained from Gelidiella acerosa (13.65%), Chamaedoris auriculata (9.0%) and G. acerosa (3.10%). G. acerosa was also found to contain relatively high amount of alpha-cellulose (8.19%). The lowest cellulose contents were recorded from Kappaphycus alvarezii (2.00%) and Sarconema scinaioides (2.1%), while the latter contained the lowest alpha-, and beta-celluloses (1.0% and 0.30%, respectively). It appears that agarophytic and alginophytic algae contain high cellulose and alpha-cellulose contents, while the carrageenophyte contains low cellulose. The brown algae, in general contain high cellulose as well as alpha- and beta-celluloses.