Neural Correlates of Online Action Preparation.

When performing movements in rapid succession, the brain needs to coordinate ongoing execution with the preparation of an upcoming action. Here we identify the processes and brain areas involved in this ability of online preparation. Human participants (both male and female) performed pairs of single-finger presses or three-finger chords in rapid succession, while 7T fMRI was recorded. In the overlap condition, they could prepare the second movement during the first response and in the nonoverlap condition only after the first response was completed. Despite matched perceptual and movement requirements, fMRI revealed increased brain activity in the overlap condition in regions along the intraparietal sulcus and ventral visual stream. Multivariate analyses suggested that these areas are involved in stimulus identification and action selection. In contrast, the dorsal premotor cortex, known to be involved in planning upcoming movements, showed no discernible signs of heightened activity. This observation suggests that the bottleneck during simultaneous action execution and preparation arises at the level of stimulus identification and action selection, whereas movement planning in the premotor cortex can unfold concurrently with the execution of a current action without requiring additional neural activity.

A smart thermoresponsive macroporous 4D structure by 4D printing of Pickering-high internal phase emulsions stabilized by plasma-functionalized starch nanomaterials for a possible delivery system.

Hierarchically porous structures combine microporosity, mesoporosity, and microporosity to enhance pore accessibility and transport, which are crucial to develop high performance materials for biofabrication, food, and pharmaceutical applications. This work aimed to develop a 4D-printed smart hierarchical macroporous structure through 3D printing of Pickering-type high internal phase emulsions (Pickering-HIPEs). The key was the utilization of surface-active (hydroxybutylated) starch nanomaterials, including starch nanocrystals (SNCs) (from waxy maize starch through acid hydrolysis) or starch nanoparticles (SNPs) (obtained through an ultrasound treatment). An innovative procedure to fabricate the functionalized starch nanomaterials was accomplished by grafting 1,2-butene oxide using a cold plasma technique to enhance their surface hydrophobicity, improving their aggregation, and thus attaining a colloidally stabilized Pickering-HIPEs with a low concentration of each surface-active starch nanomaterial. A flocculation of droplets in Pickering-HIPEs was developed after the addition of modified SNCs or SNPs, leading to the formation of a gel-like structure. The 3D printing of these Pickering-HIPEs developed a highly interconnected large pore structure, possessing a self-assembly property with thermoresponsive behavior. As a potential drug delivery system, this thermoresponsive macroporous 3D structure offered a lower critical solution temperature (LCST)-type phase transition at body temperature, which can be used in the field of smart releasing of bioactive compounds.

3D Printing of Bioactive Gel-like Double Emulsion into a Biocompatible Hierarchical Macroporous Self-Lubricating Scaffold for 3D Cell Culture.

The interconnected hierarchically porous structures are of key importance for potential applications as substrates for drug delivery, cell culture, and bioscaffolds, ensuring cell adhesion and sufficient diffusion of metabolites and nutrients. Here, encapsulation of a vitamin C-loaded gel-like double emulsion using a hydrophobic emulsifier and soy particles was performed to develop a bioactive bioink for 3D printing of highly porous scaffolds with enhanced cell biocompatibility. The produced double emulsions suggested a mechanical strength with the range of elastic moduli of soft tissues possessing a thixotropic feature and recoverable matrix. The outstanding flow behavior and viscoelasticity broaden the potential of gel-like double emulsion to engineer 3D scaffolds, in which 3D constructs showed a high level of porosity and excellent shape fidelity with antiwearing and self-lubricating properties. Investigation of cell viability and proliferation using fibroblasts (NIH-3T3) within vitamin C-loaded gel-like bioinks revealed that printed 3D scaffolds offered brilliant biocompatibility and cell adhesion. Compared to scaffolds without encapsulated vitamin C, 3D scaffolds containing vitamin C showed higher cell viability after 1 week of cell proliferation. This work represented a systematic investigation of hierarchical self-assembly in double emulsions and offered insights into mechanisms that control microstructure within supramolecular structures, which could be instructive for the design of advanced functional tissues.

Insights into the Supramolecular Structure and Degradation Mechanisms of Starch from Different Botanical Sources as Affected by Extrusion-based 3D Printing.

Extrusion-based 3D printing has emerged as the most versatile additive manufacturing technique for the printing of practically any material. However, 3D printing of functional materials often activates thermo-mechanical degradation, which affects the 3D shape quality. Herein, we describe the structural changes of eight different starch sources (normal or waxy) as a consequence of the temperature of an extrusion-based 3D printing system through in-depth characterization of their molecular and structural changes. The combination of size-exclusion chromatography, small-angle X-ray scattering, X-ray diffraction, dynamic viscoelasticity measurements, and in vitro digestion has offered an extensive picture of the structural and biological transformations of starch varieties. Depending on the 3D printing conditions, either gelatinization was attained ("moderate" condition) or single-amylose helix formation was induced ("extreme" condition). The stiff amylopectin crystallites in starch granules were more susceptible to thermo-mechanical degradation compared to flexible amorphous amylose. The crystalline morphology of the starch varieties varied from B-type crystallinity for the starch 3D printing at the "moderate" condition to a mixture of C- and V-type crystallinity regarding the "extreme" condition. The "extreme" condition reduced the viscoelasticity of 3D-printed starches but increased the starch digestibility rate/extent. In contrast, the "moderate" condition increased the viscoelastic moduli, decreasing the starch digestion rate/extent. This was more considerable mainly regarding the waxy starch varieties. Finally, normal starch varieties presented a well-defined shape fidelity, being able to form a stable structure, whereas waxy starches exhibited a non-well-defined structure and were not able to maintain their integrity after printing. The results of this research allow us to monitor the degradability of a variety of starch cultivars to create starch-based 3D structures, in which the local structure can be controlled based on the 3D printing parameters.

Dual-Grafting of Microcrystalline Cellulose by Tea Polyphenols and Cationic ε-Polylysine to Tailor a Structured Antimicrobial Soy-Based Emulsion for 3D Printing.

An imperative processing way to produce 3D printed structures with enhanced multifunctional properties is printing inks in the form of a gel-like colloidal emulsion. The surface-modified microcrystalline cellulose (MCC) is an excipient of outstanding merit as a particulate emulsifier to manufacture a stable Pickering emulsion gel. The tuning of the MCC structure by cationic antimicrobial compounds, such as ε-polylysine (ε-PL), can offer a surface activity with an antimicrobial effect. However, the MCC/ε-PL lacks the appropriate emulsifying ability due to the development of electrostatic complexes. To overcome this challenge, (i) a surface-active MCC conjugate was synthesized by a sustainable dual-grafting technique (ii) to produce a highly stable therapeutic soy-based Pickering emulsion gel (iii) for potential application in 3D printing. In this regard, the tea polyphenols were initially introduced into MCC by the free-radical grafting method to decrease the charge density of anionic MCC. Then, the antioxidative MCC-g-tea polyphenols were reacted by ε-PL to produce a dual-grafted therapeutic MCC conjugate (micro-biosurfactant), stabilizing the soy-based emulsion system. The results indicated that the dual-grafted micro-biosurfactant formed a viscoelastic and thixotropic soy-based emulsion gel with reduced droplet size and long-term stability. Besides, there was an improvement in the interfacial adsorption features of soy-protein particles after micro-biosurfactant incorporation, where the interfacial pressure and surface dilatational viscoelastic moduli were enhanced. Consequently, it was revealed that the therapeutic Pickering emulsion gel was more suitable to manufacture a well-defined 3D architecture with high resolution and retained permanent deformation after unloading (i.e., a recoverable matrix). This work established that the modification of the MCC backbone by tea polyphenols and ε-PL advances its bioactive properties and emulsifying performance, which finally obtains a soy-based 3D printed structure with noteworthy mechanical strength.

A Promising Therapeutic Soy-Based Pickering Emulsion Gel Stabilized by a Multifunctional Microcrystalline Cellulose: Application in 3D Food Printing.

The feasible application of additive manufacturing in the food and pharmaceutical industries strongly depends on the development of highly stable inks with bioactive properties. Surface-modified microcrystalline cellulose (MCC) shows the potential of being a useful particulate (i.e., Pickering)-type emulsifier to stabilize emulsions. To attain desired therapeutic properties, MCC can also be tuned with cationic antimicrobial compounds to fabricate an antimicrobial printable ink. However, due to the formation of complex coacervates between the two, the Pickering emulsion is very susceptible to phase separation with an insufficient therapeutic effect. To address this drawback, we reported a green method to produce antioxidant and antimicrobial three-dimensional (3D)-printed objects, illustrated here using a printable ink based on a soy-based particulate-type emulsion gel stabilized by a surface-active MCC conjugate (micro-biosurfactant). A sustainable method for the modification of MCC is investigated by grafting gallic acid onto the MCC backbone, followed by in situ reacting via lauric arginate through Schiff-base formation and/or Michael-type addition. Our results show that the grafted micro-biosurfactant was more efficient in providing the necessary physical stability of soy-based emulsion gel. The grafted micro-biosurfactant produced a multifunctional ink with viscoelastic behavior, thixotropic property, and outstanding bioactivities. Following the 3D printing process, highly porous 3D structures with a more precise geometry were fabricated after addition of the micro-biosurfactant. Dynamic sensory evaluation showed that the micro-biosurfactant has a remarkable ability to improve the temporal perceptions of fibrousness and juiciness in printed meat analogue. The results of this study showed the possibility of the development of a therapeutic 3D-printed meat analogue with desired sensory properties, conceiving it as a promising meat analogue product.

Development of an Antioxidative Pickering Emulsion Gel through Polyphenol-Inspired Free-Radical Grafting of Microcrystalline Cellulose for 3D Food Printing.

The manufacture of next-generation 3D-printed foods with personalized requirements can be accelerated by in-depth knowledge of the development of a multifunctional biopolymeric-based ink. As a fat replacer in the food industry, microcrystalline cellulose (MCC) has the potential to address the growing need for sustainable healthy reduced-fat 3D printed foods. The modification of MCC structure by polyphenols gives the way to produce a multifunctional antioxidative Pickering emulsion with improved emulsifying properties. In this study, different types of polyphenols, including gallic acid (GA), tannic acid (TA), and cyanidin-3-O-glucoside (C3G), were individually used to synthesize the grafted MCC-g-polyphenol conjugates by the free-radical grafting method. Then, the antioxidative grafted microconjugates were added to a soy protein-based emulsion gel to partially substitute its oil, and each Pickering emulsion gel variant was printed through an extrusion-based 3D printing system. Emulsifying properties and antioxidant character of MCC were proven to be enhanced after the fabrication of grafted microconjugates. Compared to MCC-g-TA, MCC-g-GA and MCC-g-C3G could efficiently improve the stability of a reduced-fat soy-based emulsion gel upon storage. Moreover, the reduced-fat soy-based emulsion gel containing grafted microconjugates endowed a characteristic shear-thinning behavior with a gel-like structure and superlative thixotropic properties. Following the printing, the antioxidative Pickering emulsion gels containing grafted microconjugates produced well-defined 3D structures with superior lubrication properties. This study demonstrated that the grafting of polyphenols onto MCC could enhance bioactive properties and improve emulsifying performance of MCC, making it a useful component in the development of personalized functional foods.

Using distance on the Riemannian manifold to compare representations in brain and in models.

Representational similarity analysis (RSA) summarizes activity patterns for a set of experimental conditions into a matrix composed of pairwise comparisons between activity patterns. Two examples of such matrices are the condition-by-condition inner product and correlation matrix. These representational matrices reside on the manifold of positive semidefinite matrices, called the Riemannian manifold. We hypothesize that representational similarities would be more accurately quantified by considering the underlying manifold of the representational matrices. Thus, we introduce the distance on the Riemannian manifold as a metric for comparing representations. Analyzing simulated and real fMRI data and considering a wide range of metrics, we show that the Riemannian distance is least susceptible to sampling bias, results in larger intra-subject reliability, and affords searchlight mapping with high sensitivity and specificity. Furthermore, we show that the Riemannian distance can be used for measuring multi-dimensional connectivity. This measure captures both univariate and multivariate connectivity and is also more sensitive to nonlinear regional interactions compared to the state-of-the-art measures. Applying our proposed metric to neural network representations of natural images, we demonstrate that it also possesses outstanding performance in quantifying similarity in models. Taken together, our results lend credence to the proposition that RSA should consider the manifold of the representational matrices to summarize response patterns in the brain and in models.

Current Status in the Utilization of Biobased Polymers for 3D Printing Process: A Systematic Review of the Materials, Processes, and Challenges.

Three-dimensional (3D) printing is a revolutionary additive manufacturing technique that allows rapid prototyping of objects with intricate architectures. This Review covers the recent state-of-the-art of biopolymers (protein and carbohydrate-based materials) application in pharmaceutical, bioengineering, and food printing and main reinforcement approaches of biomacromolecular structure for the development of 3D constructs. Some perspectives and main important limitations with the biomaterials utilization for advanced 3D printing procedures are also provided. Because of the improved the ink's flow behavior and enhance the mechanical strength of resulting printed architectures, biopolymers are the most used materials for 3D printing applications. Biobased polymers by taking advantage of modifying the ink viscosity could improve the resolution of deposited layers, printing precision, and consequently, develop well-defined geometries. In this regard, the rheological properties of printable biopolymeric-based inks and factors affecting ink flow behavior related to structural properties of printed constructs are discussed. On the basis of successful applications of biopolymers in 3D printing, it is suggested that other biomacromolecules and nanoparticles combined with the matrix can be introduced into the ink dispersions to enhance the multifunctionality of 3D structures. Furthermore, tuning the biopolymer's structural properties offers the most common and essential approach to attain the printed architectures with precisely tailored geometry. We finish the Review by giving a viewpoint of the upcoming 3D printing process and recognize some of the existing bottlenecks facing the blossoming 3D pharmaceutical, bioengineering, and food printing applications.

Electron beam crosslinking of alginate/nanoclay ink to improve functional properties of 3D printed hydrogel for removing heavy metal ions.

A printable nanocomposite hydrogel was fabricated with intercalation of alginate into clay galleries followed by irradiation crosslinking graft copolymerization acrylic acid to remove inorganic micropollutants from wastewater. In this regard, nanocomposite-based ink was treated by electron beam irradiation (5-60 kGy), and then irradiated inks were printed using an extrusion-based printer. Structural investigates showed that ink suspension formed a crosslinked network upon irradiation, which could preserve its shape during printing and maintain 3D printed architecture. No additional post-print crosslinking was required due to the formation of free radical and remaining in printed hydrogels as shown by electron spin resonance. Printed hydrogels treated with 5 and 60 kGy irradiation experienced instrumental changes, while functional properties of 15-45 kGy irradiated samples were unaffected upon printing. Losing crystallinity and thermal instability of hydrogels after printing were inhibited through irradiation crosslinking. Metal ion adsorption capacity showed that crosslinked printed hydrogels effectively removed heavy metal ions with high-capacity and fast-responsive. Moreover, metal ions adsorption by printed hydrogels was not selective, thus they can be used to remove various metal ion pollutants from wastewater.

Relation between structural, mechanical and sensory properties of gluten-free bread as affected by modified dietary fibers.

Gluten-free bread was fortified with modified dietary fibers (wheat bran, resistant starch and inulin) and their effects on water mobility, friction coefficient, thermal behavior, crystalline pattern and textural properties were evaluated. Moreover, time-intensity evaluation was used to study temporal dynamics of sensory attributes of fortified-breads. Dietary fibers increased gelatinization temperature while decreasing gelatinization enthalpy, more notably when inulin was used. X-ray diffraction patterns of bread showed the appearance of new peaks after addition of resistant starch and wheat bran, coinciding with an increase in crumb hardness. In contrast, inulin considerably decreased starch crystallinity in the bread, resulting in a softer crumb. Faster decay and shifting of protons to shorter times were found with incorporation of dietary fibers. Friction coefficient determined by tribology measurement was higher in the breads containing resistant starch and wheat bran compared to other samples. Pearson's correlation analysis indicated the sensory attributes of firmness, chewiness and dryness were positively correlated with instrumental findings. Time-intensity evaluation revealed inulin-fortified bread had the lowest firmness and chewiness with less dryness, whereas resistant starch-fortified bread showed the highest intensity of these descriptors.

Functional characteristics, wettability properties and cytotoxic effect of starch film incorporated with multi-walled and hydroxylated multi-walled carbon nanotubes.

Two types of multi-walled carbon nanotubes (CNT and CNT-OH) at different levels (0.1-0.9wt%) were introduced into starch matrix in order to modify its functional properties. The optimum concentration of each nanotube was selected based on the results of water solubility, water permeability and mechanical experiments. The physico-mechanical data showed that CNT up to 0.7wt% led to a notable increase in water resistance, water barrier property and tensile strength, whilst regarding CNT-OH, these improvements found at 0.9wt%. Therefore, effects of optimized level of each nanotube on the starch film were evaluated by XRD, surface hydrophobicity, wettability and surface energy tests. XRD revealed that the position of starch characteristic peak shifted to higher degree after nanotubes introducing. The hydrophobic character of the film was greatly increased with incorporation of nanoparticles, as evidenced by increased contact angle with greatest value regarding CNT-OH. Moreover, CNT-OH notably decreased the surface free energy of the starch film. Finally, the conformity of both nanocomposites with actual food regulations on biodegradable materials was tested by cytotoxicity assay to evaluate the possibility of application in food packaging sector. Both nanocomposite films had potential of cytotoxic effects, since they could increase cytoplasmic lactate dehydrogenase release from L-929 fibroblast cells in contact with their surface.

Characterization of nanocomposite film based on chitosan intercalated in clay platelets by electron beam irradiation.

Different electron beam doses (10, 20, 30 and 40kGy) were tested with the purpose of investigating their influences on chitosan/clay (cloisite 20A) nanocomposite film to improve its functional performance by providing a crosslinked matrix. Water resistance, water contact angle and water barrier property of nanocomposite film were increased up to 30kGy, and then drastically decreased at the level of 40kGy. Characteristic diffraction peak of chitosan shifted to low angle with an increase in the interlayer spacing of the nanoclay after 30kGy irradiation, indicating a superlative intercalation. Crystallinity degree of chitosan/clay nanocomposite was increased in the amorphous region as the irradiation dose increased up to 30kGy. However, irradiation at level of 40kGy was converted the crystalline region of nanocomposite film to the amorphous state with losing the chitosan crystallinity. Irradiation increased the film tensile strength due to crosslinking of chitosan chains, with more pronounced effect at 30kGy and decreased it by chain degradation at 40kGy. A glass transition temperature was detected in DSC thermogram of chitosan/clay film, and it shifted to higher temperatures as the irradiation dose increased. Moreover, cold-crystallization exothermic peak of the chitosan/clay film moved to the lower temperature after irradiation, suggesting a faster crystallization rate. FE-SEM showed that the chitosan chains were more intercalated between the nanoclay platelets with increasing the irradiation dose. A progressive decrease in the roughness parameters of 20 and 30kGy irradiated nanocomposite films revealed by atomic force microscopy, whereas irradiation at 40kGy increased roughness values.

Physico-mechanical analysis data in support of compatibility of chitosan/κ-carrageenan polyelectrolyte films achieved by ascorbic acid, and the thermal degradation theory of κ-carrageenan influencing the properties of its blends.

This article presents the complementary data regarding compatibilization of chitosan/κ-carrageenan polyelectrolyte complex for synthesizing of a soft film using ascorbic acid. It includes the thermal-theory for estimating the degradation of κ-carrageenan, as reflected in alteration of the structural properties of the blend. The data has been provided to demonstrate that the blend solution based on chitosan, a polycation, and κ-carrageenan, a polyanion polymer, produces an incompatible polyelectrolyte composite, susceptible to coaservative phase separation. We present further data on water resistance, water barrier property, mechanical parameters, scanning electron micrograph, as well as contact angle image dataset of the chitosan/κ-carrageenan film. The physical data were collected by water solubility and water permeability assays, with a view to elucidate the role of ascorbic acid in the compatibility of polyelectrolyte blends. The mechanical data is obtained from a stress-strain curve for evaluation of tensile strength and elongation at break point of the chitosan/κ-carrageenan film. The microstructure observations were performed using scanning electron micrograph. These dataset confirm fabrication of a soft film in the presence of ascorbic acid, with reduced heterogeneities in the polyelectrolyte film structure. The κ-carrageenan was also treated by a thermal process, prior to inclusion into the chitosan solution, to investigate the impact of this on the mechanical and structural features of the resulting blend. We present the required data and the theoretical analysis supporting the thermal chain degradation of a polymer and its effects on behavior of the film. Additional information, characterizing the hydrophobicity of the surface of the blend layers is obtained by measuring water contact angles using a contact anglemeter.

Kinetic study of κ-carrageenan degradation and its impact on mechanical and structural properties of chitosan/κ-carrageenan film.

The purpose of the current research was to study κ-carrageenan degradation behavior under thermal treatment, and its influence on chitosan κ-carrageenan film properties. A pseudo-first-order reaction equation was applied by using reciprocal plots of κ-carrageenan molecular mass versus heating time, which showed a strong dependence on heating time. Incorporation of thermally treated κ-carrageenan into the chitosan had diminished both water resistance and water vapor permeability of the blend, in contrast to those for intact or untreated κ-carrageenan. A dramatic decrease of equilibrium moisture content and tensile strength were noticed, and these parameters were more affected by the longer times. Furthermore, the contact angle of the films was found to be a function of the heating time. Scanning electron microscopy revealed apparent agglomeration of κ-carrageenan through the thermal process. Atomic force microscopy demonstrated that the intact blend had the flattest surface, whilst the blend containing treated κ-carrageenan had high roughness.