Crosslinker Concentration Research Articles

Effects of Modified Cross-Linkers on the Rheology of Water-Based Fracturing Fluids and Reservoir Water Environment

Improving the chemical structure of the cross-linker is a potential method for reducing reservoir pollution and enhancing the fracturing efficiency of shale reservoirs. In this investigation, a three-dimensional (3-D) spherical cross-linker comprising branched chains was synthesized, and the 3-D structure of the cross-linker was analyzed through scanning electron microscopy (SEM). Furthermore, we constructed a multifunctional coupled collaborative evaluation device that can be used to evaluate numerous properties associated with water-based fracturing fluids, including fluid viscosity, adsorption capacity, and water pollution. Meanwhile, the influence of varying reservoir conditions and cross-linker content on the fluid viscosity of water-based fracturing fluids and the potential for reservoir contamination has been evaluated and elucidated. The results indicated that the synthesized cross-linker exhibited a superior environmental protection of the shale reservoir and an enhanced capacity for thickening fracturing fluids in comparison to commercial cross-linkers. Moreover, cross-linker content, reservoir temperature, reservoir pressure, and fracture width can affect fluid viscosity and reservoir residual in different trends. The addition of 0.3% nano-cross-linker (Synthetic products) to a water-based fracturing fluid resulted in an apparent viscosity of 160 mPa·s at 200 °C, and the adsorption capacity and water content of the shale reservoir were only 0.22 µg/m3 and 0.05 µg/L, respectively. Additionally, an elevation in reservoir temperature resulted in a reduction in the adsorption capacity. However, the cross-linker content in groundwater underwent a notable increase, and the cross-linker residue in water increased by 0.009 µg/L. The impact of reservoir pressure on fluid viscosity and groundwater pollution potential exhibited an inverse correlation compared to that of reservoir temperature, and the above two parameters changed by +18 mPa·s and −0.012 µg/L, respectively. This investigation provides basic data support for the efficient fracturing and reservoir protection of shale reservoirs.

Kinetic principles of chemical cross-link formation for protein–protein interactions

Proteins play a central role in most biological processes within the cell, and deciphering how they interact is key to understand their function. Cross-linking coupled with mass spectrometry is an essential tool for elucidating protein-protein interactions (PPIs). Despite its importance, we still know surprisingly little about the principles that underlie the process of chemical cross-link formation itself and how it is influenced by different physicochemical factors. To understand the molecular details of cross-link formation, we have set up a comprehensive kinetic model and carried out simulations of protein cross-linking on large protein complexes. We dissect the contribution on the cross-link yield of parameters such as amino acid reactivity, cross-linker concentration, and hydrolysis rate. Our model can compute cross-link formation based solely on the structure of a protein complex, thereby enabling realistic predictions for a diverse set of systems. We quantitatively show how cross-links and mono-links are in direct competition and how the hydrolysis rate and abundance of cross-linker and proteins directly influence their relative formation. We show how cross-links and mono-links exist in an "all-against-all" competition due to their simultaneous formation, resulting in a nonintuitive network of interdependence. We show that this interdependence is locally confined and mainly limited to direct neighbors or residues in direct vicinity. These results enable us to identify the optimal cross-linker concentration at which the maximal number of cross-links is formed. Taken together, our study establishes a comprehensive kinetic model to quantitatively describe cross-link formation for PPIs.

Influence of copper ion cross-linked CMC-PVA film on cell viability and cell proliferation study

In this study, films composed of carboxymethyl cellulose and polyvinyl alcohol were fabricated using the solution casting method. Citric acid (4 %) was employed as a cross-linking agent, while glycerol (3 %) as a plasticizer. Cupric chloride (CuCl2·2H2O) was used for cross-linking at concentrations 0.5 %, 1 %, and 3 % over different times. The cross-linking with copper ions led to a noticeable reduction in elasticity, with the breaking strain ranging from 17.9 %–52.9 %. The ion hydration phenomenon increased the contact angle and swelling ratio. Fourier-transform infrared (FTIR) spectroscopy confirmed esterification reactions and copper ion cross-linking with sodium carboxymethyl cellulose (Na-CMC). The films showed antibacterial activity against Staphylococcus aureus and Escherichia coli. The ion-released mechanism followed was the non-Fickian super case-II type. The concentration and duration of cross-linking significantly influenced cell viability and proliferation. FE-SEM analysis revealed that effective concentrations of CuCl2.2H2O were 0.5 % and 1 %, and cross-linking times were 5–15 min, facilitating cell attachment and proliferation. Films are non-adhesive with water vapor permeation 800–900 g/m2/day. These results indicate the potential use of the films in treating second-degree burn wounds with low to medium exudate levels. This study provides valuable insights into the development of copper-infused materials for advanced wound healing applications.

Tailoring Dielectric Properties and Dimensional Stability of Poly(Phenylene Ether) Using Bismaleimide Crosslinkers for High-Frequency PCB Applications.

With the increasing demand for high-performance printed circuit boards (PCBs) in the 6G communication era, dielectric substrate materials must exhibit a low dielectric constant (Dk), low dielectric loss (Df), and high dimensional stability. In this study, a series of bismaleimide-incorporated poly(phenylene ether) resins (PPE-BMI) with varying bismaleimide (BMI) crosslinker contents is developed, exhibiting significantly enhanced dielectric properties and dimensional stability, owing to the restricted polymer chain mobility and increased crosslinking density. Dielectric property measurements reveal that the PPE-BMI resins exhibit low Dk and Df values at frequencies above 100GHz, while maintaining an excellent dielectric performance even after an 85 °C/85% relative humidity reliability test. A significant reduction in the coefficient of thermal expansion is observed with an increase in the BMI content. Molecular dynamics simulations are employed to clarify the role of BMI crosslinkers in reducing the free volume, enhancing the crosslinking in the PPE (poly(phenylene ether)) matrix, and influencing the thermophysical properties of PPE-BMI. The infiltration of PPE-BMI into glass fabrics and liquid crystal fabrics highlights their potential for practical use in advanced PCB applications operating at high frequencies.

Preparation of Hydrogels of Methacrylamide with Mono and Dicarboxylic Acids: Investigation of Their Swelling Behavior

Methacrylamide (MAAm) hydrogels were synthesized with mono- (crotonic acid, CrA) and dicarboxylic (maleic acid, MAA) acids via radical copolymerization, utilizing potassium persulfate (KPS) as the initiator and methylenebisacrylamide (MBAAm) as the crosslinker. The swelling behavior of the resulting hydrogels was systematically investigated, with particular focus on the effects of monomer ratio, initiator and crosslinker concentrations, as well as polymerization temperature. These parameters were optimized to maximize the swelling ratio. For poly(MAAm/CrA) hydrogels, the formulation containing 85/15 MAAm/CrA (mol/mol), 2 mol% KPS, 1 mol% MBAAm, and synthesized at 55 °C exhibited the highest swelling capacity (480%) in distilled water. In contrast, for poly(MAAm/MAA) hydrogels, the composition of 75/25 MAAm/MAA (mol/mol) with 1 mol% KPS, 1 mol% MBAAm, and polymerized at 55 °C showed a maximum swelling of 1100%. Further investigations explored the influence of pH, temperature, and electrolyte concentration and type on the swelling properties of the hydrogels prepared under optimized conditions. Both hydrogels demonstrated peak swelling behavior at pH 7, with their swelling profiles varying in response to changes in temperature, electrolyte concentration, and electrolyte type. Swelling kinetics studies revealed that the MAAm/CrA hydrogel exhibited Fickian diffusion in distilled water at room temperature, while the MAAm/MAA hydrogel followed a non-Fickian diffusion mechanism. Scanning electron microscopy (SEM) analysis indicated that the hydrogels synthesized under optimal conditions possessed a porous and well-organized network structure.

Less Is More: Influence of Cross-Linking Agent Concentration on PFOS Adsorption in Chitosan

Less Is More: Influence of Cross-Linking Agent Concentration on PFOS Adsorption in Chitosan

Hybrid Chitosan Biosorbents: Tunable Adsorption at Surface and Micropore Domains

Herein, we report a study that provides new insight on the knowledge gaps that relate to the role of biopolymer structure and adsorption properties for chitosan adsorbents that are cross-linked with glutaraldehyde. The systematic modification of chitosan cross-linked with glutaraldehyde (CG) and its quaternized forms (QCG) was studied in relation to the reaction conditions: mole ratios of reactants and pH conditions. Complementary adsorbent characterization employed 13C NMR/FTIR spectroscopy, TGA and DSC, point-zero-charge (PZC), solvent swelling, and sorption studies using selected dye probes. The spectral and thermal techniques provide complementary evidence that affirm the key role of cross-linker content and quaternization on variation of the physicochemical properties of chitosan. The PZC results reveal a neutral surface charge for the modified materials between pH 6.0 to 6.3 ± 0.3, as compared with pH 8.7 ± 0.4 for pristine chitosan. Solvent swelling in water decreased with greater cross-linking, while the QCG materials had greater swelling over CG materials due to enhanced hydration. The adsorption results reveal variable dye uptake properties according to the cross-linker content. Similarly, surface versus micropore adsorption was demonstrated, according to the nature and ionization state of the dye for the modified adsorbents, where the CG and QCG materials had tunable sorption properties that exceeded that of unmodified chitosan. A key step in tuning the structure and surface chemical properties of cross-linked chitosan involves pH control during synthesis. The facile tunability of the physicochemical properties of the modified biopolymers reported herein means that they possess features of biomimetics that are relevant to advanced drug delivery, antimicrobial materials for wound healing, biosensors, and biosorbents for biomedical applications.

Exploring the potential of a pH-sensitive hydrogel sponge: interpenetrating network of tragacanth and pectin for controlled delivery of levosulpiride.

The development of drug delivery systems that allow precise control over drug release pattern has fetched significant attention in the pharmaceutical field. This research work investigates the potential of a pH-sensitive interpenetrating network (IPN) composed of tragacanth and pectin as a carrier for the controlled release of levosulpiride. To enhance the solubility of poorly soluble drug levosulpiride, inclusion complexes were formed with beta cyclodextrin (βCD). The IPN was prepared by cross-linking tragacanth with pectin by adopting a green chemistry approach. The resulting cross-linked polymeric network was subjected to repetitive freeze-drying cycles for preparation of spongy mass. The physicochemical properties of the resultant product were thoroughly characterized using a range of analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal analyses (DSC/TGA), and X-ray diffraction (XRD). The physical parameters like sol-gel fraction (%), drug loading (%), swelling behavior, electrolyte responsiveness, and in vitro drug release profile of the developed sponge were systematically evaluated under varying pH conditions. Results of FTIR demonstrated the formation of cross-linked network, ruling out drug-excipient interaction. SEM analysis unveiled porous and rough geometry. Thermal analyses proved the hydrogel network thermally stable whereas, PXRD demonstrated the overall amorphous nature of the hydrogel sponge. The outcomes of physical parameters demonstrated an incremental trend in gel fraction from 63 to 85% on raising the molar concentration of cross-linker from TP1 to TP3. However, increasing tragacanth content escalation in gel fraction from 75 to 79% was noticed. While gel fraction was augmented from 79 to 83% with increasing pectin contents. The maximum drug loading formulation TP3 was computed to be 89%. Hydrogel sponges also demonstrated electrolyte responsiveness. The release profile indicated a pH-responsive behavior, with sustained release up to 10h observed in a buffer solution of pH 6.8 and 7.4. In an acidic medium, a minor amount of drug was released during 10h dissolution. Drug release kinetics was observed to be in zero order. The findings of this study highlight the promising potential of the tragacanth/pectin hydrogel sponge as a pH-sensitive dais for the controlled delivery of levosulpiride, emphasizing its potential application in personalized drug therapy and the treatment of gastrointestinal disorders.

Investigation of In Situ Gelation Behavior and Enhanced Oil Recovery Ability of Polymer Gel Used for Controlling CO2 Channeling in Tight Fractured Reservoir.

Polymer gels are one of the most common plugging agents used for controlling CO2 channeling and improving sweep efficiency and oil recovery in tight fractured reservoirs. However, the in situ gelation behavior and enhanced oil recovery ability of polymer gel in fractured porous media is still unclear. Thus, in this study, the bulk and in situ gelation behavior of crosslinked phenolic resin gel in a long stainless microtube as the fractured porous media was investigated. The enhanced oil recovery ability of phenolic resin gel used for CO2 channeling was investigated by means of a fractured core model. Results show that, with the increase of polymer and crosslinker concentrations, the bulk gelation time shortens and gel strength improves during the static gelation process. With the increase of polymer concentration and temperature, the in situ static gelation time and dynamic gelation time of the gel system in the microtube are shortened, and the breakthrough pressure gradient increases after gelation. Compared with the in situ static gelation behavior, the in situ dynamic gelation time is prolonged and the breakthrough pressure gradient decreases after gelation. The in situ static gelation time in the microtube is 1.2 times that of bulk gelation time in an ampoule bottle, and the in situ dynamic gelation time is nearly 3 times that of ampoule bottles. When the injected slug volume was 1.0 FV (fracture volume), as the polymer concentration increased from 3000 mg·L-1 to 4000 mg·L-1, the incremental oil recovery increased from 3.53% to 4.73%.

Effect of N,N′-Methylenebisacrylamide on properties of porous semi-IPN hydrogels from Acrylamide, Maleic Acid, and its use for Urea absorption

Hydrogel is a three-dimensional polymer that can absorb large amounts of reagents while maintaining structural integrity. This material has been applied in many fields especially in smart agriculture. To improve the economic viability, the reusability of hydrogels in agricultural engineering over multiple cycles of adsorption and desorption is an urgent requirement. This can be solved if the crosslinker is used properly. Therefore, in this work, a series of porous semi-IPN hydrogels based on linear polyacrylamide, acrylamide, maleic acid, and N,N′-methylenebisacrylamide (MBA) were synthesized. The hydrogels were evaluated for the impact of MBA content on the characteristics and applicability as a urea fertilizer carrier. The chemical composition, morphology, mechanical, and rheological properties, swelling behavior, urea absorption and desorption of hydrogels with crosslinker content in the range of 0.5-2.0 % were investigated. The porous structure was confirmed by scanning electron microscopy images. Changing the MBA content significantly affected all characteristics of the hydrogels. In particular, increasing the MBA content decreased the equilibrium swelling ratios in all investigated environments. The maximum amount of urea loaded into the hydrogel was also reduced from 435.88 to 188.50 mg/g. This increase also changed the swelling mechanism from non-Fickian to Fickian, whereas the urea release mechanism changed from Fickian to non-Fickian. Finally, the hydrogels demonstrated stability in soil over multiple cycles of water absorption and release. This study provides valuable insights into designing a semi-IPN hydrogel with desired properties that meet the application requirements of modern farming techniques.

In vitro bioprinted 3D model enhancing osteoblast-to-osteocyte differentiation

In vitrobone models are pivotal for understanding tissue behavior and cellular responses, particularly in unravelling certain pathologies' mechanisms and assessing the impact of new therapeutic interventions. A desirablein vitrobone model should incorporate primary human cells within a 3D environment that mimics the mechanical properties characteristics of osteoid and faithfully replicate all stages of osteogenic differentiation from osteoblasts to osteocytes. However, to date, no bio-printed model using primary osteoblasts has demonstrated the expression of osteocytic protein markers. This study aimed to develop bio-printedin vitromodel that accurately captures the differentiation process of human primary osteoblasts into osteocytes. Given the considerable impact of hydrogel stiffness and relaxation behavior on osteoblast activity, we employed three distinct cross-linking solutions to fabricate hydrogels. These hydrogels were designed to exhibit either similar elastic behavior with different elastic moduli, or similar elastic moduli with varying relaxation behavior. These hydrogels, composed of gelatin (5% w/v), alginate (1%w/v) and fibrinogen (2%w/v), were designed to be compatible with micro-extrusion bioprinting and proliferative. The modulation of their biomechanical properties, including stiffness and viscoelastic behavior, was achieved by applying various concentrations of cross-linkers targeting both gelatin covalent bonding (transglutaminase) and alginate chains' ionic cross-linking (calcium). Among the conditions tested, the hydrogel with a low elastic modulus of 8 kPa and a viscoelastic behavior over time exhibited promising outcomes regarding osteoblast-to-osteocyte differentiation. The cessation of cell proliferation coincided with a significant increase in alkaline phosphatase activity, the development of dendrites, and the expression of the osteocyte marker PHEX. Within this hydrogel, cells actively influenced their environment, as evidenced by hydrogel contraction and the secretion of collagen I. This bio-printed model, demonstrating primary human osteoblasts expressing an osteocyte-specific protein, marks a significant achievement. We envision its substantial utility in advancing research on bone pathologies, including osteoporosis and bone tumors.

SnO2 Encapsulated in Alginate Matrix: Evaluation and Optimization of Bioinspired Nanoadsorbents for Azo Dye Removal.

Synthesized SnO2 nanoparticles (NPs) demonstrate potential capacity to adsorb toxic azo Congo red dye. The formation of rutile phase SnO2 NPs was confirmed using Powder X-ray diffraction and spherical morphology was corroborated through SEM imaging. TEM analysis confirms average particle size of SnO2 NPs is nearly 3 nm. High azo dye removal efficiency is attributed to large surface area and presence of oxygen vacancies which were substantiated through BET and XPS analysis, respectively. To mitigate the leaching of NPs in treated water, NPs are encapsulated in sodium alginate (SA) matrix, which is proposed as an environmentally friendly, biocompatible, and economic solution. This study specifically focuses on investigating the parameters for the encapsulation of NPs within a sodium alginate matrix using CaCl2 as cross-linker. This work investigates the effect of physical shape of encapsulation, effect of SA and cross-linker (CaCl2) concentration on the feasibility of NP encapsulation and overall adsorption efficiency. Experimental results indicated that the physical form of encapsulation, such as spherical, wire-like, or irregular shape maintained consistent adsorption efficiency, which indicates its versatility. For effective encapsulation of NPs and adsorption, SA and CaCl2 concentration are suggested to be within the range of 0.2-0.3 g and >0.5 M, respectively.

Toward a Plasmon-Based Biosensor throughout a Thermoresponsive Hydrogel.

This study investigates the potential of thermoresponsive hydrogels as innovative substrates for future in vitro diagnostic (IVD) applications using AVAC technology, developed and patented by the Mecwins biomedical company. In order to convert the hydrogel in a substrate compatible with AVAC technology, the following prerequisites were established: (1) the hydrogel layer needs to be permeable to gold nanoparticles (AuNPs), and (2) the optical properties of the hydrogel should not interfere with the detection of AuNPs with AVAC technology. These two key aspects are evaluated in this work. A silicon substrate (Sil) was coated with a layer of a thermosensitive hydrogel (TSH) based on poly(N-isopropylacrylamide-co-N,N'-methylene bis(acrylamide) (PNIPAAm-co-MBA). The TSH offers the advantage of easy modulation of its porosity through cross-linker adjustments, crucial for the plasmonic nanoparticle (NP) permeation. The platforms, denominated as (Sil)-g-(PNIPAAm-co-MBA), were fabricated by changing the cross-linker concentrations and exploring three deposition methods: drop casting (DC), spin coating (SC), and 3D printing (3D); the DC approach resulted in a very homogeneous and thin hydrogel layer, very suitable for the final application. Furthermore, after physical-chemical characterization, the TSH demonstrated its functionality in regulating nanoparticle absorption, and AVAC technology's capability to precisely identify such NPs through the hydrogel matrix was validated. The proposed hydrogel platform fulfills the initial requirements, opening the possibility for employing these hydrogels as dynamic substrates in sandwich immunoassay devices. The next step in the development of the hydrogel substrate would be its functionalization with biorecognition groups to allow for biomarker detection. By leveraging their enhanced capture efficiency and the ability to manipulate particle flow thermally, we anticipate a significant advancement in diagnostic methodologies, combining the spatial benefits of three-dimensional hydrogel structures with the precision of AVAC's digital detection.

Tunable macroscopic self-healing of supramolecular gel through host–guest inclusion

Supramolecular gels (SGs) consisted of noncovalent cross-linking network structures are fascinating due to their efficient energy dissipation and reversible self-healing properties. However, it is unknown how the noncovalent interactions alter the macroscopic self-healing and mechanical properties of SGs. Herein, the peculiar nature of SGs manufactured by combining covalent and noncovalent (host–guest inclusion of β-cyclodextrin and C16 hydrophobic chain) cross-linking structures was studied and compared with covalent cross-linking preformed particle gels. The macroscopic self-healing behaviors, rheology, mechanical tensile properties, as well as the tunable mechanisms of self-healing were explored by visual inspection, rheological, and atomic force microscopy probing methods. The results show that the SGs exhibit excellent self-healing efficiency and mechanical strength after interfacial cutting. Moreover, the SGs exhibited excellent mechanical tensile properties, including loading–unloading, successive loading–unloading, and recovery loading–unloading tensile performances. Notably, the macroscopic self-healing of SGs has good tunability by changing the covalent and noncovalent crosslinker contents and salt contents. This peculiar phenomenon is attributed to certain host–guest inclusion forces (4.7 and 0.3 nN) between different SGs under the distilled and high-salinity water conditions, respectively. This study is beneficial for the development of stimuli–response supramolecular gels in different applications, such as oil recovery in fractured reservoirs.

3D-printed artificial cornea featuring aligned fibrous structure and enhanced mechanical strength

The global shortage of donor eye bank tissue has significantly impeded advancements in biomaterial for corneal implantation. To address this issue, we have developed a 3D-printed artificial cornea using a composite hydrogel of sodium alginate (SA) and cellulose nanofibers (CNF), crosslinked with poly-L-lysine-co-L-glutamic acid (PLL80GA20, PG) and calcium chloride (CaCl2, CC). The 2 wt% SA/CNF composite hydrogel offers several advantages, including low toxicity, cost-effectiveness, excellent printability, and high mechanical strength, even with low crosslinker concentrations. The PG was synthesized via ring-opening polymerization of L-glutamate N-carboxyl anhydride (BGNCA) and L-lysine N-carboxyl anhydride (CBZNCA). The purity of the monomers was verified through DSC analysis, revealing a melting point of 97 ℃. The molecular weight of the synthesized PG was determined to be 47 kDa. A dual crosslinking strategy was employed, starting with electrostatic crosslinking, followed by ionic crosslinking using varying concentrations of PG and CC at different effective charge concentrations of 6.25 mM, 12.25 mM, and 25 mM. The hydrogel and 3D-printed cornea were comprehensively evaluated for chemical structure, surface functional groups, water content, mechanical strength, orientation, cytotoxicity, biocompatibility, and transparency. Notably, the inclusion of PG significantly enhanced the mechanical properties of the 3D-printed cornea, with the hydrogel achieving a storage modulus of 2,360 kPa at 6.25 mM of PG/CC, while maintaining over 95% water content. The artificial cornea demonstrated 86% transparency, and the cell viability showed 96% viable on Day 7 with degradation rate of 35.9% in 28 days. The superior hydrophilicity, transparency, and mechanical strength of the printed hydrogel highlights its potential for the development of full-thickness corneal structures, making it a promising candidate for future corneal implants.

The Effect of Carbodiimide Crosslinkers on Gelatin Hydrogel as a Potential Biomaterial for Gingival Tissue Regeneration.

Connective tissue grafts for gingival recession treatment present significant challenges as they require an additional surgical site, leading to increased morbidity, extended operative times, and a more painful postoperative recovery for patients. Gelatin contains the arginine-glycine-aspartic acid (RGD) sequence, which supports cell adhesion and interactions. The development of gelatin hydrogels holds significant promise due to their biocompatibility, ease of customization, and structural resemblance to the extracellular matrix, making them a potential candidate for gingival regeneration. This study aimed to assess the physical and biological properties of crosslinked gelatin hydrogels using EDC/NHS with two crosslinker concentrations (GelCL12 and GelCL24) and compare these to non-crosslinked gelatin. Both groups underwent morphological, rheological, and chemical analysis. Biological assessments were conducted to evaluate human gingival fibroblast (HGF) proliferation, migration, and COL1 expression in response to the scaffolds. The crosslinked gelatin group exhibited greater interconnectivity and better physical characteristics without displaying cytotoxic effects on the cells. FTIR analysis revealed no significant chemical differences between the groups. Notably, the GelCL12 group significantly enhanced HGF migration and upregulated COL1 expression. Overall, GelCL12 met the required physical characteristics and biocompatibility, making it a promising scaffold for future gingival tissue regeneration applications.

The e-Flower: A hydrogel-actuated 3D MEA for brain spheroid electrophysiology.

Traditional microelectrode arrays (MEAs) are limited to measuring electrophysiological activity in two dimensions, failing to capture the complexity of three-dimensional (3D) tissues such as neural organoids and spheroids. Here, we introduce a flower-shaped MEA (e-Flower) that can envelop submillimeter brain spheroids following actuation by the sole addition of the cell culture medium. Inspired by soft microgrippers, its actuation mechanism leverages the swelling properties of a polyacrylic acid hydrogel grafted to a polyimide substrate hosting the electrical interconnects. Compatible with standard electrophysiology recording systems, the e-Flower does not require additional equipment or solvents and is ready to use with preformed 3D tissues. We designed an e-Flower achieving a curvature as low as 300 micrometers within minutes, a value tunable by the choice of reswelling media and hydrogel cross-linker concentration. Furthermore, we demonstrate the ability of the e-Flower to detect spontaneous neural activity across the spheroid surface, demonstrating its potential for comprehensive neural signal recording.

Curcumin-loaded lignin nanoparticles: Exploring sonication effects on drug loading and particle properties for future biomedical use

The present study investigates the effects of sonication and cross-linker (oxalic acid) concentration on drug loading and the properties of curcumin-loaded lignin nanoparticles. Selected samples were further assessed for their toxicity and antioxidant potential using the eukaryotic model organism Saccharomyces cerevisiae. Transmission electron microscopy analyses revealed the formation of spherical nanoparticles with diameters in the range of 39–49 nm. Differential scanning calorimetry experiments confirmed the encapsulation of curcumin. Factorial experimental design analyses indicated that sonication time, wave amplitude, cross-linker concentration, and their interactions significantly influenced both ζ-potential – from (−37.0 ± 1.7) mV to (−48.4 ± 0.6) mV – and curcumin loading – from (3.70 ± 0.32) % to (7.10 ± 0.57) %. These parameters are critical for biomedical applications as they relate to the clearance of nanoparticles from the human bloodstream and drug dosage optimization. Although sonication has been previously reported for the preparation of lignin nanoparticles, this study represents the first documented instance of manipulating drug loading by controlled sonication parameters. While none of the investigated factors significantly affected the mean particle diameter, observations from TEM micrographs suggest that cross-linker concentration and wave amplitude notably influence nanoparticle morphology. Moreover, the curcumin-loaded nanoparticles exhibited non-toxicity toward Saccharomyces cerevisiae and demonstrated the ability to enhance yeast cell tolerance to H2O2-induced oxidative stress, underscoring their antioxidant potential. Therefore, this research significantly contributes to the scientific understanding of how the control of sonication parameters and cross-linkers can modulate the properties of curcumin-loaded lignin nanoparticles for future biomedical applications.

Cross-Linker Architectures Impact Viscoelasticity in Dynamic Covalent Hydrogels.

Dynamic covalent cross-linked (DCC) hydrogels represent a significant advance in biomaterials for regenerative medicine and mechanobiology, offering viscoelasticity, and self-healing properties that more closely mimic in vivo tissue mechanics than traditional, predominantly elastic, covalent hydrogels. However, the effects of varying cross-linker architecture on DCC hydrogel viscoelasticity have not been thoroughly investigated. This study introduces hydrazone-based alginate hydrogels to explore how cross-linker architectures impact stiffness and viscoelasticity. In hydrogels with side-chain cross-linker (SCX), higher cross-linker concentrations enhance stiffness and decelerate stress relaxation, while an off-stoichiometric hydrazine-to-aldehyde ratio reduces stiffness and shortens relaxation time. In hydrogels with telechelic cross-linking, maximal stiffness and relaxation time occurs at intermediate cross-linker mixing ratio for both linear cross-linker (LX) and star cross-linker (SX), with higher cross-linker valency further enhancing these properties. Further, the ranges of stiffness and viscoelasticity accessible with the different cross-linker architectures are found to be distinct, with SCX hydrogels leading to slower stress relaxation relative to the other architectures, and SX hydrogels providing increased stiffness and slower stress relaxation versus LX hydrogels. This research underscores the pivotal role of cross-linker architecture in defining hydrogel stiffness and viscoelasticity, providing insights for designing DCC hydrogels with tailored mechanical properties for specific biomedical applications.

Formulation-Property Effects in Novel Injectable and Resilient Natural Polymer-Based Hydrogels for Soft Tissue Regeneration

The development of injectable hydrogels for soft tissue regeneration has gained significant attention due to their minimally invasive application and ability to conform precisely to the shape of irregular tissue cavities. This study presents a novel injectable porous scaffold based on natural polymers that undergoes in situ crosslinking, forming a highly resilient hydrogel with tailorable mechanical and physical properties to meet the specific demands of soft tissue repair. By adjusting the formulation, we achieved a range of stiffness values that closely mimic the mechanical characteristics of native tissues while maintaining very high resilience (>90%). The effects of gelatin, alginate, and crosslinker concentrations, as well as porosity, on the hydrogel’s properties were elucidated. The main results indicated a compression modulus range of 2.7–89 kPa, which fits all soft tissues, and gelation times ranging from 5 to 30 s, which enable the scaffold to be successfully used in various operations. An increase in gelatin and crosslinker concentrations results in a higher modulus and lower gelation time, i.e., a stiffer hydrogel that is created in a shorter time. In vitro cell viability tests on human fibroblasts were performed and indicated high biocompatibility. Our findings demonstrate that these injectable hydrogel scaffolds offer a promising solution for enhancing soft tissue repair and regeneration, providing a customizable and resilient framework that is expected to support tissue integration and healing with minimal surgical intervention.