Cobalt/Bioglass Nanoparticles Enhanced Dermal Regeneration in a 3-Layered Electrospun Scaffold

Purpose

Due to the multilayered structure of the skin tissue, the architecture of its engineered scaffolds needs to be improved. In the present study, 45s5 bioglass nanoparticles were selected to induce fibroblast proliferation and their protein secretion, although cobalt ions were added to increase their potency.

Methods

A 3-layer scaffold was designed as polyurethane (PU) - polycaprolactone (PCL)/ collagen/nanoparticles-PCL/collagen. The scaffolds examined by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), tensile, surface hydrophilicity and weight loss. Biological tests were performed to assess cell survival, adhesion and the pattern of gene expression.

Results

The mechanical assay showed the highest young modulus for the scaffold with the doped nanoparticles and the water contact angle of this scaffold after chemical crosslinking of collagen was reduced to 52.34±7.7°. In both assessments, the values were statistically compared to other groups. The weight loss of the corresponding scaffold was the highest value of 82.35±4.3 % due to the alkaline effect of metal ions and indicated significant relations in contrast to the scaffold with non-doped particles and bare one (P value<0.05). Moreover, better cell expansion, greater cell confluence and a lower degree of toxicity were confirmed. The up-regulation of TGF β1 and VEGF genes introduced this scaffold as a better model for the fibroblasts commitment to a new skin tissue among bare and nondoped scaffold (P value<0.05).

Conclusion

The 3-layered scaffold which is loaded with cobalt ions-bonded bioglass nanoparticles, is a better substrate for the culture of the fibroblasts.

The role of three-dimensional scaffolds based on polyglycerol sebacate/ polycaprolactone/ gelatin in the presence of Nanohydroxyapatite in promoting chondrogenic differentiation of human adipose-derived mesenchymal stem cells

BACKGROUND

Tissue engineering for cartilage regeneration has made great advances in recent years, although there are still challenges to overcome. This study aimed to evaluate the chondrogenic differentiation of human adipose-derived mesenchymal stem cells (hADSCs) on three-dimensional scaffolds based on polyglycerol sebacate (PGS) / polycaprolactone (PCL) / gelatin(Gel) in the presence of Nanohydroxyapatite (nHA).

MATERIALS AND METHODS

In this study, a series of nHA-nanocomposite scaffolds were fabricated using 100:0:0, 60:40:0, and 60:20:20 weight ratios of PGS to PCL: Gel copolymers through salt leaching method. The morphology and porosity of prepared samples was characterized by SEM and EDX mapping analysis. Also, the dynamic contact angle and PBS adsorption tests are used to identify the effect of copolymerization and nanoparticles on scaffolds' hydrophilicity. The hydrolytic degradation properties were also analyzed. Furthermore, cell viability and proliferation as well as cell adhesion are evaluated to find out the biocompatibility. To determine the potential ability of nHA-nanocomposite scaffolds in chondrogenic differentiation, RT-PCR assay was performed to monitor the expression of collagen II, aggrecan, and Sox9 genes as markers of cartilage differentiation.

RESULTS

The nanocomposites had an elastic modulus within a range of 0.71-1.30 MPa and 0.65-0.43 MPa, in dry and wet states, respectively. The PGS/PCL sample showed a water contact angle of 72.44 ± 2.2°, while the hydrophilicity significantly improved by adding HA nanoparticles. It was found from the hydrolytic degradation study that HA incorporation can accelerate the degradation rate compared with PGS and PGS/PCL samples. Furthermore, the in vitro biocompatibility tests showed significant cell attachment, proliferation, and viability of adipose-derived mesenchymal stem cells (ADMSCs). RT-PCR also indicated a significant increase in collagen II, aggrecan and Sox9 mRNA levels.

CONCLUSIONS

Our findings demonstrated that these nanocomposite scaffolds promote the differentiation of hADSCs into chondrocytes possibly by the increase in mRNA levels of collagen II, aggrecan, and Sox9 as markers of chondrogenic differentiation. In conclusion, the addition of PCL, Gelatin, and HA into PGS is a practical approach to adjust the general features of PGS to prepare a promising scaffold for cartilage tissue engineering.

Design and manufacture of 3D-cylindrical scaffolds based on PLA/TPU/n-HA with the help of dual salt leaching technique suggested for use in cancellous bone tissue engineering

A series of 3-D scaffolds based on polylactic acid (PLA) and thermoplastic polyurethane (TPU) as major phase and hydroxyapatite nanoparticles (n-HA) were prepared by using the dual leaching technique. Fourier-transform infrared spectroscopy analysis showed that almost the interactions between the constituent materials can be identified based on their functional groups. The results of thermogravimetric analysis were used to obtain the best time to prepare the samples without residual of any progen additives. The scanning electron macroscopy images clearly proved that the dual leaching technique is an effective method to prepare the appropriate morphology and also a very good dispersion and distribution for n-HA can be obtained. Dynamic contact angles showed that the presence of TPU in the PLA matrix has a positive effect on the hydrophilicity of the scaffolds. The bulk modulus (κ) values of S-PLA70TPU30H5 in dry and wet conditions were 321 and 212 Pa, respectively and the compressibility coefficient (β) of pure samples was higher than that of other scaffolds, while among the nanocomposite samples, the compressibility coefficient of S-PLA70TPU30H5 and S-PLA50TPU50H5 samples in dry and wet conditions was higher than that of other samples. Biological tests such as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium reduction assay, cell adhesion, 4',6-diamidino-2-phenylindole (DAPI) analysis and alizarin red were also performed, and the results obtained for 3D scaffolds were good. In the DAPI analysis test, sample 3D-S-PLA70TPU30H5 showed good behavior, and also in the alizarin red test, the amount of minerals created in 3D-S-PLA50TPU50H5 was significant.

Preparation and characterization of a new sustainable bio-based elastomer nanocomposites containing poly(glycerol sebacate citrate)/chitosan/n-hydroxyapatite for promising tissue engineering applications

Poly (glycerol sebacate citrate) (PGSC) has potential applications in tissue engineering due to its biodegradability and suitable elasticity. However, its applications are restricted owing to its acidity and high degradation rate. In this study, a new bio-nanocomposite based on PGSC has been synthesized by incorporating chitosan (CS) and various concentrations of hydroxyapatite nanoparticles (n-HA). It is assumed that the basicity of a CS and hydroxyl groups of n-HA will reduce the acidity of PGSC and control the rate of degradation. Also, the biocompatibility of n-HA and inherent hydrophilicity of CS can improve cell adhesion and proliferation of PGSC-based scaffolds. FTIR, XRD, FESEM, and EDX tests confirmed the synthesis of these nanocomposites and the interaction between each of the components. The results of the DMTA test also indicated the elastic behavior of the samples embedded with n-HA. The hydrophilicity assay demonstrated that the water contact angle of the scaffolds decreased as the concentration of n-HA augmented, and it reached the value of 44 ± 0.9° for nanocomposite containing 5 wt.% n-HA. The degradation rate of all PGSC nanocomposites was reduced due to the anionic groups of n-HA and CS. TGA assay indicated that the incorporation of n-HA led to the enhancement of scaffolds' thermal stability. Furthermore, the synergistic effect of CS and n-HA on the enhancement of protein adsorption and cell proliferation was confirmed through protein adhesion and MTT assay, respectively. Consequently, the addition of n-HA and CS perform the new bio-nanocomposites scaffolds based on PGSC with sufficient hydrophilicity, flexibility, and thermal stability in tissue engineering applications.

Preparation and properties investigation of biodegradable poly (glycerol sebacate-co-gelatin) containing nanoclay and graphene oxide for soft tissue engineering applications

This study has attempted to systematically investigate the influence of nanoclay and graphene oxide (GO) on thermal, mechanical, hydrophobic, and, most importantly, biological properties of poly(glycerol sebacate)/gelatin (PGS/gel) nanocomposites. The PGS/gel copolymer nanocomposites were successfully synthesized via in situ polymerization, approved by rudimentary characterization methods. The nanofillers were appropriately dispersed within the elastomeric matrix according to morphological studies. Also, the fillers posed as a hydrophobic entity that slightly decreased the hydrophilic properties of PGS/gel. This could be sensed clearly in hybrid composite due to the robust network of GO and clay. Water contact angle values for gelatin-contained nanocomposites were reported in the range of 38.42° to 66.7°, indicating the hydrophilic nature of the prepared samples. Thermal and mechanical studies of nanocomposites displayed rather contradicting results as the former improved while a slight decrease in the latter was noticed compared to the pristine specimens. In dry conditions, their storage modulus was in the range of 0.94-6.4 MPa, making them suitable for mimicking some soft tissues. The swelling ratio for nanocomposites containing nanoparticles was associated with an ascending trend so that GO improved the swelling rate by up to 45%. Biological analyses, such as Ames and in vitro cell viability tests, exhibited promising outcomes. As for the mutagenesis effect, the PGS and hybrid samples showed negative results. The presence of functional groups on the nanofillers' surface positively influenced the cells' metabolic activity as well as its attachment to the matrix. After 7 days, the cell proliferation rate resulted in an 82% improvement for the GO-containing nanocomposite, significantly higher than its neat counterpart (65%). This study has shown the feasibility of the prepared bio-elastomer nanocomposites for diverse tissue engineering applications.

Preparation and characterization of a new bio nanocomposites based poly(glycerol sebacic-urethane) containing nano-clay (Cloisite Na+ ) and its potential application for tissue engineering

Nanocomposites containing clay nanoparticles often present favorable properties such as good mechanical and thermal properties. They frequently have been studied for tissue engineering (TE) and regenerative medicine applications. On the other hand, poly(glycerol sebacate) (PGS), a revolutionary bioelastomer, has exhibited substantial potential as a promising candidate for biomedical application. Here, we present a facile approach to synthesizing stiff, elastomeric nanocomposites from sodium-montmorillonite nano-clay (MMT) in the commercial name of Cloisite Na⁺ and poly(glycerol sebacate urethane) (PGSU). The strong physical interaction between the intercalated Cloisite Na⁺ platelets and PGSU chains resulted in desirable property combinations for TE application to follow. The addition of 5% MMT nano-clay resulted in an over two-fold increase in the tensile modulus, increased the onset thermal decomposition temperature of PGSU matrix by 18°C, and noticeably improved storage modulus of the prepared scaffolds, compared with pure PGSU. As well, Cloisite Na⁺ enhanced the hydrophilicity and water uptake ability of the samples and accelerated the in-vitro biodegradation rate. Finally, in-vitro cell viability assay using L929 mouse fibroblast cells indicated that incorporating Cloisite Na⁺ nanoparticles into the PGSU network could improve the cell attachment and proliferation, rendering the synthesized bioelastomers potentially suitable for TE and regenerative medicine applications.

Novel electrospun conduit based on polyurethane/collagen enhanced by nanobioglass for peripheral nerve tissue engineering

Peripheral nerve injury can significantly affect the daily life of individuals with impaired nerve function and permanent nerve deformity. One of the most common treatments is autograft transplantation. Tissue engineering is one of the efficient methods to regenerate injured nerves using scaffolds, cells, and growth factors. Conduits, which are produced by a variety of techniques, could be used as an alternative treatment for patients with damaged nerves. The electrospinning technique is one of the most important and widely used methods for generating nanofiber conduits from biocompatible polymers. In this study, using the electrospinning method, three different conduits, including polyurethane (PU), polyurethane/collagen (PU/C), and a new conduit based on polyurethane + collagen + nanobioglass (PU/C/NBG), were prepared. The characteristics of these three types of conduits were evaluated by SEM, XRD, and various experiments, including porosity, degradation, contact angle, DMTA, FTIR, MTT, and DAPI staining. The results of MTT and DAPI assays revealed the safety of conduits and proper cell attachment. Overall, the results obtained from various experiments showed that the novel PU/C/NBG conduit has better mechanical properties in terms of porosity, hydrophilicity, and biocompatibility in comparison with PU and PU/C conduits and could be a suitable candidate for peripheral nerve regeneration and axonal growth due to its repair potential.

COVID-19 and industrial waste mitigation via thermochemical technologies towards a circular economy: A state-of-the-art review

The increasing awareness of waste circular economy has motivated valorization strategies for minimizing resource consumption and waste production in the private sector. With the rise of various industrial wastes and with the emergence of COVID-19 wastes, a sustainable approach is needed to mitigate the growing concern about wastes. Thermochemical treatment technologies in the form of direct combustion, torrefaction, pyrolysis, and gasification have been identified to have vital roles in the value-creation of various waste streams. Moreover, the alignment of thermochemical processes for waste mitigation concerning the circular economy framework needs to be established. Accordingly, a comprehensive review of the different thermochemical treatment options for industrial and the novel COVID-19 medical wastes streams is conducted in this study. This review focuses on highlighting the instrumental role of thermochemical conversion platforms in achieving a circular economy in the industrial sector. Various strategies in waste mitigation through various thermochemical processes such as management, recovery, reduction, and treatment are discussed. The results show that thermochemical technologies are beneficial in addressing the sustainability concerns on mitigating wastes from the industrial sector and wastes brought by the COVID-19 pandemic. This also includes the current issues faced as well as future perspectives of the thermochemical conversion technologies.

Introducing a bio sorbent for removal of methylene blue dye based on flexible poly(glycerol sebacate)/chitosan/graphene oxide ecofriendly nanocomposites

As a consequence of industrial activities, one of the most prevalent components in wastewater is Water-soluble dyes needed to be removed. In this research, eco-friendly adsorbents based on poly(glycerol sebacate) (PGS), including PGS-graphene oxide nanoparticles (GO), PGS-graft-chitosan(CS), and PGS-CS-GO nanocomposites, have been proposed as efficient dye adsorbents for the wastewater treatment procedure. FESEM images showed that a smooth and uniform structure was created over incorporating CS into PGS. Besides, the presence of CS within PGS/GO nanocomposites had a positive impact on the exfoliation of GO. Moreover, it was found that the incorporation of both CS and GO into PGS reduced the glass transition of PGS. Besides, their coexistence can probably increase the chain regularity in the polymer matrix and cause a relatively larger crystal size of PGS. In this regard, the ternary nanocomposite saw a Tg value of -29.4 °C. A high adsorption capacity of 178 mg g^-1, as well as 99 removal% efficiency, were observed in the case of the PGS-CS-GO sample after 300 min at a dye concentration of 100 mg L^-1 and pH 7. Additionally, the adsorption capacity value of the adsorbent was preserved around 129 mg g^-1 after 7 cycles of adsorption-desorption. The findings revealed that innovatively synthesized PGS-g-CS/GO nanocomposites could efficiently remove methylene blue from water solutions. Hence, they can be used as a powerful and influential dye adsorbent to purify water solutions.

Simultaneous nanocarrier-mediated delivery of siRNAs and chemotherapeutic agents in cancer therapy and diagnosis: Recent advances

Recently, investigations have revealed that RNA interference (RNAi) has a remarkable potential to decrease cancer burden by downregulating genes. Among various RNAi molecules, small interfering RNA (siRNA) has been more attractive for this goal and is able to silence a target pathological path and promote the degradation of a certain mRNA, resulting in either gain or loss of function of proteins. Moreover, therapeutic siRNAs have exhibited low side effects compared to other therapeutic molecular candidates. Nevertheless, siRNA delivery has its own limitations including quick degradation in circulation, ineffective internalization and low passive uptake by cells, possible toxicity against off-target sites, and inducing unfavorable immune responses. Therefore, delivery tools must be able to specifically direct siRNAs to their target locations without inflicting detrimental effects on other sites. To conquer the mentioned problems, nanocarrier-mediated delivery of siRNAs, using inorganic nanoparticles (NPs), polymers, and lipids, has been developed as a biocompatible delivery approach. In this review, we have discussed recent advances in the siRNA delivery methods that employ nanoparticles, lipids, and polymers, as well as the inorganic-based co-delivery systems used to deliver siRNAs and anticancer agents to target cells.

Removal of methylene blue from wastewater using ternary nanocomposite aerogel systems: Carboxymethyl cellulose grafted by polyacrylic acid and decorated with graphene oxide

In this study, environmentally-friendly nanocomposite hydrogels were fabricated. These hydrogels consisted of semi-interpenetrating networks of carboxymethyl cellulose (CMC) molecules grafted to polyacrylic acid (PAA), as an eco-friendly and non-toxic polymer with numerous carboxyl and hydroxyl functional groups, which were reinforced with different levels of graphene oxide particles (0.5, 1.5 or 3% wt). Field-emission electron scanning microscopy (FESEM) images indicated that the pore size of the nanocomposites decreased with increasing graphic oxide concentration. The presence of the graphic oxide increased the storage modulus and thermal stability of the nanocomposite hydrogels. The hydrogels had an adsorption capacity of 138 mg/g of a model cationic dye pollutant (methylene blue) after 250 min. Moreover, a reusability test showed that the adsorption capacity remained at around 90% after 9 cycles. Density functional theory (DFT) simulations suggested that the adsorption of methylene blue was mainly a result of π-π bonds, hydrogen bonds, and electrostatic interactions with graphene oxide. Our results indicated that the nanocomposite hydrogels fabricated in this study may be eco-friendly, stable, efficient, and reusable adsorbents for ionic pollutants in wastewater treatment.

A novel environmentally friendly nanocomposite aerogel based on the semi-interpenetrating network of polyacrylic acid into Xanthan gum containing hydroxyapatite for efficient removal of methylene blue from wastewater

Eco-friendly nanocomposite aerogels were prepared as adsorbents for the removal of a model pollutant (methylene blue, MB) from water. These aerogels were comprised of hydroxyapatite (HA) nanoparticles embedded within a polymer matrix consisting of a semi-interpenetrating network of xanthan gum (XG) and polyacrylic acid (PAA). Microscopy and BET analysis showed that the aerogels formed had a nanofibrous porous microstructure with a surface area of 89 m²/g. Rheological analysis showed that the aerogels were viscoelastic materials whose elasticity increased with increasing HA concentration (up to 5 w/w%). The aerogels were effective at removing MB from water, exhibiting an adsorption capacity of 130 mg/g after 200 min. The binding of the MB to the aerogels was mainly attributed to hydrogen bonding and electrostatic attraction. A reusability test showed that the MB removal efficiency of over 86% was preserved after 10 cycles of adsorption-desorption. These results suggest that our nanocomposite aerogels may be useful for the efficient removal of anionic pollutants from wastewater and water supplies due to their ease of synthesis, cost-effectiveness, good mechanical properties, high thermal stability, and good adsorption performance.

Nanobioglass enhanced polyurethane/collagen conduit in sciatic nerve regeneration

The main purpose of neural tissue engineering and regenerative medicine is the development of biological substitutions to preserve, improve, and regenerate the damaged functions of tissues and organs. Three novel conduits, including polyurethane (PU), polyurethane/collagen (PU/C), and polyurethane/collagen/nano-bio glass (PU/C/NBG), were fabricated by the electrospinning technique. After confirming the suitability of conduits in the in-vitro environment, conduits were surgically sutured in a 10-mm gap in the sciatic nerve of a rat to evaluate their role in sciatic nerve reconstruction. After 4, 8, and 12 weeks of surgery, nerve regeneration was assessed by the hot plate test, sciatic functional index, electromyography, histology, and immunohistochemistry against S100, NF200, and CD31 antibodies. The results of various examinations revealed that the PU/C/NBG conduit is significantly more suitable than PU and PU/C conduits in terms of nerve regeneration. However, all three groups of conduits had the potential to be used for nerve regeneration. Overall, this study discovered that the PU/C/NBG conduit is a biocompatible neural conduit, which is a favorable candidate for peripheral nerve regeneration and axonal growth.

Introducing a flexible drug delivery system based on poly(glycerol sebacate)-urethane and its nanocomposite: potential application in the prevention and treatment of oral diseases

In this study, a novel biopolymer based on poly(glycerol sebacic)-urethane (PGS-U) and its nanocomposites containing Cloisite@30B were synthesized by facile approach in which the crosslinking was created by aliphatic hexamethylene diisocyanate (HDI) at room temperature and 80 °C. Moreover, metronidazole and tetracycline drugs were selected as target drugs and loaded into PGSU based nanocomposites. A uniform and continuous microstructure with smooth surface is observed in the case of pristine PGS-U sample. The continuity of microstructure is observed in the case of all bionanocomposites. XRD result confirmed an intercalated morphology for PGSU containing 5 wt% of clay nanoparticles with a d-spacing 3.4 nm. The increment of nanoclay content up to 5%, the ultimate tensile stress and elastic modulus were obtained nearly 0.32 and 0.83 MPa, which the latter was more than eight-fold than that of pristine PGS-U. A sustained release for both dugs was observed by 200 h. The slowest and controlled drug release rate was determined in the case of PGSU containing 5 wt% clay and cured at 80 °C. A non-Fickian diffusion can be concluded in the case of tetracycline release via PGS-U/nanoclay bionanocomposites, while a Fickian process was detected in the case of metronidazole release by PGS-U/nanoclay bionanocomposites. As a result, the designed scaffold showed high flexibility, which makes it an appropriate option for utilization in the treatment of periodontal disease.

Electrically conductive biocompatible composite aerogel based on nanofibrillated template of bacterial cellulose/polyaniline/nano-clay

Bacterial cellulose (BC) aerogel owing to its porous and 3D structure, poses a suitable matrix for embedding nanomaterials and polymers. Herein, BC composites comprising nano-clay/polyaniline (PANI) were synthesized via a two-step procedure. Clay nanoplatelets were dispersed in the BC membrane to form a nanofibrillated template for aniline in-situ polymerization leading to formation of a double interconnected network of electrically conductive path within the aerogel. Deposition of PANI particles on BC/clay nanocomposite was confirmed by FTIR, XRD, FESEM, and EDX techniques. The surface electrical conductivity of 0.49 S/cm was obtained for the composite aerogel comprising 5 wt% nano-clay which is 16 folds higher than that of the sample without nano-clay. Thermal stability and storage modulus of the aerogels was improved by inclusion of PANI and nano-clay. Synergistic effect of clay and polyaniline on biocompatibility and cell adhesion was obtained with no mutagenic or carcinogenic effects. The developed electrically conductive composite aerogels can be utilized as suitable scaffolds for tissue engineering applications demanding a good balance of flexibility, dimensional and thermal stability and biocompatibility.

Development of physical, mechanical, antibacterial and cell growth properties of poly(glycerol sebacate urethane) (PGSU) with helping of curcumin and hydroxyapatite nanoparticles

Biocompatible and antimicrobial elastomers with controlled hydrophilicity and degradation rate, as well as appropriate stiffness and elasticity, are interesting for biomedical applications, such as regenerative medicine and tissue engineering.

Design and fabrication of bone tissue scaffolds based on PCL/PHBV containing hydroxyapatite nanoparticles: dual-leaching technique

Scaffolds are the important part of the tissue-engineering field that are made from different biomaterials using various techniques. In this study, new scaffold based on polycaprolactone (PCL) and poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV) containing hydroxyapatite nanopraticles (n-HA) were fabricated using the dual-leaching technique (DLT). Morphology, porosity, degradation rate, Fourier transfer infrared ray (FTIR) spectra, surface, and mechanical properties as well as capacity of cell binding and cell proliferation on the constructed scaffolds were evaluated. FTIR analysis showed that n-HA particles have some interest interactions with polymeric chains. The best 3D-structure was seen in PCL70PHBV30 scaffold using the scanning electron microscopy (SEM) and its structure improved in the presence of 3, 5 wt% of n-HA. Results of energy dispersive x-ray analysis (EDXA, map of Ca) showed that the nanoparticles have the uniform distribution within the fabricated scaffolds. Porosity analysis showed that the particulate salt leaching technique is a successful approach to building a 3D structure. Increasing of PHBV content and n-HA up to 3 and 5 wt% in the PCL matrix led to increase porosity in all samples. Mechanical properties analysis showed that values of compression modulus and strength are decreased with addition of PHBV and HA nanoparticles. These results were directly in line with the results of morphology and porosity. Cell culture experiments demonstrated that the PCL/PHBV/nHA nanocomposite scaffold has a better tendency of proliferation to cells than that of the pure PCL/PHBV scaffold. All of these results suggest promising potentials of the developed PCL/PHBV/nHA scaffolds in this study desire for bone tissue engineering.

Lightweight aerogels based on bacterial cellulose/silver nanoparticles/polyaniline with tuning morphology of polyaniline and application in soft tissue engineering

Herein, polyaniline (PANI) with tuning morphology was in-situ synthesized within bacterial cellulose (BC)/silver nanoparticles hydrogels (AgNPs) that were prepared by green hydrothermal reduction method in different molarity of 0.01 and 0.25 of HCl solution along with the presence of polyethylene glycol (PEG). The synthesis of PANI in the presence of PEG in 0.01 M HCl led to the formation of rose-like morphology within nanocomposite aerogels with a size of 1.5-5.2 μm. All aerogels had the porosity and shrinkage of higher than 80% and lower than 10%, respectively. Rheology results showed a higher value of storage modulus (G') than that of loss modulus (G″) for all samples over the whole frequency regime. It confirmed by the loss factor (tan δ) value of less than 1 for all hydrogel samples. The synthesis of PANI within BC/Ag in 0.25 M of HCl solution resulted in a substantial rise of G' to nearly 1.5 × 10⁴ Pa that was one order of magnitude higher than that of other hydrogels. However, the synthesis condition of PANI did not influence the antibacterial activity. In spite of unfavorable cell attachment onto nanocomposite aerogels, the cell proliferation increased steadily over the whole period of incubation.

Mixing Performance of a Cost-effective Split-and-Recombine 3D Micromixer Fabricated by Xurographic Method

This paper presents experimental and numerical investigations of a novel passive micromixer based on the lamination of fluid layers. Lamination-based mixers benefit from increasing the contact surface between two fluid phases by enhancing molecular diffusion to achieve a faster mixing. Novel three-dimensional split and recombine (SAR) structures are proposed to generate fluid laminations. Numerical simulations were conducted to model the mixer performance. Furthermore, experiments were conducted using dyes to observe fluid laminations and evaluate the proposed mixer's characteristics. Mixing quality was experimentally obtained by means of image-based mixing index (MI) measurement. The multi-layer device was fabricated utilizing the Xurography method, which is a simple and low-cost method to fabricate 3D microfluidic devices. Mixing indexes of 96% and 90% were obtained at Reynolds numbers of 0.1 and 1, respectively. Moreover, the device had an MI value of 67% at a Reynolds number of 10 (flow rate of 116 µL/min for each inlet). The proposed micromixer, with its novel design and fabrication method, is expected to benefit a wide range of lab-on-a-chip applications, due to its high efficiency, low cost, high throughput and ease of fabrication.