Flow induced HeLa cell detachment kinetics show that oxygen-containing functional groups in graphene oxide are potent cell adhesion enhancers

Carboxyl graphene modified PEDOT:PSS organic electrochemical transistor for in situ detection of cancer cell morphology

Circulating tumor cells in human peripheral blood play an important role in cancer metastasis. In addition to the size-based and antibody-based capture and separation of cancer cells, their electrical characterization is important for rare cell detection, which can prove fatal in point-of-care testing. Herein, an organic electrochemical transistor (OECT) biosensor made of solution-gated carboxyl graphene mixed with PEDOT:PSS for the detection of cancer cells in situ is reported. Carboxyl graphene was used in this work to modulate cancer cell morphology, which differs significantly from normal blood cells, to achieve rare cancer cell detection. When the concentration of carboxyl graphene mixed in PEDOT:PSS was increased from 0 to 5 mg mL-1, the cancer cell surface area increased from 218 μm2 to 530 μm2, respectively. A change in cell morphology was also detected by the OECT. Negative charges in the cancer cells induced a positive shift in gate voltage, which was approximately 40 mV for spherical-shaped cells. When the cell surface area increased, transfer curves of transistor revealed a negative shift in gate voltage. Therefore, the sensor can be used for in situ detection of cancer cell morphology during the cell capture process, which can be used to identify whether the captured cells are deformable.

Effect of Plasma pretreatment and Graphene oxide ratios on the transport properties of PVA/PVP membranes for fuel cells

In this study, a novel proton-conducting polymer electrolyte membrane based on a mixture of polyvinyl alcohol (PVA)/polyvinyl pyrrolidone (PVP) (1:1) mixed with different ratios of graphene oxide (GO) and plasma-treated was successfully synthesized. Dielectric barrier dielectric (DBD) plasma was used to treat the prepared samples at various dose rates (2, 4, 6, 7, 8, and 9 min) and at fixed power input (2 kV, 50 kHz). The treated samples (PVA/PVP:GO wt%) were soaked in a solution of styrene and tetrahydrofuran (70:30 wt%) with 5 × 10-3 g of benzoyl peroxide as an initiator in an oven at 60 °C for 12 h and then sulfonated to create protonic membranes (PVA/PVP-g-PSSA:GO). The impacts of graphene oxide (GO) on the physical, chemical, and electrochemical properties of plasma-treated PVA/PVP-g-PSSA:x wt% GO membranes (x = 0, 0.1, 0.2, and 0.3) were investigated using different techniques. SEM results showed a better dispersion of nanocomposite-prepared membranes; whereas the AFM results showed an increase in total roughness with increasing the content of GO. FTIR spectra provide more information about the structural variation arising from the grafting and sulfonation processes to confirm their occurrence. The X-ray diffraction pattern showed that the PVA/PVP-g-PSSA:x wt% GO composite is semi-crystalline. As the level of GO mixing rises, the crystallinity of the mixes decreases. According to the TGA curve, the PVA/PVP-g-PSSA:x wt% GO membranes are chemically stable up to 180 °C which is suitable for proton exchange membrane fuel cells. Water uptake (WU) was also measured and found to decrease from 87.6 to 63.3% at equilibrium with increasing GO content. Ion exchange capacity (IEC) was calculated, and the maximum IEC value was 1.91 meq/g for the PVA/PVP-g-PSSA: 0.3 wt% GO composite membrane. At room temperature, the maximum proton conductivity was 98.9 mS/cm for PVA/PVP-g-PSSA: 0.3 wt% GO membrane. In addition, the same sample recorded a methanol permeability of 1.03 × 10-7 cm2/s, which is much less than that of Nafion NR-212 (1.63 × 10-6 cm2/s). These results imply potential applications for modified polyelectrolytic membranes in fuel cell technology.

Biological Characterization of Polymeric Matrix and Graphene Oxide Biocomposites Filaments for Biomedical Implant Applications: A Preliminary Report

Carbon nanostructures application, such as graphene (Gr) and graphene oxide (GO), provides suitable efforts for new material acquirement in biomedical areas. By aiming to combine the unique physicochemical properties of GO to Poly L-lactic acid (PLLA), PLLA-GO filaments were produced and characterized by X-ray diffraction (XRD). The in vivo biocompatibility of these nanocomposites was performed by subcutaneous and intramuscular implantation in adult Wistar rats. Evaluation of the implantation inflammatory response (21 days) and mesenchymal stem cells (MSCs) with PLLA-GO took place in culture for 7 days. Through XRD, new crystallographic planes were formed by mixing GO with PLLA (PLLA-GO). Using macroscopic analysis, GO implanted in the subcutaneous region showed particles' organization, forming a structure similar to a ribbon, without tissue invasion. Histologically, no tissue architecture changes were observed, and PLLA-GO cell adhesion was demonstrated by scanning electron microscopy (SEM). Finally, PLLA-GO nanocomposites showed promising results due to the in vivo biocompatibility test, which demonstrated effective integration and absence of inflammation after 21 days of implantation. These results indicate the future use of PLLA-GO nanocomposites as a new effort for tissue engineering (TE) application, although further analysis is required to evaluate their proliferative capacity and viability.

Tuning protein adsorption on graphene surfaces via laser-induced oxidation

An approach for controlled protein immobilization on laser-induced two-photon (2P) oxidation patterned graphene oxide (GO) surfaces is described. Selected proteins, horseradish peroxidase (HRP) and biotinylated bovine serum albumin (b-BSA) were successfully immobilized on oxidized graphene surfaces, via non-covalent interactions, by immersion of graphene-coated microchips in the protein solution. The effects of laser pulse energy, irradiation time, protein concentration and duration of incubation on the topography of immobilized proteins and consequent defects upon the lattice of graphene were systemically studied by atomic force microscopy (AFM) and Raman spectroscopy. AFM and fluorescence microscopy confirmed the selective aggregation of protein molecules towards the irradiated areas. In addition, the attachment of b-BSA was detected by a reaction with fluorescently labelled avidin-fluorescein isothiocyanate (Av-FITC). In contrast to chemically oxidized graphene, laser-induced oxidation introduces the capability for localization on oxidized areas and tunability of the levels of oxidation, resulting in controlled guidance of proteins by light over graphene surfaces and progressing towards graphene microchips suitable for biomedical applications.

Graphene Oxide Substrate Promotes Neurotrophic Factor Secretion and Survival of Human Schwann-Like Adipose Mesenchymal Stromal Cells

Mesenchymal stromal cells from adipose tissue (AD-MSCs) exhibit favorable clinical traits for autologous transplantation and can develop 'Schwann-like' phenotypes (sAD-MSCs) to improve peripheral nerve regeneration, where severe injuries yield insufficient recovery. However, sAD-MSCs regress without biochemical stimulation and detach from conduits under unfavorable transplant conditions, negating their paracrine effects. Graphene-derived materials support AD-MSC attachment, regulating cell adhesion and function through physiochemistry and topography. Graphene oxide (GO) is a suitable substrate for human sAD-MSCs incubation toward severe peripheral nerve injuries by evaluating transcriptome changes, neurotrophic factor expression over a 7-days period, and cell viability in apoptotic conditions is reported. Transcriptome changes from GO incubation across four patients are minor compared to biological variance. Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and glial-derived neurotrophic factor (GDNF) gene expression is unchanged from sAD-MSCs on GO substrates, but NGF and GDNF protein secretion increase at day 3 and 7. Secretome changes do not improve dorsal root ganglia neuron axon regeneration in conditioned media culture models. Fewer sAD-MSCs detach from GO substrates compared to glass following phosphate buffer saline exposure, which simulates apoptotic conditions. Overall, GO substrates are compatible with sAD-MSC primed for peripheral nerve regeneration strategies and protect the cell population in harsh environments.

Unique cellular network formation guided by heterostructures based on reduced graphene oxide - Ti3C2Tx MXene hydrogels

Two-dimensional (2D) materials remain highly interesting for assembling three-dimensional (3D) structures, amongst others, in the form of macroscopic hydrogels. Herein, we present a novel approach for inducing chemical inter-sheet crosslinks via an ethylenediamine mediated reaction between Ti₃C₂T_x and graphene oxide in order to obtain a reduced graphene oxide-MXene (rGO-MXene) hydrogel. The composite hydrogels are hydrophilic with a stiffness of ~20 kPa. They also possess a unique inter-connected porous architecture, which led to a hitherto unprecedented ability of human cells across three different types, epithelial adenocarcinoma, neuroblastoma and fibroblasts, to form inter-connected three-dimensional networks. The attachments of the cells to the rGO-MXene hydrogels were superior to those of the sole rGO-control gels. This phenomenon stems from the strong affinity of cellular protrusions (neurites, lamellipodia and filopodia) to grow and connect along architectural network paths within the rGO-MXene hydrogel, which could lead to advanced control over macroscopic formations of cellular networks for technologically relevant bioengineering applications, including tissue engineering and personalized diagnostic networks-on-chip. STATEMENT OF SIGNIFICANCE: Conventional hydrogels are made of interconnected polymeric fibres. Unlike conventional case, we used hydrothermal and chemical approach to form interconnected porous hydrogels made of two-dimensional flakes from graphene oxide and metal carbide from a new family of MXenes (Ti₃C₂T_x). This way, we formed three-dimensional porous hydrogels with unique porous architecture of well-suited chemical surfaces and stiffness. Cells from three different types cultured on these scaffolds formed extended three-dimensional networks - a feature of extended cellular proliferation and pre-requisite for formation of organoids. Considering the studied 2D materials typically constitute materials exhibiting enhanced supercapacitor performances, our study points towards better understanding of design of tissue engineering materials for the future bioengineering fields including personalized diagnostic networks-on-chip, such as artificial heart actuators.

The Interactions of Quantum Dot-Labeled Silk Fibroin Micro/Nanoparticles with Cells

When silk fibroin particles are used for controlled drug delivery, particle size plays a key role in the location of the carrier on the cells as well as the transport pathway, utilization efficiency, and therapeutic effect of the drugs. In this study, the interactions of different-sized silk fibroin particles and cell lines were investigated. Silk fibroin microparticles with dry size of 1.9 ± 0.4 μm (2.7 ± 0.3 μm in wet state) and silk fibroin nanoparticles with dry size of 51.5 ± 11.0 nm (174.8 ± 12.5 nm in wet state) were prepared by salting-out method and high-voltage electrospray method, respectively. CdSe/ZnS quantum dots were coupled to the surface of the micro/nanoparticles. Photostability observations indicated that the fluorescence stability of the quantum dots was much higher than that of fluorescein isothiocyanate. In vitro, microparticles and nanoparticles were co-cultured with human umbilical vein endothelial cells EA.hy 926 and cervical cancer cells HeLa, respectively. The fluorescence test and cell viability showed that the EA.hy926 cells tended to be adhered to the microparticle surfaces and the cell proliferation was significantly promoted, while the nanoparticles were more likely to be internalized in HeLa cells and the cell proliferation was notably inhibited. Our findings might provide useful information concerning effective drug delivery that microparticles may be preferred if the drugs need to be delivered to normal cell surface, while nanoparticles may be preferred if the drugs need to be transmitted in tumor cells.

Effect of electrical stimulation combined with graphene-oxide-based membranes on neural stem cell proliferation and differentiation

The combination of composite nerve materials prepared using degradable polymer materials with biological or physical factors has received extensive attention as a means to treat nerve injuries. This study focused on the potential application of graphene oxide (GO) composite conductive materials combined with electrical stimulation (ES) in nerve repair. A conductive poly(L-lactic-co-glycolic acid) (PLGA)/GO composite membrane was prepared, and its properties were tested using a scanning electron microscope (SEM), a contact angle meter, and a mechanical tester. Next, neural stem cells (NSCs) were planted on the PLGA/GO conductive composite membrane and ES was applied. NSC proliferation and differentiation and neurite elongation were observed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, immunofluorescence, and PCR, respectively. The results showed that the PLGA/GO membrane had good hydrophilicity, mechanical strength, and protein adsorption. ES combined with the PLGA/GO membrane significantly promoted NSC proliferation and neuronal differentiation on the material surface and promoted significant neurite elongation. Our results suggest that ES combined with GO-related conductive composite materials can be used as a new therapeutic combination to treat nerve injuries.

Fabrication and Application of Novel Porous Scaffold in Situ-Loaded Graphene Oxide and Osteogenic Peptide by Cryogenic 3D Printing for Repairing Critical-Sized Bone Defect

Osteogenic peptides have been reported as highly effective in directing mesenchymal stem cell osteogenic differentiation in vitro and bone formation in vivo. Therefore, developing novel biomaterials for the controlled delivery of osteogenic peptides in scaffolds without lowering the peptide’s biological activity is highly desirable. To repair a critical-sized bone defect to efficiently achieve personalized bone regeneration, a novel bioactive poly(lactic-co-glycolic acid) (PLGA)/β-tricalcium phosphate (β-TCP) composite scaffold, in which graphene oxide (GO) and bone morphogenetic protein (BMP)-2-like peptide were loaded in situ (PTG/P), was produced by an original cryogenic 3D printing method. The scaffolds were mechanically comparable to human cancellous bone and hierarchically porous. The incorporation of GO further improved the scaffold wettability and mechanical strength. The in situ loaded peptides retained a high level of biological activity for an extended time, and the loading of GO in the scaffold further tuned the peptide release so that it was more sustained. Our in vitro study showed that the PTG/P scaffold promoted rat bone marrow-derived mesenchymal stem cell ingrowth into the scaffold and enhanced osteogenic differentiation. Moreover, the in vivo study indicated that the novel PTG/P scaffold with sustained delivery of the peptide could significantly promote bone regeneration in a critical bone defect. Thus, the novel bioactive PTG/P scaffold with a customized shape, improved mechanical strength, sustainable peptide delivery, and excellent osteogenic ability has great potential in bone tissue regeneration.