Electrical field stimulated modulation of cell fate of pre-osteoblasts on PVDF/BT/MWCNT based electroactive biomaterials

The present study reports the impact of the interplay between electroactive properties of the biomaterials and electrical stimulation (ES) toward the cell proliferation, migration and maturation of osteoprogenitors (preosteoblasts; MC3T3-E1) on the electroactive poly (vinylidene difluoride) (PVDF)-based composites. The barium titanate (BaTiO_3; BT; 30 wt%) and multiwalled carbon nanotubes (MWCNT; 3 wt%) were introduced into the PVDF via melt mixing, which led to an enhancement of the dielectric permittivity, electrical conductivity, and surface roughness. We also present the design and development of an in-house customized 12-well plate-based device for providing different types (DC, square, biphasic) of ES to cells in culture in a programmable manner. In the presence of ES of 1 V cm^-1 , biophysical stimulation experiments performed using 12-well plate-based device revealed that PVDF composite (PVDF/30BT/3MWCNT) can facilitate the enhanced adhesion and proliferation of the MC3T3-E1 in non-osteogenic media, with respect to non-stimulated conditions. Importantly, MC3T3-E1 cells demonstrated significantly better migration and differentiation on the PVDF/30BT/3MWCNT under ES when compared to ES-free culture conditions. Similar enhancement with respect to alkaline phosphatase activity, intracellular Ca²⁺ concentration, and calcium deposition in MC3T3-E1 cells was recorded, when pre-osteoblasts were grown for 21 days on electroactive substrates. All these observations supported the activation of osteo-differentiation fates, which were further promoted in the osteogenic medium. The present study demonstrates that the synergistic interactions of ES with piezoelectric PVDF-based polymer composite can potentially enhance the proliferation, migration, and osteogenesis of the pre-osteoblast cells, rendering it a promising bioengineering strategy for bone tissue engineering.

Biomaterialomics: Data science-driven pathways to develop fourth-generation biomaterials

Conventional approaches to developing biomaterials and implants require intuitive tailoring of manufacturing protocols and biocompatibility assessment. This leads to longer development cycles, and high costs. To meet existing and unmet clinical needs, it is critical to accelerate the production of implantable biomaterials, implants and biomedical devices. Building on the Materials Genome Initiative, we define the concept 'biomaterialomics' as the integration of multi-omics data and high-dimensional analysis with artificial intelligence (AI) tools throughout the entire pipeline of biomaterials development. The Data Science-driven approach is envisioned to bring together on a single platform, the computational tools, databases, experimental methods, machine learning, and advanced manufacturing (e.g., 3D printing) to develop the fourth-generation biomaterials and implants, whose clinical performance will be predicted using 'digital twins'. While analysing the key elements of the concept of 'biomaterialomics', significant emphasis has been put forward to effectively utilize high-throughput biocompatibility data together with multiscale physics-based models, E-platform/online databases of clinical studies, data science approaches, including metadata management, AI/ Machine Learning (ML) algorithms and uncertainty predictions. Such integrated formulation will allow one to adopt cross-disciplinary approaches to establish processing-structure-property (PSP) linkages. A few published studies from the lead author's research group serve as representative examples to illustrate the formulation and relevance of the 'Biomaterialomics' approaches for three emerging research themes, i.e. patient-specific implants, additive manufacturing, and bioelectronic medicine. The increased adaptability of AI/ML tools in biomaterials science along with the training of the next generation researchers in data science are strongly recommended. STATEMENT OF SIGNIFICANCE: This leading opinion review paper emphasizes the need to integrate the concepts and algorithms of the data science with biomaterials science. Also, this paper emphasizes the need to establish a mathematically rigorous cross-disciplinary framework that will allow a systematic quantitative exploration and curation of critical biomaterials knowledge needed to drive objectively the innovation efforts within a suitable uncertainty quantification framework, as embodied in 'biomaterialomics' concept, which integrates multi-omics data and high-dimensional analysis with artificial intelligence (AI) tools, like machine learning. The formulation of this approach has been demonstrated for patient-specific implants, additive manufacturing, and bioelectronic medicine.

Electrical waveform dependent osteogenesis on PVDF/BaTiO3 composite using a customized and programmable cell stimulator

Directing cellular functionalities using biomaterial-based bioelectronic stimulation remains a significant constraint in translating research outcomes to address specific clinical challenges. Electrical stimulation is now being clinically used as a therapeutic treatment option to promote bone tissue regeneration and to improve neuromuscular functionalities. However, the nature of the electrical waveforms during the stimulation and underlying biophysical rationale are still not scientifically well explored. Furthermore, bone-mimicking implant-based bioelectrical regulation of osteoinductivity has not been translated to clinics. The present study demonstrates the role of the waveform in electrical signal to direct differentiation of stem cells on an electroactive polymeric substrate, using monophasic DC, square wave, and biphasic wave. In this regard, an in-house electrical stimulation device has been fabricated for the uninterrupted delivery of programmed electrical signals to stem cells in culture. To provide a functional platform for stem cells to differentiate, barium titanate (BaTiO₃ , BT) reinforced PVDF has been developed with mechanical properties similar to bone. The electrical stimulation of human mesenchymal stem cells (hMSCs) on PVDF/BT composite inhibited proliferation rate at day 7, indicating early commitment for differentiation. The phenotypical characteristics of DC stimulated hMSCs provided signatures of differentiation towards osteogenic lineage, which was subsequently confirmed using ALP assay, collagen deposition, matrix mineralization, and genetic expression. Our findings suggest that DC stimulation induced early osteogenesis in hMSCs with a higher level of intracellular reactive oxygen species (ROS), whereas the stimulation with square wave directed late osteogenesis with a lower ROS regeneration. In summary, the present study critically analyzes the role of electrical stimulation and its waveforms in regulating osteogenesis, without external biochemical differentiation inducers, on a bone-mimicking functional substrate. Such a strategy can potentially be adopted to develop orthopedic implant-based bioelectronic medicine for bone regeneration. This article is protected by copyright. All rights reserved.

Tunable Substrate Functionalities Direct Stem Cell Fate toward Electrophysiologically Distinguishable Neuron-like and Glial-like Cells

Engineering cellular microenvironment on a functional platform using various biophysical cues to modulate stem cell fate has been the central theme in regenerative engineering. Among the various biophysical cues to direct stem cell differentiation, the critical role of physiologically relevant electric field (EF) stimulation was established in the recent past. The present study is the first to report the strategy to switch EF-mediated differentiation of human mesenchymal stem cells (hMSCs) between neuronal and glial pathways, using tailored functional properties of the biomaterial substrate. We have examined the combinatorial effect of substrate functionalities (conductivity, electroactivity, and topography) on the EF-mediated stem cell differentiation on polyvinylidene-difluoride (PVDF) nanocomposites in vitro, without any biochemical inducers. The functionalities of PVDF have been tailored using conducting nanofiller (multiwall-carbon nanotube, MWNT) and piezoceramic (BaTiO₃, BT) by an optimized processing approach (melt mixing-compression molding-rolling). The DC conductivity of PVDF nanocomposites was tuned from ∼10^-11 to ∼10^-4 S/cm and the dielectric constant from ∼10 to ∼300. The phenotypical changes and genotypical expression of hMSCs revealed the signatures of early differentiation toward neuronal pathway on rolled-PVDF/MWNT and late differentiation toward glial lineage on rolled-PVDF/BT/MWNT. Moreover, we were able to distinguish the physiological properties of differentiated neuron-like and glial-like cells using membrane depolarization and mechanical stimulation. The excitability of the EF-stimulated hMSCs was also determined using whole-cell patch-clamp recordings. Mechanistically, the roles of intracellular reactive oxygen species (ROS), Ca²⁺ oscillations, and synaptic and gap junction proteins in directing the cellular fate have been established. Therefore, the present work critically unveils complex yet synergistic interaction of substrate functional properties to direct EF-mediated differentiation toward neuron-like and glial-like cells, with distinguishable electrophysiological responses.

Electric field stimulation for tissue engineering applications

Electric fields are involved in numerous physiological processes, including directional embryonic development and wound healing following injury. To study these processes in vitro and/or to harness electric field stimulation as a biophysical environmental cue for organised tissue engineering strategies various electric field stimulation systems have been developed. These systems are overall similar in design and have been shown to influence morphology, orientation, migration and phenotype of several different cell types. This review discusses different electric field stimulation setups and their effect on cell response.

Critical comparison of image analysis workflows for quantitative cell morphological evaluation in assessing cell response to biomaterials

Quantitative image analysis is an important tool in understanding cell fate processes through the study of cell morphological changes in terms of size, shape, number, and orientation. In this context, this work explores systematically the main challenges involved in the quantitative analysis of fluorescence microscopy images and also proposes a new protocol while comparing its outcome with the widely used Image J analysis. It is important to mention that fluorescence microscopy is by far most widely used in biocompatibility analysis (observing cell fate changes) of implantable biomaterials. In this study, we employed two different image analyses toolsets: (i) the conventionally employed ImageJ software, and (ii) a recently developed automated digital image analyses framework, called ImageMKS. While ImageJ offers a powerful toolset for image analyses, it requires sophisticated user expertise to design and iteratively refine the analyses workflow. This workflow primarily comprises a sequence of image transformations that typically involve de-noising and labelling of features. On the other hand, ImageMKS automates the image analyses protocol to a large extent, and thereby mitigates the influence of the user bias on the final results. This aspect is addressed using a case study of C2C12 mouse myoblast cells grown on Poly(vinyldiene difluoride) based polymeric substrates in the presence of an external electric field. In particular, we used a number of fluorescence microscopy images of murine myoblasts (muscle precursor cells) grown on Poly (vinylidene difluoride), PVDF based nanobiocomposites under the influence of electric field. It was observed that when compared with the findings obtained from ImageJ, ImageMKS workflows consistently produced more reliable results that correlated better with the prior studies. Furthermore, the MKS workflows required much less user time, because of their automation.

Design of high conductive and piezoelectric poly (3,4-ethylenedioxythiophene)/chitosan nanofibers for enhancing cellular electrical stimulation

Electroactive nanofibrous scaffold is a vital tool for the study of the various biological research fields from bioelectronics to regenerative medicine, which can provide cell preferable 3D nanofiber architecture and programmed electrical signal. However, intrinsic non-biodegradability is a major problem that hinders its widespread application in the clinic. Herein, we designed, synthesized, and characterized shell/core poly (3,4-ethylenedioxythiophene) (PEDOT)/chitosan (CS) nanofibers by combining the electrospinning and recrystallization processes. Upon incorporating a trace amount of PEDOT (1.0 wt%), the resultant PEDOT/CS nanofibers exhibited low interfacial charge transfer impedance, high electrochemical stability, high electrical conductivity (up to 0.1945 S/cm), and ultrasensitive piezoelectric property (output voltage of 22.5 mV by a human hair prodding). With such unique electrical and conductive properties, PEDOT/CS nanofibers were further applied to brain neuroglioma cells (BNCs) to stimulate their adhesion, proliferation, growth, and development under an optimal external electrical stimulation (ES) and a pulse voltage of 400 mV/cm. ES-responsive PEDOT/CS nanofibers indeed promoted BNCs growth and development as indicated by a large number and density of axons. The synergetic interplay between external ES and piezoelectric voltage demonstrates new PEDOT-based nanofibers as implantable electroactive scaffolds for numerous applications in nerve tissue engineering, human health monitoring, brain mantle information extraction, and degradable microelectronic devices.

A Review on Biomaterials for 3D Conductive Scaffolds for Stimulating and Monitoring Cellular Activities

During the last years, scientific research in biotechnology has been reporting a considerable boost forward due to many advances marked in different technological areas. Researchers working in the field of regenerative medicine, mechanobiology and pharmacology have been constantly looking for non-invasive methods able to track tissue development, monitor biological processes and check effectiveness in treatments. The possibility to control cell cultures and quantify their products represents indeed one of the most promising and exciting hurdles. In this perspective, the use of conductive materials able to map cell activity in a three-dimensional environment represents the most interesting approach. The greatest potential of this strategy relies on the possibility to correlate measurable changes in electrical parameters with specific cell cycle events, without affecting their maturation process and considering a physiological-like setting. Up to now, several conductive materials has been identified and validated as possible solutions in scaffold development, but still few works have stressed the possibility to use conductive scaffolds for non-invasive electrical cell monitoring. In this picture, the main objective of this review was to define the state-of-the-art concerning conductive biomaterials to provide researchers with practical guidelines for developing specific applications addressing cell growth and differentiation monitoring. Therefore, a comprehensive review of all the available conductive biomaterials (polymers, carbon-based, and metals) was given in terms of their main electric characteristics and range of applications.

Epithelial cell functionality on electroconductive Fe/Sr co-doped biphasic calcium phosphate

In the perspective of dental restorative applications, co-doped bioceramics have not been explored much. From the clinical perspective, a successful dental implant is expected to interact with peri-prosthetic bones, gingival tissue, and surrounding connective tissues. The interaction of implant and implant coating materials with bone tissue is well studied. However, their interaction with surrounding epithelial components needs scientific validation. In this context, the present study aims at quantitative evaluation of the electrical properties of Fe/Sr co-doped biphasic calcium phosphate (BCP) samples and assessment of their cytocompatibility with epithelial (vero) cells. Sr/Fe co-doped BCPs were prepared by sol-gel synthesis technique, with different dopant concentration. Impact of co-doping on conductivity was assessed and interestingly an increase in conductivity with dopant amount was recorded in different co-doped BCPs. Cellular study showed the significant ( p = 0.01) increase in both cellular viability and functionality with increasing conductivity of samples. Higher epithelial cell adhesion indicates that (Sr/Fe) co-doped BCP would be favorable for faster epithelial sealing and also would reduce the chances of infection. Real-time PCR and immunofluorescence studies indicated that the expression of the epithelial marker (E-cadherin) significantly ( p = 0.01) increased in 10, 30 and 40 mol% co-doped samples in comparison to undoped BCP. In contrast to E-cadherin, fold change of β-catenin remains unchanged amongst the co-doped ceramics, implying the absence of tumorigenic potential of (Sr/Fe) co-doped BCP. In addition, immune-fluorescence signatures for cellular polarity are established from enhanced expression PARD3 protein, which has major relevance for cellular morphogenesis and cell division. Summarizing, the present study establishes the efficacy of Sr/Fe co-doped BCPs as a dental implant coating material and its ability to modulate vero cell functionality.

Unraveling the mechanistic effects of electric field stimulation towards directing stem cell fate and function: A tissue engineering perspective

Electric field (EF) stimulation can play a vital role in eliciting appropriate stem cell response. Such an approach is recently being established to guide stem cell differentiation through osteogenesis/neurogenesis/cardiomyogenesis. Despite significant recent efforts, the biophysical mechanisms by which stem cells sense, interpret and transform electrical cues into biochemical and biological signals still remain unclear. The present review critically analyses the variety of EF stimulation approaches that can be employed to evoke appropriate stem cell response and also makes an attempt to summarize the underlying concepts of this notion, placing special emphasis on stem cell based tissue engineering and regenerative medicine. This review also discusses the major signaling pathways and cellular responses that are elicited by electric stimulation, including the participation of reactive oxygen species and heat shock proteins, modulation of intracellular calcium ion concentration, ATP production and numerous other events involving the clustering or reassembling of cell surface receptors, cytoskeletal remodeling and so on. The specific advantages of using external electric stimulation in different modalities to regulate stem cell fate processes are highlighted with explicit examples, in vitro and in vivo.

3D printable conducting hydrogels containing chemically converted graphene

The development of conducting 3D structured biocompatible scaffolds for the growth of electroresponsive cells is critical in the field of tissue engineering. This work reports the synthesis and 3D processing of UV-crosslinkable conducting cytocompatible hydrogels that are prepared from methacrylated chitosan (ChiMA) containing graphenic nanosheets. The addition of chemically converted graphene resulted in mechanical and electrical properties of the composite that were significantly better than ChiMA itself, as well as improved adhesion, proliferation and spreading of L929 fibroblasts cells. The chemically converted graphene/ChiMA hydrogels were amenable to 3D printing and this was used to produce multilayer scaffolds with enhanced mechanical properties through UV-crosslinking.

A critical analysis of the α, β and γ phases in poly(vinylidene fluoride) using FTIR

A universal but simple procedure for identifying the α, β and γ phases in PVDF using FTIR is proposed and validated. An integrated quantification methodology for individual β and γ phase in mixed systems is also proposed.

P(VDF-TrFE)/BaTiO3 Nanoparticle Composite Films Mediate Piezoelectric Stimulation and Promote Differentiation of SH-SY5Y Neuroblastoma Cells

Poly(vinylidene fluoride-trifluoroethylene, P(VDF-TrFE)) and P(VDF-TrFE)/barium titanate nanoparticle (BTNP) films are prepared and tested as substrates for neuronal stimulation through direct piezoelectric effect. Films are characterized in terms of surface, mechanical, and piezoelectric features before in vitro testing on SH-SY5Y cells. In particular, BTNPs significantly improve piezoelectric properties of the films (4.5-fold increased d31 ). Both kinds of films support good SH-SY5Y viability and differentiation. Ultrasound (US) stimulation is proven to elicit Ca(2+) transients and to enhance differentiation in cells grown on the piezoelectric substrates. For the first time in the literature, this study demonstrates the suitability of polymer/ceramic composite films and US for neuronal stimulation through direct piezoelectric effect.