Precise control of cell adhesion by combination of surface chemistry and soft lithography

Micro/nanoengineered agricultural by-products for biomedical and environmental applications

Agriculturally derived by-products generated during the growth cycles of living organisms as secondary products have attracted increasing interest due to their wide range of biomedical and environmental applications. These by-products are considered promising candidates because of their unique characteristics including chemical stability, profound biocompatibility and offering a green approach by producing the least impact on the environment. Recently, micro/nanoengineering based techniques play a significant role in upgrading their utility, by controlling their structural integrity and promoting their functions at a micro and nano scale. Specifically, they can be used for biomedical applications such as tissue regeneration, drug delivery, disease diagnosis, as well as environmental applications such as filtration, bioenergy production, and the detection of environmental pollutants. This review highlights the diverse role of micro/nano-engineering techniques when applied on agricultural by-products with intriguing properties and upscaling their wide range of applications across the biomedical and environmental fields. Finally, we outline the future prospects and remarkable potential that these agricultural by-products hold in establishing a new era in the realms of biomedical science and environmental research.

Nanoscale surface coatings and topographies for neural interfaces

With the lack of minimally invasive tools for probing neuronal systems across spatiotemporal scales, understanding the working mechanism of the nervous system and limited assessments available are imperative to prevent or treat neurological disorders. In particular, nanoengineered neural interfaces can provide a solution to this technological barrier. This review covers recent surface engineering approaches, including nanoscale surface coatings, and a range of topographies from the microscale to the nanoscale, primarily focusing on neural-interfaced biosystems. Specifically, the immobilization of bioactive molecules to fertilize the neural cell lineage, topographical engineering to induce mechanotransduction in neural cells, and enhanced cell-chip coupling using three-dimensional structured surfaces are highlighted. Advances in neural interface design will help us understand the nervous system, thereby achieving the effective treatments for neurological disorders. STATEMENT OF SIGNIFICANCE: • This review focuses on designing bioactive neural interface with a nanoscale chemical modification and topographical engineering at multiscale perspective. • Versatile nanoscale surface coatings and topographies for neural interface are summarized. • Recent advances in bioactive materials applicable for neural cell culture, electrophysiological sensing, and neural implants are reviewed.

Polymeric and biological membranes for organ-on-a-chip devices

Membranes are fundamental elements within organ-on-a-chip (OOC) platforms, as they provide adherent cells with support, allow nutrients (and other relevant molecules) to permeate/exchange through membrane pores, and enable the delivery of mechanical or chemical stimuli. Through OOC platforms, physiological processes can be studied in vitro, whereas OOC membranes broaden knowledge of how mechanical and chemical cues affect cells and organs. OOCs with membranes are in vitro microfluidic models that are used to replace animal testing for various applications, such as drug discovery and disease modeling. In this review, the relevance of OOCs with membranes is discussed as well as their scaffold and actuation roles, properties (physical and material), and fabrication methods in different organ models. The purpose was to aid readers with membrane selection for the development of OOCs with specific applications in the fields of mechanistic, pathological, and drug testing studies. Mechanical stimulation from liquid flow and cyclic strain, as well as their effects on the cell's increased physiological relevance (IPR), are described in the first section. The review also contains methods to fabricate synthetic and ECM (extracellular matrix) protein membranes, their characteristics (e.g., thickness and porosity, which can be adjusted depending on the application, as shown in the graphical abstract), and the biological materials used for their coatings. The discussion section joins and describes the roles of membranes for different research purposes and their advantages and challenges.

Osteogenesis-Inducing Chemical Cues Enhance the Mechanosensitivity of Human Mesenchymal Stem Cells for Osteogenic Differentiation on a Microtopographically Patterned Surface

Mechanical cues are widely used for regulating cell behavior because of their overarching, extensive, and non-invasive advantages. However, unlike chemical cues, mechanical cues are not efficient enough to determine cell fate independently and improving the mechanosensitivity of cells is rather challenging. In this study, the combined effect of chemical and mechanical cues on the osteogenic differentiation of human mesenchymal stem cells is examined. These results show that chemical cues such as the presence of an osteogenic medium, induce cells to secrete more collagen, and induce integrin for recruiting focal adhesion proteins that mature and cascade a series of events with the help of the mechanical force of the scaffold material. High-resolution, highly ordered hollow-micro-frustum-arrays using double-layer lithography, combined with modified methacrylate gelatin loaded with pre-defined soluble chemicals to provide both chemical and mechanical cues to cells. This approach ultimately facilitates the achievement of cellular osteodifferentiation and enhances bone repair efficiency in a model of femoral fracture in vivo in mice. Moreover, the results also reveal these pivotal roles of Integrin α2/Focal adhesion kinase/Ras homolog gene family member A/Large Tumor Suppressor 1/Yes-associated protein in human mesenchymal stem cells osteogenic differentiation both in vitro and in vivo. Overall, these results show that chemical cues enhance the microtopographical sensitivity of cells.

3D-bioprinted gradient-structured scaffold generates anisotropic cartilage with vascularization by pore-size-dependent activation of HIF1α/FAK signaling axis

Articular cartilage injury is one of the most common diseases in orthopedics, which seriously affects patients' life quality, the development of a biomimetic scaffold that mimics the multi-layered gradient structure of native cartilage is a new cartilage repair strategy. It has been shown that scaffold topography affects cell attachment, proliferation, and differentiation; the underlying molecular mechanism of cell-scaffold interaction is still unclear. In the present study, we construct an anisotropic gradient-structured cartilage scaffold by three-dimensional (3D) bioprinting, in which bone marrow stromal cell (BMSC)-laden anisotropic hydrogels micropatterns were used for heterogeneous chondrogenic differentiation and physically gradient synthetic poly (ε-caprolactone) (PCL) to impart mechanical strength. In vitro and in vivo, we demonstrated that gradient-structured cartilage scaffold displayed better cartilage repair effect. The heterogeneous cartilage tissue maturation and blood vessel ingrowth were mediated by a pore-size-dependent mechanism and HIF1α/FAK axis activation. In summary, our results provided a theoretical basis for employing 3D bioprinting gradient-structured constructs for anisotropic cartilage regeneration and revealed HIF1α/FAK axis as a crucial regulator for cell-material interactions, so as to provide a new perspective for cartilage regeneration and repair.

Bioinspired membrane provides periosteum-mimetic microenvironment for accelerating vascularized bone regeneration

Periosteum plays a pivotal role in vascularization, ossification and remodeling during the healing process of bone injury. However, there are few studies focused on the construction of artificial implants with periosteum-mimetic effect. To emulate the primary role of natural periosteum or endosteal tissues in bone regeneration, here we provide a functional biomimetic membrane with micropatterns of site-specific biomineralization. The micropattern is generated by using printed hydroxyapatite nanoparticles (HANPs), combined with selective growth of biomineralized apatite and in situ coprecipitation with growth factors. The biomimetic membrane can sustainably provide a periosteum-mimetic microenvironment, such as long-term topographical guidance for cell recruitment and induced cell differentiation, by releasing calcium phosphate and growth factors. We demonstrated that rat mesenchymal stem cells (rMSCs) on such biomimetic membrane exhibited highly aligned organization, leading to enhanced angiogenesis and osteogenesis. In the rat calvarial defect model, our biomimetic membranes with biomineralized micropatterns could significantly enhance vascularized ossification and accelerate new bone formation. The current work suggests that the functionally biomimetic membranes with specific biomineralized micropatterns can be a promising alternative to periosteal autografts, with great potential for bench-to-bedside translation in orthopedics.

Graphene Oxide-Based Nanomaterials: An Insight into Retinal Prosthesis

Retinal prosthesis has recently emerged as a treatment strategy for retinopathies, providing excellent assistance in the treatment of age-related macular degeneration (AMD) and retinitis pigmentosa. The potential application of graphene oxide (GO), a highly biocompatible nanomaterial with superior physicochemical properties, in the fabrication of electrodes for retinal prosthesis, is reviewed in this article. This review integrates insights from biological medicine and nanotechnology, with electronic and electrical engineering technological breakthroughs, and aims to highlight innovative objectives in developing biomedical applications of retinal prosthesis.

Engineering Biocompatible Interfaces via Combinations of Oxide Films and Organic Self-Assembled Monolayers

In this paper, we demonstrate that cell adhesion and neuron maturation can be guided by patterned oxide surfaces functionalized with organic molecular layers. It is shown that the difference in the surface potential of various oxides (SiO₂, Ta₂O₅, TiO₂, and Al₂O₃) can be increased by functionalization with a silane, (3-aminopropyl)-triethoxysilane (APTES), which is deposited from the gas phase on the oxide. Furthermore, it seems that only physisorbed layers (no chemical binding) can be achieved for some oxides (Ta₂O₅ and TiO₂), whereas self-assembled monolayers (SAM) form on other oxides (SiO₂ and Al₂O₃). This does not only alter the surface potential but also affects the neuronal cell growth. The already high cell density on SiO₂ is increased further by the chemically bound APTES SAM, whereas the already low cell density on Ta₂O₅ is even further reduced by the physisorbed APTES layer. As a result, the cell density is ∼8 times greater on SiO₂ compared to Ta₂O₅, both coated with APTES. Furthermore, neurons form the typical networks on SiO₂, whereas they tend to cluster to form neurospheres on Ta₂O₅. Using lithographically patterned Ta₂O₅ layers on SiO₂ substrates functionalized with APTES, the guided growth can be transferred to complex patterns. Cell cultures and molecular layers can easily be removed, and the cell experiment can be repeated after functionalization of the patterned oxide surface with APTES. Thus, the combination of APTES-functionalized patterned oxides might offer a promising way of achieving guided neuronal growth on robust and reusable substrates.

Microfluidics-Based Biomaterials and Biodevices

The rapid development of microfluidics technology has promoted new innovations in materials science, particularly by interacting with biological systems, based on precise manipulation of fluids and cells within microscale confinements. This article reviews the latest advances in microfluidics-based biomaterials and biodevices, highlighting some burgeoning areas such as functional biomaterials, cell manipulations, and flexible biodevices. These areas are interconnected not only in their basic principles, in that they all employ microfluidics to control the makeup and morphology of materials, but also unify at the ultimate goals in human healthcare. The challenges and future development trends in biological application are also presented.

Plasma Polymer Coatings To Direct the Differentiation of Mouse Kidney-Derived Stem Cells into Podocyte and Proximal Tubule-like Cells

Kidney disease is now recognized as a global health problem and is associated with increased morbidity and mortality, along with high economic costs. To develop new treatments for ameliorating kidney injury and preventing disease progression, there is a need for appropriate renal culture systems for screening novel drugs and investigating the cellular mechanisms underlying renal pathogenesis. There is a need for in vitro culture systems that promote the growth and differentiation of specialized renal cell types. In this work, we have used plasma polymerization technology to generate gradients of chemical functional groups to explore whether specific concentrations of these functional groups can direct the differentiation of mouse kidney-derived stem cells into specialized renal cell types. We found that amine-rich (-NH₂) allylamine-based plasma-polymerized coatings could promote differentiation into podocyte-like cells, whereas methyl-rich (CH₃) 1,7-octadiene-based coatings promoted differentiation into proximal tubule-like cells (PTC). Importantly, the PT-like cells generated on the substrates expressed the marker megalin and were able to endocytose albumin, indicating that the cells were functional.

Cell membrane-covered nanoparticles as biomaterials

Surface engineering of synthetic carriers is an essential and important strategy for drug delivery in vivo. However, exogenous properties make synthetic nanosystems invaders that easily trigger the passive immune clearance mechanism, increasing the retention effect caused by the reticuloendothelial systems and bioadhesion, finally leading to low therapeutic efficacy and toxic effects. Recently, a cell membrane cloaking technique has been reported as a novel interfacing approach from the biological/immunological perspective, and has proved useful for improving the performance of synthetic nanocarriers in vivo. After cell membrane cloaking, nanoparticles not only acquire the physiochemical properties of natural cell membranes but also inherit unique biological functions due to the presence of membrane-anchored proteins, antigens, and immunological moieties. The derived biological properties and functions, such as immunosuppressive capability, long circulation time, and targeted recognition integrated in synthetic nanosystems, have enhanced their potential in biomedicine in the future. Here, we review the cell membrane-covered nanosystems, highlight their novelty, introduce relevant biomedical applications, and describe the future prospects for the use of this novel biomimetic system constructed from a combination of cell membranes and synthetic nanomaterials.

Synthesizing Living Tissues with Microfluidics

In native tissues, various cell types organize and spatiotemporally function and communicate with neighboring or remote cells in a highly regulated way. How can we replicate these amazing functional structures in vitro? From the view of a chemist, the heterogeneous cells and extracellular matrix (ECM) could be regarded as various chemical substrate materials for "synthetic" reactions during tissue engineering. But how can we accelerate these reactions? Microfluidics provides ideal solutions. Microfluidics could be metaphorically regarded as a miniature "biofactory", whereas the on-chip critical chemical cues such as biomolecule gradients and physical cues such as geometrical confinement, topological guidance, and mechanical stimulations, along with the external stimulations such as light, electricity, acoustics, and magnetics, could be regarded as "catalytic cues" which can accelerate the "synthetic reactions" by precisely and effectively manipulating a series of cell behaviors including cell adhesion, migration, growth, proliferation, differentiation, cell-cell interaction, and cell-matrix interaction to reduce activation energy of the "synthetic reactions". Thus, on the microfluidics platform, the "biofactory", various "synthetic" reactions take place to change the substrate materials (cells and ECM) into products (tissues) in a nonlinear way, which is a typical feature of a biological process. By precisely organizing the substrate materials and spatiotemporally controlling the activity of the products, as a "biofactory", the microfluidics system can not only "synthesize" living tissues but also recreate physiological or pathophysiological processes such as immune responses, angiogenesis, wound healing, and tumor metastasis in vitro to bring insights into the mechanisms underlying these processes taking place in vivo. In this Account, we borrow the concept of chemical "synthesis" to describe how to "synthesize" artificial tissues using microfluidics from a chemist's view. Accelerated by the built-in physiochemical cues on microfluidics and external stimulations, various tissues could be "synthesized" on a microfluidics platform. We summarize that there are "step-by-step synthesis" and "one-step synthesis" on microfluidics for creating desired tissues with unprecedented precision, accuracy, and speed. In recent years, researchers developed various microfluidic techniques including creating adhesive domains for mediating reverse and precise adhesion, chemical gradients for directing cell growth, geometrical confinements and topological cues for manipulating cell migration, and mechanics for stimulating cell differentiation. By employing and orchestrating these on-chip tissue "synthetic" conditions, "step-by-step synthesis" could be realized on chips to develop multilayered tissues such as blood vessels. "One-step synthesis" on chips could develop functional three-dimensional tissue structures such as neural networks or nephron-like structures. Based on these on-chip studies, many critical physiological and pathophysiological processes such as wound healing, tumor metastasis, and atherosclerosis could be deeply investigated, and the drugs or therapeutic approaches could also be evaluated or screened conveniently. The "synthetic tissues on microfluidics" system would pave an avenue for precise creation of artificial tissues for not only fundamental research but also biomedical applications such as tissue engineering.

Biomimetic nanofibers can construct effective tissue-engineered intervertebral discs for therapeutic implantation

We present a total tissue engineered (TE) intervertebral disc (IVD) to address IVD degradation, which is a major cause of chronic neck and back pain. The TE IVD is comprised of an alginate hydrogel-based nucleus pulposus (NP) and hierarchically organized, concentric ring-aligned electrospun (ES) polycaprolactone (PCL)/poly (d,l-lactide-co-glycolide) (PLGA)/Collagen type I (PPC)-based annulus fibrosus (AF). The TE IVD exhibits excellent hydrophilicity to simulate highly hydrated native IVD. Long-term in vivo implantation assays demonstrate the excellent structural (shape maintenance, hydration, and integration with surrounding tissues) and functional (mechanical supporting and flexibility) performances of the TE IVD. Our study provides a novel approach for treating IVD degeneration.

Morphology, Migration, and Transcriptome Analysis of Schwann Cell Culture on Butterfly Wings with Different Surface Architectures

It has been shown that material surface topography greatly affects cell attachment, growth, proliferation, and differentiation. However, the underlying molecular mechanisms for cell-material interactions are still not understood well. Here, two kinds of butterfly wings with different surface architectures were employed for addressing such an issue. Papilio ulysses telegonus (P.u.t.) butterfly wing surface is composed of micro/nanoconcaves, whereas Morpho menelaus (M.m.) butterfly wings are decorated with grooves. RSC96 cells grown on M.m. wings showed a regular sorting pattern along with the grooves. On the contrary, the cells seeded on P.u.t. wings exhibited random arrangement. Transcriptome sequencing and bioinformatics analysis revealed that huntingtin (Htt)-regulated lysosome activity is a potential key factor for determining cell growth behavior on M.m. butterfly wings. Gene silence further confirmed this notion. In vivo experiments showed that the silicone tubes fabricated with M.m. wings markedly facilitate rat sciatic nerve regeneration after injury. Lysosome activity and Htt expression were greatly increased in the M.m. wing-fabricated graft-bridged nerves. Collectively, our data provide a theoretical basis for employing butterfly wings to construct biomimetic nerve grafts and establish Htt lysosome as a crucial regulator for cell-material interactions.

Stability of a biodegradable microcarrier surface: physically adsorbed versus chemically linked shells

Mesenchymal stem cells (MSCs) have gained increasing interest for tissue engineering and cellular therapy. MSC expansion on microcarriers (MCs) in stirred bioreactors has emerged as an attractive method for their scaled up production. Some MCs have been developed based on polyesters as a hydrophobic biodegradable core. However, most of these MCs are formulated by an emulsion/organic solvent evaporation (E/E) process using poly(vinyl alcohol) as a shell steric stabilizer, which is biocompatible but not degradable in vivo. Moreover, in most of these MCs, the polymer shell is only physically adsorbed at the particle surface. To the best of our knowledge, no study deals with the stability of such a shell when the MCs are in contact with competitive surfactants or with proteins contained in the culture medium. In this study, fully in vivo bioresorbable dextran-covered polylactide-based MCs were formulated using an E/E process, which allowed to control their surface chemistry. Different dextran derivatives with alkyne or ammonium groups were firstly synthesised. Then, on the one hand, some MCs (non-clicked MCs) were formulated with a physically adsorbed polysaccharide shell onto the core. On the other hand, the polysaccharide shell was linked to the core via in situ CuAAC click-chemistry carried out during the E/E process (clicked MCs). The stability of such coverage was first studied in the presence of competitive surfactants (sodium dodecyl sulfate-SDS, or proteins contained in the culture medium) using nanoparticles (NPs) exhibiting the same chemical composition (core/shell) as MCs. The results revealed the total desorption of the dextran shell for non-clicked NPs after treatment with SDS or the culture medium, while this shell desorption was greatly decreased for clicked NPs. A qualitative study of this shell stability was finally carried out on MCs formulated using a new fluorescent dextran-based surfactant. The results were in agreement with those observed for NPs, and showed that non-clicked MCs are characterized by poor shell stability in contact with a competitive surfactant, which could be quite an issue during MSC expansion. In contrast, clicked MCs possess better shell stability, which allow a better control of the MC surface chemistry, especially during cell culture.

Hepatocyte Aggregate Formation on Chitin-Based Anisotropic Microstructures of Butterfly Wings

Scaffold nanotopography plays the most significant role in the mimicry of the in vivo microenvironment of the hepatocytes. Several attempts have been made to develop methods and substrates suited to growing hepatocytes into aggregates. Functional biomaterials, particularly biodegradable polymers, have been used in several studies aimed to develop improved scaffolds with ordered geometry and nanofibrous architecture for tissue engineering. However, there are still some limitation in their fabrication: it is not cost-efficient, is time-consuming, and exhibits some technological complications. The synthetic scaffolds are usually non-biodegradable and can be non-biocompatible compared to the naturally derived biomaterials. Here, we utilized a simple, cost-effective, and green method with two-step chemical treatment to get more selected hydrophilic butterfly wings from Morpho menelaus, Papilio ulysses telegonus, and Ornithoptera croesus lydius as a chitin-based natural scaffolds to growing hepatocyte aggregates. We established a three-dimensional (3D) in vitro model for culture of HepG2 cells and aggregate formation that maintained the hepatocytes function on these natural anisotropic microstructures. Cells cultured on these substrates show higher viability than those cultured on a two-dimensional (2D) culture plate. Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay results revealed excellent viability of HepG2 cells on P. u. telegonus wings (fibrous area). The results also demonstrated appropriate cell activity, cell retention, and stable and functional expression in terms of albumin secretion and urea synthesis activity compared to the 2D monolayer culture of hepatocytes on the culture dish surface. With a slightly different degree, the other substrates also shown similar results. We anticipate that these natural anisotropic, biodegradable, and biocompatible substrates can maintain long-term hepatic culture as an in vitro 3D model for potential therapeutic applications and regenerative tissue applications. The model presented here provides a feasible alternative to the synthetic scaffolds and is expected to be more reliable for 3D organotypic liver culture models based on such scaffolds.

Three-dimensional hierarchical cultivation of human skin cells on bio-adaptive hybrid fibers

The human skin comprises a complex multi-scale layered structure with hierarchical organization of different cells within the extracellular matrix (ECM). This supportive fiber-reinforced structure provides a dynamically changing microenvironment with specific topographical, mechanical and biochemical cell recognition sites to facilitate cell attachment and proliferation. Current advances in developing artificial matrices for cultivation of human cells concentrate on surface functionalizing of biocompatible materials with different biomolecules like growth factors to enhance cell attachment. However, an often neglected aspect for efficient modulation of cell-matrix interactions is posed by the mechanical characteristics of such artificial matrices. To address this issue, we fabricated biocompatible hybrid fibers simulating the complex biomechanical characteristics of native ECM in human skin. Subsequently, we analyzed interactions of such fibers with human skin cells focusing on the identification of key fiber characteristics for optimized cell-matrix interactions. We successfully identified the mediating effect of bio-adaptive elasto-plastic stiffness paired with hydrophilic surface properties as key factors for cell attachment and proliferation, thus elucidating the synergistic role of these parameters to induce cellular responses. Co-cultivation of fibroblasts and keratinocytes on such fiber mats representing the specific cells in dermis and epidermis resulted in a hierarchical organization of dermal and epidermal tissue layers. In addition, terminal differentiation of keratinocytes at the air interface was observed. These findings provide valuable new insights into cell behaviour in three-dimensional structures and cell-material interactions which can be used for rational development of bio-inspired functional materials for advanced biomedical applications.

Bioprinting-Based PDLSC-ECM Screening for in Vivo Repair of Alveolar Bone Defect Using Cell-Laden, Injectable and Photocrosslinkable Hydrogels

Periodontitis is an inflammatory disease worldwide that may result in periodontal defect (especially alveolar bone defect) and even tooth loss. Stem-cell-based approach combined with injectable hydrogels has been proposed as a promising strategy in periodontal treatments. Stem cells fate closely depends on their extracellular matrix (ECM) characteristics. Hence, it is necessary to engineer an appropriate injectable hydrogel to deliver stem cells into the defect while serving as the ECM during healing. Therefore, stem cell-ECM interaction should be studied for better stem cell transplantation. In this study, we developed a bioprinting-based strategy to study stem cell-ECM interaction and thus screen an appropriate ECM for in vivo repair of alveolar bone defect. Periodontal ligament stem cells (PDLSCs) were encapsulated in injectable, photocrosslinkable composite hydrogels composed of gelatin methacrylate (GelMA) and poly(ethylene glycol) dimethacrylate (PEGDA). PDLSC-laden GelMA/PEGDA hydrogels with varying composition were efficiently fabricated via a 3D bioprinting platform by controlling the volume ratio of GelMA-to-PEGDA. PDLSC behavior and fate were found to be closely related to the engineered ECM composition. The 4/1 GelMA/PEGDA composite hydrogel was selected since the best performance in osteogenic differentiation in vitro. Finally, in vivo study indicated a maximal and robust new bone formation in the defects treated with the PDLSC-laden hydrogel with optimized composition as compared to the hydrogel alone and the saline ones. The developed approach would be useful for studying cell-ECM interaction in 3D and paving the way for regeneration of functional tissue.

Open-label phase I clinical trial of Ad5-EBOV in Africans in China

BACKGROUND

To determine the safety and immunogenicity of a novel recombinant adenovirus type 5 vector based Ebola virus disease vaccine (Ad5-EBOV) in Africans in China.

METHODS

A phase 1, dose-escalation, open-label trial was conducted. 61 healthy Africans were sequentially enrolled, with 31 participants receiving one shot intramuscular injection and 30 participants receiving a double-shot regimen. Primary and secondary end points related to safety and immunogenicity were assessed within 28 d after vaccination. This study was registered with ClinicalTrials.gov (NCT02401373).

RESULTS

Ad5-EBOV is well tolerated and no adverse reaction of grade 3 or above was observed. 53 (86.89%) participants reported at least one adverse reaction within 28 d of vaccination. The most common reaction was fever and the mild pain at injection site, and there were no significant difference between these 2 groups. Ebola glycoprotein-specific antibodies appeared in all 61 participants and antibodies titers peaked after 28 d of vaccination. The geometric mean titres (GMTs) were similar between these 2 groups (1919.01 vs 1684.70 P = 0.5562). The glycoprotein-specific T-cell responses rapidly peaked after 14 d of vaccination and then decreased, however, the percentage of subjects with responses were much higher in the high-dose group (60.00% vs 9.68%, P = 0.0014). Pre-existing Ad5 neutralizing antibodies could significantly dampen the specific humoral immune response and cellular response to the vaccine.

CONCLUSION

The application of Ad5-EBOV demonstrated safe in Africans in China and a specific GP antibody and T-cell response could occur 14 d after the first immunization. This acceptable safety profile provides a reliable basis to proceed with trials in Africa.

Chitin-Based Anisotropic Nanostructures of Butterfly Wings for Regulating Cells Orientation

In recent years, multiple types of substrates have been applied for regulating cell orientation. Among them, surface topography patterns with grooves or ridges have been widely utilizing for cell culturing. However, this construction is still complicated, low cost-effective and exhibits some technological limitations with either "top-down" or "bottom-up" approaches. Here, a simple and green method was developed by utilizing butterfly wings (Morpho menelaus, Papilio ulysses telegonus and Ornithoptera croesus lydius) with natural anisotropic nanostructures to generate cell alignment. A two-step chemical treatment was proposed to achieve more hydrophilic butterfly wings preceding cell culturing. Furthermore, calcein acetoxymethyl ester (Calcein-AM) staining and Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay results demonstrated the appropriate viability of NIH-3T3 fibroblast cells on those butterfly wings. Moreover, the cells displayed a high degree of alignment in each specimen of these wings. We anticipate that those originating from natural butterfly wings will pose important applications for tissue engineering.

Modulation of Heterotypic and Homotypic Cell-Cell Interactions via Zwitterionic Lipid Masks

Since the pioneering work by Whitesides, innumerable platforms that aim to spatio-selectively seed cells and control the degree of cell-cell interactions in vitro have been developed. These methods, however, have generally been technically and methodologically complex, or demanded stringent materials and conditions. In this work, we introduce zwitterionic lipids as patternable, cell-repellant masks for selectively seeding cells. The lipid masks are easily removed with a routine washing step under physiological conditions (37 °C, pH 7.4), and are used to create patterned cocultures, as well as to conduct cell migration studies. We demonstrate, via patterned cocultures of NIH 3T3 fibroblasts and HeLa cells, that HeLa cells proliferate far more aggressively than NIH 3T3 cells, regardless of initial population sizes. We also show that fibronectin-coated substrates induce cell movement akin to collective migration in NIH 3T3 fibroblasts, while the cells cultured on unmodified substrates migrate independently. Our lipid mask platform offers a rapid and highly biocompatible means of selectively seeding cells, and acts as a versatile tool for the study of cell-cell interactions.

Emerging Droplet Microfluidics

Droplet microfluidics generates and manipulates discrete droplets through immiscible multiphase flows inside microchannels. Due to its remarkable advantages, droplet microfluidics bears significant value in an extremely wide range of area. In this review, we provide a comprehensive and in-depth insight into droplet microfluidics, covering fundamental research from microfluidic chip fabrication and droplet generation to the applications of droplets in bio(chemical) analysis and materials generation. The purpose of this review is to convey the fundamentals of droplet microfluidics, a critical analysis on its current status and challenges, and opinions on its future development. We believe this review will promote communications among biology, chemistry, physics, and materials science.

Constructing Tissuelike Complex Structures Using Cell-Laden DNA Hydrogel Bricks

Tissue engineering has long been a challenge because of the difficulty of addressing the requirements that such an engineered tissue must meet. In this paper, we developed a new "brick-to-wall" based on unique properties of DNA supramolecular hydrogels to fabricate three-dimensional (3D) tissuelike structures: different cell types are encapsulated in DNA hydrogel bricks which are then combined to build 3D structures. Signal responsiveness of cells through the DNA gels was evaluated and it was discovered that the gel permits cell migration in 3D. The results demonstrated that this technology is convenient, effective and reliable for cell manipulation, and we believe that it will benefit artificial tissue fabrication and future large-scale production.

Gradient and Patterned Protein Films Stabilized via Nanoimprint Lithography for Engineered Interactions with Cells

Protein-based biomaterials provide versatile scaffolds for generating functional surfaces for biomedical applications. However, tailoring the functional and biological properties of protein films remains a challenge. Here, we describe a high-throughput method to designing stable, functional biomaterials by combining inkjet deposition of protein inks with a nanoimprint lithography based methodology. The translation of the intrinsically charged proteins into functional materials properties was demonstrated through controlled cellular adhesion. This modular strategy offers a rapid method to produce customizable biomaterials.

Surface chemistry from wettability and charge for the control of mesenchymal stem cell fate through self-assembled monolayers

Self-assembled monolayers (SAMs) of alkanethiols on gold are highly controllable model substrates and have been employed to mimic the extracellular matrix for cell-related studies. This study aims to systematically explore how surface chemistry influences the adhesion, morphology, proliferation and osteogenic differentiation of mouse mesenchymal stem cells (mMSCs) using various functional groups (-OEG, -CH₃, -PO₃H₂, -OH, -NH₂ and -COOH). Surface analysis demonstrated that these functional groups produced a wide range of wettability and charge: -OEG (hydrophilic and moderate iso-electric point (IEP)), -CH₃ (strongly hydrophobic and low IEP), -PO₃H₂ (moderate wettability and low IEP), -OH (hydrophilic and moderate IEP), -NH₂ (moderate wettability and high IEP) and -COOH (hydrophilic and low IEP). In terms of cell responses, the effect of wettability may be more influential than charge for these groups. Moreover, compared to -OEG and -CH₃ groups, -PO₃H₂, -OH, -NH₂ and -COOH functionalities tended to promote not only cell adhesion, proliferation and osteogenic differentiation but also the expression of α_v and β₁ integrins. This finding indicates that the surface chemistry may guide mMSC activities through α_v and β₁ integrin signaling pathways. Model surfaces with controllable chemistry may provide insight into biological responses to substrate surfaces that would be useful for the design of biomaterial surfaces.

Cell surface engineering to control cellular interactions

Cell surface composition determines all interactions of the cell with is environment, thus cell functions such as adhesion, migration and cell-cell interactions are likely to be controlled by engineering and manipulating cell membrane. Cell membranes present a rich repertoire of molecules, therefore a versatile ground for modification. However the complex and dynamic nature of the cell surface is also a major challenge for cell surface engineering that should also involve strategies compatible with cell viability. Cell surface engineering by selective chemical reactions or by the introduction of exogenous targeting ligands can be powerful tools for engineering novel interactions and control cell function. In addition to chemical conjugation and modification of functional groups, ligands of interest to modify the surface of cells include recombinant proteins, liposomes or nanoparticles. Here, we review recent efforts to perform changes to cell surface composition. We focus on the engineering of the cell surface with biological, chemical or physical methods to modulate cell functions and control cell-cell and cell-microenvironment interactions. Potential applications of cell surface engineering are also stated.

The influence of anisotropic nano- to micro-topography on in vitro and in vivo osteogenesis

AIM

Topographically modified substrates are increasingly used in tissue engineering to enhance biomimicry. The overarching hypothesis is that topographical cues will control cellular response at the cell-substrate interface.

MATERIALS & METHODS

The influence of anisotropically ordered poly(lactic-co-glycolic acid) substrates (constant groove width of ~1860 nm; constant line width of ~2220 nm; variable groove depth of ~35, 306 and 2046 nm) on in vitro and in vivo osteogenesis were assessed.

RESULTS & DISCUSSION

We demonstrate that substrates with groove depths of approximately 306 and 2046 nm promote osteoblast alignment parallel to underlined topography in vitro. However, none of the topographies assessed promoted directional osteogenesis in vivo.

CONCLUSION

2D imprinting technologies are useful tools for in vitro cell phenotype maintenance.

A strategy for rapid and facile fabrication of controlled, layered blood vessel-like structures

With the aid of fibrin glue, we wrap thin films into multi-layered tubes with a precisely-arranged cell distribution within 70 min.

Endogenous signalling control of cell adhesion by using aptamer functionalized biocompatible hydrogel

Design of biological signal-responsive biomaterials is essential for controlling cell-cell and cell-matrix interactions. Herein, we developed a dynamic hydrogel to control cell adhesion with biological signals in a cellular microenvironment. The basic principle was based on using nucleic acid aptamer to recognize cell signalling and control the display of bioligands on the hydrogel. Not only exogenous signalling but also endogenous signalling secreted by surrounding cells could activate the dynamic scaffold and tune the cell adhesion state. Since diverse aptamers have been developed, our design can be extended to multiple biological inputs. The biochemical signal-responsive system will greatly enhance the understanding of complex biological processes as well as the ability to manipulate cellular behaviors.

Harnessing Hierarchical Nano- and Micro-Fabrication Technologies for Musculoskeletal Tissue Engineering

Cells within a tissue are able to perceive, interpret and respond to the biophysical, biomechanical, and biochemical properties of the 3D extracellular matrix environment in which they reside. Such stimuli regulate cell adhesion, metabolic state, proliferation, migration, fate and lineage commitment, and ultimately, tissue morphogenesis and function. Current scaffold fabrication strategies in musculoskeletal tissue engineering seek to mimic the sophistication and comprehensiveness of nature to develop hierarchically assembled 3D implantable devices of different geometric dimensions (nano- to macrometric scales) that will offer control over cellular functions and ultimately achieve functional regeneration. Herein, advances and shortfalls of bottom-up (self-assembly, freeze-drying, rapid prototype, electrospinning) and top-down (imprinting) scaffold fabrication approaches, specific to musculoskeletal tissue engineering, are discussed and critically assessed.

Engineering cell-compatible paper chips for cell culturing, drug screening, and mass spectrometric sensing

Paper-supported cell culture is an unprecedented development for advanced bioassays. This study reports a strategy for in vitro engineering of cell-compatible paper chips that allow for adherent cell culture, quantitative assessment of drug efficiency, and label-free sensing of intracellular molecules via paper spray mass spectrometry. The polycarbonate paper is employed as an excellent alternative bioscaffold for cell distribution, adhesion, and growth, as well as allowing for fluorescence imaging without light scattering. The cell-cultured paper chips are thus amenable to fabricate 3D tissue construction and cocultures by flexible deformation, stacks and assembly by layers of cells. As a result, the successful development of cell-compatible paper chips subsequently offers a uniquely flexible approach for in situ sensing of live cell components by paper spray mass spectrometry, allowing profiling the cellular lipids and quantitative measurement of drug metabolism with minimum sample pretreatment. Consequently, the developed paper chips for adherent cell culture are inexpensive for one-time use, compatible with high throughputs, and amenable to label-free and rapid analysis.

Single-crystal-conjugated polymers with extremely high electron sensitivity through template-assisted in situ polymerization

Single-crystal-conjugated polymer (SCCP) arrays are prepared successfully via a simple method, which is a combination of the contact thermochemical reaction and solvent-free in situ polymerization. The dramatic X-ray diffraction and selective-area electron diffraction results show the high crystallinity of the SCCP arrays. These SCCP arrays display unique physical properties and show great potential in flexible electronics.

A near-infrared light-controlled system for reversible presentation of bioactive ligands using polypeptide-engineered functionalized gold nanorods

A near-infrared light-controlled hybrid platform with polypeptide-engineered functionalized gold nanorods has been designed for reversible presentation of the immobilized ligands to cell surface receptors on the engineered materials.

Surface amorphization of NiTi alloy induced by Ultrasonic Nanocrystal Surface Modification for improved mechanical properties

We report herein the effects of Ultrasonic Nano-crystal Surface Modification (UNSM), a severe surface plastic deformation process, on the microstructure, mechanical (hardness, wear), wettability and biocompatibility properties of NiTi shape memory alloy. Complete surface amorphization of NiTi was achieved by this process, which was confirmed by X-ray diffraction and high-resolution transmission electron microscopy. The wear resistance of the samples after UNSM processing was significantly improved compared with the non-processed samples due to increased surface hardness of the alloy by this process. In addition, cell culture study demonstrated that the biocompatibility of the samples after UNSM processing has not been compromised compared to the non-processed sample. The combination of high wear resistance and good biocompatibility makes UNSM an appealing process for treating alloy-based biomedical devices.

Enhancement of VEGF-Mediated Angiogenesis by 2-N,6-O-Sulfated Chitosan-Coated Hierarchical PLGA Scaffolds

Rapid and controlled vascularization within scaffolds remains one of the key limitations in tissue engineering applications. This study describes the fabrication and characterization of 2-N,6-O-sulfated chitosan (26SCS)-coated hierarchical scaffold composed of poly(lactic-co-glycolic acid) (PLGA) microspheres, as a desirable vehicle for vascular endothelial growth factor (VEGF) delivery and consequent angiogenic boosting in vitro. Owing to the hierarchical porous structure and high affinity between VEGF and 26SCS, the 26SCS-modified PLGA (S-PLGA) scaffold possesses excellent entrapment and sustained release of VEGF. Using human umbilical vein endothelial cells (HUVECs) as a cell model, the VEGF-loaded S-PLGA scaffold shows desirable cell viability and attachment. The bioactivity of released VEGF is validated by intracellular nitric oxide secretion and capillary tube formation, demonstrating the improved capacity of VEGF-mediated pro-angiogenesis ascribed to 26SCS incorporation. Such a strategy will afford an effective method to prepare a scaffold with promoted angiogenesis.

Matrix-Immobilized BMP-2 on Microcontact Printed Fibronectin as an in vitro Tool to Study BMP-Mediated Signaling and Cell Migration

During development, growth factors (GFs) such as bone morphogenetic proteins (BMPs) exert important functions in several tissues by regulating signaling for cell differentiation and migration. In vivo, the extracellular matrix (ECM) not only provides support for adherent cells, but also acts as reservoir of GFs. Several constituents of the ECM provide adhesive cues, which serve as binding sites for cell trans-membrane receptors, such as integrins. In conveying adhesion-mediated signaling to the intracellular compartment, integrins do not function alone but rather crosstalk and cooperate with other receptors, such as GF receptors. Here, we present a strategy for the immobilization of BMP-2 onto cellular fibronectin (cFN), a key protein of the ECM, to investigate GF-mediated signaling and migration. Following biotinylation, BMP-2 was linked to biotinylated cFN using NeutrAvidin as cross-linker. Characterization with quartz crystal microbalance with dissipation monitoring and enzyme-linked immunosorbent assay confirmed the efficient immobilization of BMP-2 on cFN over a period of 24 h. To validate the bioactivity of matrix-immobilized BMP-2 (iBMP-2), we investigated short- and long-term responses of C2C12 myoblasts, which are an established in vitro model for BMP-2 signaling, in comparison to soluble BMP-2 (sBMP-2) or in absence of GFs. Similarly to sBMP-2, iBMP-2 triggered Smad 1/5 phosphorylation and translocation of the complex to the nucleus, corresponding to the activation of BMP-mediated Smad-dependent pathway. Additionally, successful suppression of myotube formation was observed after 6 days in sBMP-2 and iBMP-2. We next implemented this approach in the fabrication of cFN micropatterned stripes by soft lithography. These stripes allowed cell-surface interaction only on the patterned cFN, since the surface in between was passivated, thus serving as platform for studies on directed cell migration. During a 10-h observation time, the migratory behavior, especially the cells' net displacement, was increased in presence of BMP-2. As such, this versatile tool retains the bioactivity of GFs and allows the presentation of ECM adhesive cues.

Impact of surface chemistry and topography on the function of antigen presenting cells

The impact of biomaterial surface topography and chemistry on antigen presenting cells’ phenotype and function.