Silica-based branched hollow microfibers as a biomimetic extracellular matrix for promoting tumor cell growth in vitro and in vivo

Engineering Biomimetic Extracellular Matrix with Silica Nanofibers: From 1D Material to 3D Network

Biomaterials at nanoscale is a fast-expanding research field with which extensive studies have been conducted on understanding the interactions between cells and their surrounding microenvironments as well as intracellular communications. Among many kinds of nanoscale biomaterials, mesoporous fibrous structures are especially attractive as a promising approach to mimic the natural extracellular matrix (ECM) for cell and tissue research. Silica is a well-studied biocompatible, natural inorganic material that can be synthesized as morpho-genetically active scaffolds by various methods. This review compares silica nanofibers (SNFs) to other ECM materials such as hydrogel, polymers, and decellularized natural ECM, summarizes fabrication techniques for SNFs, and discusses different strategies of constructing ECM using SNFs. In addition, the latest progress on SNFs synthesis and biomimetic ECM substrates fabrication is summarized and highlighted. Lastly, we look at the wide use of SNF-based ECM scaffolds in biological applications, including stem cell regulation, tissue engineering, drug release, and environmental applications.

Hollow fibers: from fabrication to applications

Hollow fibers have attracted more and more attention due to their broad range of applications in numerous fields. We review the latest advance and summarize the fabrication methods, types and applications of hollow fibers. We mainly introduce the fabrication methods of hollow fibers, including co-extrusion/co-axial spinning methods, template methods, 3D printing methods, electrospinning methods, self-crimping methods and gas foaming process. Meanwhile, we summarize four types of hollow fibers: one-layered hollow fibers, multi-layered hollow fibers, multi-hollow fibers and branched hollow fibers. Next, we focus on the main applications of hollow fibers, such as gas separation, cell culture, microfluidic channels, artificial tubular tissues, etc. Finally, we present the prospects of the future trend of development. The review would promote the further development of hollow fibers and benefit their advance in sensing, bioreactors, electrochemical catalysis, energy conversion, microfluidics, gas separation, air purification, drug delivery, functional materials, cell culture and tissue engineering. This review has great significance for the design of new functional materials and development of devices and systems in the related fields.

The Role of Biomimetic Hypoxia on Cancer Cell Behaviour in 3D Models: A Systematic Review

Simple Summary

Cancer remains one of the leading causes of death worldwide. The advancements in 3D tumour models provide in vitro test-beds to study cancer growth, metastasis and response to therapy. We conducted this systematic review on existing experimental studies in order to identify and summarize key biomimetic tumour microenvironmental features which affect aspects of cancer biology. The review noted the significance of in vitro hypoxia and 3D tumour models on epithelial to mesenchymal transition, drug resistance, invasion and migration of cancer cells. We highlight the importance of various experimental parameters used in these studies and their subsequent effects on cancer cell behaviour.

Abstract

The development of biomimetic, human tissue models is recognized as being an important step for transitioning in vitro research findings to the native in vivo response. Oftentimes, 2D models lack the necessary complexity to truly recapitulate cellular responses. The introduction of physiological features into 3D models informs us of how each component feature alters specific cellular response. We conducted a systematic review of research papers where the focus was the introduction of key biomimetic features into in vitro models of cancer, including 3D culture and hypoxia. We analysed outcomes from these and compiled our findings into distinct groupings to ascertain which biomimetic parameters correlated with specific responses. We found a number of biomimetic features which primed cancer cells to respond in a manner which matched in vivo response.

Self-Assembly of a Monochromophore-Based Polymer Enables Unprecedented Ratiometric Tracing of Hypoxia

The accuracy of traditional bischromophore-based ratiometric probes is always compromised by undesirable energy/charge transferring interactions between the internal reference moiety and the sensing chromophore. In this regard, ratiometric sensing with a monochromophore system is highly desirable. Herein, an unprecedented monochromophore-based ratiometric probe, which consists of a hydrophilic backbone poly(N-vinylpyrrolidone) (PVP) and single chromophore of platinum(II) tetraphenylporphyrin (Pt-TPP) is reported. Combination of the specific assembled clustering-triggered fluorescent emission (oxygen-insensitive) with the original Pt-TPP phosphorescence (oxygen-sensitive) enables successful construction of a monochromophore-based ratiometric nanosensor for directly tracing hypoxia in vivo, along with the preferable facilitation of enhanced permeation and retention effect and long excitation wavelength. The unique ratiometric signals enable the direct observation from normoxic to hypoxic environment in both living A549 cells and a tumor-bearing mice model, providing a significant paradigm of a monochromophore-based dual-emissive system with the specific assembled cluster emission. The work satisfactorily demonstrates a valuable strategy for designing monochromophore-based dual-emissive materials, and validates its utility for in vivo ratiometric biological sensing without the common energy/charge interference in bischromophore-based system.

Rapidly responsive silk fibroin hydrogels as an artificial matrix for the programmed tumor cells death

Timely and spatially-regulated injectable hydrogels, able to suppress growing tumors in response to conformational transitions of proteins, are of great interest in cancer research and treatment. Herein, we report rapidly responsive silk fibroin (SF) hydrogels formed by a horseradish peroxidase (HRP) crosslinking reaction at physiological conditions, and demonstrate their use as an artificial biomimetic three-dimensional (3D) matrix. The proposed SF hydrogels presented a viscoelastic nature of injectable hydrogels and spontaneous conformational changes from random coil to β-sheet conformation under physiological conditions. A human neuronal glioblastoma (U251) cell line was used for screening cell encapsulation and in vitro evaluation within the SF hydrogels. The transparent random coil SF hydrogels promoted cell viability and proliferation up to 10 days of culturing, while the crystalline SF hydrogels converted into β-sheet structure induced the formation of TUNEL-positive apoptotic cells. Therefore, this work provides a powerful tool for the investigation of the microenvironment on the programed tumor cells death, by using rapidly responsive SF hydrogels as 3D in vitro tumor models.

Functional hepatocyte clusters on bioactive blend silk matrices towards generating bioartificial liver constructs

The creation of in vitro functional hepatic tissue simulating micro-environmental niche of native liver is a keen area of research due to its demand in bioartificial liver (BAL) and cell-based tissue engineering. Here, we investigated the potential of novel blend (BA) silk scaffold fabricated by blending mulberry (Bombyx mori, BM) silk fibroin with cell adhesion motif (RGD) rich non-mulberry (Antheraea assamensis, AA) silk fibroin, in generating a functional liver construct. Three-dimensional (3D) porous silk scaffolds (BM, AA and BA) were physico-chemically characterized and functionally evaluated using human hepatocarcinoma cells (HepG2) and primary neonatal rat hepatocytes. The growth and distribution of hepatocytes within the scaffolds were tracked by FESEM, alamar blue proliferation assay and live/dead staining. Hemocompatible BA scaffolds supported the formation of high density hepatocyte clusters, facilitating cell-matrix and cell-cell interactions. Blend scaffolds evinced enhanced liver-specific functions of cultured hepatocytes in terms of albumin synthesis, urea synthesis and cytochrome P450 enzyme activity over 21 days. Subcutaneous implantation of scaffolds demonstrated minimal macrophage infiltration in blend scaffolds. These findings substantiate that the integral property of blend (BA) scaffold offers a befitting environment by influencing spheroidal growth of hepatocytes with enhanced biological activity. Collectively, the present study provides a new 3D bio-matrix niche for growing functional liver cells that would have future prospects in BAL as well as regenerative medicine.

STATEMENT OF SIGNIFICANCE

An end stage liver disease called cirrhosis perturbs the self-healing ability and physiological functions of liver. Due to the scarcity of healthy donors, a functional in vitro hepatic construct retaining the liver-specific functions is in great demand for its prospects in bioartificial liver (BAL) and cell-based tissue engineering. Physicochemical attributes of a matrix influence the behavior of cultured hepatocytes in terms of attachment, morphology and functionality. Mulberry and non-mulberry silk fibroin presents unique amino acid sequence with difference in hydrophobicity and crystallinity. Considering this, the present study focuses on the development of a suitable three-dimensional (3D) bioactive matrix incorporating both mulberry silk fibroin and cell adhesion motif (RGD) rich non-mulberry silk fibroin. Porous silk blend scaffolds facilitated the formation of hepatocyte clusters with enhanced liver-specific functions emphasizing both cell-cell and cell-matrix interactions. Hemocompatibility and integral property of blend scaffolds offers a biological niche for seeding functional liver cells that would have future prospects in biohybrid devices.

Fabrication of highly modulable fibrous 3D extracellular microenvironments

Three-dimensional (3D) in vitro scaffolds that mimic the irregular fibrous structures of in vivo extracellular matrix (ECM) are critical for many important biological applications. However, structural properties modulation of fibrous 3D scaffolds remains a challenge. Here, we report the first highly modulable 3D fibrous scaffolds self-assembled by high-aspect-ratio (HAR) microfibers. The scaffolds structural properties can be easily tailored to incorporate various physical cues, including geometry, stiffness, heterogeneity and nanotopography. Moreover, the fibrous scaffolds are readily and accurately patterned on desired locations of the substrate. Cell culture exhibits that our scaffolds can elicit strong bidirectional cell-material interactions. Furthermore, a functional disparity between the two-dimensional substrate and our 3D scaffolds is identified by cell spreading and proliferation data. These results prove the potential of the proposed scaffold as a biomimetic extracellular microenvironment for cell study.

Honeysuckle flowers extract loaded Bombyx mori silk fibroin films for inducing apoptosis of HeLa cells

This study aimed to prepare silk fibroin (SF) films loaded with honeysuckle flowers extract (HFE) for inducing apoptosis of HeLa cells. We mixed solution of SF and HFE by air-drying for preparing the honeysuckle flowers extract loaded silk fibroin (SFH) films. The physical properties including morphologies, contact angle, roughness, and Z range were characterized. MTS assay and fluorescence micrographs proved that SFH films inhibited the proliferation rate of HeLa cells due to induction of HFE into SF films. Furthermore, cell apoptosis assay and cell cycle analysis confirmed that the apoptosis of HeLa cells resulted from SFH films. Therefore, SFH films designed in our study might be a promising candidate material for cancer therapy.

Drug delivery vectors based on filamentous bacteriophages and phage-mimetic nanoparticles

With the development of nanomedicine, a mass of nanocarriers have been exploited and utilized for targeted drug delivery, including liposomes, polymers, nanoparticles, viruses, and stem cells. Due to huge surface bearing capacity and flexible genetic engineering property, filamentous bacteriophage and phage-mimetic nanoparticles are attracting more and more attentions. As a rod-like bio-nanofiber without tropism to mammalian cells, filamentous phage can be easily loaded with drugs and directly delivered to the lesion location. In particular, chemical drugs can be conjugated on phage surface by chemical modification, and gene drugs can also be inserted into the genome of phage by recombinant DNA technology. Meanwhile, specific peptides/proteins displayed on the phage surface are able to conjugate with nanoparticles which will endow them specific-targeting and huge drug-loading capacity. Additionally, phage peptides/proteins can directly self-assemble into phage-mimetic nanoparticles which may be applied for self-navigating drug delivery nanovehicles. In this review, we summarize the production of phage particles, the identification of targeting peptides, and the recent applications of filamentous bacteriophages as well as their protein/peptide for targeting drug delivery in vitro and in vivo. The improvement of our understanding of filamentous bacteriophage and phage-mimetic nanoparticles will supply new tools for biotechnological approaches.

Mesoporous Silica Nanoparticles as an Antitumoral-Angiogenesis Strategy

Tumors depend heavily on angiogenesis for nutrient derivation and their subsequent metastasis. Targeting tumor induced angiogenesis per se can address both tumor growth and progression simultaneously. Here, we show that we could elegantly restrict the endothelial cells angiogenic behavior through digital size control of mesoporous silica nanoparticle (MSN). This antiangiogenesis effect was derived from the particle size dependent uptake and production of intracellular reactive oxygen species (ROS) that directly interfered with p53 tumor suppressor pathway. The resulting signaling cascade wrestled back the tumoral control of endothelial cells' migration, invasion, and proliferation. Overall, a mere control over the size of a highly oxidative reactive surfaced nanoparticle could provide an alternative strategy to curb the tumor induced angiogenesis process in a conventional drug-free manner.

Hierarchical chirality transfer in the formation of chiral silica fibres with DNA–porphyrin co-templates

Screw-like hierarchical chiral fibres were constructed by the co-assembly of two biomolecules, from a multilevel chirality transfer and amplification process.

Size-Dependent Mechanism of Intracellular Localization and Cytotoxicity of Mono-Disperse Spherical Mesoporous Nano- and Micron-Bioactive Glass Particles

Mono-disperse spherical mesoporous nano- and micro- bioactive glass particles (NMBGs) can find potential use in bone tissue engineering. However, their size-dependent interaction with osteoblasts has never been studied. Herein, the proliferation, morphology, cytoskeleton organization and apoptosis of MC3T3-E1 osteoblasts are studied in response to the NMBGs with varying sizes (from 61 to 1085 nm) at different concentrations. Generally, smaller NMBGs at a lower dose show weaker cytotoxicity compared to the larger particles and higher doses, arising from a novel size-dependent mechanisrm of intracellular localization of NMBGs observed by electron and confocal microscopy. Specifically, NMBGs pass through perinuclear membrane of the cells to initiate endocytosis. Once internalized, the sizes of NMBGs are found to play a significant role in determining their intracellular localization. When the NMBGs are smaller than 174 nm, they are transported via the lysosomal pathway and phagocytized in lysosomes, resulting in little cytotoxicity at later time points. On the contrary, larger NMBGs (over 174 nm) escape from the lysosomes after endocytosis, and are localized inside the intra-cytoplasmic vacuoles or randomly in the cytoplasm of cells. Their lysosomal escape may damage the lysosomes, inducing cell apoptosis and thus the greater cytotoxicity.

Tuning Endothelial Permeability with Functionalized Nanodiamonds

Cancer nanomedicine vehicles are required to cross the vascular barrier to reach the tumor site in order to ensure the successful delivery of their therapeutic load. Here, nanodiamond (ND) variants were shown to induce surface dependent vascular barrier leakiness. The ND-induced leakiness was found to be mediated by the increase in intracellular reactive oxygen species (ROS) and Ca(2+). These then in turn triggered the loss in endothelial cell-endothelial cell connections of the vascular barrier and also triggered their quasi-stable cytoskeletal remodelling. This ND driven increase in leakiness allowed more doxorubicin drug to penetrate through the vascular barrier to reach the cancer cells. This increase in the doxorubicin penetration subsequently led to an increase in the cancer killing effect. Overall, tuning the vascular barrier leakiness through ND surface group functionalization could provide an alternative strategy for the cancer nanomedicine to traverse across the vascular barrier.

Selenite-Releasing Bone Mineral Nanoparticles Retard Bone Tumor Growth and Improve Healthy Tissue Functions In Vivo

Selenite-doped bone mineral nanoparticles can retard the growth of osteosarcoma in a nude mice model, through sustained release of selenite ions. The selenite ions released from the nanoparticles through a degradation-mediated fashion inhibit tumor metastasis. Blood routine analysis indicates that selenite ions can also improve the functions of liver, kidney, and heart.

Concentration ranges of antibacterial cations for showing the highest antibacterial efficacy but the least cytotoxicity against mammalian cells: implications for a new antibacterial mechanism

Antibacterial metal ions, such as Ag(+), Zn(2+) and Cu(2+), have been extensively used in medical implants and devices due to their strong broad spectrum of antibacterial activity. However, it is still a controversial issue as to whether they can show the desired antibacterial activity while being toxic to mammalian cells. It is very important to balance their antibacterial effectiveness with minimal damage to mammalian cells. Toward this end, this study is to identify the suitable concentrations of these three ions at which they can effectively kill two types of clinically relevant bacteria (Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli)) but show no obvious cytotoxicity on fibroblasts. Such concentration ranges are found to be 2.5 × 10(-7) M-10(-6) M, 10(-5) M-10(-4) M, and 10(-5) M-10(-4) M for Ag(+), Zn(2+), and Cu(2+), respectively. Investigation of their antibacterial mechanism shows that these three metal ions all show antibacterial property through a mechanism of damaging bacterial cell membranes by the generation of reactive oxygen species but surprisingly preserving the integrity of bacterial genomic DNA. The encouraging results indicate that antibacterial metal ions with controlled concentrations can bring considerable benefits to biomedical applications.

Stem cells loaded with nanoparticles as a drug carrier for in vivo breast cancer therapy

A novel anti-cancer drug carrier, mesenchymal stem cells (MSCs) encapsulating drug-loaded hollow silica nanoparticles, is used to carry a photosensitizer drug and deliver it to breast tumors, due to the natural high tumor affinity of the MSCs, and inhibit tumor growth by photo dynamic therapy. This new strategy for delivering a photo sensitizer to tumors by using tumor-affinitive MSCs addresses the challenge of the accumulation of photosensitizer drugs in tumors in photodynamic therapy.