Coding cell micropatterns through peptide inkjet printing for arbitrary biomineralized architectures

Nanoengineered Silica-Based Biomaterials for Regenerative Medicine

The paradigm of regenerative medicine is undergoing a transformative shift with the emergence of nanoengineered silica-based biomaterials. Their unique confluence of biocompatibility, precisely tunable porosity, and the ability to modulate cellular behavior at the molecular level makes them highly desirable for diverse tissue repair and regeneration applications. Advancements in nanoengineered silica synthesis and functionalization techniques have yielded a new generation of versatile biomaterials with tailored functionalities for targeted drug delivery, biomimetic scaffolds, and integration with stem cell therapy. These functionalities hold the potential to optimize therapeutic efficacy, promote enhanced regeneration, and modulate stem cell behavior for improved regenerative outcomes. Furthermore, the unique properties of silica facilitate non-invasive diagnostics and treatment monitoring through advanced biomedical imaging techniques, enabling a more holistic approach to regenerative medicine. This review comprehensively examines the utilization of nanoengineered silica biomaterials for diverse applications in regenerative medicine. By critically appraising the fabrication and design strategies that govern engineered silica biomaterials, this review underscores their groundbreaking potential to bridge the gap between the vision of regenerative medicine and clinical reality.

Nanoparticle Assembly: From Self-Organization to Controlled Micropatterning for Enhanced Functionalities

Nanoparticles form long-range micropatterns via self-assembly or directed self-assembly with superior mechanical, electrical, optical, magnetic, chemical, and other functional properties for broad applications, such as structural supports, thermal exchangers, optoelectronics, microelectronics, and robotics. The precisely defined particle assembly at the nanoscale with simultaneously scalable patterning at the microscale is indispensable for enabling functionality and improving the performance of devices. This article provides a comprehensive review of nanoparticle assembly formed primarily via the balance of forces at the nanoscale (e.g., van der Waals, colloidal, capillary, convection, and chemical forces) and nanoparticle-template interactions (e.g., physical confinement, chemical functionalization, additive layer-upon-layer). The review commences with a general overview of nanoparticle self-assembly, with the state-of-the-art literature review and motivation. It subsequently reviews the recent progress in nanoparticle assembly without the presence of surface templates. Manufacturing techniques for surface template fabrication and their influence on nanoparticle assembly efficiency and effectiveness are then explored. The primary focus is the spatial organization and orientational preference of nanoparticles on non-templated and pre-templated surfaces in a controlled manner. Moreover, the article discusses broad applications of micropatterned surfaces, encompassing various fields. Finally, the review concludes with a summary of manufacturing methods, their limitations, and future trends in nanoparticle assembly.

Biomedical applications of solid-binding peptides and proteins

Over the past decades, solid-binding peptides (SBPs) have found multiple applications in materials science. In non-covalent surface modification strategies, solid-binding peptides are a simple and versatile tool for the immobilization of biomolecules on a vast variety of solid surfaces. Especially in physiological environments, SBPs can increase the biocompatibility of hybrid materials and offer tunable properties for the display of biomolecules with minimal impact on their functionality. All these features make SBPs attractive for the manufacturing of bioinspired materials in diagnostic and therapeutic applications. In particular, biomedical applications such as drug delivery, biosensing, and regenerative therapies have benefited from the introduction of SBPs. Here, we review recent literature on the use of solid-binding peptides and solid-binding proteins in biomedical applications. We focus on applications where modulating the interactions between solid materials and biomolecules is crucial. In this review, we describe solid-binding peptides and proteins, providing background on sequence design and binding mechanism. We then discuss their application on materials relevant for biomedicine (calcium phosphates, silicates, ice crystals, metals, plastics, and graphene). Although the limited characterization of SBPs still represents a challenge for their design and widespread application, our review shows that SBP-mediated bioconjugation can be easily introduced into complex designs and on nanomaterials with very different surface chemistries.

3D Printing-Enabled Nanoparticle Alignment: A Review of Mechanisms and Applications

3D printing (additive manufacturing (AM)) has enormous potential for rapid tooling and mass production due to its design flexibility and significant reduction of the timeline from design to manufacturing. The current state-of-the-art in 3D printing focuses on material manufacturability and engineering applications. However, there still exists the bottleneck of low printing resolution and processing rates, especially when nanomaterials need tailorable orders at different scales. An interesting phenomenon is the preferential alignment of nanoparticles that enhance material properties. Therefore, this review emphasizes the landscape of nanoparticle alignment in the context of 3D printing. Herein, a brief overview of 3D printing is provided, followed by a comprehensive summary of the 3D printing-enabled nanoparticle alignment in well-established and in-house customized 3D printing mechanisms that can lead to selective deposition and preferential orientation of nanoparticles. Subsequently, it is listed that typical applications that utilized the properties of ordered nanoparticles (e.g., structural composites, heat conductors, chemo-resistive sensors, engineered surfaces, tissue scaffolds, and actuators based on structural and functional property improvement). This review's emphasis is on the particle alignment methodology and the performance of composites incorporating aligned nanoparticles. In the end, significant limitations of current 3D printing techniques are identified together with future perspectives.

Diatom-inspired multiscale mineralization of patterned protein-polysaccharide complex structures

Marine diatoms construct their hierarchically ordered, three-dimensional (3D) external structures called frustules through precise biomineralization processes. Recapitulating the remarkable architectures and functions of diatom frustules in artificial materials is a major challenge that has important technological implications for hierarchically ordered composites. Here, we report the construction of highly ordered, mineralized composites based on fabrication of complex self-supporting porous structures-made of genetically engineered amyloid fusion proteins and the natural polysaccharide chitin-and performing in situ multiscale protein-mediated mineralization with diverse inorganic materials, including SiO2, TiO2 and Ga2O3. Subsequently, using sugar cubes as templates, we demonstrate that 3D fabricated porous structures can become colonized by engineered bacteria and can be functionalized with highly photoreactive minerals, thereby enabling co-localization of the photocatalytic units with a bacteria-based hydrogenase reaction for a successful semi-solid artificial photosynthesis system for hydrogen evolution. Our study thus highlights the power of coupling genetically engineered proteins and polysaccharides with biofabrication techniques to generate hierarchically organized mineralized porous structures inspired by nature.

Cell guidance on peptide micropatterned silk fibroin scaffolds

Guiding neuronal cell growth is desirable for neural tissue engineering but is very challenging. In this work, a self-assembling ultra-short surfactant-like peptide I₃K which possesses positively charged lysine head groups, and hydrophobic isoleucine tails, was chosen to investigate its potential for guiding neuronal cell growth. The peptides were able to self-assemble into nanofibrous structures and interact strongly with silk fibroin (SF) scaffolds, providing a niche for neural cell attachment and proliferation. SF is an excellent biomaterial for tissue engineering. However neuronal cells, such as rat PC12 cells, showed poor attachment on pure regenerated SF (RSF) scaffold surfaces. Patterning of I₃K peptide nanofibers on RSF surfaces significantly improved cellular attachment, cellular density, as well as morphology of PC12 cells. The live / dead assay confirmed that RSF and I₃K have negligible cytotoxicity against PC12 cells. Atomic force microscopy (AFM) was used to image the topography and neurite formation of PC12 cells, where results revealed that self-assembled I₃K nanofibers can support the formation of PC12 cell neurites. Immunolabelling also demonstrated that coating of I₃K nanofibers onto the RSF surfaces not only increased the percentage of cells bearing neurites but also increased the average maximum neurite length. Therefore, the peptide I₃K could be used as an alternative to poly-l-lysine for cell culture and tissue engineering applications. As micro-patterning of neural cells to guide neurite growth is important for developing nerve tissue engineering scaffolds, inkjet printing was used to pattern self-assembled I₃K peptide nanofibers on RSF surfaces for directional control of PC12 cell growth. The results demonstrated that inkjet-printed peptide micro-patterns can effectively guide the cell alignment and organization on RSF scaffold surfaces, providing great potential for nerve regeneration applications.

Scientometric Analysis and Systematic Review of Multi-Material Additive Manufacturing of Polymers

Multi-material additive manufacturing of polymers has experienced a remarkable increase in interest over the last 20 years. This technology can rapidly design and directly fabricate three-dimensional (3D) parts with multiple materials without complicating manufacturing processes. This research aims to obtain a comprehensive and in-depth understanding of the current state of research and reveal challenges and opportunities for future research in the area. To achieve the goal, this study conducts a scientometric analysis and a systematic review of the global research published from 2000 to 2021 on multi-material additive manufacturing of polymers. In the scientometric analysis, a total of 2512 journal papers from the Scopus database were analyzed by evaluating the number of publications, literature coupling, keyword co-occurrence, authorship, and countries/regions activities. By doing so, the main research frame, articles, and topics of this research field were quantitatively determined. Subsequently, an in-depth systematic review is proposed to provide insight into recent advances in multi-material additive manufacturing of polymers in the aspect of technologies and applications, respectively. From the scientometric analysis, a heavy bias was found towards studying materials in this field but also a lack of focus on developing technologies. The future trend is proposed by the systematic review and is discussed in the directions of interfacial bonding strength, printing efficiency, and microscale/nanoscale multi-material 3D printing. This study contributes by providing knowledge for practitioners and researchers to understand the state of the art of multi-material additive manufacturing of polymers and expose its research needs, which can serve both academia and industry.

Biomimetic and bioinspired silicifications: Recent advances for biomaterial design and applications

The rational design and controllable synthesis of functional silica-based materials have gained increased interest in a variety of biomedical and biotechnological applications due to their unique properties. The current review shows that marine organisms, such as siliceous sponges and diatoms, could be the inspiration for the fabrication of advanced biohybrid materials. Several biomolecules were involved in the molecular mechanism of biosilicification in vivo. Mimicking their behavior, functional silica-based biomaterials have been generated via biomimetic and bioinspired silicification in vitro. Additionally, several advanced technologies were developed for in vitro and in vivo immobilization of biomolecules with potential applications in biocatalysis, biosensors, bioimaging, and immunoassays. A thin silica layer could coat a single living cell or virus as a protective shell offering new opportunities in biotechnology and nanomedicine fields. Promising nanotechnologies have been developed for drug encapsulation and delivery in a targeted and controlled manner, in particular for poorly soluble hydrophobic drugs. Moreover, biomimetic silica, as a morphogenetically active biocompatible material, has been utilized in the field of bone regeneration and in the development of biomedical implantable devices. STATEMENT OF SIGNIFICANCE: In nature, silica-based biomaterials, such as diatom frustules and sponge spicules, with high mechanical and physical properties were created under biocompatible conditions. The fundamental knowledge underlying the molecular mechanisms of biosilica formation could inspire engineers and chemists to design novel hybrid biomaterials using molecular biomimetic strategies. The production of such biohybrid materials brings the biosilicification field closer to practical applications. This review starts with the biosilicification process of sponges and diatoms with recently updated researches. Then, this article covers recent advances in the design of silica-based biomaterials and their potential applications in the fields of biotechnology and nanomedicine, highlighting several promising technologies for encapsulation of functional proteins and living cells, drug delivery and the preparation of scaffolds for bone regeneration.

Role of temperature on bio-printability of gelatin methacryloyl bioink in two-step cross-linking strategy for tissue engineering applications

Additive manufacturing has shown promising results in reconstructing three-dimensional (3D) living tissues for various applications, including tissue engineering, regenerative medicine, drug discovery, and high-throughput drug screening. In extrusion-based bioprinters, stable formation of filaments and high-fidelity deposition of bioinks are the primary challenges in fabrication of physiologically relevant tissue constructs. Among various bioinks, gelatin methacryloyl (GelMA) is known as a photocurable and physicochemically tunable hydrogel with a demonstrated biocompatibility and tunable biodegradation properties. The two-step crosslinking of GelMA (reversible thermal gelation and permanent photo-crosslinking) has attracted researchers to make complex tissue constructs. Despite promising results in filament formation and printability of this hydrogel, the effect of temperature on physicochemical properties, cytocompatibility, and biodegradation of the hydrogel are to be investigated. This work studies the effect of thermoreversible, physical crosslinking on printability of GelMA. The results of 3D printing of GelMA at different temperatures followed by irreversible chemical photo-crosslinking show that the decrease in temperature improves the filament formation and shape fidelity of the deposited hydrogel, particularly at the temperatures around 15 °C. Time dependant mechanical testing of the printed samples revealed that decreasing the extruding temperature increases the elastic properties of the extruded filaments. Furthermore, our novel approach in minimizing the slippage effect during rheological study enabled to measure changes in linear and non-linear viscoelastic properties of the printed samples at different temperatures. A considerable increase in storage modulus of the extruded samples printed at lower temperatures confirms their higher solid behavior. Scanning electron microscopy revealed a remarkable decrease in porosity of the extruded hydrogels by decreasing the temperature. Chemical analysis by Fourier-transform infrared spectroscopy and circular dichroism showed a direct relationship between the coil-helix transition in hydrogel macromers and its physical alterations. Finally, biodegradation and cytocompatibility of the extruded hydrogels decreased at lower extruding temperatures.

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.

Aqueous Processed Biopolymer Interfaces for Single-Cell Microarrays

Single-cell microarrays are emerging tools to unravel intrinsic diversity within complex cell populations, opening up new approaches for the in-depth understanding of highly relevant diseases. However, most of the current methods for their fabrication are based on cumbersome patterning approaches, employing organic solvents and/or expensive materials. Here, we demonstrate an unprecedented green-chemistry strategy to produce single-cell capture biochips onto glass surfaces by all-aqueous inkjet printing. At first, a chitosan film is easily inkjet printed and immobilized onto hydroxyl-rich glass surfaces by electrostatic immobilization. In turn, poly(ethylene glycol) diglycidyl ether is grafted on the chitosan film to expose reactive epoxy groups and induce antifouling properties. Subsequently, microscale collagen spots are printed onto the above surface to define the attachment area for single adherent human cancer cells harvesting with high yield. The reported inkjet printing approach enables one to modulate the collagen area available for cell attachment in order to control the number of captured cells per spot, from single-cells up to double- and multiple-cell arrays. Proof-of-principle of the approach includes pharmacological treatment of single-cells by the model drug doxorubicin. The herein presented strategy for single-cell array fabrication can constitute a first step toward an innovative and environmentally friendly generation of aqueous-based inkjet-printed cellular devices.

Peptide Nanotube-Templated Biomineralization of Cu2-x S Nanoparticles for Combination Treatment of Metastatic Tumor

1D peptide nanostructures (i.e., peptide nanotubes, PNTs) exhibit tunable chemo-physical properties and functions such as improved tissue adhesion, increased cellular uptake, and elongated blood circulation. In this study, the application of PNTs as a desirable 1D template for biomineralization of Cu_2-x S nanoparticles (Cu_2-x S NPs, x = 1-2) is reported. Monodisperse Cu_2-x S NPs are uniformly coated on the peptide nanotubes owing to the specific high binding affinity of Cu ions to the imidazole groups exposed on the surface of nanotubes. The Cu_2-x S NP-coated PNTs are further covalently grafted with an oxaliplatin prodrug (Pt-CuS-PNTs) to construct a versatile nanoplatform for combination cancer therapy. Upon 808 nm laser illumination, the nanoplatform induces significant hyperthermia effect and elicits reactive oxygen species generation through electron transfer and Fenton-like reaction. It is demonstrated that the versatile nanoplatform dramatically inhibits tumor growth and lung metastasis of melanoma in a B16-F10 melanoma tumor-bearing mouse model by combined photo- and chemotherapy. This study highlights the ability of PNTs for biomineralization of metal ions and the promising potential of such nanoplatforms for cancer treatment.

Photolithographic Masking Method to Chemically Pattern Silk Film Surfaces

A method has been developed for selectively patterning silk surfaces using a photolithographic process to mask off sections of silk films, which allows selective and precise patterning of features down to 40 μm. This process is highly versatile, utilizes only low-cost equipment and can be used to rapidly prototype flat silk substrates with spatially controlled chemical patterns. Here we demonstrate the usefulness of this technique to deposit fluorescent dyes, labeled proteins and conducting polymers or to modify the surface charge of the silk protein in desired regions on a silk film surface.

Inkjet Printing of Patterned, Multispectral, and Biocompatible Photonic Crystals

Patterning of photonic crystals to generate rationally designed color-responsive materials has drawn considerable interest because of promising applications in optical storage, encryption, display, and sensing. Here, an inkjet-printing based strategy is presented for noncontact, rapid, and direct approaches to generate arbitrarily patterned photonic crystals. The strategy is based on the use of water-soluble biopolymer-based opal structures that can be reformed with high resolution through precise deposition of fluids on the photonic crystal lattice. The resulting digitally designed photonic lattice formats simultaneously exploit structural color and material transience opening avenues for information encoding and combining functions of optics, biomaterials, and environmental interfaces in a single device.

Understanding Secondary Structures of Silk Materials via Micro- and Nano-Infrared Spectroscopies

The secondary structures (also termed conformations) of silk fibroin (SF) in animal silk fibers and regenerated SF materials are critical in determining mechanical performance and function of the materials. In order to understand the structure-mechanics-function relationships of silk materials, a variety of advanced infrared spectroscopic techniques, such as micro-infrared spectroscopies (micro-IR spectroscopies for short), synchrotron micro-IR spectroscopy, and nano-infrared spectroscopies (nano-IR spectroscopies for short), have been used to determine the conformations of SF in silk materials. These IR spectroscopic methods provide a useful toolkit to understand conformations and conformational transitions of SF in various silk materials with spatial resolution from the nano-scale to the micro-scale. In this Review, we first summarize progress in understanding the structure and structure-mechanics relationships of silk materials. We then discuss the state-of-the-art micro- and nano-IR spectroscopic techniques used for silk materials characterization. We also provide a systematic discussion of the strategies to collect high-quality spectra and the methods to analyze these spectra. Finally, we demonstrate the challenges and directions for future exploration of silk-based materials with IR spectroscopies.

Aligned Scaffolds with Biomolecular Gradients for Regenerative Medicine

Aligned topography and biomolecular gradients exist in various native tissues and play pivotal roles in a set of biological processes. Scaffolds that recapitulate the complex structure and microenvironment show great potential in promoting tissue regeneration and repair. We begin with a discussion on the fabrication of aligned scaffolds, followed by how biomolecular gradients can be immobilized on aligned scaffolds. In particular, we emphasize how electrospinning, freeze drying, and 3D printing technology can accomplish aligned topography and biomolecular gradients flexibly and robustly. We then highlight several applications of aligned scaffolds and biomolecular gradients in regenerative medicine including nerve, tendon/ligament, and tendon/ligament-to-bone insertion regeneration. Finally, we finish with conclusions and future perspectives on the use of aligned scaffolds with biomolecular gradients in regenerative medicine.

Direct ink writing with high-strength and swelling-resistant biocompatible physically crosslinked hydrogels

The 3D printing of physically crosslinked hydrogel architectures with high strength and swelling resistance is achieved with biocompatible PVA and natural κ-carrageenan hybrid inks.

Design, Fabrication, and Function of Silk-Based Nanomaterials

Animal silks are built from pure protein components and their mechanical performance, such as strength and toughness, often exceed most engineered materials. The secret to this success is their unique nanoarchitectures that are formed through the hierarchical self-assembly of silk proteins. This natural material fabrication process in sharp contrast to the production of artificial silk materials, which usually are directly constructed as bulk structures from silk fibroin (SF) molecular. In recent years, with the aim of understanding and building better silk materials, a variety of fabrication strategies have been designed to control nanostructures of silks or to create functional materials from silk nanoscale building blocks. These emerging fabrication strategies offer an opportunity to tailor the structure of SF at the nanoscale and provide a promising route to produce structurally and functionally optimized silk nanomaterials. Here, we review the critical roles of silk nanoarchitectures on property and function of natural silk fibers, outline the strategies of utilization of these silk nanobuilding blocks, and we provide a critical summary of state of the art in the field to create silk nanoarchitectures and to generate silk-based nanocomponents. Further, such insights suggest templates to consider for other materials systems.

De Novo Design of Recombinant Spider Silk Proteins for Material Applications

Spider silks are well known for their superior mechanical properties that are stronger and tougher than steel despite being assembled at close to ambient conditions and using water as the solvent. However, it is a significant challenge to utilize spider silks for practical applications due to their limited sources. Fortunately, genetic engineering techniques offer a promising approach to produce useable amounts of spider silk variants. Starting from these recombinant spider silk proteins, a series of experiments and simulations strategies are developed to improve the recombinant spider silk proteins (RSSP) material design and fabrication with the aim of biomimicking the structure-property-function relationships of spider silks. Accordingly, in this review, the authors first introduce the structure-property-function relationship of spider silks. Then, the recent progress in the genetic synthesis of RSSPs is discussed and their related multiscale self-assembly behaviors is summarized. Finally, the authors outline works utilizing multiscale modeling to assist RSSP material design.