Cross-linked cellulose nanocrystal aerogels as viable bone tissue scaffolds

Surface modification of cellulose nanocrystals for biomedical and personal hygiene applications

The increasing demand for sustainable and effective materials in biomedical and personal hygiene applications has driven the exploration of cellulose nanocrystals (CNCs) derived from biomass. These nanomaterials are highly valued for their exceptional mechanical properties, biocompatibility, and renewable nature. Researchers are exploring CNCs for advancing medical and hygiene products, but surface modification is often needed to maximize their benefits. Techniques such as chemical functionalization, physical coating, and hybridization can significantly enhance CNCs dispersibility, stability, and interaction with biological systems. This versatility makes CNCs suitable for a variety of applications, including drug delivery systems, wound dressings, and personal hygiene products. Despite their advantages, maintaining the inherent properties of CNCs while integrating new functionalities through modification poses a challenge. Understanding the impact of various modification techniques on CNC performance is crucial for optimizing their effectiveness. This review aimed to consolidate current knowledge on the surface modification of biomass-derived CNCs, offering insights into different methods and their implications for biomedical and personal hygiene applications. By highlighting advancements, challenges, and prospects, it served as a crucial resource for advancing the development and application of CNCs in these critical fields.

Foams with 3D Spatially Programmed Mechanics Enabled by Autonomous Active Learning on Viscous Thread Printing

Foams are versatile by nature and ubiquitous in a wide range of applications, including padding, insulation, and acoustic dampening. Previous work established that foams 3D printed via Viscous Thread Printing (VTP) can in principle combine the flexibility of 3D printing with the mechanical properties of conventional foams. However, the generality of prior work is limited due to the lack of predictable process-property relationships. In this work, a self-driving lab is utilized that combines automated experimentation with machine learning to identify a processing subspace in which dimensionally consistent materials are produced using VTP with spatially programmable mechanical properties. In carrying out this process, an underlying self-stabilizing characteristic of VTP layer thickness is discovered as an important feature for its extension to new materials and systems. Several complex exemplars are constructed to illustrate the newly enabled capabilities of foams produced via VTP, including 1D gradient rectangular slabs, 2D localized stiffness zones on an insole orthotic and living hinges, and programmed 3D deformation via a cable-driven humanoid hand. Predictive mapping models are developed and validated for both thermoplastic polyurethane (TPU) and polylactic acid (PLA) filaments, suggesting the ability to train a model for any material suitable for material extrusion (ME) 3D printing.

Comparative histomorphological assessment of the osteoinductive capacity of a nanofibrillated cellulose-based composite and autologous blood clot

Purpose

The present study aimed to evaluate and compare the effect of nanofibrillated cellulose (NFC)-based composite with dicalcium phosphate dihydrate and an autologous blood clot (ABC) on the formation of new bone tissue in vivo by histological and histomorphometric assessment.

Materials and Methods

A total of 72 rats with created femoral defects (2 mm) were used. The rats were divided into three groups: (1) with filling of the defect with an ABC, (2) NFC-1-with filling of both the cortical plate and intramedullary space in the defect area, and (3) NFC-2-with filling of only the intramedullary space in the defect area. Histological and histomorphometric analysis was performed to assess the healing of the bone defect after 14, 30 and 60 days.

Results

Complete closure of the cortical plate defect was detected in the NFC-2 group on Day 30 (p < 0.0001). Moreover, in both NFC groups on the 30th and 60th days, ongoing osteogenesis was observed, characterized by a large volume of newly formed circular pattern bone tissue in the intramedullary space.

Сonclusion

This study demonstrated that the NFC-based composite, which is located below the level of the cortical plate, tamponing only the intramedullary space (NFC-2), improves bone tissue repair at the site of a bone defect of the cortical plate and has the potential of prolonged osteoinductivity.

Level of Evidence

Not applicable.

Synthesis, functionalization, and commercial application of cellulose-based nanomaterials

In recent times, cellulose, an abundant and renewable biopolymer, has attracted considerable interest due to its potential applications in nanotechnology. This review explores the latest developments in cellulose-based nanomaterial synthesis, functionalization, and commercial applications. Beginning with an overview of the diverse sources of cellulose and the methods employed for its isolation and purification, the review delves into the various techniques used for the synthesis of cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs), highlighting their unique properties and potential applications. Furthermore, the functionalization strategies employed to enhance the properties and tailor the functionalities of cellulose-based nanomaterials were discussed. The review also provides insights into the emerging commercial applications of cellulose-based nanomaterials across diverse sectors, including packaging, biomedical engineering, textiles, and environmental remediation. Finally, challenges and prospects for the widespread adoption of cellulose-based nanomaterials are outlined, emphasizing the need for further research and development to unlock their full potential in sustainable and innovative applications.

BioMOF@cellulose Glycerogel Scaffold with Multifold Bioactivity: Perspective in Bone Tissue Repair

The development of new biomaterials for musculoskeletal tissue repair is currently an important branch in biomedicine research. The approach presented here is centered around the development of a prototypic synthetic glycerogel scaffold for bone regeneration, which simultaneously features therapeutic activity. The main novelty of this work lies in the combination of an open meso and macroporous nanocrystalline cellulose (NCC)-based glycerogel with a fully biocompatible microporous bioMOF system (CaSyr-1) composed of calcium ions and syringic acid. The bioMOF framework is further impregnated with a third bioactive component, i.e., ibuprofen (ibu), to generate a multifold bioactive system. The integrated CaSyr-1(ibu) serves as a reservoir for bioactive compounds delivery, while the NCC scaffold is the proposed matrix for cell ingrowth, proliferation and differentiation. The measured drug delivery profiles, studied in a phosphate-buffered saline solution at 310 K, indicate that the bioactive components are released concurrently with bioMOF dissolution after ca. 30 min following a pseudo-first-order kinetic model. Furthermore, according to the semi-empirical Korsmeyer-Peppas kinetic model, this release is governed by a case-II mechanism, suggesting that the molecular transport is influenced by the relaxation of the NCC matrix. Preliminary in vitro results denote that the initial high concentration of glycerol in the NCC scaffold can be toxic in direct contact with human osteoblasts (HObs). However, when the excess of glycerol is diluted in the system (after the second day of the experiment), the direct and indirect assays confirm full biocompatibility and suitability for HOb proliferation.

Nanocellulose-based hydrogels as versatile materials with interesting functional properties for tissue engineering applications

Tissue engineering has emerged as a remarkable field aiming to restore or replace damaged tissues through the use of biomimetic constructs. Among the diverse materials investigated for this purpose, nanocellulose-based hydrogels have garnered attention due to their intriguing biocompatibility, tunable mechanical properties, and sustainability. Over the past few years, numerous research works have been published focusing on the successful use of nanocellulose-based hydrogels as artificial extracellular matrices for regenerating various types of tissues. The review emphasizes the importance of tissue engineering, highlighting hydrogels as biomimetic scaffolds, and specifically focuses on the role of nanocellulose in composites that mimic the structures, properties, and functions of the native extracellular matrix for regenerating damaged tissues. It also summarizes the types of nanocellulose, as well as their structural, mechanical, and biological properties, and their contributions to enhancing the properties and characteristics of functional hydrogels for tissue engineering of skin, bone, cartilage, heart, nerves and blood vessels. Additionally, recent advancements in the application of nanocellulose-based hydrogels for tissue engineering have been evaluated and documented. The review also addresses the challenges encountered in their fabrication while exploring the potential future prospects of these hydrogel matrices for biomedical applications.

Biopolymer-Based Biomimetic Aerogel for Biomedical Applications

Aerogels are lightweight and highly porous materials that have been found to have great potential in biomedical research because of some of their unique properties, such as their high surface area, tunable porosity, and biocompatibility. Researchers have been exploring ways to use aerogels to create biomimetic scaffolds inspired by natural extracellular matrices (ECMs) for various biomedical applications. Aerogel scaffolds can serve as three-dimensional (3D) templates for cell growth and tissue regeneration, promoting wound healing and tissue repair. Additionally, aerogel-based scaffolds have great potential in controlled drug delivery systems, where their high surface area and porosity enable the efficient loading and release of therapeutic agents. In this review, we discuss biopolymer-based biomimetic aerogel scaffolds for tissue engineering, drug delivery, and biosensors. Finally, we also discuss the potential directions in the development of aerogel-based biomimetic scaffolds.

Recent advances and biomedical application of 3D printed nanocellulose-based adhesive hydrogels: A review

Nanocellulose-based tissue adhesives show promise for achieving rapid hemostasis and effective wound healing. Conventional methods, such as sutures and staples, have limitations, prompting the exploration of bioadhesives for direct wound adhesion and minimal tissue damage. Nanocellulose, a hydrolysis product of cellulose, exhibits superior biocompatibility and multifunctional properties, gaining interest as a base material for bioadhesive development. This study explores the potential of nanocellulose-based adhesives for hemostasis and wound healing using 3D printing techniques. Nanocellulose enables the creation of biodegradable adhesives with minimal adverse effects and opens avenues for advanced wound healing and complex tissue regeneration, such as skin, blood vessels, lungs, cartilage, and muscle. This study reviews recent trends in various nanocellulose-based 3D printed hydrogel patches for tissue engineering applications. The review also introduces various types of nanocellulose and their synthesis, surface modification, and bioadhesive fabrication techniques via 3D printing for smart wound healing.

Cytotoxicity and Inflammatory Effects of Chitin Nanofibrils Isolated from Fungi

Fungal nanochitin can assist the transition from the linear fossil-based economy to a circular biobased economy given its environmental benefits over conventional crustacean-nanochitin. Its real-world implementation requires carefully assessing its toxicity so that unwanted human health and environmental issues are avoided. Accordingly, the cytotoxicity and inflammatory effects of chitin nanofibrils (ChNFs) from white mushroom is assessed. ChNFs are few nanometers in diameter, with a 75.8% N-acetylation degree, a crystallinity of 59.1%, and present a 44:56 chitin/glucan weight ratio. Studies are conducted for aqueous colloidal ChNF dispersions (0-5 mg·mL-1) and free-standing films having physically entangled ChNFs. Aqueous dispersions of chitin nanocrystals (ChNCs) isolated via hydrochloric acid hydrolysis of α-chitin powder are also evaluated for comparison. Cytotoxicity studies conducted in human fibroblasts (MRC-5 cells) and murine brain microglia (BV-2 cells) reveal a comparatively safer behavior over related biobased nanomaterials. However, a strong inflammatory response was observed when BV-2 cells were cultured in the presence of colloidal ChNFs. These novel cytotoxicity and inflammatory studies shed light on the potential of fungal ChNFs for biomedical applications.

Nanocellulose-based porous materials: Regulation and pathway to commercialization in regenerative medicine

We review the recent progress that have led to the development of porous materials based on cellulose nanostructures found in plants and other resources. In light of the properties that emerge from the chemistry, shape and structural control, we discuss some of the most promising uses of a plant-based material, nanocellulose, in regenerative medicine. Following a brief discussion about the fundamental aspects of self-assembly of nanocellulose precursors, we review the key strategies needed for material synthesis and to adjust the architecture of the materials (using three-dimensional printing, freeze-casted porous materials, and electrospinning) according to their uses in tissue engineering, artificial organs, controlled drug delivery and wound healing systems, among others. For this purpose, we map the structure-property-function relationships of nanocellulose-based porous materials and examine the course of actions that are required to translate innovation from the laboratory to industry. Such efforts require attention to regulatory aspects and market pull. Finally, the key challenges and opportunities in this nascent field are critically reviewed.

Aerogel-Based Materials in Bone and Cartilage Tissue Engineering-A Review with Future Implications

Aerogels are fascinating solid materials known for their highly porous nanostructure and exceptional physical, chemical, and mechanical properties. They show great promise in various technological and biomedical applications, including tissue engineering, and bone and cartilage substitution. To evaluate the bioactivity of bone substitutes, researchers typically conduct in vitro tests using simulated body fluids and specific cell lines, while in vivo testing involves the study of materials in different animal species. In this context, our primary focus is to investigate the applications of different types of aerogels, considering their specific materials, microstructure, and porosity in the field of bone and cartilage tissue engineering. From clinically approved materials to experimental aerogels, we present a comprehensive list and summary of various aerogel building blocks and their biological activities. Additionally, we explore how the complexity of aerogel scaffolds influences their in vivo performance, ranging from simple single-component or hybrid aerogels to more intricate and organized structures. We also discuss commonly used formulation and drying methods in aerogel chemistry, including molding, freeze casting, supercritical foaming, freeze drying, subcritical, and supercritical drying techniques. These techniques play a crucial role in shaping aerogels for specific applications. Alongside the progress made, we acknowledge the challenges ahead and assess the near and far future of aerogel-based hard tissue engineering materials, as well as their potential connection with emerging healing techniques.

3D-Printed Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)-Cellulose-Based Scaffolds for Biomedical Applications

While biomaterials have become indispensable for a wide range of tissue repair strategies, second removal procedures oftentimes needed in the case of non-bio-based and non-bioresorbable scaffolds are associated with significant drawbacks not only for the patient, including the risk of infection, impaired healing, or tissue damage, but also for the healthcare system in terms of cost and resources. New biopolymers are increasingly being investigated in the field of tissue regeneration, but their widespread use is still hampered by limitations regarding mechanical, biological, and functional performance when compared to traditional materials. Therefore, a common strategy to tune and broaden the final properties of biopolymers is through the effect of different reinforcing agents. This research work focused on the fabrication and characterization of a bio-based and bioresorbable composite material obtained by compounding a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) matrix with acetylated cellulose nanocrystals (CNCs). The developed biocomposite was further processed to obtain three-dimensional scaffolds by additive manufacturing (AM). The 3D printability of the PHBH-CNC biocomposites was demonstrated by realizing different scaffold geometries, and the results of in vitro cell viability studies provided a clear indication of the cytocompatibility of the biocomposites. Moreover, the CNC content proved to be an important parameter in tuning the different functional properties of the scaffolds. It was demonstrated that the water affinity, surface roughness, and in vitro degradability rate of biocomposites increase with increasing CNC content. Therefore, this tailoring effect of CNC can expand the potential field of use of the PHBH biopolymer, making it an attractive candidate for a variety of tissue engineering applications.

A review on recent advances towards sustainable development of bio-inspired agri-waste based cellulose aerogels

Cellulose aerogel (CA) is considered to be the most promising material due to its extraordinary properties like unique microstructure, porosity, large specific surface area, biodegradability, renewable nature and lightweight. Cellulosic aerogels are thus found to have potential applications in different fields especially in water purification and biomedical field. Agricultural waste based cellulose aerogels are recently getting wider attention owing to its sustainability. The synthesis methods of agri-waste based cellulose aerogels, its properties and application in different fields especially in the field of water purification are detailed in a comprehensive manner. This review tries to bring light into the commercialization of value-added products from sustainable, cheap agricultural waste material and tries to motivate young researchers.

Aerogel-Based Biomaterials for Biomedical Applications: From Fabrication Methods to Disease-Targeting Applications

Aerogel-based biomaterials are increasingly being considered for biomedical applications due to their unique properties such as high porosity, hierarchical porous network, and large specific pore surface area. Depending on the pore size of the aerogel, biological effects such as cell adhesion, fluid absorption, oxygen permeability, and metabolite exchange can be altered. Based on the diverse potential of aerogels in biomedical applications, this paper provides a comprehensive review of fabrication processes including sol-gel, aging, drying, and self-assembly along with the materials that can be used to form aerogels. In addition to the technology utilizing aerogel itself, it also provides insight into the applicability of aerogel based on additive manufacturing technology. To this end, how microfluidic-based technologies and 3D printing can be combined with aerogel-based materials for biomedical applications is discussed. Furthermore, previously reported examples of aerogels for regenerative medicine and biomedical applications are thoroughly reviewed. A wide range of applications with aerogels including wound healing, drug delivery, tissue engineering, and diagnostics are demonstrated. Finally, the prospects for aerogel-based biomedical applications are presented. The understanding of the fabrication, modification, and applicability of aerogels through this study is expected to shed light on the biomedical utilization of aerogels.

Cellulose Nanocrystal (CNC) Gels: A Review

The aim of this article is to review the research conducted in the field of aqueous and polymer composites cellulose nanocrystal (CNC) gels. The experimental techniques employed to characterize the rheological behavior of these materials will be summarized, and the main advantages of using CNC gels will also be addressed in this review. In addition, research devoted to the use of numerical simulation methodologies to describe the production of CNC-based materials, e.g., in 3D printing, is also discussed. Finally, this paper also discusses the application of CNC gels along with additives such as cross-linking agents, which can represent an enormous opportunity to develop improved materials for manufacturing processes.

Bioengineering Composite Aerogel-Based Scaffolds That Influence Porous Microstructure, Mechanical Properties and In Vivo Regeneration for Bone Tissue Application

Tissue regeneration of large bone defects is still a clinical challenge. Bone tissue engineering employs biomimetic strategies to produce graft composite scaffolds that resemble the bone extracellular matrix to guide and promote osteogenic differentiation of the host precursor cells. Aerogel-based bone scaffold preparation methods have been increasingly improved to overcome the difficulties in balancing the need for an open highly porous and hierarchically organized microstructure with compression resistance to withstand bone physiological loads, especially in wet conditions. Moreover, these improved aerogel scaffolds have been implanted in vivo in critical bone defects, in order to test their bone regeneration potential. This review addresses recently published studies on aerogel composite (organic/inorganic)-based scaffolds, having in mind the various cutting-edge technologies and raw biomaterials used, as well as the improvements that are still a challenge in terms of their relevant properties. Finally, the lack of 3D in vitro models of bone tissue for regeneration studies is emphasized, as well as the need for further developments to overcome and minimize the requirement for studies using in vivo animal models.

Application of Nanocellulose-Based Aerogels in Bone Tissue Engineering: Current Trends and Outlooks

The complex or compromised bone defects caused by osteomyelitis, malignant tumors, metastatic tumors, skeletal abnormalities, and systemic diseases are difficult to be self-repaired, leading to a non-union fracture. With the increasing demands of bone transplantation, more and more attention has been paid to artificial bone substitutes. As biopolymer-based aerogel materials, nanocellulose aerogels have been widely utilized in bone tissue engineering. More importantly, nanocellulose aerogels not only mimic the structure of the extracellular matrix but could also deliver drugs and bioactive molecules to promote tissue healing and growth. Here, we reviewed the most recent literature about nanocellulose-based aerogels, summarized the preparation, modification, composite fabrication, and applications of nanocellulose-based aerogels in bone tissue engineering, as well as giving special focus to the current limitations and future opportunities of nanocellulose aerogels for bone tissue engineering.

Cellulose nanocrystalline from biomass wastes: An overview of extraction, functionalization and applications in drug delivery

Cellulose nanocrystals (CNC) have been extensively used in various fields due to their renewability, excellent biocompatibility, large specific surface area, and high tensile strength. Most biomass wastes contain significant amounts of cellulose, which forms the basis of CNC. Biomass wastes are generally made up of agricultural waste, and forest residues, etc. CNC can be produced from biomass wastes by removing the non-cellulosic components through acid hydrolysis, enzymatic hydrolysis, oxidation hydrolysis, and other mechanical methods. However, biomass wastes are generally disposed of or burned in a random manner, resulting in adverse environmental consequences. Hence, using biomass wastes to develop CNC-based carrier materials is an effective strategy to promote the high value-added application of biomass wastes. This review summarizes the advantages of CNC applications, the extraction process, and recent advances in CNC-based composites, such as aerogels, hydrogels, films, and metal complexes. Furthermore, the drug release characteristics of CNC-based material are discussed in detail. Additionally, we discuss some gaps in our understanding of the current state of knowledge and potential future directions of CNC-based materials.

Emerging Trends in Nanotechnology: Aerogel-Based Materials for Biomedical Applications

At present, aerogel is one of the most interesting materials globally. The network of aerogel consists of pores with nanometer widths, which leads to a variety of functional properties and broad applications. Aerogel is categorized as inorganic, organic, carbon, and biopolymers, and can be modified by the addition of advanced materials and nanofillers. Herein, this review critically discusses the basic preparation of aerogel from the sol-gel reaction with derivation and modification of a standard method to produce various aerogels for diverse functionalities. In addition, the biocompatibility of various types of aerogels were elaborated. Then, biomedical applications of aerogel were focused on this review as a drug delivery carrier, wound healing agent, antioxidant, anti-toxicity, bone regenerative, cartilage tissue activities and in dental fields. The clinical status of aerogel in the biomedical sector is shown to be similarly far from adequate. Moreover, due to their remarkable properties, aerogels are found to be preferably used as tissue scaffolds and drug delivery systems. The advanced studies in areas including self-healing, additive manufacturing (AM) technology, toxicity, and fluorescent-based aerogel are crucially important and are further addressed.

Nanosilk Template-Guided/Induced Construction of Brush-/Flower-like 3D Nanostructures

Biomaterials with natural hierarchical structures typically exhibit extraordinary properties because of their multilevel structural designs. They offer many templates and models as well as inspiration for material design, particularly for fabricating structure-regulated, performance-enhanced, and function-enriched materials. Biopolymer-based nanocomposites with ingenious nanostructures constructed through ecofriendly and sustainable approaches are highly desirable to meet the multifunctional requirements of developing bioinspired materials. Herein, an all-silk fibroin-based nanocomposite with a brush-like nanostructure was constructed for the first time using a nanotemplate-guided assembly approach in which dissolved silk assembled directly on a silk nanowhisker (SNW) backbone to form peculiar nanobrushes based on the classical micelle model. Three-dimensional spider-like or centipede-like silk nanobrushes (SNBs) were fabricated by varying the SNW backbone length from 0.16 to 6 μm. The branches with average lengths of 32-290 nm were also adjustable. SNBs were further designed to regulate and induce biomineralization of hydroxyapatite (HAP) to form interesting flower-like nanostructures, in which the HAP nanosphere (diameters ∼16 nm) "core" was covered by SNBs with branches extending to form a "shell" (∼101 nm in length). Based on such protein nanotemplate-guided formation of nanoscale structures, practical hollow conduits with remarkable mechanical properties, biocompatibility, shape memory behavior, and bone engineering potential were fabricated. This study inspires the design of polymorphous biopolymer-based nanostructures with enhanced performance at multiple length scales where the weaknesses of individual building blocks are offset.

Biobased Nanomaterials─The Role of Interfacial Interactions for Advanced Materials

This review presents recent advances regarding biomass-based nanomaterials, focusing on their surface interactions. Plant biomass-based nanoparticles, like nanocellulose and lignin from industry side streams, hold great potential for the development of lightweight, functional, biodegradable, or recyclable material solutions for a sustainable circular bioeconomy. However, to obtain optimal properties of the nanoparticles and materials made thereof, it is crucial to control the interactions both during particle production and in applications. Herein we focus on the current understanding of these interactions. Solvent interactions during particle formation and production, as well as interactions with water, polymers, cells and other components in applications, are addressed. We concentrate on cellulose and lignin nanomaterials and their combination. We demonstrate how the surface chemistry of the nanomaterials affects these interactions and how excellent performance is only achieved when the interactions are controlled. We furthermore introduce suitable methods for probing interactions with nanomaterials, describe their advantages and challenges, and introduce some less commonly used methods and discuss their possible applications to gain a deeper understanding of the interfacial chemistry of biobased nanomaterials. Finally, some gaps in current understanding and interesting emerging research lines are identified.

Natural silk nanofibers as building blocks for biomimetic aerogel scaffolds

Protein nanofibers offer great promise for tissue engineering scaffolds owing to biomimetic architecture and exceptional biocompatibility. Natural silk nanofibrils (SNFs) are promising but unexplored protein nanofibers for biomedical applications. In this study, the SNF-assembled aerogel scaffolds with ECM-mimicking architecture and ultra-high porosity are developed based on a polysaccharides-assisted strategy. The SNFs exfoliated from silkworm silks can be utilized as building blocks to construct 3D nanofibrous scaffolds with tunable densities and desirable shapes on a large scale. We demonstrate that the natural polysaccharides can regulate SNF assembly through multiple binding modes, endowing the scaffolds with structural stability in water and tunable mechanical properties. As a proof of concept, the biocompatibility and biofunctionality of the chitosan-assembled SNF aerogels were investigated. The nanofibrous aerogels have excellent biocompatibility, and their biomimetic structure, ultra-high porosity, and large specific surface area endow the scaffolds with enhanced cell viability to mesenchymal stem cells. The nanofibrous aerogels were further functionalized by SNF-mediated biomineralization, demonstrating their potential as a bone-mimicking scaffold. Our results show the potential of natural nanostructured silks in the field of biomaterials and provide a feasible strategy to construct protein nanofiber scaffolds.

Convergence of 3D Bioprinting and Nanotechnology in Tissue Engineering Scaffolds

Three-dimensional (3D) bioprinting has emerged as a promising scaffold fabrication strategy for tissue engineering with excellent control over scaffold geometry and microstructure. Nanobiomaterials as bioinks play a key role in manipulating the cellular microenvironment to alter its growth and development. This review first introduces the commonly used nanomaterials in tissue engineering scaffolds, including natural polymers, synthetic polymers, and polymer derivatives, and reveals the improvement of nanomaterials on scaffold performance. Second, the 3D bioprinting technologies of inkjet-based bioprinting, extrusion-based bioprinting, laser-assisted bioprinting, and stereolithography bioprinting are comprehensively itemized, and the advantages and underlying mechanisms are revealed. Then the convergence of 3D bioprinting and nanotechnology applications in tissue engineering scaffolds, such as bone, nerve, blood vessel, tendon, and internal organs, are discussed. Finally, the challenges and perspectives of convergence of 3D bioprinting and nanotechnology are proposed. This review will provide scientific guidance to develop 3D bioprinting tissue engineering scaffolds by nanotechnology.

Microscale 3D Printing and Tuning of Cellulose Nanocrystals Reinforced Polymer Nanocomposites

The increasing demand for functional materials and an efficient use of sustainable resources makes the search for new material systems an ever growing endeavor. With this respect, architected (meta-)materials attract considerable interest. Their fabrication at the micro- and nanoscale, however, remains a challenge, especially for composites with highly different phases and unmodified reinforcement fillers. This study demonstrates that it is possible to create a non-cytotoxic nanocomposite ink reinforced by a sustainable phase, cellulose nanocrystals (CNCs), to print and tune complex 3D architectures using two-photon polymerization, thus, advancing the state of knowledge toward the microscale. Micro-compression, high-res scanning electron microscopy, (polarised) Raman spectroscopy, and composite modeling are used to study the structure-property relationships. A 100% stiffness increase is observed already at 4.5 wt% CNC while reaching a high photo-polymerization degree of ≈80% for both neat polymers and CNC-composites. Polarized Raman and the Halpin-Tsai composite-model suggest a random CNC orientation within the polymer matrix. The microscale approach can be used to tune arbitrary small scale CNC-reinforced polymer-composites with comparable feature sizes. The new insights pave the way for future applications where the 3D printing of small structures is essential to improve performances of tissue-scaffolds, extend bio-electronics applications or tailor microscale energy-absorption devices.

Electroactive Biomaterials for Facilitating Bone Defect Repair under Pathological Conditions

Bone degeneration associated with various diseases is increasing due to rapid aging, sedentary lifestyles, and unhealthy diets. Living bone tissue has bioelectric properties critical to bone remodeling, and bone degeneration under various pathological conditions results in significant changes to these bioelectric properties. There is growing interest in utilizing biomimetic electroactive biomaterials that recapitulate the natural electrophysiological microenvironment of healthy bone tissue to promote bone repair. This review first summarizes the etiology of degenerative bone conditions associated with various diseases such as type II diabetes, osteoporosis, periodontitis, osteoarthritis, rheumatoid arthritis, osteomyelitis, and metastatic osteolysis. Next, the diverse array of natural and synthetic electroactive biomaterials with therapeutic potential are discussed. Putative mechanistic pathways by which electroactive biomaterials can mitigate bone degeneration are critically examined, including the enhancement of osteogenesis and angiogenesis, suppression of inflammation and osteoclastogenesis, as well as their anti-bacterial effects. Finally, the limited research on utilization of electroactive biomaterials in the treatment of bone degeneration associated with the aforementioned diseases are examined. Previous studies have mostly focused on using electroactive biomaterials to treat bone traumatic injuries. It is hoped that this review will encourage more research efforts on the use of electroactive biomaterials for treating degenerative bone conditions.

Sponges from Plasma Treated Cellulose Nanofibers Grafted with Poly(ethylene glycol)methyl Ether Methacrylate

In this work, cellulose nanofibers (CNF) were surface treated by plasma and grafted with poly(ethylene glycol)methyl ether methacrylate (PEGMMA) for increasing mechanical strength and hydrophobicity. The surface characteristics of the sponges were studied by scanning electron microscopy, micro-computed tomography, and Fourier transform infrared spectroscopy, which demonstrated successful surface modification. Plasma treatment applied to CNF suspension led to advanced defibrillation, and the resulting sponges (CNFpl) exhibited smaller wall thickness than CNF. The grafting of PEGMMA led to an increase in the wall thickness of the sponges and the number of larger pores when compared with the non-grafted counterparts. Sponges with increased hydrophobicity demonstrated by an almost 4 times increase in the water contact angle and better mechanical strength proved by 2.5 times increase in specific compression strength were obtained after PEGMMA grafting of plasma treated CNF. Cells cultivated on both neat and PEGMMA-grafted CNF sponges showed high viability (>99%). Remarkably, CNF grafted with PEGMMA showed better cell viability as compared with the untreated CNF sample; this difference is statistically significant (p < 0.05). In addition, the obtained sponges do not trigger an inflammatory response in macrophages, with TNF-α secretion by cells in contact with CNFpl, CNF-PEGMMA, and CNFpl-PEGMMA samples being lower than that observed for the CNF sample. All these results support the great potential of cellulose nanofibers surface treated by plasma and grafted with PEGMMA for biomedical applications.

Advanced cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) aerogels: Bottom-up assembly perspective for production of adsorbents

The most common and abundant polymer in nature is the linear polysaccharide cellulose, but processing it requires a new approach since cellulose degrades before melting and does not dissolve in ordinary organic solvents. Cellulose aerogels are exceptionally porous (>90 %), have a high specific surface area, and have low bulk density (0.0085 mg/cm³), making them suitable for a variety of sophisticated applications including but not limited to adsorbents. The production of materials with different qualities from the nanocellulose based aerogels is possible thanks to the ease with which other chemicals may be included into the structure of nanocellulose based aerogels; despite processing challenges, cellulose can nevertheless be formed into useful, value-added products using a variety of traditional and cutting-edge techniques. To improve the adsorption of these aerogels, rheology, 3-D printing, surface modification, employment of metal organic frameworks, freezing temperature, and freeze casting techniques were all investigated and included. In addition to exploring venues for creation of aerogels, their integration with CNC liquid crystal formation were also explored and examined to pursue "smart adsorbent aerogels". The objective of this endeavour is to provide a concise and in-depth evaluation of recent findings about the conception and understanding of nanocellulose aerogel employing a variety of technologies and examination of intricacies involved in enhancing adsorption properties of these aerogels.

Nanofibrous scaffolds based on bacterial cellulose crosslinked with oxidized sucrose

In this work, oxidized sucrose (OS), which is a safe bio-based and non-toxic polyaldehyde, was used as a crosslinker in defibrillated bacterial cellulose (BC) sponges obtained by freeze-drying. For mimicking the proteins' crosslinking, BC was first modified with an aminosilane to partially replace the OH groups on the BC surface with more reactive amino groups. Further, the aminosilane-grafted bacterial cellulose (BCA) was crosslinked with OS in different concentrations and thermally cured. Functionalized bacterial celluloses showed a good thermal stability, comparable to that of unmodified cellulose and much improved mechanical properties. A threefold increase in the compression strength was obtained for the BCA scaffold after crosslinking and curing. This was correlated with the uniform pore structure emphasized by the micro-CT and SEM analyses. The OS-crosslinked BCA scaffolds were not cytotoxic and showed a porosity of around 80 %, which was almost 100 % open porosity. This study shows that the crosslinking of aminated BC scaffolds with OS allows the obtaining of 3D cellulose structures with good mechanical properties and high porosity, suitable for soft tissue engineering. The results recommend this new method as an innovative approach to obtaining biomaterial scaffolds that mimic the natural extracellular matrix.

Mechanically Tough and Regenerable Antibacterial Nanofibrillated Cellulose-Based Aerogels for Oil/Water Separation

Nanofibrillated cellulose (NFC)-based aerogels have been widely used for various applications. However, the disadvantages of poor structural stability, low mechanical toughness, and easy contamination by bacteria hinder their large-scale application. In this work, 3-(3'-acrylicacidpropylester)-5,5-dimethyl hydantoin (APDMH) was grafted on oxidized NFC (ONC) to prepare antibacterial poly(APDMH)-g-ONC (PAC). PAC and poly(ethyleneimine) (PEI) were chemically cross-linked using 3-glycidoxypropyltrimethox (GPTMS), aiming at constructing a PAC-g-PEI aerogel with multiple network structures. The mechanical behaviors of composite aerogel and oil/water separation performances under different conditions were investigated. PAC-g-PEI aerogel exhibits outstanding fatigue resistance (>50 cycles of compression) and superior elasticity (96.76% height recovery after five compression-release cycles at 50% strain). The obtained superhydrophilic and underwater-oleophobic properties endow the aerogel with excellent oil/water separation performances, achieving a satisfactory separation efficiency of over 99% and flux of over 9500 L·m^-2·h^-1. Furthermore, the chlorinated aerogel of PAC-g-PEI-Cl shows highly efficient and rechargeable antibacterial properties, can inactivate 6.72-log Escherichia coli and 6.60-log Staphylococcus aureus within 10 min, and can still kill all inoculated bacteria after 50 cycles. In addition, PAC-g-PEI-Cl aerogel can inhibit biofilm formation, making it a promising candidate for highly efficient oil/water separation applications in diverse harsh conditions.

Technological limitations in obtaining and using cellulose biocomposites

Among the many possible types of polymer composite materials, the most important are nanocomposites and biocomposites, which have received tremendous attention in recent years due to their unique properties. The fundamental benefits of using biocomposites as alternative materials to “petroleum-based” products are certainly shaping current development trends and setting directions for future research and applications of polymer composites. A dynamic growth of the production and sale of biocomposites is observed in the global market, which results not only from the growing interest and demand for this type of materials, but also due to the fact that for the developed and modified, thus improved materials, the area of their application is constantly expanding. Already today, polymer composites with plant raw materials are used in various sectors of the economy. In particular, this concerns the automotive and construction industries, as well as widely understood packaging. Bacterial cellulose, for example, also known as bionanocellulose, as a natural polymer with specific and unique properties, has been used extensively,primarily in numerous medical applications. Intensive research is also being carried out into composites with natural fibres composed mainly of organic compounds such as cellulose, hemicellulose and lignin. However, three aspects seem to be associated with the popularisation of biopolymers: performance, processing and cost. This article provides a brief overview of the topic under discussion. What can be the technological limitations considering the methods of obtaining polymer composites with the use of plant filler and the influence on their properties? What properties of cellulose constitute an important issue from the point of view of its applicability in polymers, in the context of compatibility with the polymer matrix and processability? What can be the ways of changing these properties through modifications, which may be crucial from the point of view of the development directions of biopolymers and bioplastics, whose further new applications will be related, among others, to the enhancement of properties? There still seems to be considerable potential to improve the cellulose material composites being produced, as well as to improve the efficiency of their manufacturing. Nevertheless, the material still needs to be well optimized before it can replace conventional materials at the industrial level in the near future. Typically, various studies discuss their comparison in terms of production, properties and highly demanding applications of plant or bacterial nanocellulose. Usually, aspects of each are described separately in the literature. In the present review, several important data are gathered in one place, providing a basis for comparing the types of cellulose described. On the one hand, this comparison aims to demonstrate the advantage of bacterial cellulose over plant cellulose, due to environmental protection and its unique properties. On the other hand, it aims to prepare a more comprehensive point of view that can objectively help in deciding which cellulosic raw material may be more suitable for a particular purpose, bacterial cellulose or plant cellulose.

A Brief Evaluation of Pore Structure Determination for Bioaerogels

This review discusses the most commonly employed methods for determining pore size and pore size distribution in bioaerogels. Aerogels are materials with high porosity and large surface areas. Most of their pores are in the range of mesopores, between 2 and 50 nm. They often have smaller or larger pores, which presents a significant challenge in determining the exact mean pore size and pore size distribution in such materials. The precision and actual value of the pore size are of considerable importance since pore size and pore size distribution are among the main properties of aerogels and are often directly connected with the final application of those materials. However, many recently published papers discuss or present pore size as one of the essential achievements despite the misinterpretation or the wrong assignments of pore size determination. This review will help future research and publications evaluate the pore size of aerogels more precisely and discuss it correctly. The study covers methods such as gas adsorption, from which BJH and DFT models are often used, SEM, mercury porosimetry, and thermoporometry. The methods are described, and the results obtained are discussed. The following paper shows that there is still no precise method for determining pore size distribution or mean pore size in aerogels until now. Knowing that, it is expected that this field will evolve in the future.

Biomedical engineering aspects of nanocellulose: a review

Cellulose is one of the most abundant renewable biopolymer in nature and is present as major constituent in both plant cell walls as well as synthesized by some microorganisms as extracellular products. In both the systems, cellulose self-assembles into a hierarchical ordered architecture to form micro to nano-fibrillated structures, on basis of which it is classified into various forms. Nanocellulose (NCs) exist as rod-shaped highly crystalline cellulose nanocrystals to high aspect ratio cellulose nanofibers, micro-fibrillated cellulose and bacterial cellulose (BC), depending upon the origin, structural and morphological properties. Moreover, NCs have been processed into diversified products ranging from composite films, coatings, hydrogels, aerogels, xerogels, organogels, rheological modifiers, optically active birefringent colored films using traditional-to-advanced manufacturing techniques. With such versatility in structure-property, NCs have profound application in areas of healthcare, packaging, cosmetics, energy, food, electronics, bioremediation, and biomedicine with promising commercial potential. Herein this review, we highlight the recent advancements in synthesis, fabrication, processing of NCs, with strategic chemical modification routes to tailor its properties for targeted biomedical applications. We also study the basic mechanism and models for biosynthesis of cellulose in both plant and microbial systems and understand the structural insights of NC polymorphism. The kinetics study for both enzymatic/chemical modifications of NCs and microbial growth behavior of BC under various reactor configurations are studied. The challenges associated with the commercial aspects as well as industrial scale production of pristine and functionalized NCs to meet the growing demands of market are discussed and prospective strategies to mitigate them are described. Finally, post chemical modification evaluation of biological and inherent properties of NC are important to determine their efficacy for development of various products and technologies directed for biomedical applications.

Effect of glutaraldehyde and calcium chloride as different crosslinking agents on the characteristics of chitosan/cellulose nanocrystals scaffold

The effect of glutaraldehyde and calcium cations as covalent and ionic crosslinkers was investigated on the main characteristics of scaffolds based on chitosan and cellulose nanocrystals. Therefore, four different scaffolds based on chitosan/cellulose nanocrystals with different crosslinking methods were fabricated using the freeze-drying method for potential use in bone tissue engineering. The structural and chemical features of prepared scaffolds were studied by the FTIR technique. FESEM images revealed that all scaffold samples are porous three-dimensional networks in which the pores are connected. TGA analysis showed that the thermal stability of scaffolds based on chitosan/cellulose nanocrystals has not been changed significantly by using different crosslinking methods. The chitosan/cellulose nanocrystals scaffold crosslinked by glutaraldehyde represented the highest compressive strength and the uncrosslinked scaffold showed the highest swelling ratio in comparison to the other scaffolds. The fastest degradation rate belonged to the scaffold crosslinked by calcium cations. FESEM images and EDX analysis confirmed that fabricated scaffolds have good biomineralization ability. The cell viability and cell attachment results indicated that all four scaffolds support cell proliferation and cell adhesion. However, the viability of NIH3T3 fibroblast cells in the presence of glutaraldehyde-containing scaffolds was lower than that of other scaffolds.

Structured Ultra-Flyweight Aerogels by Interfacial Complexation: Self-Assembly Enabling Multiscale Designs

The rapid co-assembly of graphene oxide (GO) nanosheets and a surfactant at the oil/water (O/W) interface is harnessed to develop a new class of soft materials comprising continuous, multilayer, interpenetrated, and tubular structures. The process uses a microfluidic approach that enables interfacial complexation of two-phase systems, herein, termed as "liquid streaming" (LS). LS is demonstrated as a general method to design multifunctional soft materials of specific hierarchical order and morphology, conveniently controlled by the nature of the oil phase and extrusion's injection pressure, print-head speed, and nozzle diameter. The as-obtained LS systems can be readily converted into ultra-flyweight aerogels displaying worm-like morphologies with multiscale porosities (micro- and macro-scaled). The presence of reduced GO nanosheets in such large surface area systems renders materials with outstanding mechanical compressibility and tailorable electrical activity. This platform for engineering soft materials and solid constructs opens up new horizons toward advanced functionality and tunability, as demonstrated here for ultralight printed conductive circuits and electromagnetic interference shields.

Biopolymer Material from Human Spongiosa for Regenerative Medicine Application

Natural biopolymers demonstrate significant bone and connective tissue-engineering application efficiency. However, the quality of the biopolymer directly depends on microstructure and biochemical properties. This study aims to investigate the biocompatibility and microstructural properties of demineralized human spongiosa Lyoplast® (Samara, Russian Federation). The graft's microstructural and biochemical properties were analyzed by scanning electron microscopy (SEM), micro-computed tomography, Raman spectroscopy, and proteomic analysis. Furthermore, the cell adhesion property of the graft was evaluated using cell cultures and fluorescence microscopy. Microstructural analysis revealed the hierarchical porous structure of the graft with complete removal of the cellular debris and bone marrow components. Moreover, the proteomic analysis confirmed the preservation of collagen and extracellular proteins, stimulating and inhibiting cell adhesion, proliferation, and differentiation. We revealed the adhesion of chondroblast cell cultures in vitro without any evidence of cytotoxicity. According to the study results, demineralized human spongiosa Lyoplast® can be effectively used as the bioactive scaffold for articular hyaline cartilage tissue engineering.

Synthesis and Optimization of Deesterified Acacia-Alginate Nanohydrogel for Amethopterin Delivery

Naturally obtained materials are preferable for the production of biomedicine in biomedical applications. Acacia gum is has recently become a hopeful one in the biomedicine production due to its excellent properties, namely, emulsifier, stabilizing mediator, suspending agent, etc. In this novel work, we synthesised and characterized the deesterified Acacia gum-alginate nanohydrogel (DEA-AG NPs) as a carrier for amethopterin (ATN) delivery. This combination is used in the drug effectiveness and tissue engineering. In this work, the Taguchi route is implemented for estimating of particle size and zeta potential (mV) through optimization. Following three parameters are considered for this work: DEA solution concentration (0.008, 0.016, 0.024, and 0.032 w/v %), alginate molecular weight (3, 6, 9, and 12 MW), and ATN/DEA ratio (1 : 4, 1 : 8, 1 : 12, and 1 : 16 w/w %). In particle size analysis and zeta potential analysis, the DEA solution concentration is highly influenced. Minimum particle size is found as 148.50 nm. Similarly, maximum zeta potential is identified as 29.5 mV.

Promotion of Adrenal Pheochromocytoma (PC-12) Cell Proliferation and Outgrowth Using Schwann Cell-Laden Gelatin Methacrylate Substrate

Peripheral nerve injuries cause different degrees of nerve palsy and function loss. Due to the limitations of autografts, nerve tissue engineering (TE) scaffolds incorporated with various neurotrophic factors and cells have been investigated to promote nerve regeneration. However, the molecular mechanism is still poorly understood. In this study, we co-cultured Schwann cells (SCs) and rat adrenal pheochromocytoma (PC-12) cells on 50% degrees of methacryloyl substitution gelatin methacrylate (GelMA) scaffold. The SCs were encapsulated within the GelMA, and PC-12 cells were on the surface. A 5% GelMA was used as the co-culture scaffold since it better supports SCs proliferation, viability, and myelination and promotes higher neurotrophic factors secretion than 10% GelMA. In the co-culture, PC-12 cells demonstrated a higher cell proliferation rate and axonal extension than culturing without SCs, indicating that the secretion of neurotrophic factors from SCs can stimulate PC-12 growth and axonal outgrowth. The mRNA level for neurotrophic factors of SCs in 5% GelMA was further evaluated. We found significant upregulation when compared with a 2D culture, which suggested that this co-culture system could be a potential scaffold to investigate the mechanism of how SCs affect neuronal behaviors.

Aerogels for Biomedical, Energy and Sensing Applications

The term aerogel is used for unique solid-state structures composed of three-dimensional (3D) interconnected networks filled with a huge amount of air. These air-filled pores enhance the physicochemical properties and the structural characteristics in macroscale as well as integrate typical characteristics of aerogels, e.g., low density, high porosity and some specific properties of their constituents. These characteristics equip aerogels for highly sensitive and highly selective sensing and energy materials, e.g., biosensors, gas sensors, pressure and strain sensors, supercapacitors, catalysts and ion batteries, etc. In recent years, considerable research efforts are devoted towards the applications of aerogels and promising results have been achieved and reported. In this thematic issue, ground-breaking and recent advances in the field of biomedical, energy and sensing are presented and discussed in detail. In addition, some other perspectives and recent challenges for the synthesis of high performance and low-cost aerogels and their applications are also summarized.

Influence of TEMPO oxidation on the properties of ethylene glycol methyl ether acrylate grafted cellulose sponges

In this study, cellulose nanofibers (CNF) obtained via high-pressure microfluidization were 2,6,6-tetra-methylpiperidine-1-oxyl (TEMPO) oxidized (TOCNF) in order to facilitate the grafting of ethylene glycol methyl ether acrylate (EGA). FTIR and XPS analyses revealed a more efficient grafting of EGA oligomers on the surface of TOCNF as compared to the original CNF. As a result, a consistent covering of the TOCNF fibers with EGA oligomers, an increased hydrophobicity and a reduction in porosity were noticed for TOCNF-EGA. However, the swelling ratio of TOCNF-EGA was similar to that of original CNF grafted with EGA and higher than that of TOCNF, because the higher amount of grafted EGA onto oxidized cellulose and the looser structure reduced the contacts between the fibrils and increased the absorption of water. All these results corroborated with a good cytocompatibility and compression strength recommend TOCNF-EGA for applications in regenerative medicine.

Safety and efficacy assessment of aerogels for biomedical applications

The unique physicochemical properties of aerogels have made them an attractive class of materials for biomedical applications such as drug delivery, regenerative medicine, and wound healing. Their low density, high porosity, and ability to regulate the pore structure makes aerogels ideal nano/micro-structures for loading of drugs and active biomolecules. As a result of this, the number of in vitro and in vivo studies on the therapeutic efficacy of these porous materials has increased substantially in recent years and continues to be an area of great interest. However, data about their in vivo performance and safety is limited. Studies have shown that polymer-based, silica-based and some hybrid aerogels are generally regarded as safe but given that studies on the acute, subacute, and chronic toxicity for the majority of aerogel types is missing, more work is still needed. This review presents a comprehensive summary of different biomedical applications of aerogels proposed to date as well as new and innovative applications of aerogels in other areas such as decontamination. We have also reviewed their biological effect on cells and living organisms with a focus on therapeutic efficacy and overall safety (in vivo and in vitro).

Hydrogel Composites with Different Dimensional Nanoparticles for Bone Regeneration

The treatment of large segmental bone defects and complex types of fractures caused by trauma, inflammation, or tumor resection is still a challenge in the field of orthopedics. Various natural or synthetic biological materials used in clinical applications cannot fully replicate the structure and performance of raw bone. This highlights how to endow materials with multiple functions and biological properties, which is a problem that needs to be solved in practical applications. Hydrogels with outstanding biocompatibility, for their casting into any shape, size, or form, are suitable for different forms of bone defects. Therefore, they have been used in regenerative medicine more widely. In this review, versatile hydrogels are compounded with nanoparticles of different dimensions, and many desirable features of these materials in bone regeneration are introduced, including drug delivery, cell factor vehicle, cell scaffolds, which have potential in bone regeneration applications. The combination of hydrogels and nanoparticles of different dimensions encourages better filling of bone defect areas and has higher adaptability. This is due to the minimally invasive properties of the material and ability to match irregular defects. These biological characteristics make composite hydrogels with different dimensional nanoparticles become one of the most attractive options for bone regeneration materials.

Simple ultrasonic-assisted approach to prepare polysaccharide-based aerogel for cell research and histocompatibility study

Salecan, a water-soluble microbial polysaccharide with attractive biocompatible characteristics, is very suitable for aerogel fabrication. However, the practical application of salecan-based aerogels for cell culture was limited by complicated preparation method, lack of cell anchorage signals, and the ability to modulate this properly. Here, a smart aerogel was designed by ultrasonic-assisted self-assembly of salecan and cationic starch (CAS) without any organic and toxic crosslinkers. The ultrasound waves generated a marked impact on self-assemble process by means of ultrasonic cavitation. Aerogel network was produced by strong electrostatic attractions between the polysaccharides. Especially, salecan/CAS ratio can be precisely modulated to tailor the hydrophilicity, mechanical stiffness, and morphologic property. The specific surface area of the aerogels gradually increased with the increase in salecan/CAS ratio. These aerogels were non-cytotoxic, and the incorporation of salecan into them promoted cell-matrix interactions by directionally supporting cell adhesion and proliferation. Most strikingly, in vivo experiment revealed that the histological features in the main organs of the mice were similar to those observed in the PBS-treated control group, and no sign of the histopathological abnormality or tissue destruction was observed, indicating the excellent histocompatibility of the aerogels. This study offered a new and powerful avenue to fabricate functional biomaterial.

How to control interactions of cellulose-based biomaterials with skin: the role of acidity in the contact area

Being able to control the interactions of biomaterials with living tissues and skin is highly desirable for many biomedical applications. This is particularly the case for cellulose-based materials which provide one of the most versatile platforms for tissue engineering due to their strength, biocompatibility and abundance. Achieving such control, however, requires detailed molecular-level knowledge of the dominant interaction mechanisms. Here, we employed both biased and unbiased atomic-scale molecular dynamics simulations to explore how cellulose crystals interact with model stratum corneum bilayers, ternary mixtures of ceramides, cholesterol, and free fatty acids. Our findings show that acidity in the contact area directly affects binding between cellulose and the stratum corneum bilayer: Protonation of free fatty acids in the bilayer promotes attractive cellulose-bilayer interactions. We identified two major factors that control the cellulose-skin interactions: (i) the electrostatic repulsion between a cellulose crystal and the charged (anionic due to deprotonated fatty acids) surface of a stratum corneum bilayer and (ii) the cellulose-stratum corneum hydrogen bonding. When less than half of the fatty acids in the bilayer are protonated, the first factor dominates and there is no binding to skin. At a larger degree of fatty acid protonation the cellulose-stratum corneum hydrogen bonding prevails yielding a tight binding. Remarkably, we found that ceramide molecules are the key component in hydrogen bonding with cellulose. Overall, our findings highlight the critical role of fatty acid protonation in biomaterial-stratum corneum interactions and can be used for optimizing the surface properties of cellulose-based materials aimed at biomedical applications such as wound dressings.

Hemocompatibility, biodegradability and acute toxicity of acetylated cellulose nanocrystals of different types in comparison

Promotion of promising cellulose nanocrystals (CNC) is largely dependent on the relationship between their morphology, surface chemical composition, and supramolecular structure with toxicity, hemocompatibility, and biodegradability. This paper outlines comparative and integrated analysis of the mentioned biocompatibility aspects of partially acetylated rod-, and disc-lake morphology of CNC with crystalline cellulose allomorphs I and II. These data have also included the study of CNC obtained from the sulfuric acid solutions. The aqueous solution of all types of tested CNC has not been toxic to mice after oral administration. Morphology of internal organs has not changed. However, in case of disc-like particles, the kidney mass coefficient noticeably changed. CNC have neither triggered platelet aggregation nor destroyed the red cell membrane. Intravenous administration to rabbits has not affected the plasma clotting time. Rod-like CNC are more resistant, and the disc-like particles are more susceptible to degradation under the influence of cellulases.

Highly porous and elastic aerogel based on ultralong hydroxyapatite nanowires for high-performance bone regeneration and neovascularization

Hydroxyapatite (HAP) is promising for the clinical treatment of bone defects because of its excellent biocompatibility and osteo-conductivity. However, highly porous HAP scaffolds usually exhibit high brittleness and poor mechanical properties, thus organic constituents are usually added to form composite materials. In this work, a highly porous and elastic aerogel made from ultralong HAP nanowires with ultrahigh porosity (∼98.5%), excellent elasticity and suitable porous structure is prepared as the high-performance scaffold for bone defect repair. The highly porous structure of the as-prepared aerogel is beneficial to bone ingrowth and matter/fluid transfer, and the high elasticity can ensure the structural integrity of the scaffold during bone regeneration. Therefore, the HAP nanowire aerogel scaffold can promote the adhesion, proliferation and migration of rat bone marrow derived mesenchymal stem cells (rBMSCs), and elevate the protein expression of osteogenesis and angiogenesis related genes. The in vivo experimental results demonstrate that the HAP nanowire aerogel scaffold is favorable for the ingrowth of new bone and blood vessels, and thus can greatly accelerate bone regeneration and neovascularization. The as-prepared HAP nanowire aerogel scaffold shows promising potential for biomedical applications such as bone defect repair.