Engineering Stem Cell Fate Controlling Biomaterials to Develop Muscle Connective Tissue Layered Myofibers.

Skeletal muscle connective tissue (MCT) surrounds myofiber bundles to provide structural support, produce force transduction from tendons, and regulate satellite cell differentiation during muscle regeneration. Engineered muscle tissue composed of myofibers layered within MCT has not yet been developed. Herein, a bioengineering strategy to create MCT-layered myofibers through the development of stem cell fate-controlling biomaterials that achieve both myogenesis and fibroblast differentiation in a locally controlled manner at the single construct is introduced. The reciprocal role of transforming growth factor-beta 1 (TGF-ß1) and its inhibitor as well as 3D matrix stiffness to achieve co-differentiation of MCT fibroblasts and myofibers from a human-induced pluripotent stem cell (hiPSC)-derived paraxial mesoderm is studied. To avoid myogenic inhibition, TGF-ß1 is conjugated on the gelatin-based hydrogel to control the fibroblasts' populations locally; the TGF-ß1 degrades after 2 weeks, resulting in increased MCT-specific extracellular matrix (ECM) production. The locations of myofibers and fibroblasts are precisely controlled by using photolithography and co-axial wet spinning techniques, which results in the formation of MCT-layered functional myofibers in 3D constructs. This advanced engineering strategy is envisioned as a possible method for obtaining biomimetic human muscle grafts for various biomedical applications.

Injectable Self-Oxygenating Cardio-Protective and Tissue Adhesive Silk-Based Hydrogel for Alleviating Ischemia After Mi Injury.

Myocardial infarction (MI) is a significant cardiovascular disease that restricts blood flow, resulting in massive cell death and leading to stiff and noncontractile fibrotic scar tissue formation. Recently, sustained oxygen release in the MI area has shown regeneration ability; however, improving its therapeutic efficiency for regenerative medicine remains challenging. Here, a combinatorial strategy for cardiac repair by developing cardioprotective and oxygenating hybrid hydrogels that locally sustain the release of stromal cell-derived factor-1 alpha (SDF) and oxygen for simultaneous activation of neovascularization at the infarct area is presented. A sustained release of oxygen and SDF from injectable, mechanically robust, and tissue-adhesive silk-based hybrid hydrogels is achieved. Enhanced endothelialization under normoxia and anoxia is observed. Furthermore, there is a marked improvement in vascularization that leads to an increment in cardiomyocyte survival by ≈30% and a reduction of the fibrotic scar formation in an MI animal rodent model. Improved left ventricular systolic and diastolic functions by ≈10% and 20%, respectively, with a ≈25% higher ejection fraction on day 7 are also observed. Therefore, local delivery of therapeutic oxygenating and cardioprotective hydrogels demonstrates beneficial effects on cardiac functional recovery for reparative therapy.

Noninvasive and Continuous Monitoring of On-Chip Stem Cell Osteogenesis Using a Reusable Electrochemical Immunobiosensor.

Noninvasive monitoring of biofabricated tissues during the biomanufacturing process is needed to obtain reproducible, healthy, and functional tissues. Measuring the levels of biomarkers secreted from tissues is a promising strategy to understand the status of tissues during biofabrication. Continuous and real-time information from cultivated tissues enables users to achieve scalable manufacturing. Label-free biosensors are promising candidates for detecting cell secretomes since they can be noninvasive and do not require labor-intensive processes such as cell lysing. Moreover, most conventional monitoring techniques are single-use, conducted at the end of the fabrication process, and, challengingly, are not permissive to in-line and continual detection. To address these challenges, we developed a noninvasive and continual monitoring platform to evaluate the status of cells during the biofabrication process, with a particular focus on monitoring the transient processes that stem cells go through during in vitro differentiation over extended periods. We designed and evaluated a reusable electrochemical immunosensor with the capacity for detecting trace amounts of secreted osteogenic markers, such as osteopontin (OPN). The sensor has a low limit of detection (LOD), high sensitivity, and outstanding selectivity in complex biological media. We used this OPN immunosensor to continuously monitor on-chip osteogenesis of human mesenchymal stem cells (hMSCs) cultured 2D and 3D hydrogel constructs inside a microfluidic bioreactor for more than a month and were able to observe changing levels of OPN secretion during culture. The proposed platform can potentially be adopted for monitoring a variety of biological applications and further developed into a fully automated system for applications in advanced cellular biomanufacturing.

Immunomodulating Hydrogels as Stealth Platform for Drug Delivery Applications.

Non-targeted persistent immune activation or suppression by different drug delivery platforms can cause adverse and chronic physiological effects including cancer and arthritis. Therefore, non-toxic materials that do not trigger an immunogenic response during delivery are crucial for safe and effective in vivo treatment. Hydrogels are excellent candidates that can be engineered to control immune responses by modulating biomolecule release/adsorption, improving regeneration of lymphoid tissues, and enhancing function during antigen presentation. This review discusses the aspects of hydrogel-based systems used as drug delivery platforms for various diseases. A detailed investigation on different immunomodulation strategies for various delivery options and deliberate upon the outlook of such drug delivery platforms are conducted.

Hybrid extracellular vesicles-liposome incorporated advanced bioink to deliver microRNA.

In additive manufacturing, bioink formulations govern strategies to engineer 3D living tissues that mimic the complex architectures and functions of native tissues for successful tissue regeneration. Conventional 3D-printed tissues are limited in their ability to alter the fate of laden cells. Specifically, the efficient delivery of gene expression regulators (i.e. microRNAs (miRNAs)) to cells in bioprinted tissues has remained largely elusive. In this study, we explored the inclusion of extracellular vesicles (EVs), naturally occurring nanovesicles (NVs), into bioinks to resolve this challenge. EVs show excellent biocompatibility, rapid endocytosis, and low immunogenicity, which lead to the efficient delivery of miRNAs without measurable cytotoxicity. EVs were fused with liposomes to prolong and control their release by altering their physical interaction with the bioink. Hybrid EVs-liposome (hEL) NVs were embedded in gelatin-based hydrogels to create bioinks that could efficiently encapsulate and deliver miRNAs at the target site in a controlled and sustained manner. The regulation of cells' gene expression in a 3D bioprinted matrix was achieved using the hELs-laden bioink as a precursor for excellent shape fidelity and high cell viability constructs. Novel regulatory factors-loaded bioinks will expedite the translation of new bioprinting applications in the tissue engineering field.

Transcriptomic Mapping of Neural Diversity, Differentiation and Functional Trajectory in iPSC-Derived 3D Brain Organoid Models.

Experimental models of the central nervous system (CNS) are imperative for developmental and pathophysiological studies of neurological diseases. Among these models, three-dimensional (3D) induced pluripotent stem cell (iPSC)-derived brain organoid models have been successful in mitigating some of the drawbacks of 2D models; however, they are plagued by high organoid-to-organoid variability, making it difficult to compare specific gene regulatory pathways across 3D organoids with those of the native brain. Single-cell RNA sequencing (scRNA-seq) transcriptome datasets have recently emerged as powerful tools to perform integrative analyses and compare variability across organoids. However, transcriptome studies focusing on late-stage neural functionality development have been underexplored. Here, we combine and analyze 8 brain organoid transcriptome databases to study the correlation between differentiation protocols and their resulting cellular functionality across various 3D organoid and exogenous brain models. We utilize dimensionality reduction methods including principal component analysis (PCA) and uniform manifold approximation projection (UMAP) to identify and visualize cellular diversity among 3D models and subsequently use gene set enrichment analysis (GSEA) and developmental trajectory inference to quantify neuronal behaviors such as axon guidance, synapse transmission and action potential. We showed high similarity in cellular composition, cellular differentiation pathways and expression of functional genes in human brain organoids during induction and differentiation phases, i.e., up to 3 months in culture. However, during the maturation phase, i.e., 6-month timepoint, we observed significant developmental deficits and depletion of neuronal and astrocytes functional genes as indicated by our GSEA results. Our results caution against use of organoids to model pathophysiology and drug response at this advanced time point and provide insights to tune in vitro iPSC differentiation protocols to achieve desired neuronal functionality and improve current protocols.

A Study of the Chemistries, Growth Mechanisms, and Antibacterial Properties of Cerium- and Yttrium-Containing Nanoparticles.

Under the current climate, physicians prescribe antibiotics for treating bacterial infections, and such a limitation to a single class of drugs is disadvantageous since antibiotic-resistant bacteria have adapted to withstanding their stresses. Antibiotic alternatives are sought, and herein metal nanoparticles comprised of the rare earth elements cerium and yttrium were determined to invoke toxicity on methicillin-resistant Staphylococcus aureus (MRSA) and a multi-drug-resistant strain of Escherichia coli (MDR E. coli). Ceria nanoparticles, yttrium-doped ceria nanoparticles, and cerium-doped yttria nanoparticles were fabricated by a wet chemical route, homogeneous precipitation in hexamethylenetetramine (HMT). To demonstrate the drastic variations in nanoparticle structure and toxicity that occur when the synthesis method and solvent are substituted, two additional approaches involving solvothermal and hydrothermal reactions were pursued in the production of yttrium-containing nanoparticles. Intrinsic nanoparticle features of size, morphology, and composition were construed by physiochemical characterizations, which aided in the elaboration of chemical reaction and growth mechanisms. It was determined by in vitro plate count assays that ceria nanoparticles which had been doped using the yttrium metal precursor after 30 min of the HMT reaction, at 500 µg/mL, were the most effective at inhibiting MRSA growth without imposing significant cytotoxicity on human dermal fibroblast cells. A total of 500 µg/mL of cerium- and yttrium-containing nanoparticles, prepared in a 1:1 molar ratio, were similarly biocompatible and antimicrobial, in the case of MDR E. coli. Indeed, as this study showed, nanoalternatives to antibiotics are feasible, adaptable, and can be facilely produced. The possible clinical applications of the rare earth metal nanoparticles are variegated, and ceria and yttria nanoparticles are additionally credited in the literature as dynamic antioxidants, regulators of tissue regeneration, and anticancer agents.

Engineering multifunctional bactericidal nanofibers for abdominal hernia repair.

The engineering of multifunctional surgical bactericidal nanofibers with inherent suitable mechanical and biological properties, through facile and cheap fabrication technology, is a great challenge. Moreover, hernia, which is when organ is pushed through an opening in the muscle or adjacent tissue due to damage of tissue structure or function, is a dire clinical challenge that currently needs surgery for recovery. Nevertheless, post-surgical hernia complications, like infection, fibrosis, tissue adhesions, scaffold rejection, inflammation, and recurrence still remain important clinical problems. Herein, through an integrated electrospinning, plasma treatment and direct surface modification strategy, multifunctional bactericidal nanofibers were engineered showing optimal properties for hernia repair. The nanofibers displayed good bactericidal activity, low inflammatory response, good biodegradation, as well as optimal collagen-, stress fiber- and blood vessel formation and associated tissue ingrowth in vivo. The disclosed engineering strategy serves as a prominent platform for the design of other multifunctional materials for various biomedical challenges.

Needle-injectable microcomposite cryogel scaffolds with antimicrobial properties.

Porous three-dimensional hydrogel scaffolds have an exquisite ability to promote tissue repair. However, because of their high water content and invasive nature during surgical implantation, hydrogels are at an increased risk of bacterial infection. Recently, we have developed elastic biomimetic cryogels, an advanced type of polymeric hydrogel, that are syringe-deliverable through hypodermic needles. These needle-injectable cryogels have unique properties, including large and interconnected pores, mechanical robustness, and shape-memory. Like hydrogels, cryogels are also susceptible to colonization by microbial pathogens. To that end, our minimally invasive cryogels have been engineered to address this challenge. Specifically, we hybridized the cryogels with calcium peroxide microparticles to controllably produce bactericidal hydrogen peroxide. Our novel microcomposite cryogels exhibit antimicrobial properties and inhibit antibiotic-resistant bacteria (MRSA and Pseudomonas aeruginosa), the most common cause of biomaterial implant failure in modern medicine. Moreover, the cryogels showed negligible cytotoxicity toward murine fibroblasts and prevented activation of primary bone marrow-derived dendritic cells ex vivo. Finally, in vivo data suggested tissue integration, biodegradation, and minimal host inflammatory responses when the antimicrobial cryogels, even when purposely contaminated with bacteria, were subcutaneously injected in mice. Collectively, these needle-injectable microcomposite cryogels show great promise for biomedical applications, especially in tissue engineering and regenerative medicine.

Hydroxyapatite and ß-TCP modified PMMA-TiO2 and PMMA-ZrO2 coatings for bioactive corrosion protection of Ti6Al4V implants.

Organic-inorganic hybrid coatings deposited on different types of metallic alloys have shown outstanding anticorrosive performance. The incorporation of osteoconductive additives such as hydroxyapatite (HA) and ß-tricalcium phosphate (ß-TCP) into organic-inorganic hybrid coatings is promising to improve the osseointegration and corrosion resistance of Ti6Al4V alloys, which are the most widely used metallic orthopedic and dental implant materials today. Therefore, this study evaluated the capability of poly(methyl methacrylate) (PMMA)-TiO2 and PMMA-ZrO2 hybrid coatings modified with HA and ß-TCP to act as bioactive and corrosion protection coatings for Ti6Al4V alloys. In terms of cell growth and mineralization, osteoblast viability, Ca+2 deposition and alkaline phosphatase assays revealed a significant improvement for the HA and ß-TCP modified coatings, compared to the bare alloy. This can be explained by an increase in nanoscale roughness and associated higher surface free energy, which lead to enhanced protein adsorption to promote osteoblast attachment and functions on the coatings. The effect of HA and ß-TCP additives on the anticorrosive efficiency was studied by electrochemical impedance spectroscopy (EIS) in a simulated body fluid (SBF) solution. The coatings presented a low-frequency impedance modulus of up to 430 GΩ cm2, 5 decades higher than the bare Ti6Al4V alloy. These findings provide clear evidence of the beneficial role of HA and ß-TCP modified hybrid coatings, improving both the biocompatibility and corrosion resistance of the Ti6Al4V alloy.

Green Synthesis of Zeolite/Fe2O3 Nanocomposites: Toxicity & Cell Proliferation Assays and Application as a Smart Iron Nanofertilizer.

PURPOSE: The aim of this study was to prepare zeolite/iron (III) oxide nanocomposites (zeolite/Fe2O3-NCs) as a smart fertilizer to improve crop yield and soil productivity. METHODS: Zeolite/Fe2O3-NCs were successfully produced by loading of Fe2O3-NPs onto the zeolite surface using a quick green precipitation method. The production of zeolite/Fe2O3 nanocomposites was performed under a mild condition using environmentally friendly raw materials as a new green chemistry method. The product was characterized using several techniques such as near and far Fourier-transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). RESULTS: The results confirmed the formation of Fe2O3-NPs with mean particle sizes of 1.45, 2.19, and 2.20 nm on the surface of the zeolite per amount of 4, 7 and 12 wt% Fe2O3-NPs, respectively. Such results indicated that the size of the Fe2O3-NPs did not significantly change when Fe amounts increased from 7 to 12 wt% for the zeolite/Fe2O3-NCs. In terms of medical applications, in vitro cell studies demonstrated that zeolites and zeolite/Fe2O3-NCs were generally non-toxic to human fibroblast cells and significantly pernicious to human malignant melanoma cells. From MTS cytotoxicity assays, the concentration of Fe2O3 within the zeolite/Fe2O3-NCs that was effective at inhibiting the growth of malignant melanoma cells by 50% (the IC50 value) was ~14.9 wt%. The three types of nanocomposites were further tested as an iron smart nanofertilizer for the slow-release of iron ions. CONCLUSION: Advantages of this project include the production of non-toxic nanocomposites as a smart fertilizer to develop crops while the reaction involves the use of commercial and natural materials as low-cost raw materials with low energy usage due to a mild reaction condition, as well as the use of an environmentally friendly solvent (water) with no toxic residues.

Advances in dual functional antimicrobial and osteoinductive biomaterials for orthopaedic applications.

A vast growing problem in orthopaedic medicine is the increase of clinical cases with antibiotic resistant pathogenic microbes, which is predicted to cause higher mortality than all cancers combined by 2050. Bone infectious diseases limit the healing ability of tissues and increase the risk of future injuries due to pathologic tissue remodelling. The traditional treatment for bone infections has several drawbacks and limitations, such as lengthy antibiotic treatment, extensive surgical interventions, and removal of orthopaedic implants and/or prosthesis, all of these resulting in long-term rehabilitation. This is a huge burden to the public health system resulting in increased healthcare costs. Current technologies e.g. co-delivery systems, where antibacterial and osteoinductive agents are delivered encounter challenges such as site-specific delivery, sustained and prolonged release, and biocompatibility. In this review, these aspects are highlighted to promote the invention of the next generation biomaterials to prevent and/or treat bone infections and promote tissue regeneration.

3-D printed Ti-6Al-4V scaffolds for supporting osteoblast and restricting bacterial functions without using drugs: Predictive equations and experiments.

Conditions resulting from musculoskeletal deficiencies (MSDs) are wide-ranging and retain the likelihood for restricting motion or producing pain, especially in the lower back, neck, and upper limbs. Engineered scaffold devices are being produced to replace antiquated modalities that suffer from structural and mechanical deficiencies in the treatment of MSDs. Here, as-fabricated Ti-6Al-4V-based Hive™ interbody fusion scaffolds, commercialized by HD Lifesciences LLC, were assayed for their osteogenicity and antibacterial potential using a series of characterization and in vitro tests, as well as by quantitative analyses. A topographical assessment of the Hive™ meshes indicated that the elementally pure substrates are microscopically porous and rough, in addition to displaying structural heterogeneity. Roughness estimations and static contact angle measurements recommended the use of the as-fabricated Ti-6Al-4V substrates for supporting osteoblast attachment, especially, due to the improved surface roughness and wettability values of these scaffolds relative to the unembellished Ti-6Al-4V surfaces. Quantitative correlations relating the surface properties of roughness and energy were applied to predict cellular behaviors. Cell growth suppositions were experimentally corroborated. Critical in vitro data indicated the competencies of the Hive™ scaffolds for promoting the adhesion and proliferation of human fetal osteoblasts (hFOBs), accumulating substantial calcium deposition from metabolizing hFOBs, and restricting the attachment of bacteria. The model system that investigated the pre-adsorption of casein proteins along the Hive™ test substrates additionally furthered the notion that bacterial attachment may be restricted, with short-scale adhesion dynamics serving as the theoretical basis for this hypothesis. In this manner, this study showed that through predictive models and experiments, these novel 3D printed Ti-based scaffolds can increase bone cell while decreasing bacteria functions without using drugs. STATEMENT OF SIGNIFICANCE: Sintered Ti-6Al-4V spinal fusion devices (Hive™) manufactured and marketed by HD Lifesciences LLC were assessed for their biocompatibility and antibacterial performance. A mixed methods approach was employed, whereby quantitative measures were used to predict the ability for Hive™ substrates to adsorb specialized proteins and to restrict bacterial surface colonization. In vitro tests that evaluated bone cell and bacterial adhesion, calcium deposition, and protein adsorption supported quantitative predictions. The data herein presented demonstrate the following: (1) surface energy is an important predictor of implant-cell interactions, (2) strong correlations exist between surface energy and surface roughness, (3) mathematical models can be used to improve and predict implant device perofrmance, and (4) porous, rough, 3D-printed materials perform well in terms of biocompatibility and antimicrobial efficacy.

The Binary Effect on Methicillin-Resistant Staphylococcus aureus of Polymeric Nanovesicles Appended by Proline-Rich Amino Acid Sequences and Inorganic Nanoparticles.

Prevalent research underscores efforts to engineer highly sophisticated nanovesicles that are functionalized to combat antibiotic-resistant bacterial infections, especially those caused by methicillin-resistant Staphylococcus aureus (MRSA), and that aid with wound healing or immunomodulation. This is especially relevant for patients who are susceptible to Staphylococcus aureus infections postoperatively. Here, antibacterial formulations are incorporated into polymeric, biocompatible vesicles called polymersomes (PsNPs) that self-assemble via hydrophobic interactions of admixed aqueous and organic substances. Nano-PsNPs are synthesized using a high molecular weight amphiphilic block copolymer, and are conjugated to include antimicrobial peptides (AMPs) along the peripheral hydrophilic region and silver nanoparticles (AgNPs) inside their hydrophobic corona. In vitro testing on bacterial and human cell lines indicates that finely tuned treatment concentrations of AMP and AgNPs in PsNPs synergistically inhibits the growth of MRSA without posing significant side effects, as compared with other potent treatment strategies. A ratio of silver-to-AMP of about 1:5.8 corresponding to ≈11.6 µg mL-1 of silver nanoparticles and 14.3 × 10-6 m of the peptide, yields complete MRSA inhibition over a 23 h time frame. This bacteriostatic activity, coupled with nominal cytotoxicity toward native human dermal fibroblast cells, extends the potential for AMP/AgNP polymersome therapies to replace antibiotics in the clinical setting.

Facile in situ generation of bismuth tungstate nanosheet-multiwalled carbon nanotube composite as unconventional affinity material for quartz crystal microbalance detection of antibiotics.

Overuse and thus a constant presence of antibiotics leads to various environmental hazards and health risks. Thus, accurate sensors are required to determine their presence. In this work, we present a mass-sensitive sensor for the detection of rifampicin. We chose this molecule as it is an important antibiotic for tuberculosis, one of the leading causes of deaths worldwide. Herein, we have prepared a carbon nanotube reinforced with bismuth tungstate nanocomposite material in a well-defined nanosheet morphology using a facile in situ synthesis mechanism. Morphological characterization revealed the presence of bismuth tungstate in the form of square nanosheets embedded in the intricate network of carbon nanotubes, resulting in higher surface roughness of the nanocomposite. The synergy of the composite, so formed, manifested a high affinity for rifampicin as compared to the individual components of the composite. The developed sensor possessed a high sensitivity toward rifampicin with a detection limit of 0.16 µM and excellent specificity, as compared to rifabutin and rifapentine. Furthermore, the sensor yielded statistically good recoveries for the monitoring of rifampicin in human urine samples. This work opens up a new horizon for the exploration of unconventional nanomaterials bearing different morphologies for the detection of pharmaceuticals.

Osteoblast responses to injectable bone substitutes of kappa-carrageenan and nano hydroxyapatite.

The combination of kappa-carrageenan (κ-CG) and hydroxyapatite (HA) to generate a bone substitute material has been underexplored to date. Carrageenans (CGs) have remarkable characteristics such as biocompatibility, hydrophilicity, and structural similarities with natural glycosaminoglycans (GAGs), and they have demonstrated the ability to stimulate cellular adhesion and proliferation. Hydroxyapatite nanoparticles have been one of the most investigated materials for bone regeneration due to their excellent biocompatibility, bioactivity and osteoconductivity. In particular, this study presents an approach for the preparation of new bioactive composites of κ-CG/nHA for numerous bone regeneration applications. We performed a set of in vitro experiments to evaluate the influence of the bone substitutes on human osteoblasts. Cell culture studies indicated that all samples tested were cytocompatible. Relative to control substrates, cellular attachment and proliferation were better on all the scaffold surfaces that were tested. The S2 and S3 samples, those permeated by 1.5 and 2.5 wt% of CG, respectively, exhibited an enhancement in cell spreading capacity compared to the S1 test materials which were comprised of 1 wt% of CG. Excellent osteoblast viability and adhesion were observed for each of the tested materials. Additionally, the bone substitutes developed for this study presented a distinct osteoconductive environment. Data supporting this claim were derived from alkaline phosphatase (ALP) and calcium deposition analyses, which indicated that, compared to the control species, ALP expression and calcium deposition were both improved on test κ-CG/nHA surfaces. In summary, the injectable bone substitute developed here demonstrated great potential for numerous bone regeneration applications, and thus, should be studied further. STATEMENT OF SIGNIFICANCE: The novelty of this work lies in the determination of the in vitro cytocompatibility behavior of carrageenan and hydroxyapatite composite materials used as injectable bone substitutes. This injectable biomaterial can fill in geometric complex defects, and it displays bioactivity as well as high bone regeneration capacity. In this study, we evaluated the behaviors of osteoblast cells in contact with the scaffolds, including cellular adhesion and proliferation, cellular metabolism, and mineralization on the fabricated injectable bone substitutes. The results show than the carrageenan and hydroxyapatite substitutes provided a biomaterial with a great capacity for promoting cellular growth, adhesion, and proliferation, as well as contributing an osteoinductive environment for osteoblast differentiation and osteogenesis.

Nanopillared Chitosan/Gelatin Films: A Biomimetic Approach for Improved Osteogenesis.

Biomimicry strategies, inspired from natural organization of living organisms, are being widely used in the design of nanobiomaterials. Particularly, nonlithographic techniques have shown immense potential in the facile fabrication of nanostructured surfaces at large-scale production. Orthopedic biomaterials or coatings possessing extracellular matrix-like nanoscale features induce desirable interactions between the bone tissue and implant surface, also known as osseointegration. In this study, nanopillared chitosan/gelatin (C/G) films were fabricated using nanoporous anodic alumina molds, and their antibacterial properties as well as osteogenesis potential were analyzed by comparing to the flat C/G films and tissue culture polystyrene as controls. In vitro analysis of the expression of RUNX2, osteopontion, and osteocalcin genes for mesenchymal stem cells as well as osteoblast-like Saos-2 cells was found to be increased for the cells grown on nano C/G films, indicating early-stage osteogenic differentiation. Moreover, the mineralization tests (quantitative calcium analysis and alizarin red staining) showed that nanotopography significantly enhanced the mineralization capacity of both cell lines. This work may provide a new perspective of biomimetic surface topography fabrication for orthopedic implant coatings with superior osteogenic differentiation capacity and fast bone regeneration potential.

Understanding the impact of crosslinked PCL/PEG/GelMA electrospun nanofibers on bactericidal activity.

Herein, we report the design of electrospun ultrathin fibers based on the combination of three different polymers polycaprolactone (PCL), polyethylene glycol (PEG), and gelatin methacryloyl (GelMA), and their potential bactericidal activity against three different bacteria Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa), and Methicillin-resistant Staphylococcus aureus (MRSA). We evaluated the morphology, chemical structure and wettability before and after UV photocrosslinking of the produced scaffolds. Results showed that the developed scaffolds presented hydrophilic properties after PEG and GelMA incorporation. Moreover, they were able to significantly reduce gram-positive, negative, and MRSA bacteria mainly after UV photocrosslinking (PCL:PEG:GelMa-UV). Furthermore, we performed a series of study for gaining a better mechanistic understanding of the scaffolds bactericidal activity through protein adsorption study and analysis of the reactive oxygen species (ROS) levels. Furthermore, the in vivo subcutaneous implantation performed in rats confirmed the biocompatibility of our designed scaffolds.

Evaluation of cytotoxicity and antimicrobial activity of an injectable bone substitute of carrageenan and nano hydroxyapatite.

A successful post-surgical implant is associated with accelerated recovery periods, involving the efficient regeneration of lost or non-viable tissue and a reduction in microbial growth. Alternatively, the long-term success of an implant is guided by the selection of an engineered biomimetic material that is biocompatible, non-biodegradable, and stable at the site of implantation, without invoking any non-essential or undesirable biological responses. The potential for developing an injectable bone substitute (IBS) was investigated here. In particular, carrageenan (CG) and nano-hydroxyapatite (nHA) injectable composites were fabricated by chemical cross-linking, and the in vitro behavior of mammalian cells and bacteria on the IBS surface structures were evaluated. Formulations consisting of 1%, 1.5%, and 2.5% CG and 60% nHA by weight were then evaluated for their interactions with human osteoblasts (or bone forming cells). MTS viability testing indicated that osteoblast adhesion and viability on the IBS were excellent and uniform among various formulation types. Bacteria assays were also performed to assess antimicrobial functions on the CG/nHA composite against both Gram-negative and Gram-positive strains. A higher CG content, as found in some samples, correlated with improved Pseudomonas aeruginosa growth inhibition, although other bacteria strains appeared unaffected by the IBS. In summary, this study highlights CG/nHA composites as innovative biomaterials that should be further studied for reduced bacteria activity and promoted osteoblast responses which was achieved without using pharmaceutical drugs. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2984-2993, 2018.

Nanofibrous scaffolds for biomedical applications.

Tissue engineering is an emergent and very interesting research field, providing potential solutions for a myriad of challenges in healthcare. Fibrous scaffolds specifically have shown promise as an effective tissue engineering method, as their high length-to-width ratio mimics that of extracellular matrix components, which in turn guides tissue formation, promotes cellular adhesion and improves mechanical properties. In this review paper, we discuss in detail both the importance of fibrous scaffolds for the promotion of tissue growth and the different methods to produce fibrous biomaterials to possess favorable and unique characteristics. Here, we focus on the pressing need to develop biomimetic structures that promote an ideal environment to encourage tissue formation. In addition, we discuss different biomedical applications in which fibrous scaffolds can be useful, identifying their importance, relevant aspects, and remaining significant challenges. In conclusion, we provide comments on the future direction of fibrous scaffolds and the best way to produce them, proposed in light of recent technological advances and the newest and most promising fabrication techniques.