The osteogenic differentiation of rat bone marrow stromal cells cultured with dexamethasone-loaded carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles

Bone Tissue Engineering and Nanotechnology: A Promising Combination for Bone Regeneration

Large bone defects are the leading contributor to disability worldwide, affecting approximately 1.71 billion people. Conventional bone graft treatments show several disadvantages that negatively impact their therapeutic outcomes and limit their clinical practice. Therefore, much effort has been made to devise new and more effective approaches. In this context, bone tissue engineering (BTE), involving the use of biomaterials which are able to mimic the natural architecture of bone, has emerged as a key strategy for the regeneration of large defects. However, although different types of biomaterials for bone regeneration have been developed and investigated, to date, none of them has been able to completely fulfill the requirements of an ideal implantable material. In this context, in recent years, the field of nanotechnology and the application of nanomaterials to regenerative medicine have gained significant attention from researchers. Nanotechnology has revolutionized the BTE field due to the possibility of generating nanoengineered particles that are able to overcome the current limitations in regenerative strategies, including reduced cell proliferation and differentiation, the inadequate mechanical strength of biomaterials, and poor production of extrinsic factors which are necessary for efficient osteogenesis. In this review, we report on the latest in vitro and in vivo studies on the impact of nanotechnology in the field of BTE, focusing on the effects of nanoparticles on the properties of cells and the use of biomaterials for bone regeneration.

Dendritic Polymers in Tissue Engineering: Contributions of PAMAM, PPI PEG and PEI to Injury Restoration and Bioactive Scaffold Evolution

The capability of radially polymerized bio-dendrimers and hyperbranched polymers for medical applications is well established. Perhaps the most important implementations are those that involve interactions with the regenerative mechanisms of cells. In general, they are non-toxic or exhibit very low toxicity. Thus, they allow unhindered and, in many cases, faster cell proliferation, a property that renders them ideal materials for tissue engineering scaffolds. Their resemblance to proteins permits the synthesis of derivatives that mimic collagen and elastin or are capable of biomimetic hydroxy apatite production. Due to their distinctive architecture (core, internal branches, terminal groups), dendritic polymers may play many roles. The internal cavities may host cell differentiation genes and antimicrobial protection drugs. Suitable terminal groups may modify the surface chemistry of cells and modulate the external membrane charge promoting cell adhesion and tissue assembly. They may also induce polymer cross-linking for healing implementation in the eyes, skin, and internal organ wounds. The review highlights all the different categories of hard and soft tissues that may be remediated with their contribution. The reader will also be exposed to the incorporation of methods for establishment of biomaterials, functionalization strategies, and the synthetic paths for organizing assemblies from biocompatible building blocks and natural metabolites.

Multimodal Potentials of Gold Nanoparticles for Bone Tissue Engineering and Regenerative Medicine: Avenues and Prospects

Osseous tissue repair has advanced due to the introduction of tissue engineering. The key elements required while engineering new tissues involve scaffolds, cells, and bioactive cues. The macrostructural to the nanostructural framework of such complex tissue has engrossed the intervention of nanotechnology for efficient neo-bone formation. Gold nanoparticles (GNPs) have recently gained interest in bone tissue regeneration due to their multimodal functionality. They are proven to modulate the properties of scaffolds and the osteogenic cells significantly. GNPs also influence different metabolic functions within the body, which directly or indirectly govern the mechanism of bone regeneration. Therefore, this review highlights nanoparticle-mediated osteogenic development, focusing on different aspects of GNPs ranging from scaffold modulation to cellular stimulation. The toxic aspects of gold nanoparticles studied so far are critically explicated, while further insight into the advancements and prospects of these nanoparticles in bone regeneration is also highlighted.

Chitosan coatings with distinct innate immune bioactivities differentially stimulate angiogenesis, osteogenesis and chondrogenesis in poly-caprolactone scaffolds with controlled interconnecting pore size

This study tested whether osseous integration into poly (ε-caprolactone) (PCL) bioplastic scaffolds with fully-interconnecting 155 ± 8 μm pores is enhanced by an adhesive, non-inflammatory 99% degree of deacetylation (DDA) chitosan coating (99-PCL), or further incorporation of pro-inflammatory 83% DDA chitosan microparticles (83-99-PCL) to accelerate angiogenesis. New Zealand White rabbit osteochondral knee defects were press-fit with PCL, 99-PCL, 83-99-PCL, or allowed to bleed (drill-only). Between day 1 and 6 weeks of repair, drill-only defects repaired by endochondral ossification, with an 8-fold higher bone volume fraction (BVF) versus initial defects, compared to a 2-fold (99-PCL), 1.1-fold (PCL), or 0.4-fold (83-99-PCL) change in BVF. Hematoma innate immune cells swarmed to 83-99-PCL, elicited angiogenesis throughout the pores and induced slight bone resorption. PCL and 99-PCL pores were variably filled with cartilage or avascular mesenchyme near the bone plate, or angiogenic mesenchyme into which repairing trabecular bone infiltrated up to 1 mm deep. More repair cartilage covered the 99-PCL scaffold (65%) than PCL (18%) or 83-99-PCL (0%) (p < 0.005). We report the novel finding that non-inflammatory chitosan coatings promoted cartilage infiltration into and over a bioplastic scaffold, and were compatible with trabecular bone integration. This study also revealed that in vitro osteogenesis assays have limited ability to predict osseous integration into porous scaffolds, because (1) in vivo, woven bone integrates from the leading edge of regenerating trabecular bone and not from mesenchymal cells adhering to scaffold surfaces, and (2) bioactive coatings that attract inflammatory cells induce bone resorption.

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Porous polycaprolactone scaffolds elicited drawn-out osteochondral wound repair.

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Regenerating trabecular bone only infiltrated angiogenic mesenchyme free of inflammatory cells.

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83% DDA chitosan stimulated sterile inflammatory angiogenesis and trabecular bone resorption.

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99% DDA chitosan coatings promoted chondrogenesis inside and over the PCL articular surface.

Amine-terminated dendritic polymers as promising nanoplatform for diagnostic and therapeutic agents' modification: A review

It is often challenging to design diagnostic and therapeutic agents that fulfill all functional requirements. So, bulk and surface modifications as a common approach for biomedical applications have been suggested. There have been considerable research interests in using nanomaterials to the prementioned methods. Among all nanomaterials, dendritic materials with three-dimensional structures, host-guest properties, and nano-polymeric dimensions have received considerable attention. Amine-terminated dendritic structures including, polyamidoamine (PAMAM), polypropyleneimine (PPI), and polyethyleneimine (PEI), have been enormously utilized in bio-modification. This review briefly described the structure of these three common dendritic polymers and their use to modify diagnostic and therapeutic agents in six major applications, including drug delivery, gene delivery, biosensor, bioimaging, tissue engineering, and antimicrobial activity. The current review covers amine-terminated dendritic polymers toxicity challenging and improvement strategies as well.

Sulfonated glycosaminoglycan bioinspired carbon dots for effective cellular labelling and promotion of the differentiation of mesenchymal stem cells

Although carbon dots (CDs) have been synthesized and applied in a variety of biological fields, such as disease diagnosis and gene/drug delivery, the exploration of facile bioinspired synthesis and applications of CDs is still of great significance. Particularly, recent increasing research has clearly confirmed that nanomaterials can affect a series of physiological behaviors and functions of mesenchymal stem cells (MSCs) (e.g., differentiation and pluripotency). Therefore, it is very important to develop multifunctional nanomaterials to simultaneously realize the cellular labelling and regulation of MSC behaviors in practical applications. Herein, sulfonated glycosaminoglycan-bioinspired CDs as bi-functional nanomaterials were ingeniously designed for cellular imaging and promoting the differentiation of rat bone MSCs (rBMSCs) in different culture media, which simultaneously met the two fundamental requirements in the field of MSC-based treatments (e.g., precisely directing the differentiation of MSCs and effective cellular labeling). These bifunctional CDs were successfully prepared via one-pot hydrothermal synthesis by using d-glucosamine hydrochloride (GA·HCl) and sodium p-styrenesulfonate (NaSS) as the reactants. The synthesized CDs with a uniform particle size (around 4 nm) dispersed well in aqueous solutions and exhibited remarkable fluorescence stability under different conditions. Additionally, cell viability and proliferation results demonstrated that the CDs possessed good biocompatibility, having negligible effects on the self-renewal potential of rBMSCs. The as-prepared CDs presented a cytoplasmatic distribution after being ingested by rBMSCs; thus, they are particularly suitable for cellular imaging. More importantly, the addition of CDs to osteogenic and chondrogenic induction media (OIM and CIM), respectively, was capable of effectively promoting the osteogenic and chondrogenic differentiation of rBMSCs due to the generation of reactive oxygen species (ROS) while having no influence on their pluripotency. In brief, this study not only implements a cellular labeling method based on CDs that were synthesized by a biomimicking strategy, but also paves a new way to regulate the differentiation of MSCs by designing multifunctional nanomaterials; this will enable the extensive development of facile synthesis methods and new applications of CDs and will also provide some research foundations for MSC-based fields.

Biomaterial-Based Nanocomposite for Osteogenic Repurposing of Doxycycline

Background

Besides its antimicrobial action, doxycycline (DX) has lately been repurposed as a small-molecule drug for osteogenic purposes. However, osteogenic DX application is impeded by its dose-dependent cytotoxicity. Further, high-dose DX impairs cell differentiation and mineralization.

Purpose

Integrating DX into a biomaterial-based delivery system that can control its release would not only ameliorate its cytotoxic actions but also augment its osteogenic activity. In this work, we managed to engineer novel composite DX–hydroxyapatite–polycaprolactone nanoparticles (DX/HAp/PCL) to modify DX osteogenic potential.

Methods

Employing a 2³-factorial design, we first optimized HApN for surface-area attributes to maximize DX loading. Composite DX/HAp/PCL were then realized using a simple emulsification technique, characterized using various in vitro methods, and evaluated for in vitro osteogenesis.

Results

The developed HApN exhibited a favorable crystalline structure, Ca:P elemental ratio (1.67), mesoporous nature, and large surface area. DX/HAp/PCL achieved the highest reported entrapment efficiency (94.77%±1.23%) of DX in PCL-based particles. The developed composite system achieved controlled release of the water-soluble DX over 24 days. Moreover, the novel composite nanosystem managed to significantly ameliorate DX cytotoxicity on bone-marrow stem cells, as well as enhance its overall proliferation potential. Alkaline phosphatase and mineralization assays revealed superior osteodifferentiation potential of the composite system. Quantification of gene expression demonstrated that while DX solution was able to drive bone-marrow stem cells down the osteogenic lineage into immature osteoblasts after 10-day culture, the innovative composite system allowed maturation of osteodifferentiated cells. To the best of our knowledge, this is the first work to elaborate the impact of DX on the expression of osteogenic genes: RUNX2, OSP, and BSP. Further, the osteogenicity of a DX-loaded particulate-delivery system has not been previously investigated.

Conclusion

Our findings indicate that repurposing low-dose DX in complementary biomaterial-based nanosystems can offer a prominent osteogenic candidate for bone-regeneration purposes.

Hybrid bioactive hydroxyapatite/polycaprolactone nanoparticles for enhanced osteogenesis

Hydroxyapatite nanoparticles (HApN) are largely employed as osteogenic inorganic material. Inorganic/polymeric hybrid nanostructures can provide versatile bioactivity for superior osteogenicity, particularly as nanoparticles. Herein, we present hybrid biomaterial-based hydroxyapatite/polycaprolactone nanoparticles (HAp/PCL NPs) realized using simple preparation techniques to augment HApN osteogenicity. Using wet chemical precipitation, we optimized HApN crystalline properties utilizing a 2³-factorial design. Optimized HApN exhibited typical Ca/P elemental ratio with high reaction yield. Surface area analysis revealed their mesoporous nature and high surface area. Hybrid HAp/PCL NPs prepared using direct emulsification-solvent evaporation maintained HApN crystallinity with no observed chemical interactions. To the best of our knowledge, we are the first to elaborate the biocompatibility and osteogenicity of nanoparticulate hybrid HAp/PCL. Hybrid HAp/PCL NPs outperformed HApN regarding mesenchymal cell proliferation and osteodifferentiation with reduction of possible cytotoxicity. Unlike HApN, hybrid HAp/PCL NPs presented moderate expression of early osteogenic markers, Runx-2 and osteopontin and significantly elevated expression of the late osteogenic marker, bone sialoprotein after 10-day culture. Our results indicate that hybrid bioactive HAp/PCL NPs could offer a more prominent osteogenic potential than plain HApN for bone regenerative applications as a standalone nanoplatform or as part of complex engineered systems.

Platelet lysates-based hydrogels incorporating bioactive mesoporous silica nanoparticles for stem cell osteogenic differentiation

Scaffolds for bone tissue regeneration should provide the right cues for stem cell adhesion and proliferation, but also lead to their osteogenic differentiation. Hydrogels of modified platelet lysates (PLMA) show the proper mechanical stability for cell encapsulation and contain essential bioactive molecules required for cell maintenance. We prepared a novel PLMA-based nanocomposite for bone repair and regeneration capable of releasing biofactors to induce osteogenic differentiation. Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) were encapsulated in PLMA hydrogels containing bioactive mesoporous silica nanoparticles previously loaded with dexamethasone and functionalized with calcium and phosphate ions. After 21 d of culture, hBM-MSCs remained viable, presented a stretched morphology, and showed signs of osteogenic differentiation, namely the presence of significant amounts of alkaline phosphatase, bone morphogenic protein-2 and osteopontin, hydroxyapatite, and calcium nodules. Developed for the first time, PLMA/MSNCaPDex nanocomposites were able to guide the differentiation of hBM-MSCs without any other osteogenic supplementation.

Supramolecular dendrimer-containing layer-by-layer nanoassemblies for bioapplications: current status and future prospects

This review provides a comprehensive and critical overview of the supramolecular dendrimer-containing multifunctional layer-by-layer nanoassemblies driven by a multitude of intermolecular interactions for biological and biomedical applications.

Fabrication of nanoparticles for bone regeneration: new insight into applications of nanoemulsion technology

Introducing synthetic bone substitutes into the clinic was a major breakthrough in the regenerative medicine of bone. Despite many advantages of currently available bone implant materials such as biocompatiblity and osteoconductivity, they still suffer from relatively poor bioactivity, osteoinductivity and osteointegration. These properties can be effectively enhanced by functionalization of implant materials with nanoparticles such as osteoinductive hydroxyapatite nanocrystals, resembling inorganic part of the bone, or bioactive polymer nanoparticles providing sustained delivery of pro-osteogenic agents directly at implantation site. One of the most widespread techniques for fabrication of nanoparticles for bone regeneration applications is nanoemulsification. It allows manufacturing of nanoscale particles (<100 nm) that are injectable, 3D-printable, offer high surface-area-to-volume-ratio and minimal mass transport limitations. Nanoparticles obtained by this technique are of particular interest for biomedical engineering due to fabrication procedures requiring low surfactant concentrations, which translates into reduced risk of surfactant-related in vivo adverse effects and improved biocompatibility of the product. This review discusses nanoemulsion technology and its current uses in manufacturing of nanoparticles for bone regeneration applications. In the first section, we introduce basic concepts of nanoemulsification including nanoemulsion formation, properties and preparation methods. In the next sections, we focus on applications of nanoemulsions in fabrication of nanoparticles used for delivery of drugs/biomolecules facilitating osteogenesis and functionalization of bone implants with special emphasis on biomimetic hydroxyapatite nanoparticles, synthetic polymer nanoparticles loaded with bioactive compounds and bone-targeting nanoparticles. We also highlight key challenges in formulation of nanoparticles via nanoemulsification and outline potential further improvements in this field.

Vibrational Spectroscopy for In Vitro Monitoring Stem Cell Differentiation

Stem cell technology has attracted considerable attention over recent decades due to its enormous potential in regenerative medicine and disease therapeutics. Studying the underlying mechanisms of stem cell differentiation and tissue generation is critical, and robust methodologies and different technologies are required. Towards establishing improved understanding and optimised triggering and control of differentiation processes, analytical techniques such as flow cytometry, immunohistochemistry, reverse transcription polymerase chain reaction, RNA in situ hybridisation analysis, and fluorescence-activated cell sorting have contributed much. However, progress in the field remains limited because such techniques provide only limited information, as they are only able to address specific, selected aspects of the process, and/or cannot visualise the process at the subcellular level. Additionally, many current analytical techniques involve the disruption of the investigation process (tissue sectioning, immunostaining) and cannot monitor the cellular differentiation process in situ, in real-time. Vibrational spectroscopy, as a label-free, non-invasive and non-destructive analytical technique, appears to be a promising candidate to potentially overcome many of these limitations as it can provide detailed biochemical fingerprint information for analysis of cells, tissues, and body fluids. The technique has been widely used in disease diagnosis and increasingly in stem cell technology. In this work, the efforts regarding the use of vibrational spectroscopy to identify mechanisms of stem cell differentiation at a single cell and tissue level are summarised. Both infrared absorption and Raman spectroscopic investigations are explored, and the relative merits, and future perspectives of the techniques are discussed.

Comprehensive Survey on Nanobiomaterials for Bone Tissue Engineering Applications

One of the most important ideas ever produced by the application of materials science to the medical field is the notion of biomaterials. The nanostructured biomaterials play a crucial role in the development of new treatment strategies including not only the replacement of tissues and organs, but also repair and regeneration. They are designed to interact with damaged or injured tissues to induce regeneration, or as a forest for the production of laboratory tissues, so they must be micro-environmentally sensitive. The existing materials have many limitations, including impaired cell attachment, proliferation, and toxicity. Nanotechnology may open new avenues to bone tissue engineering by forming new assemblies similar in size and shape to the existing hierarchical bone structure. Organic and inorganic nanobiomaterials are increasingly used for bone tissue engineering applications because they may allow to overcome some of the current restrictions entailed by bone regeneration methods. This review covers the applications of different organic and inorganic nanobiomaterials in the field of hard tissue engineering.

Exosome-like Nanoparticles: A New Type of Nanocarrier

Nanoparticles are one of the most commonly used systems for imaging or therapeutic drug delivery. Exosomes are nanovesicular carriers that transport cargo for intercellular communication. These nanovesicles are linked to the pathology of some major diseases, in some cases with a central role in their progression. The use of these carriers to transport therapeutic drugs is a recent and promising approach to treat diseases such as cancer and Alzheimer disease. The physiological production of these structures is limited impairing its collection and subsequent purification. These drawbacks inspired the search for mimetic alternatives. The collection of exosome-like nanoparticles from plants can be a good alternative, since they are easier to extract and do not have the drawbacks of those produced in animal cells. Both natural and synthetic exosome-like nanoparticles, produced from serial extrusion of cells or by bottom up synthesis, are currently some of the most promising, biocompatible, high efficiency systems for drug delivery.

The sustained release of dexamethasone from TiO2 nanotubes reinforced by chitosan to enhance osteoblast function and anti-inflammation activity

Controlling macrophage response to biomaterials is critical for the reduction of inflammation after implantation. Here we designed a sustained release system from TiO₂ nanotubes (TNTs) to improve osteogenesis on titanium implants with anti-inflammatory properties. TNTs (around 70 nm diameter) were first fabricated on titanium surfaces by anodization, directly filled with the anti-inflammatory drug, dexamethasone (DEX) and then covered by chitosan (CHI) multilayer films. Primary osteoblast and macrophage (RAW 264.7) cells were cultured on untreated and treated titanium surfaces in vitro. Osteoblasts grown on CHI-coated Dex-filled TNTs surfaces displayed higher alkaline phosphatase (ALP) and mineralization, which was consistent with qRT-PCR analysis of osteoblastic genes including collagen type I (Col I), osteocalcin (OCN), osteopontin (OPN) and runt related transcription factor 2 (Runx2). In contrast, protein levels of nitric oxide (NO) and proinflammatory cytokines (TNF-α and IL-1β) from macrophages on Dex-filled TNTs, CHI-coated TNTs and CHI-coated Dex-filled TNTs were significantly lower, especially on CHI-coated Dex-filled TNTs surfaces compared to levels on titanium and TNTs. These results indicate that CHI-coated Dex-filled TNTs enhanced osteoblast differentiation and decreased the inflammatory response of macrophages. The approach presented here provides new insight into the modification of TNTs for the development of titanium-based implants.

Dendrimer nanoparticles for colorectal cancer applications

Cancer nanotechnology is a prolific field of research, where nanotools are employed to diagnose and treat cancer with unprecedented precision. Targeted drug delivery is fundamental for more efficient cancer treatments. For this, nanoparticles have been extensively used during the past few years in order to improve the specificity, selectivity and controlled release of drug delivery. It holds potential in minimizing systemic toxicity through the development of functionalized particles for targeted treatment. Among all the type of nanoparticles, dendrimers display several advantages, which make them ideal candidates for improved and targeted drug delivery in cancer research. Dendrimers can transport large amounts of drug into specific areas. In addition, they can be employed for monitoring the progress of the treatment process, with an unprecedented theranostic capability. Special emphasis is given to colorectal cancer and to the preferred employed strategies for producing drug-loaded/functionalized NPs for cancer therapy in the past few years.

Exploring Poly(Ethylene Glycol)-Poly(Trimethylene Carbonate) Nanoparticles as Carriers of Hydrophobic Drugs to Modulate Osteoblastic Activity

Current treatment options for bone-related disorders rely on a systemic administration of therapeutic agents that possess low solubility and intracellular bioavailability, as well as a high pharmacokinetic variability, which in turn lead to major off-target side effects. Hence, there is an unmet need of developing drug delivery systems that can improve the clinical efficacy of such therapeutic agents. Nanoparticle delivery systems might serve as promising carriers of hydrophobic molecules. Here, we propose 2 nanoparticle-based delivery systems based on monomethoxy poly(ethylene glycol)-poly(trimethyl carbonate) (mPEG-PTMC) and poly(lactide-co-glycolide) for the intracellular controlled release of a small hydrophobic drug (dexamethasone) to osteoblast cells in vitro. mPEG-PTMC self-assembles into stable nanoparticles in the absence of surfactant and shows a greater entrapment capacity of dexamethasone, while assuring bioactivity in MC3T3-E1 and bone marrow stromal cells cultured under apoptotic and osteogenic conditions, respectively. The mPEG-PTMC nanoparticles represent a potential vector for the intracellular delivery of hydrophobic drugs in the framework of bone-related diseases.

Advances of nanotechnology in osteochondral regeneration

In the past few decades, nanotechnology has proven to be one of the most powerful engineering strategies. The nanotechnologies for osteochondral tissue engineering aim to restore the anatomical structures and physiological functions of cartilage, subchondral bone, and osteochondral interface. As subchondral bone and articular cartilage have different anatomical structures and the physiological functions, complete healing of osteochondral defects remains a great challenge. Considering the limitation of articular cartilage to self-healing and the complexity of osteochondral tissue, osteochondral defects are in urgently need for new therapeutic strategies. This review article will concentrate on the most recent advancements of nanotechnologies, which facilitates chondrogenic and osteogenic differentiation for osteochondral regeneration. Moreover, this review will also discuss the current strategies and physiological challenges for the regeneration of osteochondral tissue. Specifically, we will summarize the latest developments of nanobased scaffolds for simultaneously regenerating subchondral bone and articular cartilage tissues. Additionally, perspectives of nanotechnology in osteochondral tissue engineering will be highlighted. This review article provides a comprehensive summary of the latest trends in cartilage and subchondral bone regeneration, paving the way for nanotechnologies in osteochondral tissue engineering. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Self-mineralizing Ca-enriched methacrylated gellan gum beads for bone tissue engineering

In this study, methacrylated gellan-gum (GG-MA) heteropolysaccharide is proposed as a hydrogel for drug delivery and bone tissue engineering applications. Calcium-enriched beads obtained from the crosslinking of 1% (w/v) GG-MA solutions with 0.1 MCaCl₂ were investigated, considering their intrinsic capacity to promote self-mineralization by ion binding and deposition. Indeed, when immersed in a physiological environment, the Ca-enriched beads promoted the development of a bone-like apatite layer, as confirmed by EDS and XRD chemical analysis. Additionally, the mild production process is compatible with drugs incorporation and release. After encapsulation, Dextran with different molecular weights as well as Dexamethasone 21-phosphate were efficiently released to the surrounding environment. The engineered system was also evaluated considering its biocompatibility, by means of qualitative determination of total complement activation, macrophage proliferation, cytokine release and in vitro cell culture. These experiments showed that the developed hydrogels may not stimulate a disproportionate pro-inflammatory reaction once transplanted. At last, when implanted subcutaneously in CD1 male mice up to 8 weeks, the beads were completely calcified, and no inflammatory reaction was observed. Summing up, these results show that calcium-enriched GG-MA hydrogel beads hold great potential as news tools for bone tissue regeneration and local drug delivery applications. STATEMENT OF SIGNIFICANCE: This work describes a low-cost and straightforward strategy to prepare bioactive methacrylated gellan gum (GG-MA) hydrogels, which can be used as drug delivery systems. GG-MA is a highly anionic polymer, that can be crosslinked with divalent ions, as calcium. Taking advantage of this feature, it was possible to prepare Ca-enriched GG-MA hydrogel beads. These beads display a bioactive behavior, since they promote apatite deposition when placed in physiological conditions. Studies on the immune response suggest that the developed beads do not trigger severe immune responses. Importantly, the mild processing method render these beads compliant with drug delivery strategies, paving the way for the application of dual-functional materials on bone tissue engineering.

Colorectal tumor-on-a-chip system: A 3D tool for precision onco-nanomedicine

Awareness that traditional two-dimensional (2D) in vitro and nonrepresentative animal models may not completely emulate the 3D hierarchical complexity of tissues and organs is on the rise. Therefore, posterior translation into successful clinical application is compromised. To address this dearth, on-chip biomimetic microenvironments powered by microfluidic technologies are being developed to better capture the complexity of in vivo pathophysiology. Here, we describe a "tumor-on-a-chip" model for assessment of precision nanomedicine delivery on which we validate the efficacy of drug-loaded nanoparticles in a gradient fashion. The model validation was performed by viability studies integrated with live imaging to confirm the dose-response effect of cells exposed to the CMCht/PAMAM nanoparticle gradient. This platform also enables the analysis at the gene expression level, where a down-regulation of all the studied genes (MMP-1, Caspase-3, and Ki-67) was observed. This tumor-on-chip model represents an important development in the use of precision nanomedicine toward personalized treatment.

Terminal chemical functions of polyamidoamine dendrimer surfaces and its impact on bone cell growth

Besides their use for drug and gene delivery, dendrimer molecules are also favorable for the design of new surface coatings for orthopedic and dental implants due to the wide variety of functional terminal groups and their multivalent character. The purpose of this work was to observe how covalently immobilized polyamidoamine (PAMAM) dendrimer molecules with different terminal chemical groups influenced serum protein adsorption and osteoblast behavior. To this end, fifth-generation PAMAM dendrimers were immobilized on silicon surfaces with an anhydride-containing silane coupling agent which results in positively charged terminal NH₂-groups. Coatings with a net negative charge were generated by introduction of terminal CO₂H- or CH₃-groups. Surface characterization was performed by static and dynamic contact angle and zeta potential. The in vitro studies with human MG-63 osteoblastic cells focused on cell adhesion, morphology, cell cycle, apoptosis and actin formation within 24 h. This work demonstrated that cell growth was dependent on surface chemistry and correlated strongly with the surface free energy and charge of the material. The positively charged NH₂ surface induced tight cell attachment with well-organized actin stress fibers and a well spread morphology. In contrast, CO₂H- and CH₃-functional groups provoked a decrease in cell adhesion and spreading and indicated higher apoptotic potential, although both were hydrophilic. The knowledge about the cell-material dialogue is of relevance for the development of bioactive implants in regenerative medicine.

Potential applications of engineered nanoparticles in medicine and biology: an update

Nanotechnology advancements have led to the development of its allied fields, such as nanoparticle synthesis and their applications in the field of biomedicine. Nanotechnology driven innovations have given a hope to the patients as well as physicians in solving the complex medical problems. Nanoparticles with a size ranging from 0.2 to 100 nm are associated with an increased surface to volume ratio. Moreover, the physico-chemical and biological properties of nanoparticles can be modified depending on the applications. Different nanoparticles have been documented with a wide range of applications in various fields of medicine and biology including cancer therapy, drug delivery, tissue engineering, regenerative medicine, biomolecules detection, and also as antimicrobial agents. However, the development of stable and effective nanoparticles requires a profound knowledge on both physico-chemical features of nanomaterials and their intended applications. Further, the health risks associated with the use of engineered nanoparticles needs a serious attention.

Recent review of the effect of nanomaterials on stem cells

The field of stem-cell-therapy offers considerable promise as a means of delivering new treatments for a wide range of diseases. Recent progress in nanotechnology has stimulated the development of multifunctional nanomaterials (NMs) for stem-cell-therapy. Several clinical trials based on the use of NMs are currently underway for stem-cell-therapy purposes, such as drug/gene delivery and imaging. However, the interactions between NMs and stem cells are far from being completed, and the effects of the NMs on cellular behavior need critical evaluation. In this review, the interactions between several types of mostly used NMs and stem cells, and their associated possible mechanisms are systematically discussed, with specific emphasis on the possible differentiation effects induced by NMs. It is expected that the enhanced understanding of NM-stem cell interactions will facilitate biomaterial design for stem-cell-therapy and regenerative medicine applications.

Nanomedicine for safe healing of bone trauma: Opportunities and challenges

Historically, high-energy extremity injuries resulting in significant soft-tissue trauma and bone loss were often deemed unsalvageable and treated with primary amputation. With improved soft-tissue coverage and nerve repair techniques, these injuries now present new challenges in limb-salvage surgery. High-energy extremity trauma is pre-disposed to delayed or unpredictable bony healing and high rates of infection, depending on the integrity of the soft-tissue envelope. Furthermore, orthopedic trauma surgeons are often faced with the challenge of stabilizing and repairing large bony defects while promoting an optimal environment to prevent infection and aid bony healing. During the last decade, nanomedicine has demonstrated substantial potential in addressing the two major issues intrinsic to orthopedic traumas (i.e., high infection risk and low bony reconstruction) through combatting bacterial infection and accelerating/increasing the effectiveness of the bone-healing process. This review presents an overview and discusses recent challenges and opportunities to address major orthopedic trauma through nanomedical approaches.

New Bioengineering Breakthroughs and Enabling Tools in Regenerative Medicine

PURPOSE OF REVIEW

In this review, we provide a general overview of recent bioengineering breakthroughs and enabling tools that are transforming the field of regenerative medicine (RM). We focus on five key areas that are evolving and increasingly interacting including mechanobiology, biomaterials and scaffolds, intracellular delivery strategies, imaging techniques, and computational and mathematical modeling.

RECENT FINDINGS

Mechanobiology plays an increasingly important role in tissue regeneration and design of therapies. This knowledge is aiding the design of more precise and effective biomaterials and scaffolds. Likewise, this enhanced precision is enabling ways to communicate with and stimulate cells down to their genome. Novel imaging technologies are permitting visualization and monitoring of all these events with increasing resolution from the research stages up to the clinic. Finally, algorithmic mining of data and soft matter physics and engineering are creating growing opportunities to predict biological scenarios, device performance, and therapeutic outcomes.

SUMMARY

We have found that the development of these areas is not only leading to revolutionary technological advances but also enabling a conceptual leap focused on targeting regenerative strategies in a holistic manner. This approach is bringing us ever more closer to the reality of personalized and precise RM.

Nanoparticles for bone tissue engineering

Tissue engineering (TE) envisions the creation of functional substitutes for damaged tissues through integrated solutions, where medical, biological, and engineering principles are combined. Bone regeneration is one of the areas in which designing a model that mimics all tissue properties is still a challenge. The hierarchical structure and high vascularization of bone hampers a TE approach, especially in large bone defects. Nanotechnology can open up a new era for TE, allowing the creation of nanostructures that are comparable in size to those appearing in natural bone. Therefore, nanoengineered systems are now able to more closely mimic the structures observed in naturally occurring systems, and it is also possible to combine several approaches - such as drug delivery and cell labeling - within a single system. This review aims to cover the most recent developments on the use of different nanoparticles for bone TE, with emphasis on their application for scaffolds improvement; drug and gene delivery carriers, and labeling techniques. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:590-611, 2017.

Cationic osteogenic peptide P15-CSP coatings promote 3-D osteogenesis in poly(epsilon-caprolactone) scaffolds of distinct pore size

P15-CSP is a biomimetic cationic fusion peptide that stimulates osteogenesis and inhibits bacterial biofilm formation when coated on 2-D surfaces. This study tested the hypothesis that P15-CSP coatings enhance 3-D osteogenesis in a porous but otherwise hydrophobic poly-(ɛ-caprolactone) (PCL) scaffold. Scaffolds of 84 µm and 141 µm average pore size were coated or not with Layer-by-Layer polyelectrolytes followed by P15-CSP, seeded with adult primary human mesenchymal stem cells (MSCs), and cultured 10 days in proliferation medium, then 21 days in osteogenic medium. Atomic analyses showed that P15-CSP was successfully captured by LbL. After 2 days of culture, MSCs adhered and spread more on P15-CSP coated pores than PCL-only. At day 10, all constructs contained nonmineralized tissue. At day 31, all constructs became enveloped in a "skin" of tissue that, like 2-D cultures, underwent sporadic mineralization in areas of high cell density that extended into some 141 µm edge pores. By quantitative histomorphometry, 2.5-fold more tissue and biomineral accumulated in edge pores versus inner pores. P15-CSP specifically promoted tissue-scaffold integration, fourfold higher overall biomineralization, and more mineral deposits in the outer 84 µm and inner 141 µm pores than PCL-only (p < 0.05). 3-D Micro-CT revealed asymmetric mineral deposition consistent with histological calcium staining. This study provides proof-of-concept that P15-CSP coatings are osteoconductive in PCL pore surfaces with 3-D topography. Biomineralization deeper than 150 µm from the scaffold edge was optimally attained with the larger 141 µm peptide-coated pores. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2171-2181, 2017.

A semiautomated microfluidic platform for real-time investigation of nanoparticles’ cellular uptake and cancer cells’ tracking

Aim: Develop a platform composed of labeled dendrimer nanoparticles (NPs) and a microfluidic device for real-time monitoring of cancer cells fate. Materials & methods: Carboxymethylchitosan/poly(amidoamine) dendrimer NPs were labeled with fluorescein-5(6)-isothiocyanate and characterized using different physicochemical techniques. After, HeLa, HCT-116 and U87MG were cultured in the presence of NPs, and cell viability and internalization efficiency in static (standard culture) and dynamic (microfluidic culture) conditions were investigated. Results: Cancer cells cultured with NPs in dynamic conditions were viable and presented higher internalization levels as compared with static 2D cultures. Conclusion: This work demonstrated that the proposed microfluidic-based platform allows real-time monitoring, which upon more studies, namely, the assessment of an anticancer drug release effect could be used for cancer theranostics.

The use of nanoscaffolds and dendrimers in tissue engineering

To avoid tissue rejection during organ transplantation, research has focused on the use of tissue engineering to regenerate required tissues or organs for patients. The biomedical applications of hyperbranched, multivalent, structurally uniform, biocompatible dendrimers in tissue engineering include the mimicking of natural extracellular matrices (ECMs) in the 3D microenvironment. Dendrimers are unimolecular architects that can incorporate a variety of biological and/or chemical substances in a 3D architecture to actively support the scaffold microenvironment during cell growth. Here, we review the use of dendritic delivery systems in tissue engineering. We discuss the available literature, highlighting the 3D architecture and preparation of these nanoscaffolds, and also review challenges to, and advances in, the use dendrimers in tissue engineering. Advances in the manufacturing of dendritic nanoparticles and scaffold architectures have resulted in the successful incorporation of dendritic scaffolds in tissue engineering.

A traceable and bone-targeted nanoassembly based on defect-related luminescent mesoporous silica for enhanced osteogenic differentiation

Osteoporosis is a degenerative bone disorder that affects millions of people worldwide. Despite many novel drugs or therapy strategies that have been developed, the curative effect of current treatments is far from satisfying. Development of effective treatments toward osteoporosis is imminent. Bone mesenchymal stem cells (BMSCs) are one kind of pluripotent stem cells, which are not only easy to separate and purify but also can self-renew and differentiate into osteogenic cells. In this work, a traceable drug delivery system based on gadolinium-labeled defect-related luminescent mesoporous silica nanoparticles (MSNs) was developed for bone marrow homing and enhanced osteogenic differentiation. The results showed that dexamethasone (DEX) could be loaded into nanocarriers and gave a sustained release behaviour. A unique defect-related luminescent property could be utilized to monitor the drug release effectively. In addition, the nanocarriers showed good biocompatibility and were uptaken mainly via an energy-dependent endocytosis process which was mediated by the macropinocytosis pathway. Furthermore, the nanocarriers can be simultaneously used as predominant contrast agents for magnetic resonance imaging. More importantly, DEX-loaded nanocarriers can significantly enhance the alkaline phosphatase activity and promote formation of matrix nodules of the BMSCs.

The potential of nanoparticles in stem cell differentiation and further therapeutic applications

Tissue regeneration could offer therapeutic advantages for individuals experiencing organ or tissue damage. Recently, advances in nanotechnology have provided various nanomaterials, with a wide range of applications, for modulating stem cell behavior and for further therapeutic applications in tissue regeneration. Defects in cell proliferation and differentiation, a low mechanical strength of scaffolds, and inefficient production of factors that are essential for stem cell differentiation are the current challenges in tissue regeneration. This review provides a brief explanation about the link between nanotechnology and tissue engineering, highlighting the current literature about the interaction between nanoparticles (NPs) and stem cells, the promotional effect of NPs on stem cell differentiation into various lineages, and their possible therapeutic applications. We also tried to describe the mechanism through which NPs regulate the spatial-temporal release and kinetics of vital growth and differentiation factors, enhance stem cell differentiation, and improve culture conditions for in vivo tissue regeneration. The field of nanotechnology is promising and provides novel nanomaterials and methods with valuable clinical applications in the regenerative medicine. Understanding the mechanism, as well as the toxic effects of NPs in stem cell biology will undoubtedly provide valuable insight into their clinical application in the regenerative medicine.

Small molecules and their controlled release that induce the osteogenic/chondrogenic commitment of stem cells

Stem cell-based tissue engineering plays a significant role in skeletal system repair and regenerative therapies. However, stem cells must be differentiated into specific mature cells prior to implantation (direct implantation may lead to tumour formation). Natural or chemically synthesised small molecules provide an efficient, accurate, reversible, and cost-effective way to differentiate stem cells compared with bioactive growth factors and gene-related methods. Thus, investigating the influences of small molecules on the differentiation of stem cells is of great significance. Here, we review a series of small molecules that can induce or/and promote the osteogenic/chondrogenic commitment of stem cells. The controlled release of these small molecules from various vehicles for stem cell-based therapies and tissue engineering applications is also discussed. The extensive studies in this field represent significant contributions to stem cell-based tissue engineering research and regenerative medicine.

Nanomaterials for Engineering Stem Cell Responses

Recent progress in nanotechnology has stimulated the development of multifunctional biomaterials for tissue engineering applications. Synergistic interactions between nanomaterials and stem cell engineering offer numerous possibilities to address some of the daunting challenges in regenerative medicine, such as controlling trigger differentiation, immune reactions, limited supply of stem cells, and engineering complex tissue structures. Specifically, the interactions between stem cells and their microenvironment play key roles in controlling stem cell fate, which underlines therapeutic success. However, the interactions between nanomaterials and stem cells are not well understood, and the effects of the nanomaterials shape, surface morphology, and chemical functionality on cellular processes need critical evaluation. In this Review, focus is put on recent development in nanomaterial-stem cell interactions, with specific emphasis on their application in regenerative medicine. Further, the emerging technologies based on nanomaterials developed over the past decade for stem cell engineering are reviewed, as well as the potential applications of these nanomaterials in tissue regeneration, stem cell isolation, and drug/gene delivery. It is anticipated that the enhanced understanding of nanomaterial-stem cell interactions will facilitate improved biomaterial design for a range of biomedical and biotechnological applications.

Nanotechnology in bone tissue engineering

Nanotechnology represents a major frontier with potential to significantly advance the field of bone tissue engineering. Current limitations in regenerative strategies include impaired cellular proliferation and differentiation, insufficient mechanical strength of scaffolds, and inadequate production of extrinsic factors necessary for efficient osteogenesis. Here we review several major areas of research in nanotechnology with potential implications in bone regeneration: 1) nanoparticle-based methods for delivery of bioactive molecules, growth factors, and genetic material, 2) nanoparticle-mediated cell labeling and targeting, and 3) nano-based scaffold construction and modification to enhance physicochemical interactions, biocompatibility, mechanical stability, and cellular attachment/survival. As these technologies continue to evolve, ultimate translation to the clinical environment may allow for improved therapeutic outcomes in patients with large bone deficits and osteodegenerative diseases.

FROM THE CLINICAL EDITOR

Traditionally, the reconstruction of bony defects has relied on the use of bone grafts. With advances in nanotechnology, there has been significant development of synthetic biomaterials. In this article, the authors provided a comprehensive review on current research in nanoparticle-based therapies for bone tissue engineering, which should be useful reading for clinicians as well as researchers in this field.

Nanoparticle-based bioactive agent release systems for bone and cartilage tissue engineering

The inability to deliver bioactive agents locally in a transient but sustained manner is one of the challenges on the development of bio-functionalized scaffolds for tissue engineering (TE) and regenerative medicine. The mode of release is especially relevant when the bioactive agent is a growth factor (GF), because the dose and the spatiotemporal release of such agents at the site of injury are crucial to achieve a successful outcome. Strategies that combine scaffolds and drug delivery systems have the potential to provide more effective tissue regeneration relative to current therapies. Nanoparticles (NPs) can protect the bioactive agents, control its profile, decrease the occurrence and severity of side effects and deliver the bioactive agent to the target cells maximizing its effect. Scaffolds containing NPs loaded with bioactive agents can be used for their local delivery, enabling site-specific pharmacological effects such as the induction of cell proliferation and differentiation, and, consequently, neo-tissue formation. This review aims to describe the concept of combining NPs with scaffolds, and the current efforts aiming to develop highly multi-functional bioactive agent release systems, with the emphasis on their application in TE of connective tissues.

Cell engineering by the internalization of bioinstructive micelles for enhanced bone regeneration

Aim: To direct precursor cells toward the osteoblastic lineage, by using an intracellular nanocarrier releasing dexamethasone. Materials & methods: Biodegradable gelatin-based micelles entrapped dexamethasone (dex-micelles). Internalization efficiency and biocompatibility of dex-micelles and their potency for in vitro osteogenic differentiation and in vivo bone regeneration were assessed. Results: Dex-micelles were internalized by rat bone marrow mesenchymal stem cells and demonstrated a pH-responsive release profile and an enhancement of 2D and 3D in vitro osteogenic differentiation. In vivo implantation of gelatin scaffolds seeded with rat bone marrow mesenchymal stem cells precultured for 24 h with dex-micelles promoted a significant enhancement of de novo bone formation in a rat ulna defect, in a dose-dependent manner. Conclusion: The proposed intracellular delivery system is a powerful tool to promote bone regeneration.

Enhanced osteogenic differentiation of stem cells via microfluidics synthesized nanoparticles

Advancement of bone tissue engineering as an alternative for bone regeneration has attracted significant interest due to its potential in reducing the costs and surgical trauma affiliated with the effective treatment of bone defects. We have improved the conventional approach of producing polymeric nanoparticles, as one of the most promising choices for drug delivery systems, using a microfluidics platform, thus further improving our control over osteogenic differentiation of mesenchymal stem cells. Molecular dynamics simulations were carried out for theoretical understanding of our experiments in order to get a more detailed molecular-scale insight into the drug-carrier interactions. In this work, with the sustained intracellular delivery of dexamethasone from microfluidics-synthesized nanoparticles, we explored the effects of particle design on controlling stem cell fates. We believe that the insights learned from this work will lead to the discovery of new strategies to tune differentiation for in situ differentiation or stem cell therapeutics.

FROM THE CLINICAL EDITOR

The use of mesenchymal stem cells has been described by many researchers as a novel therapy for bone regeneration. One major hurdle in this approach is the control of osteogenic differentiation. In this article, the authors described elegantly their microfluidic system in which dexamethasone loaded nanoparticles were produced. This system would allow precise fabrication of nanoparticles and consequently higher efficiency in cellular differentiation.

Nanostructured gellan and xanthan hydrogel depot integrated within a baghdadite scaffold augments bone regeneration

Controlled delivery of biological cues through synthetic scaffolds to enhance the healing capacity of bone defects is yet to be realized clinically. The purpose of this study was development of a bioactive tissue-engineered scaffold providing the sustained delivery of an osteoinductive drug, dexamethasone disodium phosphate (DXP), encapsulated within chitosan nanoparticles (CN). Porous baghdadite (BD; Ca₃ ZrSi₂ O₉ ) scaffolds, a zirconia-modified calcium silicate ceramic, was coated with DXP-encapsulated CN nanoparticles (DXP-CN) using nanostructured gellan and xanthan hydrogel (GX). Crosslinker and GX polymer concentrations were optimized to achieve a homogeneous distribution of hydrogel coating within BD scaffolds. Dynamic laser scattering indicated an average size of 521 ± 21 nm for the DXP-CN nanoparticles. In vitro drug-release studies demonstrated that the developed DXP-CN-GX hydrogel-coated BD scaffolds (DXP-CN-GX-BD) resulted in a sustained delivery of DXP over the 5 days (78 ± 6% of drug release) compared with burst release over 1 h, seen from free DXP loaded in uncoated BD scaffolds (92 ± 8% release in 1 h). To estimate the influence of controlled delivery of DXP from the developed scaffolds, the effect on MG 63 cells was evaluated using various bone differentiation assays. Cell culture within DXP-CN-GX-BD scaffolds demonstrated a significant increase in the expression of early and late osteogenic markers of alkaline phosphatase activity, collagen type 1 and osteocalcin, compared to the uncoated BD scaffold. The results suggest that the DXP-releasing nanostructured hydrogel integrated within the BD scaffold caused sustained release of DXP, improving the potential for osteogenic differentiation. Copyright © 2015 John Wiley & Sons, Ltd.

A dual-delivery system of pH-responsive chitosan-functionalized mesoporous silica nanoparticles bearing BMP-2 and dexamethasone for enhanced bone regeneration

Bone morphogenetic protein-2 (BMP-2) is considered one of the most effective and extensively used growth factors to induce osteoblast differentiation and accelerate bone regeneration. Dexamethasone (Dex) with suitable dosage can enhance BMP-2-induced osteoblast differentiation. To strengthen this synergistic osteoinductive effect, a pH-responsive chitosan-functionalized mesoporous silica nanoparticle (chi-MSN) ensemble was fabricated for dual-delivery of BMP-2 and Dex. The MSNs are prepared by a CTAB-templated sol-gel method, and further coated by chitosan via the crosslinking of glycidoxypropyltrimethoxysilane (GPTMS). The small Dex is encapsulated in the mesopores and the large BMP-2 is incorporated into the chitosan coating. These chi-MSNs can quickly release BMP-2 in a bioactive form and can then be efficiently endocytosed and further realize a controlled release of Dex with the decreased pH value into/in cells. With the synergistic action of BMP-2 and Dex outside and inside the cell, this dual hybrid delivery system can significantly stimulate osteoblast differentiation and bone regeneration in vitro and in vivo. Together, this dual-delivery strategy for osteogenic protein delivery may enhance clinical outcomes by retaining the bioactivity and optimizing the release mode of the drug/protein.