Remote actuation and on-demand activation of biomaterials pre-incorporated with physical cues for bone repair.

The high incidence of bone defect-related diseases caused by trauma, infection, and tumor resection has greatly stimulated research in the field of bone regeneration. Generally, bone healing is a long and complicated process wherein manipulating the biological activity of interventional scaffolds to support long-term bone regeneration is significant for treating bone-related diseases. It has been reported that some physical cues can act as growth factor substitutes to promote osteogenesis through continuous activation of endogenous signaling pathways. This review focuses on the latest progress in bone repair by remote actuation and on-demand activation of biomaterials pre-incorporated with physical cues (heat, electricity, and magnetism). As an alternative method to treat bone defects, physical cues show many advantages, including effectiveness, noninvasiveness, and remote manipulation. First, we introduce the impact of different physical cues on bone repair and potential internal regulatory mechanisms. Subsequently, biomaterials that mediate various physical cues in bone repair and their respective characteristics are summarized. Additionally, challenges are discussed, aiming to provide new insights and suggestions for developing intelligent biomaterials to treat bone defects and promote clinical translation.

3D-printed titanium scaffolds loaded with gelatin hydrogel containing strontium-doped silver nanoparticles promote osteoblast differentiation and antibacterial activity for bone tissue engineering.

Bone tissue engineering offers a promising alternative to stimulate the regeneration of damaged tissue, overcoming the limitations of conventional autografts and allografts. Recently, titanium alloy (Ti) implants have garnered significant attention for treating critical-sized bone defects, especially with the advancement of 3D printing technology. Although Ti alloys have impressive versatility, their lack of cellular adhesion, osteogenic and antibacterial properties are significant factors that contribute to their failure. Hence, to overcome these obstacles, this study aimed to incorporate osteoinductive and antibacterial cue-loaded hydrogels into 3D-printed Ti (3D-Ti) scaffolds. 3D-Ti scaffolds were synthesized using the direct metal laser sintering method and loaded with a gelatin (Gel) hydrogel containing strontium-doped silver nanoparticles (Sr-Ag NPs). Compared with Ag NPs, Sr-doped Ag NPs increased the expression of Runx2 mRNA, which is a key bone transcription factor. We subjected the bioactive 3D-hybrid scaffolds (3D-Ti/Gel/Sr-Ag NPs) to physicochemical and material characterization, followed by cytocompatibility and osteogenic evaluation. The microporous and macroporous topographies of the scaffolds with Sr-Ag NPs showed increased Runx2 expression and matrix mineralization, with potent antibacterial properties. Therefore, the 3D-Ti scaffolds incorporated with Sr-Ag NP-loaded Gel hydrogels favored osteoblast differentiation and antibacterial activity, indicating their potential for orthopedic applications.

Engineered vascular grafts lend unique insight to pathophysiology of aortic aneurysms.

Yang et al.1 generate tissue engineered blood vessels from hiPSC-derived smooth muscle cells harboring a mutation found in Loeys-Dietz syndrome. In vitro and in vivo data from these vessels provide new insight into the molecular physiology of aortic aneurysms and may create a paradigm for understanding a suite of vascular diseases.

Macrophages: A missing key in cardiac tissue engineering for sustained vascularization.

Macrophages regulate angiogenesis, repair, conduction, and homeostasis in heart tissue. Landau et al.1 demonstrate that incorporating primitive macrophages into engineered heart tissues significantly promotes long-term vascularization and cardiac maturation. This advance demonstrates the importance of resident immune-vascular microenvironments in cardiac tissue engineering, marking an important step forward for heart-on-chip technologies.

Bioactive Materials That Promote the Homing of Endogenous Mesenchymal Stem Cells to Improve Wound Healing.

Endogenous stem cell homing refers to the transport of endogenous mesenchymal stem cells (MSCs) to damaged tissue. The paradigm of using well-designed biomaterials to induce resident stem cells to home in to the injured site while coordinating their behavior and function to promote tissue regeneration is known as endogenous regenerative medicine (ERM). ERM is a promising new avenue in regenerative therapy research, and it involves the mobilizing of endogenous stem cells for homing as the principal means through which to achieve it. Comprehending how mesenchymal stem cells home in and grasp the influencing factors of mesenchymal stem cell homing is essential for the understanding and design of tissue engineering. This review summarizes the process of MSC homing, the factors influencing the homing process, analyses endogenous stem cell homing studies of interest in the field of skin tissue repair, explores the integration of endogenous homing promotion strategies with cellular therapies and details tissue engineering strategies that can be used to modulate endogenous homing of stem cells. In addition to providing more systematic theories and ideas for improved materials for endogenous tissue repair, this review provides new perspectives to explore the complex process of tissue remodeling to enhance the rational design of biomaterial scaffolds and guide tissue regeneration strategies.

In vitrodegradation of a chitosan-based osteochondral construct points to a transient effect on cellular viability.

Bioresorbable chitosan scaffolds have shown potential for osteochondral repair applications. Thein vivodegradation of chitosan, mediated by lysozyme and releasing glucosamine, enables progressive replacement by ingrowing tissue. Here the degradation process of a chitosan-nHA based bioresorbable scaffold was investigated for mass loss, mechanical properties and degradation products released from the scaffold when subjected to clinically relevant enzyme concentrations. The scaffold showed accelerated mass loss during the early stages of degradation but without substantial reduction in mechanical strength or structure deterioration. Although not cytotoxic, the medium in which the scaffold was degraded for over 2 weeks showed a transient decrease in mesenchymal stem cell viability, and the main degradation product (glucosamine) demonstrated a possible adverse effect on viability when added at its peak concentration. This study has implications for the design and biomedical application of chitosan scaffolds, underlining the importance of modelling degradation products to determine suitability for clinical translation.

Adult Mesenchymal Stem Cells in Presence of Glycosaminoglycans.

The application of adult mesenchymal stem cells (MSCs) in the field of tissue regeneration is of increasing interest to the scientific community. In particular, scaffolds and/or hydrogel based on glycosaminoglycans (GAGs) play a pivotal role due to their ability to support the in vitro growth and differentiation of MSCs toward a specific phenotype. Here, we describe different possible approaches to develop GAGs-based biomaterials, hydrogel, and polymeric viscous solutions in order to assess/develop a suitable biomimetic environment. To sustain MSCs viability and promote their differentiation for potential therapeutic applications.

Isolation and Characterization of Human Dental Pulp Stem Cells Derived from Dental Pulp of Permanent Teeth.

Dental pulp stem cells (DPSCs) are a promising alternative to the source of mesenchymal stem cells (MSCs), as they are readily available in minimally invasive procedures compared to more invasive methods associated with harvesting other MSCs sources. Despite the encouraging pre-clinical outcomes in animal disease models, culture-expanding procedures are needed to obtain a sufficient number of MSCs required for delivery to the damaged site. However, this contributes to increasing regulatory difficulties in translating stem cells and tissue engineering therapy to clinical use. Moreover, discussions continue as to which isolation method is to be preferred when obtaining DPSCs from extracted molars. This protocol describes a simple explant isolation technique of human dental pulp stem cells from the dental pulp of permanent teeth based upon the plastic adherence of MSCs and subsequent outgrowth of cells out of tissue fragments with high efficacy.

Three-Dimensional Electrically Conductive Scaffolds to Culture Cardiac Progenitor Cells.

Three-dimensional (3D) scaffolds provide cell support while improving tissue regeneration through amplified cellular responses between implanted materials and native tissues. So far, highly conductive cardiac, nerve, and muscle tissues have been engineered by culturing stem cells on electrically inert scaffolds. These scaffolds, even though suitable, may not be very useful compared to the results shown by cells when cultured on conductive scaffolds. Noticing the mature phenotype the stem cells develop over time when cultured on conductive scaffolds, scientists have been trying to impart conductivity to traditionally nonconductive scaffolds. One way to achieve this goal is to blend conductive polymers (polyaniline, polypyrrole, PEDOT:PSS) with inert biomaterials and produce a 3D scaffold using various fabrication techniques. One such technique is projection micro-stereolithography, which is an additive manufacturing technique. It uses a photosensitive solution blended with conductive polymers and uses visible/UV light to crosslink the solution. 3D scaffolds with complex architectural features down to microscale resolution can be printed with this technique promptly. This chapter reports a protocol to fabricate electrically conductive scaffolds using projection micro-stereolithography.

Electrospun Fibers for Use in Implantable Materials to Support Cell Therapy.

Hydrogels are a class of biomaterials that can provide a three-dimensional (3D) environment capable of mimicking the extracellular matrix of native tissues. In this chapter, we present a method to generate electrospun nanofibers for the purpose of reinforcing hydrogels. The addition of electrospun fibers can be used to improve the mechanical properties of hydrogels and broaden their range of applications. First, the polymer for making the electrospun fibers is formulated using chloroform/ethanol, polycaprolactone (PCL), polyethylene glycol (PEG), and polyethylene glycol diacrylate (PEGDA). Second, the polymer is used to generate thin electrospun nanofibers by an electrospinning technique using aluminum foil as a collector, which acts as the conductive substrate that collects the charged fibers. Third, the resulting electrospun fibers undergo a filtration process using nylon membrane filters, followed by lyophilization, ensuring complete removal of water from the sample.

Antimicrobial Surface for Devices Used in Stem Culture Manipulation and In Vitro Biofabrication of Tissues.

Cell therapy and engineered tissue creation based on the use of human stem cells involves cell isolation, expansion, and cell growth and differentiation on the scaffolds. Microbial infections dramatically can affect stem cell survival and increase the risk of implant failure. To prevent these events, it is necessary to develop new materials with antibacterial properties for coating scaffold surfaces as well as medical devices, and all other surfaces at high risk of contamination. This chapter describes strategies for obtaining antibacterial blends for coating inert surfaces (polymethylmethacrylate, polycarbonate, Carbon Fiber Reinforced Polymer (CFRP)). In particular, the procedures for preparing antibacterial blends by mixing polymer resins with two types of antibacterial additives and depositing these blends on inert surfaces are described.

Preparation of Monodispersed Nanofibrous Gelatin Microspheres Using Homebuilt Microfluidics.

Gelatin, a protein derivative from collagen, is a versatile material with promising applications in tissue engineering. Among the various forms of gelatin scaffolds, nanofibrous gelatin microspheres (NFGMs) are attracting research efforts due to their fibrous nature and injectability. However, current methods for synthesizing nanofibrous gelatin microspheres (NFGMs) have limitations, such as wide size distributions and the use of toxic solvents. To address these challenges, the article introduces a novel approach. First, it describes the creation of a microfluidic device using readily available supplies. Subsequently, it outlines a unique process for producing monodispersed NFGMs through a combination of the microfluidic device and thermally induced phase separation (TIPS). This innovative method eliminates the need for sieving and the use of toxic solvents, making it a more ecofriendly and efficient alternative.

Endogenous Tissue Engineering for Chondral and Osteochondral Regeneration: Strategies and Mechanisms.

Increasing attention has been paid to the development of effective strategies for articular cartilage (AC) and osteochondral (OC) regeneration due to their limited self-reparative capacities and the shortage of timely and appropriate clinical treatments. Traditional cell-dependent tissue engineering faces various challenges such as restricted cell sources, phenotypic alterations, and immune rejection. In contrast, endogenous tissue engineering represents a promising alternative, leveraging acellular biomaterials to guide endogenous cells to the injury site and stimulate their intrinsic regenerative potential. This review provides a comprehensive overview of recent advancements in endogenous tissue engineering strategies for AC and OC regeneration, with a focus on the tissue engineering triad comprising endogenous stem/progenitor cells (ESPCs), scaffolds, and biomolecules. Multiple types of ESPCs present within the AC and OC microenvironment, including bone marrow-derived mesenchymal stem cells (BMSCs), adipose-derived mesenchymal stem cells (AD-MSCs), synovial membrane-derived mesenchymal stem cells (SM-MSCs), and AC-derived stem/progenitor cells (CSPCs), exhibit the ability to migrate toward injury sites and demonstrate pro-regenerative properties. The fabrication and characteristics of scaffolds in various formats including hydrogels, porous sponges, electrospun fibers, particles, films, multilayer scaffolds, bioceramics, and bioglass, highlighting their suitability for AC and OC repair, are systemically summarized. Furthermore, the review emphasizes the pivotal role of biomolecules in facilitating ESPCs migration, adhesion, chondrogenesis, osteogenesis, as well as regulating inflammation, aging, and hypertrophy-critical processes for endogenous AC and OC regeneration. Insights into the applications of endogenous tissue engineering strategies for in vivo AC and OC regeneration are provided along with a discussion on future perspectives to enhance regenerative outcomes.

Reinforcing ß-tricalcium phosphate scaffolds for potential applications in bone tissue engineering: impact of functionalized multi-walled carbon nanotubes.

Beta-tricalcium phosphate (ß-TCP) scaffolds manufactured through the foam replication method are widely employed in bone tissue regeneration. The mechanical strength of these scaffolds is a significant challenge, partly due to the rheological properties of the original suspension. Various strategies have been explored to enhance the mechanical properties. In this research, ß-TCP scaffolds containing varying concentrations (0.25-1.00 wt%) of multi-walled carbon nanotubes (MWCNT) were developed. The findings indicate that the addition of MWCNTs led to a concentration-dependent improvement in the viscosity of ß-TCP suspensions. All the prepared slurries exhibited viscoelastic behavior, with the storage modulus surpassing the loss modulus. The three time interval tests revealed that MWCNT-incorporated ß-TCP suspensions exhibited faster structural recovery compared to pure ß-TCP slurries. Introducing MWCNT modified compressive strength, and the optimal improvement was obtained using 0.75 wt% MWCNT. The in vitro degradation of ß-TCP was also reduced by incorporating MWCNT. While the inclusion of carbon nanotubes had a marginal negative impact on the viability and attachment of MC3T3-E1 cells, the number of viable cells remained above 70% of the control group. Additionally, the results demonstrated that the scaffold increased the expression level of osteocalcin, osteoponthin, and alkaline phosphatase genes of adiposed-derived stem cells; however, higher levels of gene expersion were obtained by using MWCNT. The suitability of MWCNT-modified ß-TCP suspensions for the foam replication method can be assessed by evaluating their rheological behavior, aiding in determining the critical additive concentration necessary for a successful coating process.

Bioengineered 3D ovarian model for long-term multiple development of preantral follicle: bridging the gap for poly(ε-caprolactone) (PCL)-based scaffold reproductive applications.

BACKGROUND: Assisted Reproductive Technologies (ARTs) have been validated in human and animal to solve reproductive problems such as infertility, aging, genetic selection/amplification and diseases. The persistent gap in ART biomedical applications lies in recapitulating the early stage of ovarian folliculogenesis, thus providing protocols to drive the large reserve of immature follicles towards the gonadotropin-dependent phase. Tissue engineering is becoming a concrete solution to potentially recapitulate ovarian structure, mostly relying on the use of autologous early follicles on natural or synthetic scaffolds. Based on these premises, the present study has been designed to validate the use of the ovarian bioinspired patterned electrospun fibrous scaffolds fabricated with poly(ε-caprolactone) (PCL) for multiple preantral (PA) follicle development. METHODS: PA follicles isolated from lamb ovaries were cultured on PCL scaffold adopting a validated single-follicle protocol (Ctrl) or simulating a multiple-follicle condition by reproducing an artificial ovary engrafted with 5 or 10 PA (AO5PA and AO10PA). The incubations were protracted for 14 and 18 days before assessing scaffold-based microenvironment suitability to assist in vitro folliculogenesis (ivF) and oogenesis at morphological and functional level. RESULTS: The ivF outcomes demonstrated that PCL-scaffolds generate an appropriate biomimetic ovarian microenvironment supporting the transition of multiple PA follicles towards early antral (EA) stage by supporting follicle growth and steroidogenic activation. PCL-multiple bioengineering ivF (AO10PA) performed in long term generated, in addition, the greatest percentage of highly specialized gametes by enhancing meiotic competence, large chromatin remodeling and parthenogenetic developmental competence. CONCLUSIONS: The study showcased the proof of concept for a next-generation ART use of PCL-patterned scaffold aimed to generate transplantable artificial ovary engrafted with autologous early-stage follicles or to advance ivF technologies holding a 3D bioinspired matrix promoting a physiological long-term multiple PA follicle protocol.

PLCL/SF/NGF nerve conduit loaded with RGD-TA-PPY hydrogel promotes regeneration of sciatic nerve defects in rats through PI3K/AKT signalling pathways.

Peripheral nerve defect are common clinical problem caused by trauma or other diseases, often leading to the loss of sensory and motor function in patients. Autologous nerve transplantation has been the gold standard for repairing peripheral nerve defects, but its clinical application is limited due to insufficient donor tissue. In recent years, the application of tissue engineering methods to synthesize nerve conduits for treating peripheral nerve defect has become a current research focus. This study introduces a novel approach for treating peripheral nerve defects using a tissue-engineered PLCL/SF/NGF@TA-PPy-RGD conduit. The conduit was fabricated by combining electrospun PLCL/SF with an NGF-loaded conductive TA-PPy-RGD gel. The gel, synthesized from RGD-modified tannic acid (TA) and polypyrrole (PPy), provides growth anchor points for nerve cells. In vitro results showed that this hybrid conduit could enhance PC12 cell proliferation, migration, and reduce apoptosis under oxidative stress. Furthermore, the conduit activated the PI3K/AKT signalling pathway in PC12 cells. In a rat model of sciatic nerve defect, the PLCL/SF/NGF@TA-PPy-RGD conduit significantly improved motor function, gastrocnemius muscle function, and myelin sheath axon thickness, comparable to autologous nerve transplantation. It also promoted angiogenesis around the nerve defect. This study suggests that PLCL/SF/NGF@TA-PPy-RGD conduits provide a conducive environment for nerve regeneration, offering a new strategy for peripheral nerve defect treatment, this study provided theoretical basis and new strategies for the research and treatment of peripheral nerve defect.

Three-Dimensional Cell Culture Micro-CT Visualization within Collagen Scaffolds in an Aqueous Environment.

Among all of the materials used in tissue engineering in order to develop bioequivalents, collagen shows to be the most promising due to its superb biocompatibility and biodegradability, thus becoming one of the most widely used materials for scaffold production. However, current imaging techniques of the cells within collagen scaffolds have several limitations, which lead to an urgent need for novel methods of visualization. In this work, we have obtained groups of collagen scaffolds and selected the contrasting agents in order to study pores and patterns of cell growth in a non-disruptive manner via X-ray computed microtomography (micro-CT). After the comparison of multiple contrast agents, a 3% aqueous phosphotungstic acid solution in distilled water was identified as the most effective amongst the media, requiring 24 h of incubation. The differences in intensity values between collagen fibers, pores, and masses of cells allow for the accurate segmentation needed for further analysis. Moreover, the presented protocol allows visualization of porous collagen scaffolds under aqueous conditions, which is crucial for the multimodal study of the native structure of samples.

Minimally invasive soft tissue repair using shrunken scaffolds.

The minimally invasive injection of tissue engineering scaffolds is of interest as it requires a smaller incision and quickens recovery. However, the engineering of scaffolds capable of injection remains a challenge. Here, we report on a shrunken scaffold inspired by the shrinking of puffed food in a humid environment. A scaffold is freeze-dried to remove water then placed in a humid atmosphere. The humidity causes the dry scaffold to shrink by up to 90%. In addition, the humidity treatment reduces the scaffolds modulus minimizing the foreign body response after implantation. The scaffolds can rapidly swell into their original size and shape after application. A tool for the delivery of the minimally invasive scaffolds is developed and we demonstrate the potential for minimally invasive delivery using this shrinking technique.

Transforming Healthcare with Nanomedicine: A SWOT Analysis of Drug Delivery Innovation.

Objective: Nanomedicine represents a transformative approach in biomedical applications. This study aims to delineate the application of nanomedicine in the biomedical field through the strengths, weaknesses, opportunities, and threats (SWOT) analysis to evaluate its efficacy and potential in clinical applications. Methods: The SWOT analysis framework was employed to systematically review and assess the internal strengths and weaknesses, along with external opportunities and threats of nanomedicine. This method provides a balanced consideration of the potential benefits and challenges. Results: Findings from the SWOT analysis indicate that nanomedicine presents significant potential in drug delivery, diagnostic imaging, and tissue engineering. Nonetheless, it faces substantial hurdles such as safety issues, environmental concerns, and high development costs. Critical areas for development were identified, particularly concerning its therapeutic potential and the uncertainties surrounding long-term effects. Conclusion: Nanomedicine holds substantial promise in driving medical innovation. However, successful clinical translation requires addressing safety, cost, and regulatory challenges. Interdisciplinary collaboration and comprehensive strategic planning are crucial for the safe and effective application of nanomedicine.

Extracellular matrix of lung scaffolds submitted to different means of sterilization: a systematic review.

Chronic respiratory diseases often necessitate lung transplantation due to irreversible damage. Organ engineering offers hope through stem cell-based organ generation. However, the crucial sterilization step in scaffold preparation poses challenges. This study conducted a systematic review of studies that analysed the extracellular matrix (ECM) conditions of decellularised lungs subjected to different sterilisation processes. A search was performed for articles published in the PubMed, Web of Sciences, Scopus, and SciELO databases according to the PRISMA guidelines. Overall, five articles that presented positive results regarding the effectiveness of the sterilisation process were selected, some of which identified functional damage in the ECM. Was possible concluded that regardless of the type of agent used, physical or chemical, all of them demonstrated that sterilisation somehow harms the ECM. An ideal protocol has not been found to be fully effective in the sterilisation of pulmonary scaffolds for use in tissue and/or organ engineering.