New prospects in skin regeneration and repair using nanophased hydroxyapatite embedded in collagen nanofibers

Nanofibrous Scaffolds' Ability to Induce Mesenchymal Stem Cell Differentiation for Soft Tissue Regenerative Applications

Mesenchymal stem cells (MSCs) have gained recognition as a highly versatile and promising cell source for repopulating bioengineered scaffolds due to their inherent capacity to differentiate into multiple cell types. However, MSC implantation techniques have often yielded inconsistent clinical results, underscoring the need for advanced approaches to enhance their therapeutic efficacy. Recent developments in three-dimensional (3D) bioengineered scaffolds have provided a significant breakthrough by closely mimicking the in vivo environment, addressing the limitations of traditional two-dimensional (2D) cell cultures. Among these, nanofibrous scaffolds have proven particularly effective, offering an optimal 3D framework, growth-permissive substrates, and the delivery of trophic factors crucial for MSC survival and regeneration. Furthermore, the selection of appropriate biomaterials can amplify the paracrine effects of MSCs, promoting both proliferation and targeted differentiation. The synergistic combination of MSCs with nanofibrous scaffolds has demonstrated remarkable potential in achieving repair, regeneration, and tissue-specific differentiation with enhanced safety and efficacy, paving the way for routine clinical applications. In this review, we examine the most recent studies (2013-2023) that explore the combined use of MSCs and nanofibrous scaffolds for differentiation into cardiogenic, epithelial, myogenic, tendon, and vascular cell lineages. Using PubMed, we identified and analyzed 275 relevant articles based on the search terms "Nanofibers", "Electrospinning", "Mesenchymal stem cells", and "Differentiation". This review highlights the critical advancements in the use of nanofibrous scaffolds as a platform for MSC differentiation and tissue regeneration. By summarizing key findings from the last decade, it provides valuable insights for researchers and clinicians aiming to optimize scaffold design, MSC integration, and translational applications. These insights could significantly influence future research directions and the development of more effective regenerative therapies.

Influence of Hydroxyapatite and Gelatin Content on Crosslinking Dynamics and HDFn Cell Viability in Alginate Bioinks for 3D Bioprinting

This study investigates how varying concentrations of hydroxyapatite (OHAp) and the addition of gelatin influence the ionic crosslinking time of alginate-based bioinks, as well as the shear stress experienced by neonatal human dermal fibroblasts (HDFn) during extrusion. These factors are crucial for validating bioinks and developing viable 3D bioprinted models. Four bioink formulations were created with a 50/50 ratio of alginate to gelatin, incorporating different calcium phosphate concentrations (0%, 1%, 5%, and 10%). The bioink compositions were confirmed via Fourier Transform Infrared (FT-IR) spectroscopy, and rheological analyses evaluated their pseudoplastic behavior, printability limits, and crosslinking times. The results indicated a notable increase in the consistency index (k) from 0.32 for the 0% OHAp formulation to 0.48 for the 10% OHAp formulation, suggesting improved viscoelastic properties. The elastic modulus recovery after crosslinking rose significantly from 245 Pa to 455 Pa. HDFn experienced a shear stress of up to 1.5436 Pa at the tip during extrusion with the HDFn-ALG5-GEL5-OHAp10 bioinks, calculated at a shear rate as low as 2 s-1. Viability assays confirmed over 70% cell viability 24 h post-extrusion and 92% viability after 7 days for the 10% OHAp formulation, highlighting the potential of hydroxyapatite-enhanced bioinks in tissue engineering applications.

Construction Form and Application of Three-Dimensional Bioprinting Ink Containing Hydroxyapatite

With the increasing prevalence of bone tissue diseases, three-dimensional (3D) bioprinting applied to bone tissue engineering for treatment has received a lot of interests in recent years. The research and popularization of 3D bioprinting in bone tissue engineering require bioinks with good performance, which is closely related to ideal material and appropriate construction form. Hydroxyapatite (HAp) is the inorganic component of natural bone and has been widely used in bone tissue engineering and other fields due to its good biological and physicochemical properties. Previous studies have prepared different bioinks containing HAp and evaluated their properties in various aspects. Most bioinks showed significant improvement in terms of rheology and biocompatibility; however, not all of them had sufficiently favorable mechanical properties and antimicrobial activity. The deficiencies in properties of bioink and 3D bioprinting technology limited the applications of bioinks containing HAp in clinical trials. This review article summarizes the construction forms of bioinks containing HAp and its modifications in previous studies, as well as the 3D bioprinting techniques adopted to print bioink containing HAp. In addition, this article summarizes the advantages and underlying mechanisms of bioink containing HAp, as well as its limitations, and suggests possible improvement to facilitate the development of bone tissue engineering bioinks containing HAp in the future.

Calcium Hydroxyapatite in Its Different Forms in Skin Tissue Repair: A Literature Review

The skin is crucial for homeostasis and body defense, requiring quick healing to maintain internal balance. Initially used for bone repair, calcium hydroxyapatite (HAp) is now being studied for soft tissue engineering. This literature review investigated HAp’s role in tissue repair through searches on PubMed, Scopus (Elsevier), Science Direct, Springer Link, and Google Scholar databases without time restrictions, using keywords “hydroxyapatite AND skin AND wound” and “hydroxyapatite AND skin repair”. Inclusion criteria encompassed in vivo studies in humans and animals, English publications, full access, and sufficient data on HAp’s role in tissue repair. Exclusions included duplicates, unrelated articles, editor letters, reviews, comments, conference abstracts, dissertations, and theses. Out of the 472 articles initially identified, 139 met the inclusion criteria, with 21 focusing on HAp for tissue repair. Findings indicate that HAp and nano-HAp in skin regeneration are promising, especially when combined with other biomaterials, offering antimicrobial and anti-inflammatory benefits and stimulating angiogenesis. This suggests their potential application in dermatology, surgery, and dentistry, extending HAp’s versatility from hard tissues to enhancing critical properties for soft tissue repair and accelerating healing.

Strategies for Constructing Tissue-Engineered Fat for Soft Tissue Regeneration

BACKGROUND

Repairing soft tissue defects caused by inflammation, tumors, and trauma remains a major challenge for surgeons. Adipose tissue engineering (ATE) provides a promising way to solve this problem.

METHODS

This review summarizes the current ATE strategies for soft tissue reconstruction, and introduces potential construction methods for ATE.

RESULTS

Scaffold-based and scaffold-free strategies are the two main approaches in ATE. Although several of these methods have been effective clinically, both scaffold-based and scaffold-free strategies have limitations. The third strategy is a synergistic tissue engineering strategy and combines the advantages of scaffold-based and scaffold-free strategies.

CONCLUSION

Personalized construction, stable survival of reconstructed tissues and functional recovery of organs are future goals of building tissue-engineered fat for ATE.

Co- and Triaxial Electrospinning for Stem Cell-based Bone Regeneration

Bone tissue is composed of organic minerals and cells. It has the capacity to heal for certain minor damages, but when the bone defects surpass the critical threshold, they need fixing. Bone regeneration through natural and synthetic biodegradable materials requires various steps, such as manufacturing methods and materials selection. A successful biodegradable bone graft should have a high surface area/ volume ratio, strength, and a biocompatible, porous structure capable of promoting cell adhesion, proliferation, and differentiation. Considering these requirements, the electrospinning technique is promising for creating functional nano-sized scaffolds. The multi-axial methods, such as coaxial and triaxial electrospinning, are the most popular techniques to produce double or tri-layered scaffolds, respectively. Recently, stem cell culture on scaffolds and the application of osteogenic differentiation protocols on these scaffolds have opened new possibilities in the field of biomaterials research. This review discusses an overview of the progress in coaxial and triaxial technology through biodegradable composite bone materials. The review also carefully elaborates the osteogenic differentiation using stem cells and their performance with nano-sized scaffolds.

Synergistic amalgamation of shellac with self-antibacterial hydroxyapatite and carboxymethyl cellulose: An interactive wound dressing for ensuring safety and efficacy in preliminary in vivo studies

This study focuses on the synergistic formulation of environmentally friendly blended materials based on carboxymethyl cellulose (CMC) for advanced interactive wound dressing. New CMC hydrogels were prepared with two degrees of functionalization and chemically crosslinked with citric acid (CA) to fine-tune their properties. Additionally, CMC-based hybrids were created by blending with shellac (SHL) and incorporating self-antibacterial hydroxyapatite (HA) to inhibit bacterial growth and promote wound healing. The results demonstrate the successful production of superabsorbent hydrogels with typical swelling degrees ranging from 81% in water to 82% in phosphate-buffered saline (PBS). These hydrogels exhibit distinct morphological features and remarkable improvements in surface mechanical properties, specifically in their tensile properties, which show a significant increase from approximately 0.03 to 2.2 N/mm2 due to the formation of CMC-SHL-HA hybrid nanostructures. Furthermore, the cytocompatibility of these CMC-based hydrogels was investigated by assessing the in vitro cell viability responses of human skin fibroblasts. The results reveal the cell viability responses over 91%, indicating their biocompatibility with human cells. Moreover, the characteristics of surgical wounds were assessed before and after the application of the hydrogel on dogs, and no signs of infection were observed at any of the surgical sites post-surgery.

Collagen-Based Biomaterials for Tissue Engineering

Collagen is commonly used as a regenerative biomaterial due to its excellent biocompatibility and wide distribution in tissues. Different kinds of hybridization or cross-links are favored to offer improvements to satisfy various needs of biomedical applications. Previous reviews have been made to introduce the sources and structures of collagen. In addition, biological and mechanical properties of collagen-based biomaterials, their modification and application forms, and their interactions with host tissues are pinpointed. However, there is still no review about collagen-based biomaterials for tissue engineering. Therefore, we aim to summarize and discuss the progress of collagen-based materials for tissue regeneration applications in this review. We focus on the utilization of collagen-based biomaterials for bones, cartilages, skin, dental, neuron, cornea, and urological applications and hope these experiences and outcomes can provide inspiration and practical techniques for the future development of collagen-based biomaterials in related application fields. Moreover, future improving directions and challenges for collagen-based biomaterials are proposed as well.

New skin tissue engineering scaffold with sulfated silk fibroin/chitosan/hydroxyapatite and its application

Repairing skin wounds has always been challenging in clinical practice. The new skin tissue engineering scaffold provides innovative ways to address these challenges with a good chance of success because of its stable mechanical properties, biodegradability, and antibacterial properties. This paper presents the fabrication and evaluation of a three-dimensional composite scaffold made with sulfated silk fibroin, chitosan, and hydroxyapatite (SSF/CS/HAP). An electron microscope shows that the scaffold has an aperture of 15-20 μm, while an absorption performance test shows that its expansion index reaches 779%. The co-culture of L929 cells and the CCK-8 experiments demonstrated good cell compatibility and low scaffold cytotoxicity, respectively. Meanwhile, in vivo experiments demonstrate that rats with SSF/CS/HAP scaffold-treated neck wounds heal faster. In the wound skin tissue of the SSF/CS/HAP scaffold group, immunohistochemistry indicates a more rapid and mature development of hair follicles. This study successfully developed a novel skin tissue engineering scaffold material with high moisture retention, high tissue compatibility, and low cytotoxicity, demonstrating its ability to improve wound repair with promising potential for tissue engineering applications.

Inorganic-based biomaterials for rapid hemostasis and wound healing

The challenge for the treatment of severe traumas poses an urgent clinical need for the development of biomaterials to achieve rapid hemostasis and wound healing. In the past few decades, active inorganic components and their derived composites have become potential clinical products owing to their excellent performances in the process of hemorrhage control and tissue repair. In this review, we provide a current overview of the development of inorganic-based biomaterials used for hemostasis and wound healing. We highlight the methods and strategies for the design of inorganic-based biomaterials, including 3D printing, freeze-drying, electrospinning and vacuum filtration. Importantly, inorganic-based biomaterials for rapid hemostasis and wound healing are presented, and we divide them into several categories according to different chemistry and forms and further discuss their properties, therapeutic mechanisms and applications. Finally, the conclusions and future prospects are suggested for the development of novel inorganic-based biomaterials in the field of rapid hemostasis and wound healing.

Bioactive inorganic particles-based biomaterials for skin tissue engineering

The challenge for treatment of severe cutaneous wound poses an urgent clinical need for the development of biomaterials to promote skin regeneration. In the past few decades, introduction of inorganic components into material system has become a promising strategy for improving performances of biomaterials in the process of tissue repair. In this review, we provide a current overview of the development of bioactive inorganic particles-based biomaterials used for skin tissue engineering. We highlight the three stages in the evolution of the bioactive inorganic biomaterials applied to wound management, including single inorganic materials, inorganic/organic composite materials, and inorganic particles-based cell-encapsulated living systems. At every stage, the primary types of bioactive inorganic biomaterials are described, followed by citation of the related representative studies completed in recent years. Then we offer a brief exposition of typical approaches to construct the composite material systems with incorporation of inorganic components for wound healing. Finally, the conclusions and future directions are suggested for the development of novel bioactive inorganic particles-based biomaterials in the field of skin regeneration.

Polycaprolactone/Gelatin/Hydroxyapatite Electrospun Nanomembrane Materials Incorporated with Different Proportions of Attapulgite Synergistically Promote Bone Formation

Purpose

To enhance the osteoinductive effect of Hydroxyapatite (HA) in bone tissue engineering, this study manufactured polycaprolactone (PCL)/gelatin (GEL)/HA nanofibrous scaffolds incorporated with different ratios of attapulgite (ATP): HA (0:3, 0:0, 1:1, 2:1 and 3:0) by high-voltage electrospinning. The synergistic effect exerted by ATP and HA on bone formation was explored both in vivo and in vitro.

Methods and Results

First, we determined the group composition and crystal structure of the nanosheets by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses. Then, the physical properties of the scaffolds, including the modulus of elasticity, porosity and water absorption were evaluated. Moreover, the surface microstructure of the nanofibrous scaffolds was captured by Scanning electron microscopy (SEM) and Transmission Electron Microscope (TEM). The biocompatibility of the fabricated scaffolds represented by cell counting kit 8 (CCK-8) and phalloidin staining was also assessed. Next, in vitro osteogenesis was evaluated. Real-time PCR, alkaline phosphatase (ALP) staining and Alizarin red S (ARS) staining results showed that the materials incorporated with HA and ATP at a ratio of 2:1 synergistically promoted more osteoblastic differentiation and extracellular mineralization than scaffolds doped with HA and ATP alone. Last, in vivo, Hematoxylin-Eosin staining (HE staining) and Masson staining showed that groups treated with HA and ATP acquired optimal patterns of bone regeneration.

Conclusion

This study clarified for the first time that the combination of HA and ATP orchestrated biomaterial-induced osseointegration, and the synergistic effect was more significant when the ratio of ATP/HA was 2:1. This conclusion also provides new ideas and a scientific basis for the development of functionalized nanomaterials in bone tissue engineering.

Preparation of Antibacterial Gelatin/Genipin Nanofibrous Membrane for Tympanic Membrane Repair

Tympanic membrane perforation (TMP), a common disease, often needs a scaffold as the patch to support surgery. Due to the environment of auditory meatus, the patch can be infected by bacteria that results in failure; therefore, the ideal scaffold may combine biomimetic and antibacterial features. In this work, gelatin was used as the electrospinning framework, genipin as the crosslinking agent, and levofloxacin as an antibacterial in order to prepare the scaffold for TMP. Different contents of levofloxacin have been added to gelatin/genipin. It was found that, with the addition of levofloxacin, the gelatin/genipin membranes exhibit improved hydrophilia and enhanced tensile strength. The antibacterial and cell-cultured experiments showed that the prepared antibacterial membranes had excellent antibacterial properties and good biocompatibility, respectively. In summary, levofloxacin is a good group for the gelatin/genipin scaffold because it improves the physical properties and antibacterial action. Compared with different amounts of levofloxacin, a gelatin/genipin membrane with 1% levofloxacin is more suitable for a TM.

Continuous Production of Highly Tuned Silk/Calcium-Based Composites: Exploring New Pathways for Skin Regeneration

Calcium plays an important role in barrier function repair and skin homeostasis. In particular, calcium phosphates (CaPs) are well established materials for biomedical engineering due to their biocompatibility. To generate biomaterials with a more complete set of biological properties, previously discarded silk sericin (SS) has been recovered and used as a template to grow CaPs. Crucial characteristics for skin applications, such as antibacterial activity, can be further enhanced by doping CaPs with cerium (Ce) ions. The effectiveness of cell attachment and growth on the materials highly depends on their morphology, particle size distribution, and chemical composition. These characteristics can be tailored through the application of oscillatory flow technology, which provides precise mixing control of the reaction medium. Thus, in the present work, CaP/SS and CaP/SS/Ce particles were fabricated for the first time using a modular oscillatory flow plate reactor (MOFPR) in a continuous mode. Furthermore, the biological behavior of both these composites and of previously produced pure CaPs was assessed using human dermal fibroblasts (HDFs). It was demonstrated that both CaP based with plate-shaped nanoparticles and CaP-SS-based composites significantly improved cell viability and proliferation over time. The results obtained represent a first step towards the reinvention of CaPs for skin engineering.

Collagen-Based Nanofibers for Skin Regeneration and Wound Dressing Applications

Skin regeneration after an injury is very vital, but this process can be impeded by several factors. Regenerative medicine is a developing biomedical field with the potential to decrease the need for an organ transplant. Wound management is challenging, particularly for chronic injuries, despite the availability of various types of wound dressing scaffolds in the market. Some of the wound dressings that are in clinical practice have various drawbacks such as poor antibacterial and antioxidant efficacy, poor mechanical properties, inability to absorb excess wound exudates, require frequent change of dressing and fails to offer a suitable moist environment to accelerate the wound healing process. Collagen is a biopolymer and a major constituent of the extracellular matrix (ECM), making it an interesting polymer for the development of wound dressings. Collagen-based nanofibers have demonstrated interesting properties that are advantageous both in the arena of skin regeneration and wound dressings, such as low antigenicity, good biocompatibility, hemostatic properties, capability to promote cellular proliferation and adhesion, and non-toxicity. Hence, this review will discuss the outcomes of collagen-based nanofibers reported from the series of preclinical trials of skin regeneration and wound healing.

An update on hydroxyapatite/collagen composites: What is there left to say about these bioinspired materials?

Hydroxyapatite (HAp)/collagen-based composite materials have been a constant in the development of bioinspired materials for bone tissue engineering. The most fundamental research works focus on combining HAp, due to its chemical similarity with the mineral component of bones, and collagen, which is the most abundant protein in the body. Modern studies have explored different two-dimensional (2D) and 3D structures, in order to obtain biomaterials with specific physicochemical, mechanical, and biological characteristics that can be applied in distinct biomedical applications. However, as there is already so much work developed with these materials, it is crucial to question: what can still be done? What is the importance of current know-how for the future of bioinspired materials? In this paper we intend to review and update the available methodologies to synthesize HAp/collagen composites, along with their characteristics. In addition, the future of these materials in terms of applications and their potential as a cutting-edge technology is discussed.

Electrospun Fibers Loaded with Natural Bioactive Compounds as a Biomedical System for Skin Burn Treatment. A Review

Burns are a major threat to public health and the economy due to their costly and laborious treatment and high susceptibility to infection. Efforts have been made recently to investigate natural bioactive compounds with potential use in wound healing. The importance lies in the capacities that these compounds could possess both in infection control by common and resistant microorganisms, as well as in the regeneration of the affected tissues, having in both cases low adverse effects. However, some bioactive molecules are chemically unstable, poorly soluble, and susceptible to oxidative degradation or have low bioavailability. Therefore, developing new technologies for an efficient treatment of wound healing poses a real challenge. In this context, electrospun nanofibers have gained increasing research interest because bioactive molecules can be easily loaded within the nanofiber, resulting in optimal burst control and enhanced drug stability. Additionally, the nanofibers can mimic the extracellular collagen matrix, providing a suitable highly porous structural support for growing cells that facilitate and accelerate skin burns healing. This review gives an overview of the current state of electrospun fibers loaded with natural bioactive compounds as a biomedical system for skin burn treatment.

Functionalized Porous Hydroxyapatite Scaffolds for Tissue Engineering Applications: A Focused Review

Biomaterials have been widely used in tissue engineering applications at an increasing rate in recent years. The increased clinical demand for safe scaffolds, as well as the diversity and availability of biomaterials, has sparked rapid interest in fabricating diverse scaffolds to make significant progress in tissue engineering. Hydroxyapatite (HAP) has drawn substantial attention in recent years owing to its excellent physical, chemical, and biological properties and facile adaptable surface functionalization with other innumerable essential materials. This focused review spotlights a brief introduction on HAP, scope, a historical outline, basic structural features/properties, various synthetic strategies, and their scientific applications concentrating on functionalized HAP in the diverse area of tissue engineering fields such as bone, skin, periodontal, bone tissue fixation, cartilage, blood vessel, liver, tendon/ligament, and corneal are emphasized. Besides clinical translation aspects, the future challenges and prospects of HAP based biomaterials involved in tissue engineering are also discussed. Furthermore, it is expected that researchers may find this review expedient in gaining an overall understanding of the latest advancement of HAP based biomaterials.