One-pot porogen free method fabricated porous microsphere-aggregated 3D PCL scaffolds for bone tissue engineering

Fabrication of polymeric microspheres for biomedical applications

Polymeric microspheres (PMs) have attracted great attention in the field of biomedicine in the last several decades due to their small particle size, special functionalities shown on the surface and high surface-to-volume ratio. However, how to fabricate PMs which can meet the clinical needs and transform laboratory achievements to industrial scale-up still remains a challenge. Therefore, advanced fabrication technologies are pursued. In this review, we summarize the technologies used to fabricate PMs, including emulsion-based methods, microfluidics, spray drying, coacervation, supercritical fluid and superhydrophobic surface-mediated method and their advantages and disadvantages. We also review the different structures, properties and functions of the PMs and their applications in the fields of drug delivery, cell encapsulation and expansion, scaffolds in tissue engineering, transcatheter arterial embolization and artificial cells. Moreover, we discuss existing challenges and future perspectives for advancing fabrication technologies and biomedical applications of PMs.

Nano zinc oxide-functionalized nanofibrous microspheres: A bioactive hybrid platform with antimicrobial, regenerative and hemostatic activities

Bioactive hybrid constructs are at the cutting edge of innovative biomaterials. PLA nanofibrous microspheres (NF-MS) were functionalized with zinc oxide nanoparticles (nZnO) and DDAB-modified nZnO (D-nZnO) for developing inorganic/nano-microparticulate hybrid constructs (nZnO@NF-MS and D-nZnO@NF-MS) merging antibacterial, regenerative, and haemostatic functionalities. The hybrids appeared as three-dimensional NF-MS frameworks made-up entirely of interconnecting nanofibers embedding nZnO or D-nZnO. Both systems achieved faster release of Zn²⁺ than their respective nanoparticles and D-nZnO@NF-MS exhibited significantly greater surface wettability than nZnO@NF-MS. Regarding bioactivity, D-nZnO@NF-MS displayed a significantly greater and fast-killing effect against Staphylococcus aureus. Both nZnO@NF-MS and D-nZnO@NF-MS showed controllable concentration-dependent cytotoxicity to human gingival fibroblasts (HGF) compared with pristine NF-MS. They were also more effective than pristine NF-MS in promoting migration of human gingival fibroblasts (HGF) in the in vitro wound healing assay. Although D-nZnO@NF-MS showed greater in vitro hemostatic activity than nZnO@NF-MS, (blood-clotting index 22.82 ± 0.65% vs.54.67 ±2.32%) both structures exhibited instant hemostasis (0 s) with no blood loss (0 mg) in the rat-tail cutting technique. By merging the multiple therapeutic bioactivities of D-nZnO and the 3D-structural properties of NF-MS, the innovative D-nZnO@NF-MS hybrid construct provides a versatile bioactive material platform for different biomedical applications.

Research Progress of Shape Memory Polymer and 4D Printing in Biomedical Application

As a kind of smart material, shape memory polymer (SMP) shows great application potential in the biomedical field. Compared with traditional metal-based medical devices, SMP-based devices have the following characteristics: 1) The adaptive ability allows the biomedical device to better match the surrounding tissue after being implanted into the body by minimally invasive implantation; 2) it has better biocompatibility and adjustable biodegradability; 3) mechanical properties can be regulated in a large range to better match with the surrounding tissue. 4D printing technology is a comprehensive technology based on smart materials and 3D printing, which has great application value in the biomedical field. 4D printing technology breaks through the technical bottleneck of personalized customization and provides a new opportunity for the further development of the biomedical field. This paper summarizes the application of SMP and 4D printing technology in the field of bone tissue scaffolds, tracheal scaffolds, and drug release, etc. Moreover, this paper analyzes the existing problems and prospects, hoping to provide a preliminary discussion and useful reference for the application of SMP in biomedical engineering.

Protein-inorganic hybrid porous scaffolds for bone tissue engineering

Porous scaffolds hold promise in the treatment of bone defects for bone tissue engineering due to their interconnected porous structure and suitable mechanical properties. Herein, LAPONITE® (LAP), which is able to promote osteogenic differentiation, was introduced into regenerated silk fibroin (RSF) porous scaffolds. Due to hydrogen bonding and electrostatic interactions between RSF and LAP, RSF/LAP 3D porous scaffolds were successfully prepared. The pore size, porosity, and mechanical properties of the RSF/LAP 3D porous scaffolds were modulated during the preparation process. Evaluation of the proliferation of bone marrow mesenchymal stem cells (BMSCs) on the RSF/LAP 3D porous scaffolds in vitro indicated that the addition of LAP improved the adhesion and proliferation of cells. Additionally, alkaline phosphatase activity and osteospecific gene expression analysis showed that the RSF/LAP 3D porous scaffolds enhanced the osteogenic differentiation of BMSCs compared to the pristine RSF porous scaffolds, especially with a higher LAP content. The subcutaneous implantation of the RSF/LAP 3D porous scaffolds in rats demonstrated good histocompatibility in vivo. Therefore, RSF/LAP 3D porous scaffolds with good biocompatibility and biodegradability have good application prospects in the field of bone tissue engineering.

Application of Collagen-Based Scaffolds for the Treatment of Spinal Cord Injuries in Animal Models: A Literature Update

SCI is regarded as one of the most devastating central nervous system (CNS) injuries, exhibiting an alarmingly rising incidence rate, indirectly connected with the expansion of the global economy. The consequences of SCI are multidimensional: SCI injuries may result in permanent voluntary motor dysfunction and loss of sensation while incurring heavy economic and psychological burdens as part of the treatment. Thus, it is crucial to develop effective and suitable SCI treatment strategies. Collagen-based scaffold application is one of the most promising methods of SCI treatment.

This review compiles newer bibliographical data regarding the application of collagen scaffolds for the treatment of Spinal cord injury (SCI) in animal models. Recently, several relevant studies have been carried out using carefully selected animals with similar pathophysiology to humans. In mouse, rat and canine models that have undergone transection or hemisection, the stump connection, the transplanted cell differentiation, and the elimination of glial scar are promising. Also, encouraging results have been found regarding the increased neuronal growth, the decreased collagen deposition, the behavioral recovery, the improved electrophysiology, and the enhanced axonal regeneration. 

Milestones and current achievements in development of multifunctional bioscaffolds for medical application

Tissue engineering (TE) is a rapidly growing interdisciplinary field, which aims to restore or improve lost tissue function. Despite that TE was introduced more than 20 years ago, innovative and more sophisticated trends and technologies point to new challenges and development. Current challenges involve the demand for multifunctional bioscaffolds which can stimulate tissue regrowth by biochemical curves, biomimetic patterns, active agents and proper cell types. For those purposes especially promising are carefully chosen primary cells or stem cells due to its high proliferative and differentiation potential. This review summarized a variety of recently reported advanced bioscaffolds which present new functions by combining polymers, nanomaterials, bioactive agents and cells depending on its desired application. In particular necessity of study biomaterial-cell interactions with in vitro cell culture models, and studies using animals with in vivo systems were discuss to permit the analysis of full material biocompatibility. Although these bioscaffolds have shown a significant therapeutic effect in nervous, cardiovascular and muscle, tissue engineering, there are still many remaining unsolved challenges for scaffolds improvement.

Recent Progress on Biodegradable Tissue Engineering Scaffolds Prepared by Thermally-Induced Phase Separation (TIPS)

Porous biodegradable scaffolds provide a physical substrate for cells allowing them to attach, proliferate and guide the formation of new tissues. A variety of techniques have been developed to fabricate tissue engineering (TE) scaffolds, among them the most relevant is the thermally-induced phase separation (TIPS). This technique has been widely used in recent years to fabricate three-dimensional (3D) TE scaffolds. Low production cost, simple experimental procedure and easy processability together with the capability to produce highly porous scaffolds with controllable architecture justify the popularity of TIPS. This paper provides a general overview of the TIPS methodology applied for the preparation of 3D porous TE scaffolds. The recent advances in the fabrication of porous scaffolds through this technique, in terms of technology and material selection, have been reviewed. In addition, how properties can be effectively modified to serve as ideal substrates for specific target cells has been specifically addressed. Additionally, examples are offered with respect to changes of TIPS procedure parameters, the combination of TIPS with other techniques and innovations in polymer or filler selection.

Progress and Prospects of Polymer-Based Drug Delivery Systems for Bone Tissue Regeneration

Despite the high regenerative capacity of bone tissue, there are some cases where bone repair is insufficient for a complete functional and structural recovery after damage. Current surgical techniques utilize natural and synthetic bone grafts for bone healing, as well as collagen sponges loaded with drugs. However, there are certain disadvantages associated with these techniques in clinical usage. To improve the therapeutic efficacy of bone tissue regeneration, a number of drug delivery systems based on biodegradable natural and synthetic polymers were developed and examined in in vitro and in vivo studies. Recent studies have demonstrated that biodegradable polymers play a key role in the development of innovative drug delivery systems and tissue engineered constructs, which improve the treatment and regeneration of damaged bone tissue. In this review, we discuss the most recent advances in the field of polymer-based drug delivery systems for the promotion of bone tissue regeneration and the physical-chemical modifications of polymers for controlled and sustained release of one or more drugs. In addition, special attention is given to recent developments on polymer nano- and microparticle-based drug delivery systems for bone regeneration.

Biomimetic Nanofibrous 3D Materials for Craniofacial Bone Tissue Engineering

Repair of large bone defects using biomaterials-based strategies has been a significant challenge due to the complex characteristics required for tissue regeneration, especially in the craniofacial region. Tissue engineering strategies aimed at restoration of function face challenges in material selection, synthesis technique, and choice of bioactive factor release in combination with all aforementioned facets. Biomimetic nanofibrous (NF) scaffolds are attractive vehicles for tissue engineering due to their ability to promote endogenous bone regeneration by mimicking the shape and chemistry of natural bone extracellular matrix (ECM). To date, several techniques for generation of biomimetic NF scaffolds have been discovered, each possessing several advantages and drawbacks. This spotlight highlights two of the more popular techniques for biomimetic NF scaffold synthesis: electrospinning and thermally-induced phase separation (TIPS), covering development from inception in each technique as well as discussing the most recent innovations in each fabrication method.