Hybrid scaffold bearing polymer-siloxane Schiff base linkage for bone tissue engineering

Recent advances in the local antibiotics delivery systems for management of osteomyelitis

Chronic osteomyelitis is a challenging disease due to its serious rates of mortality and morbidity while the currently available treatment strategies are suboptimal. In contrast to the adopted systemic treatment approaches after surgical debridement in chronic osteomyelitis, local drug delivery systems are receiving great attention in the recent decades. Local drug delivery systems using special carriers have the pros of enhancing the feasibility of penetration of antimicrobial agents to bone tissues, providing sustained release and localized concentrations of the antimicrobial agents in the infected area while avoiding the systemic side effects and toxicity. Most important, the incorporation of osteoinductive and osteoconductive materials in these systems assists bones proliferation and differentiation, hence the generation of new bone materials is enhanced. Some of these systems can also provide mechanical support for the long bones during the healing process. Most important, if the local systems are designed to be injectable to the affected site and biodegradable, they will reduce the level of invasion required for implantation and can win the patients’ compliance and reduce the healing period. They will also allow multiple injections during the course of therapy to guard against the side effect of the long-term systemic therapy. The current review presents different available approaches for delivering antimicrobial agents for the treatment of osteomyelitis focusing on the recent advances in researches for local delivery of antibiotics.

HIGHLIGHTS

Chronic osteomyelitis is a challenging disease due to its serious mortality and morbidity rates and limited effective treatment options.

Local drug delivery systems are receiving great attention in the recent decades.

Osteoinductive and osteoconductive materials in the local systems assists bones proliferation and differentiation

Local systems can be designed to provide mechanical support for the long bones during the healing process.

Designing the local system to be injectable to the affected site and biodegradable will reduces the level of invasion and win the patients’ compliance.

Bone Repair and Regenerative Biomaterials: Towards Recapitulating the Microenvironment

Biomaterials and tissue engineering scaffolds play a central role to repair bone defects. Although ceramic derivatives have been historically used to repair bone, hybrid materials have emerged as viable alternatives. The rationale for hybrid bone biomaterials is to recapitulate the native bone composition to which these materials are intended to replace. In addition to the mechanical and dimensional stability, bone repair scaffolds are needed to provide suitable microenvironments for cells. Therefore, scaffolds serve more than a mere structural template suggesting a need for better and interactive biomaterials. In this review article, we aim to provide a summary of the current materials used in bone tissue engineering. Due to the ever-increasing scientific publications on this topic, this review cannot be exhaustive; however, we attempted to provide readers with the latest advance without being redundant. Furthermore, every attempt is made to ensure that seminal works and significant research findings are included, with minimal bias. After a concise review of crystalline calcium phosphates and non-crystalline bioactive glasses, the remaining sections of the manuscript are focused on organic-inorganic hybrid materials.

A review on applications of chitosan-based Schiff bases

Biopolymers have become very attractive as they are degradable, biocompatible, non-toxic and renewable. Due to the intrinsic reactive amino groups, chitosan is vibrant in the midst of other biopolymers. Using the versatility of these amino groups, various structural modifications have been accomplished on chitosan through certain chemical reactions. Chemical modification of chitosan via imine functionalization (RR'CNR″; R: alkyl/aryl, R': H/alkyl/aryl and R″: chitosan ring) is significant as it recommends the resultant chitosan-based Schiff bases (CSBs) for the important applications in the fields like biology, catalysis, sensors, water treatment, etc. CSBs are usually synthesized by the Schiff condensation reaction between chitosan's amino groups and carbonyl compounds with the removal of water molecules. In this review, we first introduce the available synthetic approaches for the preparation of CSBs. Then, we discuss the biological applications of CSBs including antimicrobial activity, anticancer activity, drug carrier ability, antioxidant activity and tissue engineering capacity. Successively, the applications of CSBs in other fields such as catalysis, adsorption and sensors are demonstrated.

The use of fractionated Kraft lignin to improve the mechanical and biological properties of PVA-based scaffolds

The mechanical properties of poly(vinyl alcohol) (PVA)-based scaffolds were successfully improved. The improvements in mechanical properties correlated with the amount of Kraft lignin in PVA matrices. The critical property for any scaffold is its capacity to allow cells to ingrow and survive within its internal structure. The ingrowth of cells was tested using bioreactors creating simulated in vivo conditions. In the context of all the mentioned parameters, the most advantageous properties were exhibited by the scaffold containing 99 wt% PVA and 1 wt% Kraft lignin. The composites with 1 wt% Kraft lignin exhibited sufficient mechanical stability, a lack of cytotoxicity, and mainly the ability to allow the ingrowth of cells into the scaffold in a rotation bioreactor.

The mechanical properties of poly(vinyl alcohol) (PVA)-based scaffolds were successfully improved.

3D-printed scaffolds of mesoporous bioglass/gliadin/polycaprolactone ternary composite for enhancement of compressive strength, degradability, cell responses and new bone tissue ingrowth

BACKGROUND

Due to the increasing number of patients with bone defects, bone nonunion and osteo-myelitis, tumor and congenital diseases, bone repair has become an urgent problem to be solved.

METHODS

In this study, the 3D-printed scaffolds of ternary composites containing mesoporous bioglass fibers of magnesium calcium silicate (mMCS), gliadin (GA) and polycaprolactone (PCL) were fabricated using a 3D Bioprinter.

RESULTS

The compressive strength and in vitro degradability of the mMCS/GA/PCL composites (MGPC) scaffolds were improved with the increase of mMCS content. In addition, the attachment and proliferation of MC3T3-E1 cells on the scaffolds were significantly promoted with the increase of mMCS content. Moreover, the cells with normal phenotype attached and spread well on the scaffolds surfaces, indicating good cytocompatibility. The scaffolds were implanted into the femur defects of rabbits, and the results demonstrated that the scaffold containing mMCS stimulated new bone formation and ingrowth into the scaffolds through scaffolds degradation in vivo. Moreover, the expression of type I collagen into scaffolds was enhanced with the increase of mMCS content.

CONCLUSION

The 3D-printed MGPC scaffold with controllable architecture, good biocompatibility, high compressive strength, proper degradability and excellent in vivo osteogenesis has great potential for bone regeneration.

A canine in vitro model for evaluation of marrow-derived mesenchymal stromal cell-based bone scaffolds

Tissue engineered bone grafts based on bone marrow mesenchymal stromal cells (MSCs) are being actively developed for craniomaxillofacial (CMF) applications. As for all tissue engineered implants, the bone-regenerating capacity of these MSC-based grafts must first be evaluated in animal models prior to human trials. Canine models have traditionally resulted in improved clinical translation of CMF grafts relative to other animal models. However, the utility of canine CMF models for evaluating MSC-based bone grafts rests on canine MSCs (cMSCs) responding in a similar manner to scaffold-based stimuli as human MSCs (hMSCs). Herein, cMSC and hMSC responses to polyethylene glycol (PEG)-based scaffolds were therefore compared in the presence or absence of osteoinductive polydimethylsiloxane (PDMS). Notably, the conjugation of PDMS to PEG-based constructs resulted in increases in both cMSC and hMSC osteopontin and calcium deposition. Based on these results, cMSCs were further used to assess the efficacy of tethered bone morphogenic protein 2 (BMP2) in enhancing PEG-PDMS scaffold osteoinductivity. Addition of low doses of tethered BMP2 (100 ng/mL) to PEG-PDMS systems increased cMSC expression of osterix and osteopontin compared to both PEG-PDMS and PEG-BMP2 controls. Furthermore, these increases were comparable to effects seen with up to five-times higher BMP2 doses noted in literature. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2382-2393, 2018.

Bone tissue engineering: Scaffold preparation using chitosan and other biomaterials with different design and fabrication techniques

In the recent years, a paradigm shift is taking place where metallic/synthetic implants and tissue grafts are being replaced by tissue engineering approach. A well designed three-dimensional scaffold is one of the fundamental tools to guide tissue formation in vitro and in vivo. Bone is a highly dynamic and an integrative tissue, and thus enormous efforts have been invested in bone tissue engineering to design a highly porous scaffold which plays a critical role in guiding bone growth and regeneration. Numerous techniques have been developed to fabricate highly interconnected, porous scaffold for bone tissue engineering applications with the help of biomolecules such as chitosan, collagen, gelatin, silk, etc. We aim, in this review, to provide an overview of different types of fabrication techniques for scaffold preparation in bone tissue engineering using biological macromolecules.

3D Printed scaffolds with bactericidal activity aimed for bone tissue regeneration

Nowadays, the incidence of bone disorders has steeply ascended and it is expected to double in the next decade, especially due to the ageing of the worldwide population. Bone defects and fractures lead to reduced patient's quality of life. Autografts, allografts and xenografts have been used to overcome different types of bone injuries, although limited availability, immune rejection or implant failure demand the development of new bone replacements. Moreover, the bacterial colonization of bone substitutes is the main cause of implant rejection. To vanquish these drawbacks, researchers from tissue engineering area are currently using computer-aided design models or medical data to produce 3D scaffolds by Rapid Prototyping (RP). Herein, Tricalcium phosphate (TCP)/Sodium Alginate (SA) scaffolds were produced using RP and subsequently functionalized with silver nanoparticles (AgNPs) through two different incorporation methods. The obtained results revealed that the composite scaffolds produced by direct incorporation of AgNPs are the most suitable for being used in bone tissue regeneration since they present appropriate mechanical properties, biocompatibility and bactericidal activity.

Polycaprolactone-laponite composite scaffold releasing strontium ranelate for bone tissue engineering applications

We report polycaprolactone-laponite composite scaffold for the controlled release of strontium ranelate (SRA), a drug for osteoporosis. Laponite-SRA complex with electrostatic interaction between the drug and laponite was obtained through an aqueous phase reaction. Structural evaluation verified complexation of the bulky SRA molecules with the negatively charged laponite tactoid surfaces, leading to extended ordering of the tactoids, leaving behind the interlayer spacing of the laponite unchanged. The laponite-SRA complex was solution blended with polycaprolactone to obtain composite scaffolds. The strategy was found improving the dispersibility of laponite in PCL due to partial organomodification imparted through interaction with the SRA. The composite scaffolds with varying laponite-SRA complex content of 3-12wt% were evaluated in vitro using human osteosarcoma cells. It was confirmed that an optimum composition of the scaffold with 3wt% laponite-SRA complex loading would be ideal for obtaining enhanced ALP activity, by maintaining cell viability.

Customized hybrid biomimetic hydroxyapatite scaffold for bone tissue regeneration

Three-dimension (3D) scaffolds for bone tissue regeneration were produced combining three different phases: nanometric hydroxyapatite (HA) was synthesized by precipitation method and the crystals nucleation took place directly within collagen fibrils following a biologically inspired mineralization process; polycaprolactone was employed to give the material a 3D structure. The chemico-physical analysis carried out to test the material's properties and composition revealed a high similarity in composition and morphology with biologically mineralized collagen fibrils and a scaffold degradation pattern suitable for physiological processes. The micro- computerized tomography (micro-CT) showed 53.53% porosity and a 97.86% mean interconnected pores. Computer-aided design and computer-aided manufacturing (CAD-CAM) technology was used for molding the scaffold's volume (design/shape) and for guiding the surgical procedure (cutting guides). The custom made scaffolds were implanted in sheep mandible using prototyped surgical guides and customized bone plates. After three months healing, scanning electron microscopy (SEM) analysis of the explanted scaffold revealed a massive cell seeding of the scaffold, with cell infiltration within the scaffold's interconnected pores. The micro-CT of the explanted construct showed a good match between the scaffold and the adjacent host's bone, to shield the implant primary stability. Histology confirmed cell penetration and widely documented neoangiogenesis within the entire scaffold's volume. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 723-734, 2017.