Rapid biomineralization of chitosan microparticles to apply in bone regeneration

Effectiveness of Chitosan Nanohydrogel as a Bone Regenerative Material in Intrabony Defects in Patients With Chronic Periodontitis: A Randomized Clinical Trial

Aim:

Different procedures have been attempted to regenerate intrabony defects in periodontitis but complete regeneration is still a herculean feat. Nanoparticles could prove to be advantageous because of their small size and increased surface area. The aim was to evaluate the effectiveness of a chitosan nanohydrogel as a periodontal regenerative material in the management of intrabony defects.

Materials and Methods:

Twenty patients within the age group of 30 to 60 years with intrabony defects >3 mm and clinical attachment levels >5 mm were selected. They were divided randomly into two groups: group-1, which received only open flap debridement with bone graft and acted as control, and group-2, which received open flap debridement, bone graft mixed with a chitosan nanohydrogel, and acted as the test site. Clinical and radiographic measurements were recorded at baseline, three months, and six months. Intragroup comparison was done using a paired t-test and intergroup comparison was done using an unpaired t-test with the statistical value set at P < .05.

Results:

Chitosan hydrogel incorporated bone grafts showed improved bone regenerative potential. The mean reduction in clinical attachment level in group-2 (8.7 ± 0.6 to 1.6 ± 0.8) was significantly higher than that of group-1 (8.6 ± 0.5 to 2.4 ± 0.7). The mean reduction in probing depths in group-2 (test group) was significantly higher (8.3 ± 0.9 to 1.6 ± 0.8) when compared to group-1 (8 ± 0.8 to 2.3 ± 0.7). Significant amount of defect fill was obtained in both the groups from baseline to six-month period.

Conclusion:

Organic materials such as chitosan could have potential bone regenerative capacity.

Local delivery of insulin/IGF-1 for bone regeneration: carriers, strategies, and effects

Bone defects caused by trauma, tumor resection, congenital malformation and infection are still a major challenge for clinicians. Biomimetic bone materials have attracted more and more attention in science and industry. Insulin and insulin-like growth factor-1 (IGF-1) have been increasingly recognized as an inducible factor for osteogenesis and angiogenesis. Spatiotemporal release of insulin may serve as the promising strategy. Considering the successful application of nanoparticles in drug loading, various insulin delivery systems have been developed, including (poly (lactic-co-glycolic acid), PLGA), hydroxyapatite (HA), gelatin, chitosan, alginate, and (γ-glutamic acid)/β-tricalcium phosphate, γ-PGA/β-TCP). Here, we have reviewed the progress on nanoparticles carrying insulin/IGF for bone regeneration. In addition, the key regulatory mechanism of insulin in bone regeneration is also summarized. The future application strategies and the challenges in bone regeneration are also discussed.

Nanostructured injectable cell microcarriers for tissue regeneration

Biodegradable polymer microspheres have emerged as cell carriers for the regeneration and repair of irregularly shaped tissue defects due to their injectability, controllable biodegradability and capacity for drug incorporation and release. Notably, recent advances in nanotechnology allowed the manipulation of the physical and chemical properties of the microspheres at the nanoscale, creating nanostructured microspheres mimicking the composition and/or structure of natural extracellular matrix. These nanostructured microspheres, including nanocomposite microspheres and nanofibrous microspheres, have been employed as cell carriers for tissue regeneration. They enhance cell attachment and proliferation, promote positive cell-carrier interactions and facilitate stem cell differentiation for target tissue regeneration. This review highlights the recent advances in nanostructured microspheres that are employed as injectable, biomimetic and cell-instructive cell carriers.

An overview of recent advances in designing orthopedic and craniofacial implants

Great deal of research is still going on in the field of orthopedic and craniofacial implant development to resolve various issues being faced by the industry today. Despite several disadvantages of the metallic implants, they continue to be used, primarily because of their superior mechanical properties. In order to minimize the harmful effects of the metallic implants and its by-products, several modifications are being made to these materials, for instance nickel-free stainless steel, cobalt-chromium and titanium alloys are being introduced to eliminate the toxic effects of nickel being released from the alloys, introduce metallic implants with lower modulus, reduce the cost of these alloys by replacing rare elements with less expensive elements etc. New alloys like tantalum, niobium, zirconium, and magnesium are receiving attention given their satisfying mechanical and biological properties. Non-oxide ceramics like silicon nitride and silicon carbide are being currently developed as a promising implant material possessing a combination of properties such as good wear and corrosion resistance, increased ductility, good fracture and creep resistance, and relatively high hardness in comparison to alumina. Polymer/magnesium composites are being developed to improve mechanical properties as well as retain polymer's property of degradation. Recent advances in orthobiologics are proving interesting as well. This paper thus deals with the latest improvements being made to the existing implant materials and includes new materials being introduced in the field of biomaterials.

Scaffold/Extracellular matrix hybrid constructs for bone-tissue engineering

The limited natural ability of the body to fully repair large bone defects often necessitates the implantation of a replacement material to promote healing. While the current clinical strategies to address such bone defects generally carry associated limitations, bone-tissue engineering approaches seek to minimize any adverse effects and facilitate complete regeneration of the lost tissue. Of particular interest are hybrid constructs that incorporate multiple components found within the native bone matrix to enhance the osteogenicity of biocompatible materials, which might otherwise be non-osteogenic. This Progress Report will focus on such hybrid constructs that incorporate multiple components from native bone matrix for bone-tissue engineering and will highlight the synthesis and characterization of the hybrid constructs, cellular attachment and proliferation within the constructs, in vitro osteogenicity of the constructs, and the biological response to in vivo implantation of the constructs at ectopic and orthotopic sites.

Exogenous mineralization of cell-seeded and unseeded collagen-chitosan hydrogels using modified culture medium

Induced biomineralization of materials has been employed as a strategy to increase integration with host tissue, and more recently as a method to control cell function in tissue engineering. However, mineralization is typically performed in the absence of cells, since hypertonic solutions that lack the nutrients and culture components required for the maintenance of cell viability are often used. In the present study, we exposed fibroblast-seeded three-dimensional collagen-chitosan hydrogels to a defined culture medium modified to have specific concentrations of ions involved in biomineralization. The modified medium caused a significant increase in calcium deposition in collagen-chitosan gels, relative to constructs incubated in a standard medium, though serum supplementation attenuated mineral deposition. Collagen-chitosan constructs became opaque over 3 days of mineralization in modified Dulbecco's modified Eagle medium (DMEM), in contrast to translucent control gels incubated in standard DMEM. Histological staining confirmed increased levels of mineral in the treated constructs. Rheological characterization showed that both the storage and loss moduli increased significantly in mineralized materials. Mineralization of fibroblast-seeded constructs resulted in decreased cell viability and proliferation rate over 3 days of incubation in modified medium, but the cell population remained over 75% viable and regained its proliferative potential after rescue in standard culture medium. The ability to mineralize protein matrices in the presence of cells could be useful in creating mechanically stable tissue constructs, as well as to study the effects of the tissue microenvironment on cell function.

Fabrication of a model continuously graded co-electrospun mesh for regeneration of the ligament-bone interface

Current scaffolds for the regeneration of anterior cruciate ligament injuries are unable to capture intricate mechanical and chemical gradients present in the natural ligament-bone interface. As a result, stress concentrations can develop at the scaffold-bone interface, leading to poor osseointegration. Hence, scaffolds that possess appropriate mechano-chemical gradients would help establish normal loading properties at the interface, while promoting scaffold integration with bone. With the long-term goal of investigating regeneration of the ligament-bone interface, this feasibility study aimed to fabricate a continuously graded mesh. Specifically, graded meshes were fabricated by co-electrospinning nanohydroxyapatite/polycaprolactone (nHAP-PCL) and poly(ester urethane) urea elastomer solutions from offset spinnerets. Next, mineral crystallites were selectively deposited on the nHAP-PCL fibers by treatment with a 5× simulated body fluid (5× SBF). X-ray diffraction and energy-dispersive spectroscopy indicated calcium-deficient hydroxyapatite-like mineral crystallites with an average Ca/P ratio of 1.48. Tensile testing demonstrated the presence of a mechanical gradient, which became more pronounced upon treatment with 5× SBF. Finally, biocompatibility of the graded meshes was verified using an MC3T3-E1 osteoprogenitor cell line. The study demonstrates that graded meshes, for potential application in interfacial tissue engineering, can be fabricated by co-electrospinning.

The use of micro- and nanospheres as functional components for bone tissue regeneration

During the last decade, the use of micro- and nanospheres as functional components for bone tissue regeneration has drawn increasing interest. Scaffolds comprising micro- and nanospheres display several advantages compared with traditional monolithic scaffolds that are related to (i) an improved control over sustained delivery of therapeutic agents, signaling biomolecules and even pluripotent stem cells, (ii) the introduction of spheres as stimulus-sensitive delivery vehicles for triggered release, (iii) the use of spheres to introduce porosity and/or improve the mechanical properties of bulk scaffolds by acting as porogen or reinforcement phase, (iv) the use of spheres as compartmentalized microreactors for dedicated biochemical processes, (v) the use of spheres as cell delivery vehicle, and, finally, (vi) the possibility of preparing injectable and/or moldable formulations to be applied by using minimally invasive surgery. This article focuses on recent developments with regard to the use of micro- and nanospheres for bone regeneration by categorizing micro-/nanospheres by material class (polymers, ceramics, and composites) as well as summarizing the main strategies that employ these spheres to improve the functionality of scaffolds for bone tissue engineering.