Imaging of nano-hydroxyapatite/chitosan scaffolds using a cone beam computed tomography device on rat calvarial defects with histological verification

Enhancing cranial defect repair in rats: investigating the effect of combining Total Flavonoids from Rhizoma Drynariae with calcium phosphate/collagen scaffolds

OBJECTIVE

To investigate the therapeutic efficacy of total flavonoids of Rhizoma Drynariae (TFRD) in conjunction with a calcium phosphate/collagen scaffold for the repair of cranial defects in rats.

METHODS

The subjects, rats, were segregated into four groups: Control, TFRD, Scaffold, and TFRD + Scaffold. Cranial critical bone defects, 5 mm in diameter, were artificially induced through precise drilling. Post-surgery, at intervals of 2, 4, and 8 weeks, micro-CT scans were conducted to evaluate the progress of skull repair. Hematoxylin-eosin and Masson staining techniques were applied to discern morphological disparities, and immunohistochemical staining was utilized to ascertain the expression levels of local osteogenic active factors, such as bone morphogenetic protein 2 (BMP-2) and osteocalcin (OCN).

RESULTS

Upon examination at the 8-week mark, cranial defects in the Scaffold and TFRD + Scaffold cohorts manifested significant repair, with the latter group displaying only negligible foramina. Micro-CT examination unveiled relative to its counterparts, and the TFRD + Scaffold groups exhibited marked bone regeneration at the 4- and 8-week intervals. Notably, the TFRD + Scaffold group exhibited substantial bone defect repair compared to the TFRD and Scaffold groups throughout the entire observation period, while histomorphological assessment demonstrated a significantly higher collagen fiber content than the other groups after 2 weeks. Immunohistochemical analysis further substantiated that the TFRD + Scaffold had augmented expression of BMP-2 at 2, 4 weeks and OCN at 2 weeks relative to other groups.

CONCLUSIONS

The synergistic application of TFRD and calcium phosphate/collagen scaffold has been shown to enhance bone mineralization, bone plasticity, and bone histomorphology especially during initial osteogenesis phases.

Nano-Hydroxyapatite Composite Scaffolds Loaded with Bioactive Factors and Drugs for Bone Tissue Engineering

Nano-hydroxyapatite (n-HAp) is similar to human bone mineral in structure and biochemistry and is, therefore, widely used as bone biomaterial and a drug carrier. Further, n-HAp composite scaffolds have a great potential role in bone regeneration. Loading bioactive factors and drugs onto n-HAp composites has emerged as a promising strategy for bone defect repair in bone tissue engineering. With local delivery of bioactive agents and drugs, biological materials may be provided with the biological activity they lack to improve bone regeneration. This review summarizes classification of n-HAp composites, application of n-HAp composite scaffolds loaded with bioactive factors and drugs in bone tissue engineering and the drug loading methods of n-HAp composite scaffolds, and the research direction of n-HAp composite scaffolds in the future is prospected.

Comparison of Two Bovine Commercial Xenografts in the Regeneration of Critical Cranial Defects

Autologous bone is the gold standard in regeneration processes. However, there is an endless search for alternative materials in bone regeneration. Xenografts can act as bone substitutes given the difficulty of obtaining bone tissue from patients and before the limitations in the availability of homologous tissue donors. Bone neoformation was studied in critical-size defects created in the parietal bone of 40 adult male Wistar rats, implanted with xenografts composed of particulate bovine hydroxyapatite (HA) and with blocks of bovine hydroxyapatite (HA) and Collagen, which introduces crystallinity to the materials. The Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated the carbonate and phosphate groups of the hydroxyapatite and the amide groups of the collagen structure, while the thermal transitions for HA and HA/collagen composites established mainly dehydration endothermal processes, which increased (from 79 °C to 83 °C) for F2 due to the collagen presence. The xenograft's X-ray powder diffraction (XRD) analysis also revealed the bovine HA crystalline structure, with a prominent peak centered at 32°. We observed macroporosity and mesoporosity in the xenografts from the morphology studies with heterogeneous distribution. The two xenografts induced neoformation in defects of critical size. Histological, histochemical, and scanning electron microscopy (SEM) analyses were performed 30, 60, and 90 days after implantation. The empty defects showed signs of neoformation lower than 30% in the three periods, while the defects implanted with the material showed partial regeneration. InterOss Collagen material temporarily induced osteon formation during the healing process. The results presented here are promising for bone regeneration, demonstrating a beneficial impact in the biomedical field.

The effect of nano-hydroxyapatite/chitosan scaffolds on rat calvarial defects for bone regeneration

BACKGROUND

This study aims at determining the biological effect of 75/25 w/w nano-hydroxyapatite/chitosan (nHAp/CS) scaffolds on bone regeneration, in terms of fraction of bone regeneration (FBR), total number of osteocytes (Ost), and osteocyte cell density (CD), as well as its biodegradability.

METHODS

Two critical-size defects (CSDs) were bilaterally trephined in the parietal bone of 36 adult Sprague-Dawley rats (18 males and 18 females); the left remained empty (group A), while the right CSD was filled with nHAp/CS scaffold (group B). Two female rats died postoperatively. Twelve, 11, and 11 rats were euthanized at 2, 4, and 8 weeks post-surgery, respectively. Subsequently, 34 specimens were resected containing both CSDs. Histological and histomorphometric analyses were performed to determine the FBR, calculated as [the sum of areas of newly formed bone in lateral and central regions of interest (ROIs)]/area of the original defect, as well as the Ost and the CD (Ost/mm2) in each ROI of both groups (A and B). Moreover, biodegradability of the nHAp/CS scaffolds was estimated via the surface area of the biomaterial (BmA) in the 2nd, 4th, and 8th week post-surgery.

RESULTS

The FBR of group B increased significantly from 2nd to 8th week compared to group A (P = 0.009). Both the mean CD and the mean Ost values of group B increased compared to group A (P = 0.004 and P < 0.05 respectively). Moreover, the mean value of BmA decreased from 2nd to 8th week (P = 0.001).

CONCLUSIONS

Based on histological and histomorphometric results, we support that 75/25 w/w nHAp/CS scaffolds provide an effective space for new bone formation.

The role of nanohydroxyapatite on the morphological, physical, and biological properties of chitosan nanofibers

OBJECTIVES

This study aimed to evaluate the effects of nanohydroxyapatite (nHAp) particles on the morphological, chemical, physical, and biological properties of chitosan electrospun nanofibers.

MATERIALS AND METHODS

nHAp particles with a 1.67 Ca/P ratio were synthesized via the aqueous precipitation method, incorporated into chitosan polymer solution (0.5 wt%), and electrospun into nHAp-loaded fibers (ChHa fibers). Neat chitosan fibers (nHAp-free, Ch fibers) were used as the control. The electrospun fiber mats were characterized using morphological, topographical, chemical, thermal, and a range of biological (antibacterial, antibiofilm, cell viability, and alkaline phosphatase [ALP] activity) analyses. Data were analyzed using ANOVA and Tukey's test (α = 0.05).

RESULTS

ChHa fibers demonstrated a bead-like morphology, with thinner (331 ± 110 nm) and smoother (Ra = 2.9 ± 0.3 μm) distribution as compared to the control fibers. Despite showing similar cell viability and ALP activity to Ch fibers, the ChHa fibers demonstrated greater antibacterial potential against most tested bacteria (except for P. intermedia), and higher antibiofilm activity against P. gingivalis biofilm.

CONCLUSIONS

The incorporation of nHAp particles did not jeopardize the overall morphology, topography, physical, and biological characteristics of the chitosan nanofibers.

CLINICAL RELEVANCE

The combination of nHAp particles with chitosan can be used to engineer bioactive, electrospun composite nanofibers with potential applications in regenerative dentistry.