Vitamin D3 Release from Traditionally and Additively Manufactured Tricalcium Phosphate Bone Tissue Engineering Scaffolds

3D printed scaffolds with quercetin and vitamin D3 nanocarriers: In vitro cellular evaluation

Increasing bone diseases and anomalies significantly challenge bone regeneration, necessitating the development of innovative implantable devices for effective healing. This study explores the potential of 3D-printed calcium phosphate (CaP) scaffolds functionalized with natural medicine to address this issue. Specifically, quercetin and vitamin D3 (QVD) encapsulated solid lipid nanoparticles (QVD-SLNs) are incorporated into the scaffold to enhance bone regeneration. The melt emulsification method is utilized to achieve high drug encapsulation efficiency (~98%) and controlled biphasic release kinetics. The process-structure-property performance of these systems allows more controlled release while maintaining healthy cell-material interactions. The functionalized scaffolds show ~1.3- and ~-1.6-fold increase in osteoblast cell proliferation and differentiation, respectively, as compared with the control. The treated scaffold demonstrates a reduction in osteoclastic activity as compared with the control. The QVD-SLN-loaded scaffolds show ~4.2-fold in vitro chemopreventive potential against osteosarcoma cells. Bacterial assessment with both Staphylococcus aureus and Pseudomonas aeruginosa shows a significant reduction in bacterial colony growth over the treated scaffold. These findings summarize that the release of QVD-SLNs through a 3D-printed CaP scaffold can treat various bone-related disorders for low or non-load-bearing applications.

Drug delivery strategies through 3D-printed calcium phosphate

3D printing has revolutionized bone tissue engineering (BTE) by enabling the fabrication of patient- or defect-specific scaffolds to enhance bone regeneration. The superior biocompatibility, customizable bioactivity, and biodegradability have enabled calcium phosphate (CaP) to gain significance as a bone graft material. 3D-printed (3DP) CaP scaffolds allow precise drug delivery due to their porous structure, adaptable structure-property relationship, dynamic chemistry, and controlled dissolution. The effectiveness of conventional scaffold-based drug delivery is hampered by initial burst release and drug loss. This review summarizes different multifunctional drug delivery approaches explored in controlling drug release, including polymer coatings, formulation integration, microporous scaffold design, chemical crosslinking, and direct extrusion printing for BTE applications. The review also outlines perspectives and future challenges in drug delivery research, paving the way for next-generation bone repair methodologies.

Garlic extract enhances bioceramic bone scaffolds through upregulating ALP & BGLAP expression in hMSC-monocyte co-culture

Bone homeostasis is predicated by osteoblast and osteoclast cell cycles where gene expressions are responsible for their differentiation from human mesenchymal stem cells (hMSC) and monocytes, respectively. The pro-osteogenic potential of an hMSC-monocyte co-culture can be measured through complementary DNA (mRNA synthesis) within the nucleus, known as quantitative polymerase chain reaction (qPCR). Through this technique, the effects of garlic extract (allicin) release from calcium phosphate bone scaffolds on gene expression of bone forming and bone remodeling cells was explored. Results show this complex biomaterial system enhances hMSC differentiation through the upregulation of bone-forming proteins. Osteoblastic gene markers alkaline phosphatase (ALP) and osteocalcin (BGLAP), are respectively upregulated by 3-fold and 1.6-fold by day 14. These mature osteoblasts then upregulate the receptor activator of nuclear factor-kB ligand (RANKL) which recruits osteoclast cells, as captured by a nearly 2-fold higher osteoclast expression of tartrate-resistance acid-phosphatase (ACP5). This also activates antagonist osteoprotegerin (OPG) expression in osteoblasts, decreasing osteoclast resorption potential and ACP5 expression by day 21. The pro-osteogenic environment with garlic extract release is further quantified by a 4× increase in phosphatase activity and visibly captured in immunofluorescent tagged confocal images. Also corroborated by enhanced collagen formation in a preliminary in vivo rat distal femur model, this work collectively reveals how garlic extract can enhance bioceramic scaffolds for bone tissue regenerative applications.

Ginger and Garlic Extracts Enhance Osteogenesis in 3D Printed Calcium Phosphate Bone Scaffolds with Bimodal Pore Distribution

Natural medicines have long been used to treat physiological ailments where both ginger (gingerol) and garlic (allicin) are key players in immune system promotion, reduction in blood pressure, and lowering inflammation response. With their efficacy in bone healing, these compounds have great value as medicinal additives in bone scaffolds for localized treatment to support tissue formation, along with providing their natural therapeutic benefits. Utilization of 3D-printed (3DP) bone tissue engineering scaffolds as drug delivery vehicles for ginger and garlic extracts enables patient specificity in bone defect applications with enhanced osseointegration. Our objective is to understand their combined efficacy on osteogenesis when released from 3DP calcium phosphate bone scaffolds designed with a bimodal pore distribution. With a porous core and dense exterior, the resulting scaffolds have good mechanical integrity with 10 ± 1 MPa compressive strengths. Results show that ginger + garlic extracts released from bone scaffolds enhance their osteogenic potential through on site drug delivery. Both compounds exhibit exponential drug release profiles which fit Weibull distribution equations. The release of ginger extract also increases osteoblast proliferation by 59%. Both compounds show decreased osteoclast resorption activity, with a greater than 20% reduction in pit area on sample surfaces. Ginger + garlic extract induces a twofold increase in early osteoid tissue formation in vivo at week 4, in addition to a 30% increase in total bone area and a 90% increase in osteocytes with respect to control 3DP tricalcium phosphate scaffolds. Late-stage bone healing at week 10 reveals healthy angiogenic tissue, a twofold higher bone mineralization, and significant enhancement of type I collagen formation in the presence of ginger and garlic extracts. Naturally sourced ginger and garlic extracts provide osteogenic promotion and improved bone tissue in-growth in a patient-specific 3DP scaffold biomedical device for low load-bearing bone tissue engineering and dental applications.

Vitamin D3 Stimulates Proliferation Capacity, Expression of Pluripotency Markers, and Osteogenesis of Human Bone Marrow Mesenchymal Stromal/Stem Cells, Partly through SIRT1 Signaling

The biology of vitamin D3 is well defined, as are the effects of its active metabolites on various cells, including mesenchymal stromal/stem cells (MSCs). However, the biological potential of its precursor, cholecalciferol (VD3), has not been sufficiently investigated, although its significance in regenerative medicine—mainly in combination with various biomaterial matrices—has been recognized. Given that VD3 preconditioning might also contribute to the improvement of cellular regenerative potential, the aim of this study was to investigate its effects on bone marrow (BM) MSC functions and the signaling pathways involved. For that purpose, the influence of VD3 on BM-MSCs obtained from young human donors was determined via MTT test, flow cytometric analysis, immunocytochemistry, and qRT-PCR. Our results revealed that VD3, following a 5-day treatment, stimulated proliferation, expression of pluripotency markers (NANOG, SOX2, and Oct4), and osteogenic differentiation potential in BM-MSCs, while it reduced their senescence. Moreover, increased sirtuin 1 (SIRT1) expression was detected upon treatment with VD3, which mediated VD3-promoted osteogenesis and, partially, the stemness features through NANOG and SOX2 upregulation. In contrast, the effects of VD3 on proliferation, Oct4 expression, and senescence were SIRT1-independent. Altogether, these data indicate that VD3 has strong potential to modulate BM-MSCs’ features, partially through SIRT1 signaling, although the precise mechanisms merit further investigation.

New Prospects in Nano Phased Co-substituted Hydroxyapatite Enrolled in Polymeric Nanofiber Mats for Bone Tissue Engineering Applications

The most common forms of tissue impairment are fracture bones and significant bone disorders caused by multiple traumas or normal aging. Surgical care sometimes necessitates the placement of a temporary or permanent prosthesis, which continues to be a challenge for orthopedic surgeons, including those with large bone defects. Electrospun scaffolds made from natural and synthetic nanofiber-based polymers are studied as natural extracellular matrix (ECM)-like scaffolds for tissue engineering. Besides, nanostructured materials have properties and functions depending on the scale of natural materials such as hydroxyapatite (HAP), ranging from 1 to 100 nm, which activity was proficient upon enrolled in nanofiber mats. The use of nanofibers in combination with nano-HAP has increased the scaffold's ability to replicate the construction of natural bone tissue that is the aim of the present text. In bone engineering, nanofiber substrates facilitate cell adhesion, proliferation, and differentiation, while HAP induces cells to secrete ECM for bone mineralization and development. This review aims to draw the reader's attention to the critical issues with synthetic and natural polymers containing HAP in bone tissue engineering; co-substituted hydroxyapatite has also been mentioned.

Natural medicine delivery from biomedical devices to treat bone disorders: A review

With an increasing life expectancy and aging population, orthopedic defects and bone graft surgeries are increasing in global prevalence. Research to date has advanced the understanding of bone biology and defect repair mechanism, leading to a marked success in the development of synthetic bone substitutes. Yet, the quest for functionalized bone grafts prompted the researchers to find a viable alternative that regulates cellular activity and supports bone regeneration and healing process without causing serious side-effects. Recently, researchers have introduced natural medicinal compounds (NMCs) in bone scaffold that enables them to release at a desirable rate, maintains a sustained release allowing sufficient time for tissue in-growth, and guides bone regeneration process with minimized risk of tissue toxicity. According to World Health Organization (WHO), NMCs are gaining popularity in western countries for the last two decades and are being used by 80% of the population worldwide. Compared to synthetic drugs, NMCs have a broader range of safety window and thus suitable for prolonged localized delivery for bone regeneration. There is limited literature focusing on the integration of bone grafts and natural medicines that provides detailed scientific evidences on NMCs, their toxic limits and particular application in bone tissue engineering, which could guide the researchers to develop functionalized implants for various bone disorders. This review will discuss the emerging trend of NMC delivery from bone grafts, including 3D-printed structures and surface-modified implants, highlighting the significance and potential of NMCs for bone health, guiding future paths toward the development of an ideal bone tissue engineering scaffold. STATEMENT OF SIGNIFICANCE: To date, additive manufacturing technology provids us with many advanced patient specific or defect specific bone constructs exhibiting three-dimensional, well-defined microstructure with interconnected porous networks for defect-repair applications. However, an ideal scaffold should also be able to supply biological signals that actively guide tissue regeneration while simultaneously preventing post-implantation complications. Natural biomolecules are gaining popularity in tissue engineering since they possess a safer, effective approach compared to synthetic drugs. The integration of bone scaffolds and natural biomolecules exploits the advantages of customized, multi-functional bone implants to provide localized delivery of biochemical signals in a controlled manner. This review presents an overview of bone scaffolds as delivery systems for natural biomolecules, which may provide prominent advancement in bone development and improve defect-healing caused by various musculoskeletal disorders.

Assessing the potential use of chitosan scaffolds for the sustained localized delivery of vitamin D

Vitamin D is a commonly used bone modulator in regenerative medicine. Several modalities have been explored for the delivery of vitamin D including nanoparticles and scaffold. The present study aimed to assess the potential use of a bio-degradable chitosan scaffold for the delivery of vitamin D. The objectives included fabrication of a bio-degradable chitosan scaffold, integration of vitamin D into the scaffold, characterization of the vitamin D integrated scaffold. Characterization was carried out using, X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The structure of the scaffold was assessed by scanning electron microscopy. The scaffold was placed in phosphate buffer saline and the release duration of vitamin D was observed using UV spectrophotometry. Dental pulp mesenchymal stem cells were added to the scaffold to study the scaffold associated toxicity and the functionality of the scaffold released vitamin D. The vitamin D release period from the scaffold was estimated to be for 80 hrs. MTT assay of the stem cells was comparable to that of the control group (stem cells cultured in media) inferring that the scaffold is not toxic towards the stem cells. The positive alizarin red S staining, a higher expression of alkaline phosphatase, osteocalcin, and RunX2 confirmed the functional capability (osteogenic differentiation of the stem cells) of the released vitamin D. Based on the data from the present study, it can be inferred that chitosan scaffold can be used for the sustained delivery of functional vitamin D for 3-5 days.

Influence of random and designed porosities on 3D printed tricalcium phosphate-bioactive glass scaffolds

Calcium phosphate (CaP)-based ceramics are a popular choice for bone-graft applications due to their compositional similarities with bone. Similarly, Bioactive glass (BG) is also common for bone tissue engineering applications due to its excellent biocompatibility and bone binding ability. We report tricalcium phosphate (TCP)-BG (45S5 BG) composite scaffolds using conventional processing and binder jetting-based 3D printing (3DP) technique. We hypothesize that BG's addition in TCP will enhance densification via liquid phase sintering and improve mechanical properties. Further, BG addition to TCP should modulate the dissolution kinetics in vitro. This work's scientific objective is to understand the influence of random vs. designed porosity in TCP-BG ceramics towards variations in compressive strength and in vitro biocompatibility. Our findings indicate that a 5 wt % BG in TCP composite shows a compressive strength of 26.7 ± 2.7 MPa for random porosity structures having a total porosity of ~47.9%. The same composition in a designed porosity structure shows a compressive strength of 21.3 ± 2.9 MPa, having a total porosity of ~54.1%. Scaffolds are also tested for their dissolution kinetics and in vitro bone cell materials interaction, where TCP-BG compositions show favorable bone cell materials interactions. The addition of BG enhances a flaky hydroxycarbonate apatite (HCA) layer in 8 weeks in vitro. Our research shows that the porous TCP- BG scaffolds, fabricated via binder jetting method with enhanced mechanical properties and dissolution properties can be utilized in bone graft applications.

Effects of surface area and topography on 3D printed tricalcium phosphate scaffolds for bone grafting applications

Additive manufacturing (AM), or 3D printing, of bioceramic scaffolds promises personalized treatment options for patients with site-specific designability for repair and reconstruction of bone defects. Although the theory for creating these complex geometries has already been made possible through AM's advancement, such shapes' manufacturability is difficult due to printing with ceramics' inherent complexities. Ceramics have the added challenge of being highly brittle, poor handleability of green (pre-sintered) parts, making complex shape high strength parts challenging to manufacture. This has led to a significant literature gap regarding the feasibility of creating bioceramic scaffolds with unique architectures that can be used in site-specific, individualized patient treatment. This work aims to successfully create complex topographical surfaces of cylindrical bone-like scaffolds to understand the correlation of increasing the scaffold surface area on mechanical properties and in vitro osteoblast cell proliferation. An increase in osteoblast cell proliferation and facilitation in cellular attachment can ultimately lead to improved bone healing. This work explores the printing parameters within an Innovent+® ExOne binder jet 3D printer to produce scaffold designs from synthesized tricalcium phosphate powder. Mechanical testing reveals the designed structures enhance scaffold compressive strength by 30% compared to control dense cylindrical scaffolds. Osteoblast cell proliferation is also increased due to changes in surface topography with a nearly 2-fold increase. Our work incorporates macro-level topographical changes to increase surface area, which is another avenue that could be combined with other scaffold features such as porosity. Results show bulk surface topography modifications via 3D printing can increase surface area to support enhanced biological response without compromising mechanical properties. This discovery may enable a future generation of porous scaffolds with external structures for further progress towards proper defect-specific synthetic bone grafts.

Natural Antibiotic Oregano in Hydroxyapatite-Coated Titanium Reduces Osteoclastic Bone Resorption for Orthopedic and Dental Applications

Traditional infection prevention and treatment methods include synthetic antibiotics, which can cause severe adverse side effects. Carvacrol and thymol are biologically active monoterpenoid extractants from oregano leaves with antibiotic capabilities; however, little is known regarding their effects on bone tissue engineering. The objective of this work is to understand their effects on osteogenesis, specifically with osteoblast and osteoclast cells, from surface-modified Ti6Al4V with plasma sprayed hydroxyapatite (HA) coatings. This system is an alternative to cemented implants to aid in bone healing. Results reveal that full carvacrol release from the HA matrix is successful in aqueous environments and modulation of release kinetics can also be made using polycaprolactone (PCL) and polyethylene glycol (PEG) polymers. From HA-pressed disc samples in physiological pH, full carvacrol release is achieved in 10 days using PCL/PEG, about 95% release in 50 days using no polymer, and 60% in 50 days when using a PCL coating. Without polymer, full carvacrol release is achieved after 3 days from HA coatings in both physiological pH and acidic pH, mimicking the post-surgery environment. The release is assessed as a diffusion-based mechanism in phosphate-buffered saline but degradation-based mechanism in acetate buffer solution. Carvacrol and thymol show bacterial inhibition of Staphylococcus epidermidis and no cytotoxic effects on osteoblast proliferation in vitro. Carvacrol and thymol also induce a significant 7% reduction in osteoclast tartrate-resistant acid phosphatase (TRAP) activity, caused by poorly attached cellular morphologies, leading to an approximately 65% reduction in osteoclast resorption pit formation. Our goal is to demonstrate a natural medicinal system that can support bone healing while providing infection prevention and reducing costly revision surgeries for orthopedic and dental applications.

Synthesis and characterization of collagen/calcium phosphate scaffolds incorporating antibacterial agent for bone tissue engineering application

In the present study, we developed a novel niosomal nanocarrier embedded into a collagen/β- tricalcium phosphate (Col/β-TCP) scaffold for the local delivery of thymol as a natural anti-bacterial reagent. The niosomal Col/β-TCP (N-Col/β-TCP) scaffolds with different weight ratios of β-TCP to Col were prepared by freeze-drying. The antimicrobial activities of the prepared samples against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were assessed by agar diffusion method. The release profile of niosomal thymol from the optimized composite scaffolds showed a sustained profile where 66% of the loaded thymol was released over 30 days. The compressive modulus of niosome added scaffolds with an equal ratio of β-TCP and Col was calculated as 972±1.3KPa. This scaffold showed significantly higher values of cell viability (as evaluated by an MTT assay) against L929 fibroblasts than a scaffold without niosomal thymol after 24 and 72 h. Among synthesized samples, Col/β-TCP1 showed the greatest effectiveness of anti-bacterial activity toward Gram-positive and Gram-negative bacteria with higher activity against Gram-positive ones. The results of this study highlight the potential of niosomal-thymol loaded Col/β-TCP1 scaffold as an anti-bacterial bone substitute for possible osteomyelitis treatment.

Enhanced osteogenesis of 3D printed β-TCP scaffolds with Cissus Quadrangularis extract-loaded polydopamine coatings

Growing demand in bone tissue replacement has shifted treatment strategy from pursuing traditional autogenous and allogeneic grafts to tissue replacement with bioactive biomaterials. Constructs that exhibit the ability to support the bone structure while encouraging tissue regeneration, integration, and replacement represent the future of bone tissue engineering. The present study aimed to understand the osteogenic and mechanical effects of binder jet 3D printed, porous β-tricalcium phosphate scaffolds modified with a natural polymer/drug coating of polydopamine and Cissus Quadrangularis extract. Compression testing was used to determine the effect the polydopamine coating process had on the mechanical strength of the scaffolds. 3D printed scaffolds with and without polydopamine coatings fractured at 3.88 ± 0.51 MPa and 3.84 ± 1 MPa, respectively, suggesting no detrimental effect on strength due to the coating process. The osteogenic potential of the extract-loaded coating was tested in vitro, under static and dynamic flow conditions, and in vivo in a rat distal femur model. Static osteoblast cultures indicated polydopamine-coated samples with and without the extract exhibited greater proliferation after 3 days (p < 0.05). Similarly, polydopamine resulted in increased proliferation and alkaline phosphatase expression under dynamic flow, but alkaline phosphatase expression was significantly enhanced (p < 0.05) only in samples treated with the extract. Histological analysis of implanted scaffolds showed substantially more new bone growth throughout the implant pores at 4 weeks post-op in polydopamine and extract-loaded implants compared to pure β-tricalcium phosphate. These results indicated that implants coated with polydopamine and Cissus Quadrangularis extract facilitated osteoblast proliferation and alkaline phosphatase production and improved early bone formation and ingrowth while maintaining mechanical strength.