Aminopropyltriethoxysilane-mediated surface functionalization of hydroxyapatite nanoparticles: synthesis, characterization, and in vitro toxicity assay

Folic acid-mediated enhancement of the diagnostic potential of luminescent europium-doped hydroxyapatite nanocrystals for cancer biomaging

Early and accurate cancer diagnosis is crucial for improving patient survival rates. Luminescent nanoparticles have emerged as a promising tool in fluorescence bioimaging for cancer diagnosis. To enhance diagnostic accuracy, ligands promoting endocytosis into cancer cells are commonly incorporated onto nanoparticle surfaces. Folic acid (FA) is one such ligand, known to specifically bind to folate receptors (FR) overexpressed in various cancer cells such as cervical and ovarian carcinoma. Therefore, surface modification of luminescent nanoparticles with FA can enhance both luminescence efficiency and diagnostic accuracy. In this study, luminescent europium-doped hydroxyapatite (EuHAp) nanocrystals were prepared via hydrothermal method and subsequently modified with (3-Aminopropyl)triethoxysilane (APTES) followed by FA to target FR-positive human cervical adenocarcinoma cell line (HeLa) cells. The sequential grafting of APTES and then FA formed a robust covalent linkage between the nanocrystals and FA. Rod-shaped FA-modified EuHAp nanocrystals, approximately 100 nm in size, exhibited emission peaks at 589, 615, and 650 nm upon excitation at 397 nm. Despite a reduction in photoluminescence intensity following FA modification, fluorescence microscopy revealed a remarkable 120-fold increase in intensity compared to unmodified EuHAp, attributed to the enhanced uptake of FA-modified EuHAp. Additionally, confocal microscope observations confirmed the specificity and the internalization of FA-modified EuHAp nanocrystals in HeLa cells. In conclusion, the modification of EuHAp nanocrystals with FA presents a promising strategy to enhance the diagnostic potential of cancer bioimaging probes.

3D-printed TCP-HA scaffolds delivering MicroRNA-302a-3p improve bone regeneration in a mouse calvarial model

OBJECTIVE

To demonstrate hydroxyapatite nanoparticles modified with cationic functional molecules. 3-aminopropyltriethoxysilane (HA-NPs-APTES) carrying microRNA-302a-3p (miR) in the 3D-printed tricalcium phosphate/Hydroxyapatite (TCP/HA) scaffold can increase healing of the critical-sized bone defect.

MATERIALS AND METHODS

3D-printed TCP/HA were modified with HA-NPs-APTES by two methods (M1, M2). The dispersion of particles was visualized by fluorescent microscopy. Biocompatibility of the scaffolds was tested by alizarin assay. Delivery of miR to the cells and osteogenic gene expression were evaluated by qPCR. After selecting best method (M2), scaffolds, scaffolds+HA-NPs-APTES with or without miR were implanted in 4 mm mouse calvarium defect (n = 4 per group). After 2,4 and 6 weeks, bone regeneration were evaluated by microCT and histology sections.

RESULTS

Both M1 and M2 scaffolds were biocompatible with cell adhesion on its surface. M2 scaffold showed significant increase of miR, suggesting successful delivery, resulted in downregulation of its target mRNA COUP-TFII, and upregulation of RUNX2 mRNA. Calvarium defect with M2 scaffold also showed significantly higher BV/TV and higher number of filled spaces at all time points. Histomorphometry demonstrated new bone formed at the center of the HA-NPs-APTES-miR scaffold earlier than controls.

CONCLUSION

TCP/HA scaffold modified with HA-NPs-APTES facilitated delivery of miR and enhanced bone regeneration.

Plasma Activation of Microplates Optimized for One-Step Reagent-Free Immobilization of DNA and Protein

Activated microplates are widely used in biological assays and cell culture to immobilize biomolecules, either through passive physical adsorption or covalent cross-linking. Covalent attachment gives greater stability in complex biological mixtures. However, current multistep chemical activation methods add complexity and cost, require specific functional groups, and can introduce cytotoxic chemicals that affect downstream cellular applications. Here, we show a method for one-step linker-free activation of microplates by energetic ions from plasma for covalent immobilization of DNA and protein. Two types of energetic ion plasma treatment were shown to be effective: plasma immersion ion implantation (PIII) and plasma-activated coating (PAC). This is the first time that PIII and PAC have been reported in microwell plates with nonflat geometry. We confirm that the plasma treatment generates radical-activated surfaces at the bottom of wells despite potential shadowing from the walls. Comprehensive surface characterization studies were used to compare the PIII and PAC microplate surface composition, wettability, radical density, optical properties, stability, and biomolecule immobilization density. PAC plates were found to have more nitrogen and lower radical density and were more hydrophobic and more stable over 3 months than PIII plates. Optimal conditions were obtained for high-density DNA (PAC, 0 or 21% nitrogen, pH 3-4) and streptavidin (PAC, 21% nitrogen, pH 5-7) binding while retaining optical properties required for typical high-throughput biochemical microplate assays, such as low autofluorescence and high transparency. DNA hybridization and protein activity of immobilized molecules were confirmed. We show that PAC activation allows for high-density covalent immobilization of functional DNA and protein in a single step on both 96- and 384-well plates without specific linker chemistry. These microplates could be used in the future to bind other user-selected ligands in a wide range of applications, for example, for solid phase polymerase chain reaction and stem cell culture and differentiation.

Dual Modification of Porous Ca-P/PLA Composites with APTES and Alendronate Improves Their Mechanical Strength and Cytobiocompatibility towards Human Osteoblasts

Synthetic implants are used to treat large bone defects that are often unable to regenerate, for example those caused by osteoporosis. It is necessary that the materials used to manufacture them are biocompatible and resorbable. Polymer-ceramic composites, such as those based on poly(L-lactide) (PLLA) and calcium phosphate ceramics (Ca-P), are often used for these purposes. In this study, we attempted to investigate an innovative strategy for two-step (dual) modification of composites and their components to improve the compatibility of composite components and the adhesion between PLA and Ca-P whiskers, and to increase the mechanical strength of the composite, as well as improve osteological bioactivity and prevent bone resorption in composites intended for bone regeneration. In the first step, Ca-P whiskers were modified with a saturated fatty acid namely, lauric acid (LA), or a silane coupling agent γ-aminopropyltriethoxysilane (APTES). Then, the composite, characterized by the best mechanical properties, was modified in the second stage of the work with an active chemical compound used in medicine as a first-line drug in osteoporosis-sodium alendronate, belonging to the group of bisphosphonates (BP). As a result of the research covered in this work, the composite modified with APTES and alendronate was found to be a promising candidate for future biomedical engineering applications.

Surface Functionalization of Nanofibers: The Multifaceted Approach for Advanced Biomedical Applications

Nanocarriers are gaining significant importance in the modern era of drug delivery. Nanofiber technology is one of the prime paradigms in nanotechnology for various biomedical and theranostic applications. Nanofibers obtained after successful electrospinning subjected to surface functionalized for drug delivery, biomedical, tissue engineering, biosensing, cell imaging and wound dressing application. Surface functionalization entirely changes physicochemical and biological properties of nanofibers. In physicochemical properties, wettability, melting point, glass transition temperature, and initial decomposition temperature significantly change offer several advantageous for nanofibers. Similarly, biological properties include cell adhesion, biocompatibility, and proliferation, also changes by functionalization of nanofibers. Various natural and synthetic materials polymers, metals, carbon materials, functional groups, proteins, and peptides, are currently used for surface modification of nanofibers. Various research studies across the globe demonstrated the usefulness of surface functionalized nanofibers in tissue engineering, wound healing, skin cancers, melanoma, and disease diagnosis. The delivery of drug through surface functionalized nanofibers results in improved permeation and bioavailability of drug which is important for better targeting of disease and therapeutic efficacy. This review provides a comprehensive insight about various techniques of surface functionalization of nanofibers along with its biomedical applications, toxicity assessment and global patent scenario.

Aminopropyltriethoxysilane (APTES)-Modified Nanohydroxyapatite (nHAp) Incorporated with Iron Oxide (IO) Nanoparticles Promotes Early Osteogenesis, Reduces Inflammation and Inhibits Osteoclast Activity

Due to its increased prevalence, osteoporosis (OP) represents a great challenge to health care systems and brings an economic burden. To overcome these issues, treatment plans that suit the need of patients should be developed. One of the approaches focuses on the fabrication of personalized biomaterials, which can restore the balance and homeostasis of disease-affected bone. In the presented study, we fabricated nanometer crystalline hydroxyapatite (nHAp) and iron oxide (IO) nanoparticles stabilized with APTES and investigated whether they can modulate bone cell metabolism and be useful in the fabrication of personalized materials for OP patients. Using a wide range of molecular techniques, we have shown that obtained nHAp@APTES promotes viability and RUNX-2 expression in osteoblasts, as well as reducing activity of critical proinflammatory cytokines while inhibiting osteoclast activity. Materials with APTES modified with nHAp incorporated with IO nanoparticles can be applied to support the healing of osteoporotic bone fractures as they enhance metabolic activity of osteoblasts and diminish osteoclasts’ metabolism and inflammation.

Poly(L-lactic acid) Reinforced with Hydroxyapatite and Tungsten Disulfide Nanotubes

Poly(L-lactic acid) (PLLA) is a biocompatible, biodegradable, and semi-crystalline polymer with numerous applications including food packaging, medical implants, stents, tissue engineering scaffolds, etc. Hydroxyapatite (HA) is the major component of natural bone. Conceptually, combining PLLA and HA could produce a bioceramic suitable for implants and bone repair. However, this nanocomposite suffers from poor mechanical behavior under tensile strain. In this study, films of PLLA and HA were prepared with small amounts of nontoxic WS2 nanotubes (INT-WS2). The structural aspects of the films were investigated via electron microscopy, X-ray diffraction, Raman microscopy, and infrared absorption spectroscopy. The mechanical properties were evaluated via tensile measurements, micro-hardness tests, and nanoindentation. The thermal properties were investigated via differential scanning calorimetry. The composite films exhibited improved mechanical and thermal properties compared to the films prepared from the PLLA and HA alone, which is advantageous for medical applications.

Light-cured hyaluronic acid composite hydrogels using riboflavin as a photoinitiator for bone regeneration applications

Objective

Self-healing of bone from damage caused by infection, trauma, or surgical removal of cysts is limited. Generally, external intervention is needed to increase bone repair and regeneration. In this study, biocompatible light-cured hyaluronic acid hydrogels loaded with nano-hydroxyapatite and chitosan were prepared using a new photoinitiating system based on riboflavin for bone regeneration applications.

Method

Four light-cured hydrogel groups were prepared as follows: Group I, a control group with no additions; Group II, loaded with nano-hydroxyapatite; Group III, loaded with chitosan; and Group IV, loaded with both nano-hydroxyapatite and chitosan. The new photoinitiating system consisted of riboflavin as a photoinitiator, dimethylaminoethyl methacrylate (DMAEMA) as a coinitiator (being used with riboflavin for the first time), and diphenyliodonium chloride as an accelerator. For each group, X-ray-diffraction, surface morphology by scanning electron microscope, mechanical properties, water uptake (%), and cell viability (%) were tested. The osteogenic potential was then tested in a rabbit model, and histomorphometric assessment was conducted.

Results

In the four groups, the light-cured hydrogels were obtained after a short irradiation time of 10 s using a dental light-curing unit. The prepared hydrogels were biocompatible. Simultaneous addition of nano-hydroxyapatite and chitosan increased the mechanical properties threefold and the osteogenic potential, twofold, with a statistically significant difference compared with the control group.

Conclusions

Light-cured hyaluronic acid composite hydrogels loaded with nano-hydroxyapatite and chitosan—prepared by using the new photoinitiating system—are promising materials that can be used in bone regeneration applications.

Chemoenzymatic Epoxidation of Limonene Using a Novel Surface-Functionalized Silica Catalyst Derived from Agricultural Waste

Limonene is one of the most important terpenes having wide applications in food and fragrance industries. The epoxide of limonene, limonene oxide, finds important applications as a versatile synthetic intermediate in the chemical industry. Therefore, attempts have been made to synthesize limonene oxide using eco-friendly processes because of stringent regulations on its production. In this regard, we have attempted to synthesize it using a cost-effective and eco-friendly process. Chemoenzymatic epoxidation of limonene to limonene oxide was carried out using in situ generation of peroxy octanoic acid from octanoic acid and H₂O₂. In this study, agricultural-waste rice husk ash (RHA)-derived silica was surface-functionalized using (3-aminopropyl) triethoxysilane (APTS), which was cross-linked using glutaraldehyde for immobilization of Candida antarctica lipase B. Furthermore, the immobilized enzyme was entrapped in calcium alginate beads to avoid enzyme leaching. Thus, limonene oxide was prepared using this catalyst under conventional and microwave heating. The microwave irradiation intensifies the process, reducing the reaction time under the same conditions. Maximum conversion of limonene to limonene oxide of 75.35 ± 0.98% was obtained in 2 h at 50 °C using a microwave power of 50 W. In the absence of microwave irradiation, the conventional heating gave 44.6 ± 1.14% conversion in 12 h. The reaction mechanism was studied using the Lineweaver-Burk plot, which follows a ternary complex mechanism with inhibition due to peroxyoctanoic acid (in other words H₂O₂). The prepared catalyst shows high reusability and operational stability up to four cycles.

3D-HA Scaffold Functionalized by Extracellular Matrix of Stem Cells Promotes Bone Repair

BACKGROUND AND PURPOSE

The extracellular matrix (ECM) derived from bone marrow mesenchymal stem cells (BMSCs) has been used in regenerative medicine because of its good biological activity; however, its poor mechanical properties limit its application in bone regeneration. The purpose of this study is to construct a three dimensional-printed hydroxyapatite (3D-HA)/BMSC-ECM composite scaffold that not only has biological activity but also sufficient mechanical strength and reasonably distributed spatial structure.

METHODS

A BMSC-ECM was first extracted and formed into micron-sized particles, and then the ECM particles were modified onto the surface of 3D-HA scaffolds using an innovative linking method to generate composite 3D-HA/BMSC-ECM scaffolds. The 3D-HA scaffolds were used as the control group. The basic properties, biocompatibility and osteogenesis ability of both scaffolds were tested in vitro. Finally, a critical skull defect rat model was created and the osteogenesis effect of the scaffolds was evaluated in vivo.

RESULTS

The compressive modulus of the composite scaffolds reached 9.45±0.32 MPa, which was similar to that of the 3D-HA scaffolds (p>0.05). The pore size of the two scaffolds was 305±47 um and 315±34 um (p>0.05), respectively. A CCK-8 assay indicated that the scaffolds did not have cytotoxicity. The composite scaffolds had good cell adhesion ability, with a cell adhesion rate of up to 76.00±6.17% after culturing for 7 hours, while that of the 3D-HA scaffolds was 51.85±4.77% (p<0.01). In addition, the composite scaffold displayed higher alkaline phosphatase (ALP) activity, osteogenesis-related mRNA expression, and calcium nodule formation, thus confirming that the composite scaffolds had good osteogenic activity. The composite scaffolds exhibited good bone repair in vivo and were superior to the 3D-HA scaffolds.

CONCLUSION

We conclude that BMSC-ECM is a good osteogenic material and that the composite scaffolds have good osteogenic ability, which provides a new method and concept for the repair of bone defects.

Recent Advances in the Control of the Degradation Rate of PEO Treated Magnesium and Its Alloys for Biomedical Applications

Mg and Mg alloys have been studied for almost two centuries; nevertheless, commercial biomedical devices are still not available. The main issue that limits their use in the biomedical field is the rapid degradation rate combined with suitable surface properties. Novel approaches need to be designed for the development of biodegradable Mg-based devices, which could include the use of multifunctional coatings and/or new alloys designed “ad hoc”. The present article reviews on various properties, parameters and improvement methods concerning plasma electrolytic oxidation (PEO) coatings on Mg alloys substrates for biomedical applications. In this regard, (i) optimizing the PEO parameters, (ii) using additives and nanoparticles, (iii) creating combined layers of hard and/or soft particles, (iv) coating the PEO layer with a biodegradable polymer, could be the way to control their degradation rate. The review of recent scientific articles highlights that none of the techniques proposed may be preferred over the others and the need to deepen the studies for allowing the use of Mg-based devices in the biomedical field.

Functionalization and Surface Modifications of Bioactive Glasses (BGs): Tailoring of the Biological Response Working on the Outermost Surface Layer

Bioactive glasses (BGs) are routinely being used as potent materials for hard and soft tissue engineering applications; however, improving their biological activities through surface functionalization and modification has been underestimated so far. The surface characteristics of BGs are key factors in determining the success of any implanted BG-based material in vivo since they regulate the affinity and binding of different biological macromolecules and thereby the interactions between cells and the implant. Therefore, a number of strategies using chemical agents (e.g., glutaraldehyde, silanes) and physical methods (e.g., laser treatment) have been evaluated and applied to design properly, tailor, and improve the surface properties of BGs. All these approaches aim at enhancing the biological activities of BGs, including the induction of cell proliferation and subsequent osteogenesis, as well as the inhibition of bacterial growth and adhesion, thereby reducing infection. In this study, we present an overview of the currently used approaches of surface functionalization and modifications of BGs, along with discussing the biological outputs induced by these changes.

Fe₃O₄ Nanoparticles for Complex Targeted Delivery and Boron Neutron Capture Therapy

Magnetic Fe₃O₄ nanoparticles (NPs) and their surface modification with therapeutic substances are of great interest, especially drug delivery for cancer therapy, including boron-neutron capture therapy (BNCT). In this paper, we present the results of boron-rich compound (carborane borate) attachment to previously aminated by (3-aminopropyl)-trimethoxysilane (APTMS) iron oxide NPs. Fourier transform infrared spectroscopy with Attenuated total reflectance accessory (ATR-FTIR) and energy-dispersive X-ray analysis confirmed the change of the element content of NPs after modification and formation of new bonds between Fe₃O₄ NPs and the attached molecules. Transmission (TEM) and scanning electron microscopy (SEM) showed Fe₃O₄ NPs’ average size of 18.9 nm. Phase parameters were studied by powder X-ray diffraction (XRD), and the magnetic behavior of Fe₃O₄ NPs was elucidated by Mössbauer spectroscopy. The colloidal and chemical stability of NPs was studied using simulated body fluid (phosphate buffer—PBS). Modified NPs have shown excellent stability in PBS (pH = 7.4), characterized by XRD, Mössbauer spectroscopy, and dynamic light scattering (DLS). Biocompatibility was evaluated in-vitro using cultured mouse embryonic fibroblasts (MEFs). The results show us an increasing of IC₅₀ from 0.110 mg/mL for Fe₃O₄ NPs to 0.405 mg/mL for Fe₃O₄-Carborane NPs. The obtained data confirm the biocompatibility and stability of synthesized NPs and the potential to use them in BNCT.

Improved Multiprotein Microcontact Printing on Plasma Immersion Ion Implanted Polystyrene

Multiprotein micropatterning allows the creation of complex, controlled microenvironments for single cells that can be used for the study of the localized effects of various proteins and signals on cell survival, development, and functions. To enable analysis of cell interactions with microprinted proteins, the multiprotein micropattern must have low cross-contamination and high long-term stability in a cell culture medium. To achieve this, we employed an optimized plasma ion immersion implantation (PIII) treatment to provide polystyrene (PS) with the ability to covalently immobilize proteins on contact while retaining sufficient transparency and suitable surface properties for contact printing and retention of protein activity. The quality and long-term stability of the micropatterns on untreated and PIII treated PS were compared with those on glass using confocal microscopy. The protein micropattern on the PIII treated PS was more uniform and had a significantly higher contrast that was not affected by long-term incubation in cell culture media because the proteins were covalently bonded to PIII treated PS. The immunostaining of mouse pancreatic β cells interacting with E-cadherin and fibronectin striped surfaces showed phosphorylated paxillin concentrated on cell edges over the fibronectin stripes. This indicates that multiprotein micropatterns printed on PIII treated PS can be used for high-resolution studies of local influence on cell morphology and protein production.

Strategies for directing cells into building functional hearts and parts

This review presents the current state-of-the-art, emerging directions and future trends to direct cells for building functional heart parts.

Formulation of a covalently bonded hydroxyapatite and poly(ether ether ketone) composite

Spinal fusion devices can be fabricated from composites based on combining hydroxyapatite and poly(ether ether ketone) phases. These implants serve as load-bearing scaffolds for the formation of new bone tissue between adjacent vertebrae. In this work, we report a novel approach to covalently bond hydroxyapatite and poly(ether ether ketone) to produce a novel composite formulation with enhanced interfacial adhesion between phases. Compared to non-linked composites (HA_PEEK), covalently linked composites (HA_L_PEEK), loaded with 1.25 vol% hydroxyapatite, possessed a greater mean flexural strength (170 ± 5.4 vs 171.7 ± 14.8 MPa (mean ± SD)) and modulus (4.8 ± 0.2 vs 5.0 ± 0.3 GPa (mean ± SD)). Although the mechanical properties were not found to be significantly different (p > 0.05), PEEK_L_HA contained substantially larger hydroxyapatite inclusions (100-1000 µm) compared to HA_PEEK (50-200 µm), due to the inherently agglomerative nature of the covalently bonded hydroxyapatite and poly(ether ether ketone) additive. Larger inclusions would expectedly weaken the HA_L_PEEK composite; however, there is no significant difference between the flexural modulus of poly(ether ether ketone) with respect to HA_L_PEEK (p = 0.13). In addition, the flexural modulus of HA_PEEK is significantly lower compared to poly(ether ether ketone) (p = 0.03). Ultimately, covalent linking reduces hydroxyapatite particulate de-bonding from the polymeric matrix and inhibits micro-crack development, culminating in enhanced transfer of stiffness between hydroxyapatite and poly(ether ether ketone) under loading.

A hybrid dielectrophoretic system for trapping of microorganisms from water

Assessment of the microbial safety of water resources is among the most critical issues in global water safety. As the current detection methods have limitations such as high cost and long process time, new detection techniques have transpired among which microfluidics is the most attractive alternative. Here, we show a novel hybrid dielectrophoretic (DEP) system to separate and detect two common waterborne pathogens, Escherichia coli (E. coli), a bacterium, and Cryptosporidium parvum (C. parvum), a protozoan parasite, from water. The hybrid DEP system integrates a chemical surface coating with a microfluidic device containing inter-digitated microelectrodes to impart positive dielectrophoresis for enhanced trapping of the cells. Trimethoxy(3,3,3-trifluoropropyl) silane, (3-aminopropyl)triethoxysilane, and polydiallyl dimethyl ammonium chloride (p-DADMAC) were used as surface coatings. Static cell adhesion tests showed that among these coatings, the p-DADMAC-coated glass surface provided the most effective cell adhesion for both the pathogens. This was attributed to the positively charged p-DADMAC-coated surface interacting electrostatically with the negatively charged cells suspended in water leading to increased cell trapping efficiency. The trapping efficiency of E. coli and C. parvum increased from 29.0% and 61.3% in an uncoated DEP system to 51.9% and 82.2% in the hybrid DEP system, respectively. The hybrid system improved the cell trapping by encouraging the formation of cell pearl-chaining. The increment in trapping efficiency in the hybrid DEP system was achieved at an optimal frequency of 1 MHz and voltage of 2.5 Vpp for C. parvum and 2 Vpp for E. coli, the latter is lower than 2.5 Vpp and 7 Vpp, respectively, utilized for obtaining similar efficiency in an uncoated DEP system.

Pulmonary surfactant augments cytotoxicity of silica nanoparticles: Studies on an in vitro air-blood barrier model

The air-blood barrier is a very thin membrane of about 2.2 µm thickness and therefore represents an ideal portal of entry for nanoparticles to be used therapeutically in a regenerative medicine strategy. Until now, numerous studies using cellular airway models have been conducted in vitro in order to investigate the potential hazard of NPs. However, in most in vitro studies a crucial alveolar component has been neglected. Before aspirated NPs encounter the cellular air-blood barrier, they impinge on the alveolar surfactant layer (10-20 nm in thickness) that lines the entire alveolar surface. Thus, a prior interaction of NPs with pulmonary surfactant components will occur. In the present study we explored the impact of pulmonary surfactant on the cytotoxic potential of amorphous silica nanoparticles (aSNPs) using in vitro mono- and complex coculture models of the air-blood barrier. Furthermore, different surface functionalisations (plain-unmodified, amino, carboxylate) of the aSNPs were compared in order to study the impact of chemical surface properties on aSNP cytotoxicity in combination with lung surfactant. The alveolar epithelial cell line A549 was used in mono- and in coculture with the microvascular cell line ISO-HAS-1 in the form of different cytotoxicity assays (viability, membrane integrity, inflammatory responses such as IL-8 release). At a distinct concentration (100 µg/mL) aSNP-plain displayed the highest cytotoxicity and IL-8 release in monocultures of A549. aSNP-NH2 caused a slight toxic effect, whereas aSNP-COOH did not exhibit any cytotoxicity. In combination with lung surfactant, aSNP-plain revealed an increased cytotoxicity in monocultures of A549, aSNP-NH2 caused a slightly augmented toxic effect, whereas aSNP-COOH did not show any toxic alterations. A549 in coculture did not show any decreased toxicity (membrane integrity) for aSNP-plain in combination with lung surfactant. However, a significant augmented IL-8 release was observed, but no alterations in combination with lung surfactant. The augmented aSNP toxicity with surfactant in monocultures appears to depend on the chemical surface properties of the aSNPs. Reactive silanol groups seem to play a crucial role for an augmented toxicity of aSNPs. The A549 cells in the coculture seem to be more robust towards aSNPs, which might be a result of a higher differentiation and polarization state due the longer culture period.

An animal experimental study of porous magnesium scaffold degradation and osteogenesis

Our objective was to observe the biodegradable and osteogenic properties of magnesium scaffolding under in vivo conditions. Twelve 6-month-old male New Zealand white rabbits were randomly divided into two groups. The chosen operation site was the femoral condyle on the right side. The experimental group was implanted with porous magnesium scaffolds, while the control group was implanted with hydroxyapatite scaffolds. X-ray and blood tests, which included serum magnesium, alanine aminotransferase (ALT), creatinine (CREA), and blood urea nitrogen (BUN) were performed serially at 1, 2, and 3 weeks, and 1, 2, and 3 months. All rabbits were killed 3 months postoperatively, and the heart, kidney, spleen, and liver were analyzed with hematoxylin and eosin (HE) staining. The bone samples were subjected to microcomputed tomography scanning (micro-CT) and hard tissue biopsy. SPSS 13.0 (USA) was used for data analysis, and values of P<0.05 were considered to be significant. Bubbles appeared in the X-ray of the experimental group after 2 weeks, whereas there was no gas in the control group. There were no statistical differences for the serum magnesium concentrations, ALT, BUN, and CREA between the two groups (P>0.05). All HE-stained slices were normal, which suggested good biocompatibility of the scaffold. Micro-CT showed that magnesium scaffolds degraded mainly from the outside to inside, and new bone was ingrown following the degradation of magnesium scaffolds. The hydroxyapatite scaffold was not degraded and had fewer osteoblasts scattered on its surface. There was a significant difference in the new bone formation and scaffold bioabsorption between the two groups (9.29 ± 1.27 vs 1.40 ± 0.49 and 7.80 ± 0.50 vs 0.00 ± 0.00 mm3, respectively; P<0.05). The magnesium scaffold performed well in degradation and osteogenesis, and is a promising material for orthopedics.