Xibo Pei

Osteogenic activity and antibacterial effect of zinc oxide/carboxylated graphene oxide nanocomposites: Preparation and in vitro evaluation.

The aim of this study was to prepare nanocomposites of carboxylated graphene oxide (GO-COOH) sheets decorated with zinc oxide (ZnO) nanoparticles (NPs) and investigate their advantages in the field of bone tissue engineering. First, ZnO/GO-COOH nanocomposites were synthesized by facile reactions, including the carboxylation of graphene oxide (GO) and the nucleation of ZnO on GO-COOH sheets. The synthesized ZnO/GO-COOH nanocomposites were then characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, and transmission electron microscopy (TEM). The biocompatibility, osteogenic activity and antibacterial effect of ZnO/GO-COOH nanocomposites were further investigated. In the nanocomposites, ZnO nanoparticles with a size of approximately 12nm were uniformly decorated on GO-COOH sheets. Compared with GO-COOH and the control group, ZnO/GO-COOH nanocomposites significantly enhanced ALP activity, osteocalcin production and extracellular matrix mineralization as well as up-regulated osteogenic-related genes (ALP, OCN, and Runx2) in MG63 osteoblast-like cells. Moreover, ZnO/GO-COOH nanocomposites had an antibacterial effect against Streptococcus mutans. These results indicated that ZnO/GO-COOH nanocomposites exhibited both osteogenic activity and antibacterial effect and had great potential for designing new biomaterials in the field of bone tissue engineering.

Osteogenic activity and antibacterial effect of porous titanium modified with metal‐organic framework films

As a new class of crystalline nanoporous materials, metal-organic frameworks (MOFs) have recently been used for biomedical applications due to their large surface area, high porosity, and theoretically infinite structures. To improve the biological performance of titanium, MOF films were applied to surface modification of titanium. Zn-based MOF films composed of zeolitic imidazolate framework-8 (ZIF-8) crystals with nanoscale and microscale sizes (nanoZIF-8 and microZIF-8) were prepared on porous titanium surfaces by hydrothermal and solvothermal methods, respectively. The ZIF-8 films were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The nanoZIF-8 film exhibited good biocompatibility, whereas the microZIF-8 film showed obvious cytotoxicity to MG63 cells. Compared to pure titanium and alkali- and heat-treated porous titanium, the nanoZIF-8 film not only enhanced alkaline phosphatase (ALP) activity, extracellular matrix mineralization, and expression of osteogenic genes (ALP, Runx2) in MG63 cells but also inhibited the growth of Streptococcus mutans. These results indicate that MOF films or coatings may be promising candidates for bone tissue engineering.

EFFECTS OF ULTRASONIC RADIATION INTENSITY ON THE OXIDATION OF SINGLE-WALLED CARBON NANOTUBES IN A MIXTURE OF SULFURIC AND NITRIC ACIDS

One of the most commonly used techniques for purification and eventual dispersion of single-wall carbon nanotubes (SWNTs) is oxidation using strong acid and ultrasonication. Literature review reveals that ultrasonication of varying radiation intensities have been used during the acid oxidation, but few have reported whether ultrasonication of different intensities would have different effects on the structure and properties of SWNTs and how the effects are. An investigation of the effects of ultrasonic radiation intensity on SWNTs during oxidation in a mixture of sulfuric and nitric acids was conducted. Ultrasonication using different intensities (50 W, 100 W, 200 W and 300 W) was used. The acid-treated SWNTs were characterized by scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, zeta potential test Boehm titration test and Raman spectrum analysis. Data from these experiments showed that high intensities provided stronger oxidizing conditions than lower ones. As ultrasonic intensity increased, larger number of SWNTs were destroyed and consumed to produce carbonaceous impurities, and more defects appeared in the tube walls.

Electrochemical synthesis of three-dimensional porous reduced graphene oxide film: Preparation and in vitro osteogenic activity evaluation

In this study, three-dimensional reduced graphene oxide (3D-rGO) porous films were fabricated using a two-step electrochemical method, including an electrochemical deposition process for the self-assembly of GO and an electrochemical bubbling-based transfer. The morphology, physical properties, and phase composition of the 3D-rGO films were characterized, and the cellular bioactivities were evaluated using pre-osteoblasts (MC3T3-E1 cells). The attachment, proliferation and differentiation of the MC3T3-E1 cells on the 3D-rGO films was analyzed by scanning electron microscopy (SEM), Cell Counting Kit-8 (CCK-8) assays and live/dead cell staining, and alkaline phosphatase (ALP) activity assays, respectively. The expression of osteogenic-related genes in MC3T3-E1 cells was evaluated by reverse transcription-polymerase chain reaction (RT-PCR). The results showed that the 3D-rGO films supported cell viability and proliferation, as well as significantly enhanced ALP activity and osteogenic-related genes (ALP, OPN, Runx2) expressions. Our findings indicate the promising potential of the 3D-rGO porous films for bone tissue engineering.

Synergistic Enhancement of Antitumor Efficacy by PEGylated Multi-walled Carbon Nanotubes Modified with Cell-Penetrating Peptide TAT

In the present study, a cell-penetrating peptide, the transactivating transcriptional factor (TAT) domain from HIV, was linked to PEGylated multi-walled carbon nanotubes (MWCNTs) to develop a highly effective antitumor drug delivery system. FITC was conjugated on MWCNTs-polyethylene glycol (PEG) and MWCNTs-PEG-TAT to provide fluorescence signal for tracing the cellular uptake of the nanocarrier. After loaded with an anticancer agent, doxorubicin (DOX) via π − π stacking interaction, the physicochemical characteristics, release profile and biological evaluation of the obtained nano-sized drug carrier were investigated. The DOX loaded MWCNTs-PEG and MWCNTs-PEG-TAT drug carriers both displayed appropriate particle size, excellent stability, high drug loading, and pH-dependent drug release profile. Nevertheless, compared with DOX-MWCNTs-PEG, DOX-MWCNTs-PEG-TAT showed improved cell internalization, intracellular distribution and potentiated anticancer efficacy due to the TAT-mediated membrane translocation, endosomal escape and nuclear targeting. Furthermore, the therapeutic efficacy of DOX was not compromised after being conjugated with MWCNTs-PEG-TAT and the proposed nanocarrier was also confirmed to have a good biocompatibility. In conclusion, our results suggested that the unique combination of TAT and MWCNTs as a multifunctional drug delivery system might be a powerful tool for improved anticancer drug development.

Speech effects of Hawley and vacuum-formed retainers by acoustic analysis: A single-center randomized controlled trial

OBJECTIVE To investigate the effects of alteration on speech articulation of adult patients between Hawley retainers and vacuum-formed retainers by an objective acoustic analysis of vowels and voiceless fricatives. MATERIALS AND METHODS Twenty adults, aged 19.0-29.0 years, who had just finished active orthodontic treatment were included in this study. They were divided into a Hawley retainer group and a vacuum-formed retainer group by sortation randomization method. The assessment of speech sounds was performed objectively using acoustic analysis before and after retainer application at the following time points: before wearing (T0), immediately after wearing (T1), and at 24 hours (T2), 1 week (T3), 1 month (T4), and 3 months (T5). RESULTS The production of /з:/, /i:/, /f/, /θ/, /s/, and /∫/ sounds for the Hawley retainer group and /i:/, /θ/, /s/, and /∫/ sounds for the vacuum-formed retainer group showed severe speech impairment according to acoustic analysis (P < .05). A comparison of the Hawley retainer group with the vacuum-formed retainer group revealed that the performance of /i:/, /f/, and /s/ sounds were significantly different (P < .05). CONCLUSION Although sound distortion could be found in both the Hawley retainer group and the vacuum-formed retainer group, changes in articulation were more obvious in the Hawley retainer group.

Comment on "amine-modified graphene: thrombo-protective safer alternative to graphene oxide for biomedical applications".

’ In a recent issue of ACS Nano, we read with great interest the excellent article by Singh et al. detailing the fabrication of amine-modified graphene (G-NH2) and their application potential in biomedicine. However, we found that the authors neglected a key point that the performances of both microand nanosized graphene in biological context were essential for guiding their biomedical applications. In this study, the authors constructed a suspended graphene-amine membrane consisting of singleor few-layer sheets. Flow cytometric analysis showed that identical size distribution of different graphene derivatives was fabricated, and high-resolution transmission electronmicroscopy (HR-TEM) revealed that the average dimension of different graphene derivatives was 2 μm. Finally, the authors concluded that G-NH2was a far safer alternative toGOandwas thuspotentially safe for biomedical applications in areas such as imaging, drug delivery, as well as photothermal therapy. However, all the graphene derivatives in this study were microsized, and nanosized graphene oxide, a widely studiedmaterial with high biocompatibility, was not mentioned as a control group in this article. As this study mentioned, graphene derivatives were finally developed to act as diagnostic or therapeutic materials. Such materials often required site-specific cellular entry to deliver their payload to subcellular locations hidden beneath cell membranes. Sahay thought that the uptake of those materials was regulated by their size. For example, Raffas study showed thatmicrosized carbon nanotubes with length longer than 2 μm could hardly enter cells, and Gratton showed that the nanosized particles seemed to enter cells more rapidly than the microparticles. Moreover, the pharmacokinetic profile analysis between the two types (microand nanosized) of GO suggested that a material with a small lateral dimension might bemore suitable for potential biomedical applications. Furthermore, microsized graphene derivatives might induce inflammation response, which might not be suitable for biomedical applications such as drug delivery and cancer therapy. Once inside the cells, themicrosized (2 μm)GOmight formwrinkles and then induce a much stronger inflammatory response with high release of key cytokines than nanosized (350 nm) GO. Yue concluded that the high cytokine level induced by 2 μm GO might be attributed to the strong steric effect of microsized GO. Besides, histological micrographics of mice showed that a large number of mononuclear cells infiltrated subcutaneous adipose tissue, and lipid-filled vacuoles as well as tissue impairment appeared after 2 μm GO injection. In contrast, the inflammation response was weak under the treatment of 350 nm GO. Such observations were in agreement with those by Schinwald, who reported that microsized graphene induced an inflammatory response and granuloma formation in lung and pleural space. Low inflammatory profiles exerted by nanosized GO can be beneficial for applications in drug carrier and cancer therapy, where improved biocompatibility is demanded. In conclusion, the size of graphene derivatives might be the control factor of biocompatibility of graphene derivatives. Therefore, when investigating the biocompatibility of graphene derivatives, both microsized and nanosized graphene derivatives should be considered. Finally, we would like to congratulate the authors for their contributions to graphene functionalization, which is innovative to biomedical research.

PCL–CNT Nanocomposites

Many biomaterial applications have been realized by using polymeric scaffolds among which the biodegradable polymers, such as polycaprolactone (PCL), have drawn extensive attention with regard to tissue regeneration. However, PCL does not have the mechanical properties to be applied in high load bearing situation, which has limited its use in bone tissue engineering. One of the most effective methods of increasing the mechanical properties (elastic modulus and tensile strength) of a polymer is by reinforcing with a second-phase material. Hence, researchers have used different types of second-phase materials for mechanical strengthening of PLA, PCL, and their copolymers (PLC). Among all of these, carbon nanotubes (CNT) seem to be the reinforcement with most potential, due to their very high mechanical properties (Youngs modulus 0.2–1 TPa, tensile strength 11–63 GPa) and fiber-like structure. Furthermore, the addition of carbon nanotubes to PCL can enhance the conductivity, thermal, mechanical and gas barrier properties of PCL. All these findings have caused carbon nanotubes to be the suitable second-phase reinforcement for biodegradable polymers in orthopedic scaffold applications.

A Systematic Review of the Survival and Complication Rates of All-Ceramic Resin-Bonded Fixed Dental Prostheses

PURPOSE The aim of this systematic review was to investigate the survival and complication rates of all-ceramic resin-bonded fixed dental prostheses (RBFDPs). MATERIALS AND METHODS The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied. A systematic search was conducted by an electronic search in PubMed, EMBASE, Cochrane Library, and CNKI databases complemented by a manual search. Only clinical studies on all-ceramic RBFDPs with a mean follow-up period of at least 3 years qualified for data analyses. RESULTS Among 1503 screened articles, one randomized controlled trial (RCT) and seven prospective or retrospective cohort studies were included in this study. The estimated 5-year survival rate of all-ceramic RBFDPs was 91.2%. Debonding and framework fracture were the two most frequent technical complications, and the estimated 5-year debonding rate and fracture rate were 12.2% and 4.8%, respectively. Additionally, cantilevered all-ceramic RBFDPs had a higher survival rate (p < 0.01), lower debonding rate, (p < 0.05), and fracture rate (p < 0.01) compared with two-retainer all-ceramic RBFDPs. Zirconia ceramic RBFDPs had a lower incidence of failure but a higher debonding rate compared with glass-ceramic RBFDPs (p < 0.01). CONCLUSION Within the limitations of this systematic review, although all-ceramic RBFDPs have a favorable 5-year survival rate, this rate cannot represent the complete success of the treatment, since it may include typical complications such as debonding and fractures. There is an urgent need for long-term clinical studies, especially for well-designed RCTs on all-ceramic RBFDPs.

Enhanced Osseointegration of Porous Titanium Modified with Zeolitic Imidazolate Framework-8

Nanoscale zeolitic imidazolate framework-8 (ZIF-8)-modified titanium (ZIF-8@AHT) can enhance osteogenesis in vitro. In this study, we systematically and quantitatively examined the effects of ZIF-8@AHT on osteogenesis, and investigated its ability to form bone in vivo. First, we coated various quantities of nanoscale ZIF-8 crystals on alkali- and heat-treated titanium (AHT) by controlling the concentration of the synthesis solution. We then characterized the ZIF-8@AHT materials using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and determination of the sessile drop contact angle. To illustrate the combined effects of micro/nanotopography and ZIF-8@AHT composition on bone regeneration, we cultured MC3T3-E1 preosteoblast cells on various titanium substrates in vitro by setting pure titanium (Ti) and AHT as control groups. The ZIF-8@AHTs enhanced cell bioactivity compared with AHT and Ti, as evidenced by increased extracellular matrix (ECM) mineralization, collagen secretion and the upregulated expression of osteogenic genes (Alp, Col1, Opg, and Runx2) and osteogenesis-related proteins (ALP and OPG). ZIF-8@AHT-1/8 exhibited better osteogenic activity compared with the other ZIF-8@AHT groups investigated. We subsequently inserted Ti, AHT, and ZIF-8@AHT-1/8 implants into the healed first molars (M1s) of mice, and found that ZIF-8@AHT-1/8 also promoted osseointegration at the bone-implant interface. These results suggest that ZIF-8@AHT-1/8 has great potential for practical application in implant modification.