A cytotoxicity study of silicon oxycarbide nanowires as cell scaffold for biomedical applications.

GOAL: Nanowires are promising biomaterials in multiple clinical applications. The goal of this study was to investigate the cytotoxicity of carbon-doped silica nanowires (SiOxCy NWs) on a fibroblastic cell line in vitro. MATERIALS AND METHODS: SiOxCy NWs were grown on Si substrates by CVD process. Murine L929 fibroblasts were cultured in complete DMEM and indirect and direct cytotoxicity tests were performed in agreement with ISO 19003-5, by quantitating cell viability at MTT and chemiluminescent assay. Cell cultures were investigated at Scanning Electron Microscope (SEM) and immunocytochemistry to observe their morphology and investigate cell-NWs interactions. Furthermore, hemocompatibility with Platelet-rich Plasma was assayed at SEM and by ELISA assay. RESULTS: SiOxCy NWs proved biocompatible and did not impair cell proliferation at contact assays. L929 were able to attach on NWs and proliferate. Most interestingly, L929 reorganised the NW scaffold by displacing the nanostructure and creating tunnels within the NW network. NWs moreover did not impair platelet activation and behaved similarly to flat SiO2. CONCLUSIONS: Our data show that SiOxCy NWs did not release cytotoxic species and acted as a viable and adaptable scaffold for fibroblastic cells, thus representing a promising platform for implantable devices.

A silicon carbide nanowire field effect transistor for DNA detection.

This work reports on the label-free electrical detection of DNA molecules for the first time, using silicon carbide (SiC) as a novel material for the realization of nanowire field effect transistors (NWFETs). SiC is a promising semiconductor for this application due to its specific characteristics such as chemical inertness and biocompatibility. Non-intentionally n-doped SiC NWs are first grown using a bottom-up vapor-liquid-solid (VLS) mechanism, leading to the NWs exhibiting needle-shaped morphology, with a length of approximately 2 µm and a diameter ranging from 25 to 60 nm. Then, the SiC NWFETs are fabricated and functionalized with DNA molecule probes via covalent coupling using an amino-terminated organosilane. The drain current versus drain voltage (I d-V d) characteristics obtained after the DNA grafting and hybridization are reported from the comparative and simultaneous measurements carried out on the SiC NWFETs, used either as sensors or references. As a representative result, the current of the sensor is lowered by 22% after probe DNA grafting and by 7% after target DNA hybridization, while the current of the reference does not vary by more than ±0.6%. The current decrease confirms the field effect induced by the negative charges of the DNA molecules. Moreover, the selectivity, reproducibility, reversibility and stability of the studied devices are emphasized by de-hybridization, non-complementary hybridization and re-hybridization experiments. This first proof of concept opens the way for future developments using SiC-NW-based sensors.

Porphyrin conjugated SiC/SiOx nanowires for X-ray-excited photodynamic therapy.

The development of innovative nanosystems opens new perspectives for multidisciplinary applications at the frontier between materials science and nanomedicine. Here we present a novel hybrid nanosystem based on cytocompatible inorganic SiC/SiOx core/shell nanowires conjugated via click-chemistry procedures with an organic photosensitizer, a tetracarboxyphenyl porphyrin derivative. We show that this nanosystem is an efficient source of singlet oxygen for cell oxidative stress when irradiated with 6 MV X-Rays at low doses (0.4-2 Gy). The in-vitro clonogenic survival assay on lung adenocarcinoma cells shows that 12 days after irradiation at a dose of 2 Gy, the cell population is reduced by about 75% with respect to control cells. These results demonstrate that our approach is very efficient to enhance radiation therapy effects for cancer treatments.

[The use of mesh in abdominal wall defects]. / Impiego delle reti nei difetti addominali parietali.

Today abdominal wall defect repair can't prescind from the use of prosthetic materials. Inguinal, femoral and incisional hernias represent more frequent events in which, only using prosthetic materials is it possible to perform "tension-free" repair. Prosthetic repairs "agree with" abdominal, wall physio-pathology, guarantee results and prevent recurrences. Permanent biomaterials like polypropylene and dacron mesh deserve special attention for their distinctive features are suitable for abdominal wall defect repair. Selection of material is an important step according to surgical technique and to avoid complications; the most alarming of which is a possible infection. However the average incidence of infection on prosthesis is about 0.5%. While infection risk is really scarce, the benefits of prosthetic repairs are clear: the recurrence rate of traditional hernia repairs is about 33% and 0-0.7% in prosthetic repairs. Likewise the recurrence rate for traditional incisional hernia repair is between 14% and 50%, whereas in prosthetic repairs it is 0-4.5%. Therefore it is necessary to use prosthesis for the following two reasons: firstly to avoid tension on the suture line, the prime cause of recurrence, and secondly to increase formation of collagen fibres on the transversalis fascia that appears histologically and biochemically altered. The authors report their experience of 660 prosthetic repairs, 600 for hernia and 60 for incisional hernia, performed, in the period April 1992-December 1994, at the General Surgery Department in San Giovanni Valdarno Hospital. The surgical techniques used were "tension-free" and "sutureless" and the prosthesis laid down always a polypropylene mesh. Complications only occurred in 33 patients, particularly 4 cases of infection (0.6%) however mesh remove was not required. The follow-up until today evidenced only two early recurrences owing to our technical mistakes in the beginning of our experience. For incisional hernia repair we laid down a giant dacron mesh on preperitoneal space. No complications were registered. The average stay in hospital was 5 days and follow-up showed no recurrence. The use of prosthetic materials in abdominal wall defect repair expressed large benefits with evident and clear reduction in recurrence rate. Traditional techniques produce tension on the suture line and high percentage of early and late recurrences since an essential surgical principle is transgressed. In fact traditionally repair has been accomplished by approximation of anatomical structures, that are not normally in apposition and by utilization of defective tissue. Metabolic alteration involving collagen turnover is evident in these patients. The answer to this problem is prosthetic repair. At present there is no ideal prosthesis, however the surgeon can use several suitable synthetic materials. The selection of prosthetic materials is a fundamental step also considering the possible infection; that however develops rarely. In conclusion the authors think that mesh repairs represent an overcoming of traditional surgical techniques in abdominal wall defect repair.

[A personal case of spontaneous pneumoperitoneum and review of the literature]. / Considerazioni su un caso di pneumoperitoneo spontaneo da noi osservato e revisione della letteratura.

A personal case of spontaneous pneumoperitoneum is reported and the nosographic importance of this form is reviewed. It is showed that primary forms, as opposed to those secondary to visceral perforation, always display a benign outcome. In some clearly-defined situations, therefore, a wait-and-see policy may be adopted, provided continuous surveillance of the position is assured.