Rational design of large flat nitrogen-doped graphene oxide quantum dots with green-luminescence suitable for biomedical applications

Rational synthesis and simple methodology for the purification of large (35–45 nm in lateral size) and flat (1.0–1.5 nm of height) nitrogen-doped graphene oxide quantum dots (GOQDs) are presented. The methodology allows robust metal-free and acid-free preparation of N-GOQDs with a yield of about 100% and includes hydrothermal treatment of graphene oxide with hydrogen peroxide and ammonia. It was demonstrated that macroscopic impurities can be separated from N-GOQD suspension by their coagulation with 0.9% NaCl solution. Redispersible in water and saline solutions, particles of N-GOQDs were characterized using tip-enhanced Raman spectroscopy (TERS), photoluminescent, XPS, and UV-VIS spectroscopies. The size and morphology of N-GOQDs were studied by dynamic light scattering, AFM, SEM, and TEM. The procedure proposed allows nitrogen-doped GOQDs to be obtained, having 60–51% of carbon, 34–45% of oxygen, and up to 7.2% of nitrogen. The N-GOQD particles obtained in two hours of synthesis contain only pyrrolic defects of the graphene core. The fraction of pyridine moieties grows with the time of synthesis, while the fraction of quaternary nitrogen declines. Application of TERS allows demonstration that the N-GOQDs consist of a graphene core with an average crystallite size of 9 nm and an average distance between nearest defects smaller than 3 nm. The cytotoxicity tests reveal high viability of the monkey epithelial kidney cells Vero in the presence of N-GOQDs in a concentration below 60 mg L⁻¹. The N-GOQDs demonstrate green luminescence with an emission maximum at 505 nm and sedimentation stability in the cell culture medium.

This paper reveals the methodology for robust preparation of purified nitrogen-doped graphene oxide quantum dots with non-cytotoxic activity against monkey epithelial kidney cells (Vero ATCC® CCL-81™).     

Manejo de la amiloidosis traqueobronquial mediante técnicas broncoscópicas terapéuticas

Amyloidosis is a systemic disease caused by abnormal deposition of amyloid material that is detected with Congo red staining and is difficult to diagnose. Involvement of the tracheobronchial tree is rare and is a challenge for pulmonologists because of the wide differential diagnosis of this disease. We present two cases where tracheobronchial affectation has been observed: in one of them as a primary disease, and in another as secondary affectation. The use of bronchoscopic techniques is essential for the diagnosis of tracheobronchial involvement. In the absence of an effective drug therapy, local management of this disease with endoscopic techniques for bronchial repermeabilization is able to provide clinical improvement and expand the treatment options and prognosis in this disease.     

Two-way television: An experiment in interactive programming for the elderly

This study was conducted to 1) assess the effectiveness of an experimental two-way cable TV system in reaching the older people for whom it was designed, and 2) assess the attraction of this locally-based age-targeted system for its viewers. The study evaluates the system's effectiveness in reaching its target audience by examining information about the types of viewers—both younger and older—who have been attracted to the system. In addition, differences in factors that predict viewing frequency for younger and older people are used to illuminate life stage differences in people's attraction to locally-based TV programming. Findings show that the system had successfully reached its target audience within two years of inception. Watching the interactive TV programs because of the system's provision of information about local events and because of the senior citizens' focus strongly predicted viewing frequency for both older and younger respondents. The ability of locally-based interactive TV programming to serve social and informational needs of older people which are unmet by traditional broadcast television is discussed.