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[Background] Considerable effort has been exerted to develop noninvasive diagnostic biomarkers that might replace or reduce the need to perform endomyocardial biopsies. In this context, graft DNA circulating on transplant recipients has been proposed as a potential biomarker of organ rejection or cellular graft injury. [Methods] We propose a digital PCR (dPCR) method based on the amplification of ten specific InDels sufficiently sensitive to detect small amounts of specific donor circulating DNA diluted on the host cell free DNA (cfDNA). We obtained 23 informative mismatches from 30 host and donor organ biopsy pairs. [Results] Patients without heart-related complications showed a high increase in the specific genomic marker levels during the first 24 h after transplantation that dropped to the basal levels on days 3–4 post-surgery. In contrast, patients with complications presented a significantly lagged decay pattern from day one after transplantation. A specific donor cfDNA increase was detected in one patient two days before rejection diagnosis, diminishing the basal levels after successful immunotherapy. A cfDNA increase was also observed during graft injury due to heart damage. [Conclusion] These results suggest that cfDNA monitoring of transplanted patients may be a useful tool to detect and probably anticipate graft rejection.

In this work, several modifications of the colloidal processing technique and spark plasma sintering (SPS) to prepare yttria tetragonal zirconia composites (YTZP) with single walled carbon nanotubes (SWNT) have been tested with the aim of eliminating SWNT agglomerates. These modifications include high versus low energy ultrasonic agitation during colloidal processing, lyophilization of the 3YTZP/SWNT slurry and electrical insulation during sintering of the composites. Semi-quantitative microstructural characterization of the carbon nanotube distribution in the sintered composites showed that high energy ultrasonic agitation reduces drastically agglomerate size. Lyophilization of the mixed suspensions avoids SWNT bundle size growth. Combination of both produces an enhanced carbon nanotube network distribution along the grain boundaries (GB) due to the absence of carbon nanotube agglomerates and to a limited SWNT bundle size. This results in an increase of the real SWNT content in the GBs up to nominal SWNT content and therefore an enhanced SWNT efficiency in the composites. The agglomerate-free highly-dispersed composites exhibit a decrease in density together with grain size refinement, a decrease in room temperature hardness, an increase in flexural strength and a most significant increase in room temperature electrical conductivity. Improved SWNT distribution also lowers electrical percolation threshold to a very low level in SWNT ceramic composites, <1 vol% SWNT.