Degradation of magnetic nanoparticles mimicking lysosomal conditions followed by AC susceptibility

[Background] A deeper knowledge on the effects of the degradation of magnetic nanoparticles on their magnetic properties is required to develop tools for the identification and quantification of magnetic nanoparticles in biological media by magnetic means.[Methods] Citric acid and phosphonoacetic acid-coated magnetic nanoparticles have been degraded in a medium that mimics lysosomal conditions. Magnetic measurements and transmission electron microscopy have been used to follow up the degradation process.[Results] Particle size is reduced significantly in 24 h at pH 4.5 and body temperature. These transformations affect the magnetic properties of the compounds. A reduction of the interparticle interactions is observed just 4 h after the beginning of the degradation process. A strong paramagnetic contribution coming from the degradation products appears with time.[Conclusions] A model for the in vivo degradation of magnetic nanoparticles has been followed to gain insight on the changes of the magnetic properties of iron oxides during their degradation. The degradation kinetics is affected by the particle coating, in our case being the phosphonoacetic acid-coated particles degraded faster than the citric acid-coated ones.LG is the beneficiary of a postdoctoral grant from the AXA Research Fund and GBdS, of a sandwich-PhD grant from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq – Brazil). This work was also supported by the 7th framework programme of the European Commission Directorate-General for Research and Innovation (Nanomag 604448). X-ray diffraction, FTIR spectroscopy, and thermogravimetric and chemical analysis were carried out in the support laboratories of Instituto de Ciencia de Materiales de Madrid (CSIC).Peer reviewe

High-dose busulfan and cyclophosphamide are an effective conditioning regimen for allogeneic bone marrow transplantation in chemosensitive multiple myeloma

The present clinical trial was undertaken to investigate the toxicity and antimyeloma activity of busulfan (BU) and cyclophosphamide (CY) at the maximum tolerated doses of, respectively, 16 mg/kg and 200 mg/kg (BU-CY 4) as conditioning therapy for allogeneic bone marrow transplantation (BMT) in 19 consecutive patients with multiple myeloma (MM). Twelve (63%) had failed to respond to prior chemotherapy, while the remaining 37% had chemosensitive disease. No life-threatening or fatal regimen-related complications were observed. The incidence of veno-occlusive disease of the liver was zero according to Jones' criteria and 21% according to McDonald's system. Transplant-related mortality was 37%. Using stringent criteria, the frequency of complete remission (CR) was 42% among all patients and 53% among those who could be evaluated. With a median follow-up of 21 months for all patients and 66 months for survivors, the actuarial probability of survival and event-free survival at 4 years from BMT was 26% (95% CI: 7-46) and 21% (95% CI: 3-39), respectively. A more favorable outcome of transplantation was observed in the subgroup of patients with chemosensitive disease who had a transplant-related mortality of 14%, an overall CR rate of 86% (95% CI: 49-97) and a 4-year projected probability of event-free survival of 57% (95% CI: 20-93). Four of these patients are currently alive in continuous CR after 54, 66, 80 and 94 months, respectively. It is concluded that BU-CY 4 as conditioning for allogeneic transplantation for MM is associated with acceptable morbidity and relatively low mortality. This regimen exerts substantial antimyeloma activity, resulting in a high CR rate and durable responses, especially in patients with chemosensitive disease. Long-lasting remission and probable cure is possible following allogeneic stem cell transplantation for MM