No abstract

Poly(amidoamine) (PAMAM) dendrimers are increasingly studied as model nanoparticles for a variety of biomedical applications, notably in systemic administrations. However, with respect to blood contacting applications, amine-terminated dendrimers have recently been shown to activate platelets and cause a fatal, disseminated intravascular coagulation (DIC)-like condition in mice and rats. We here demonstrate that, upon addition to blood, cationic G7 PAMAM dendrimers induce fibrinogen aggregation, which may contribute to the in vivo DIC-like phenomenon. We demonstrate that amine-terminated dendrimers act directly on fibrinogen in a thrombin-independent manner to generate dense, high-molecular-weight fibrinogen aggregates with minimal fibrin fibril formation. In addition, we hypothesize this clot-like behavior is likely mediated through electrostatic interactions between the densely charged cationic dendrimer surface and negatively charged fibrinogen domains. Interestingly, cationic dendrimers also induced aggregation of albumin, suggesting that many negatively charged blood proteins may be affected by cationic dendrimers. To investigate this further, zebrafish embryos (ZFE) were employed to more specifically determine the speed of this phenomenon and the pathway- and dose-dependency of the resulting vascular occlusion phenotype. These novel findings show that G7 PAMAM dendrimers significantly and adversely impact many blood components to produce rapid coagulation and strongly suggest that these effects are independent of classic coagulation mechanisms. These results also strongly suggest the need to fully characterize amine-terminated PAMAM dendrimers in regards to their adverse effects on both coagulation and platelets, which may contribute to blood toxicity.

Poly(amidoamine) (PAMAM) dendrimers have been proposed for a variety of biomedical applications and are increasingly studied as model nanomaterials for such use. The dendritic structure features both modular synthetic control of molecular size and shape and presentation of multiple equivalent terminal groups. These properties make PAMAM dendrimers highly functionalizable, versatile single-molecule nanoparticles with a high degree of consistency and low polydispersity. Recent nanotoxicological studies showed that intravenous administration of amine-terminated PAMAM dendrimers to mice was lethal, causing a disseminated intravascular coagulation-like condition. To elucidate the mechanisms underlying this coagulopathy, in vitro assessments of platelet functions in contact with PAMAM dendrimers were undertaken. This study demonstrates that cationic G7 PAMAM dendrimers activate platelets and dramatically alter their morphology. These changes to platelet morphology and activation state substantially altered platelet function, including increased aggregation and adherence to surfaces. Surprisingly, dendrimer exposure also attenuated platelet-dependent thrombin generation, indicating that not all platelet functions remained intact. These findings provide additional insight into PAMAM dendrimer effects on blood components and underscore the necessity for further research on the effects and mechanisms of PAMAM-specific and general nanoparticle toxicity in blood.

Here we report an ultra-long-acting tunable, biodegradable, and removable polymer-based delivery system that offers sustained drug delivery for up to one year for HIV treatment or prophylaxis. This robust formulation offers the ability to integrate multiple drugs in a single injection, which is particularly important to address the potential for drug resistance with monotherapy. Six antiretroviral drugs were selected based on their solubility in N-methyl-2-pyrrolidone and relevance as a combination therapy for HIV treatment or prevention. All drugs released with concentrations above their protein-adjusted inhibitory concentration and retained their physical and chemical properties within the formulation and upon release. The versatility of this formulation to integrate multiple drugs and provide sustained plasma concentrations from several weeks to up to one year, combined with its ability to be removed to terminate the treatment if necessary, makes it attractive as a drug delivery platform technology for a wide range of applications.

Chromosomal region 11q23 is frequently rearranged in acute lymphocytic leukemias (ALLs) and in acute myeloid leukemlas (AMLs), mostly In reciprocal ex n with various transocation partners. The most of these translocations is t(4;11)(q21;q23). It Is present in -10% ofALL patients, most frequently in very young children. We have recently cloned a region of chromosome 11, the ALL-i locus, found to be rearranged in maligant cells from patients with the t(4;11), t(9;11),) t(11;19)9 t(1;11), t(6;11)9 t(10;11)9 and del(11q23) chromosomal abnormalities. Here we report the cloning and characterization ofchromosomal breakpoints from leukemic cells with t(4;11) aberrations. The breakpoints cluster in regions of 7-8 kilobases on both chromosomes 4 and 11. The presence of heptamer-and nonamer-like sequences at the sites of breakage sggess that the VDJ recombinase utilized for immunoglobulin gene rearrangement is also dily involved in these translocations. We also show that leukenic cells with t(4;11) express altered RNAs transcribed from the derivative chromosomes 11 and 4.Specific reciprocal chromosome translocations are the cytogenetic hallmark of lymphomas and leukemias. These chromosomal abnormalities have a molecular basis in alterations of normal cellular genes leading to their deregulation (1). Chromosome 11 region 11q23 is frequently rearranged in acute lymphocytic leukemia (ALL) and in acute myelogenous leukemia (AML). Reciprocal translocations t(4;11)(q21;q23), t(11;19)(q23;p13), and t(1;11)(p32;q23) are found in up to 10-15% of ALL cases (2). Translocations between 11q23 and chromosomal regions 9p23, 6q27, 1p21, 2p2l, 10pil, 17q23, and 19p13 are found in 5-6% of AML cases. In addition, interstitial deletions in 11q23 have been detected both in ALL and in AML (2). Chromosome 11q23-associated leukemias, in particular those with t(4;11), often appear in very young children and are characterized by heavy tumor load, poor prognosis, and frequent expression of both