Identification of the Proteins Determining the Blood Circulation Time of Nanoparticles

The therapeutic efficacy and adverse impacts of nanoparticles (NPs) are strongly dependent on their systemic circulation time. The corona proteins adsorbed on the NPs determine their plasma half-lives, and hence, it is crucial to identify the proteins shortening or extending their circulation time. In this work, the in vivo circulation time and corona composition of superparamagnetic iron oxide nanoparticles (SPIONs) with different surface charges/chemistries were analyzed over time. SPIONs with neutral and positive charges showed the longest and shortest circulation times, respectively. The most striking observation was that corona-coated NPs with similar opsonin/dysopsonin content showed different circulation times, implying these biomolecules are not the only contributing factors. Long-circulating NPs adsorb higher concentrations of osteopontin, lipoprotein lipase, coagulation factor VII, matrix Gla protein, secreted phosphoprotein 24, alpha-2-HS-glycoprotein, and apolipoprotein C-I, while short-circulating NPs adsorb higher amounts of hemoglobin. Therefore, these proteins may be considered to be determining factors governing the NP systemic circulation time.

Comparative Study of Nanoparticle Blood Circulation after Forced Clearance of Own Erythrocytes (Mononuclear Phagocyte System-Cytoblockade) or Administration of Cytotoxic Doxorubicin- or Clodronate-Loaded Liposomes

Recent developments in the field of nanomedicine have introduced a wide variety of nanomaterials that are capable of recognizing and killing tumor cells with increased specificity. A major limitation preventing the widespread introduction of nanomaterials into the clinical setting is their fast clearance from the bloodstream via the mononuclear phagocyte system (MPS). One of the most promising methods used to overcome this limitation is the MPS-cytoblockade, which forces the MPS to intensify the clearance of erythrocytes by injecting allogeneic anti-erythrocyte antibodies and, thus, significantly prolongs the circulation of nanoagents in the blood. However, on the way to the clinical application of this approach, the question arises whether the induced suppression of macrophage phagocytosis via the MPS-cytoblockade could pose health risks. Here, we show that highly cytotoxic doxorubicin- or clodronate-loaded liposomes, which are widely used for cancer therapy and biomedical research, induce a similar increase in the nanoparticle blood circulation half-life in mice as the MPS-cytoblockade, which only gently and temporarily saturates the macrophages with the organism's own erythrocytes. This result suggests that from the point of view of in vivo macrophage suppression, the MPS-cytoblockade should be less detrimental than the liposomal anti-cancer drugs that are already approved for clinical application while allowing for the substantial improvement in the nanoagent effectiveness.

The feasibility of low iodine dynamic CT angiography with test bolus for evaluation of lower extremity peripheral artery disease

OBJECTIVE

This study aims to determine if low iodine dynamic computed tomography angiography performed after a fixed delay or test bolus acquisition demonstrates high concordance with clinical computed tomography angiography (using a routine amount of iodinated contrast) to display lower extremity peripheral arterial disease.

METHODS

After informed consent, low iodine dynamic computed tomography angiography examination (using either a fixed delay or test bolus) using 50 ml of iodine contrast media was performed. A subsequent clinical computed tomography angiography using standard iodine dose (115 or 145 ml) served as the reference standard. A vascular radiologist reviewed dynamic and clinical computed tomography angiography images to categorize the lumen into "not opacified", "<50% stenosis", " 50 ̶70% stenosis", ">70% stenosis", and "occluded" for seven arterial segments in each lower extremity. Concordance between low iodine dynamic computed tomography angiography and the routine iodine reference standard was calculated. The clinical utility of 4D volume-rendered images was also evaluated.

RESULTS

Sixty-eight patients (average age 66.1 ± 12.3 years, male; female = 49: 19) were enrolled, with 34 patients each undergoing low iodine dynamic computed tomography angiography using fixed delay and test bolus techniques, respectively. One patient assigned to the test bolus group did not undergo low iodine computed tomography angiography due to unavailable delayed time. The fixed delay was 13 s, with test bolus acquisition resulting in a mean variable delay prior to image acquisition of 19.5 s (range; 8-32 s). Run-off to the ankle was observed using low iodine dynamic computed tomography angiography following fixed delay and test bolus acquisition in 76.4% (26/34) and 100% (33/33) of patients, respectively (p = 0.005). Considering extremities with run-off to the ankle and without severe artifact, the concordance rate between low iodine dynamic computed tomography angiography and the routine iodine reference standard was 86.8% (310/357) using fixed delay and 97.9% (425/434) using test bolus (p < 0.001). 4D volume-rendered images using fixed delay and test bolus demonstrated asymmetric flow in 57.7% (15/26) and 58.1% (18/31) (p = 0.978) of patients, and collateral blood flow in 11.5% (3/26) and 22.6% (7/31) of patients (p = 0.319), respectively.

CONCLUSION

Low iodine dynamic computed tomography angiography with test bolus acquisition has a high concordance with routine peripheral computed tomography angiography performed with standard iodine dose, resulting in improved run-off to the ankle compared to dynamic computed tomography angiography performed after a fixed delay. This method is useful for minimizing iodine dose in patients at risk for contrast-induced nephropathy. 4D volume-rendered computed tomography angiography images provide useful dynamic information.

Antifouling Manganese Oxide Nanoparticles: Synthesis, Characterization, and Applications for Enhanced MR Imaging of Tumors

Antifouling manganese oxide (Mn₃O₄) nanoparticles (NPs) were synthesized by solvothermal decomposition of tris(2,4-pentanedionato) manganese(III) in the presence of trisodium citrate, followed by surface modification with polyethylene glycol and l-cysteine. The as-prepared nanoparticles have a uniform size distribution, good colloidal stability and good cytocompatibility. The modification of l-cysteine rendered the particles with much longer blood circulation time (half-decay time of 28.4 h) than those without l-cysteine modification (18.5 h), and decreased macrophage cellular uptake. Thanks to desirable antifouling property and relatively high r₁ relaxivity (3.66 mM^-1 s^-1), the l-cysteine-modified Mn₃O₄ NPs can be used for enhanced tumor magnetic resonance imaging applications.

A novel cabazitaxel-loaded polymeric micelle system with superior in vitro stability and long blood circulation time

Cabazitaxel (CTX) is a second-generation semisynthetic taxane that demonstrates antitumor activity superior to docetaxel. However, the low aqueous solubility of CTX has hampered its use as a therapeutic agent. In this work, CTX-loaded N-t-butoxycarbonyl-L-phenylalanine end-capped monomethyl poly (ethylene glycol)-block-poly (D,L-lactide) (mPEG-PLA-Phe(Boc)/CTX) micelles were prepared to improve the solubility of CTX while retaining its superior stability before accessing the tumor site. The mPEG-PLA-Phe(Boc)/CTX micelles showed excellent stability in vitro compared with mPEG-PLA/CTX micelles. When stored at 25 °C, the mPEG-PLA/CTX micelles tended to aggregate within 1 h, whereas the mPEG-PLA-Phe(Boc)/CTX micelles were uniformly transparent even after three weeks. Dilution of mPEG-PLA/CTX micelles widened their size distribution and decreased the encapsulation efficiency, while significant change was not found in mPEG-PLA-Phe(Boc)/CTX micelles, even when diluted 1000-fold. Pharmacokinetic results in Sprague-Dawley rats indicated that, compared with Jevtana(®), intravenous administration of mPEG-PLA-Phe(Boc)/CTX micelles stably retained the CTX in plasma with 26.03-fold larger of the area under the time-concentration curve, 2.13-fold longer of the half-life, and 9.99-fold higher of the maximum concentration. In conclusion, mPEG-PLA-Phe(Boc) micelle may be a potential nanocarrier not only to improve the solubility of CTX but also to prolong the blood circulation time, which results in improved biological activity.