Absorption reconstruction improves biodistribution assessment of fluorescent nanoprobes using hybrid Fluorescence-mediated tomography

Aim: Fluorescence-mediated tomography (FMT) holds potential for accelerating diagnostic and theranostic drug development. However, for proper quantitative fluorescence reconstruction, knowledge on optical scattering and absorption, which are highly heterogeneous in different (mouse) tissues, is required. We here describe methods to assess these parameters using co-registered micro Computed Tomography (µCT) data and nonlinear whole-animal absorption reconstruction, and evaluate their importance for assessment of the biodistribution and target site accumulation of fluorophore-labeled drug delivery systems.\ud \ud Methods: Besides phantoms with varying degrees of absorption, mice bearing A431 tumors were imaged 15 min and 48 h after i.v. injection of a fluorophore-labeled polymeric drug carrier (pHPMA-Dy750) using µCT-FMT. The outer shape of mice and a scattering map were derived using automated segmentation of the µCT data. Furthermore, a 3D absorption map was reconstructed from the trans-illumination data. We determined the absorption of five interactively segmented regions (heart, liver, kidney, muscle, tumor). Since blood is the main near-infrared absorber in vivo, the absorption was also estimated from the relative blood volume (rBV), determined by contrast-enhanced µCT. We compared the reconstructed absorption with the rBV-based values and analyzed the effect of using the absorption map on the fluorescence reconstruction.\ud \ud Results: Phantom experiments demonstrated that absorption reconstruction is possible and necessary for quantitative fluorescence reconstruction. In vivo, the reconstructed absorption showed high values in strongly blood-perfused organs such as the heart, liver and kidney. The absorption values correlated strongly with the rBV-based absorption values, confirming the accuracy of the absorption reconstruction. Usage of homogenous absorption instead of the reconstructed absorption map resulted in reduced values in the heart, liver and kidney, by factors of 3.5, 2.1 and 1.4, respectively. For muscle and subcutaneous tumors, which have a much lower rBV and absorption, absorption reconstruction was less important.\ud \ud Conclusion: Quantitative whole-animal absorption reconstruction is possible and can be validated in vivo using the rBV. Usage of an absorption map is important when quantitatively assessing the biodistribution of fluorescently labeled drugs and drug delivery systems, to avoid a systematic underestimation of fluorescence in strongly absorbing organs, such as the heart, liver and kidney

Facile synthesis of 4H-chromene derivatives via base-mediated annulation of ortho-hydroxychalcones and 2-bromoallyl sulfones

Abstract The cesium carbonate-mediated reaction of 2-bromoallyl sulfones and ortho-hydroxychalcones furnished 3-arylsulfonyl-4H-chromene derivatives in 58-67% yield (18 examples). 2-Bromoallyl sulfones functioned as synthetic surrogates for allenyl sulfones in the reaction. Findings Benzo [b]dihydropyran, commonly known as 4H-chromene (1), is a privileged heterocyclic scaffold that is found in a variety of biologically active natural and synthetic products The utility of some of these methods are limited by drawbacks such as lengthy substrate synthesis, high cost of catalysts and tedious procedures. Therefore, general synthetic methods for accessing substituted chromene derivatives from readily available materials are still in demand. During the course of our recent investigations on annulation reactions of unsaturated sulfones The facile cyclocondenzation of salicylaldehyde with 2a (Scheme 1, path c) prompted us to explore analogous annulation reactions for the synthesis of functionalized chromene derivatives. The biological activities exhibited by many 4H-chromene derivatives provided an added incentive for this investigation Scheme 2: Base-mediated cyclization reaction of o-hydroxychalcone 7a and 2-bromoallyl sulfone 2a. In the 1 H NMR spectrum of 8aa, three sets of doublet of doublets were visible at δ 4.52 (1H, J = 2.3 and 9.0 Hz), δ 3.58 (1H, J = 2.3 and 17.1 Hz) and δ 3.33 (1H, J = 9.0 and 17.1 Hz) arising from the -CH 2 -CH-fragment. The methyl group protons resonated as a singlet at δ 2.51. A peak at δ 197.4 in the 13 C NMR spectrum along with the absorption peak at 1680 cm −1 in the IR spectrum confirmed the presence of the keto group. All other signals were in agreement with the assigned structure. In order to explore the scope and generality of this facile 4H-chromene synthesis, a variety of o-hydroxychalcones were prepared as previously described (Scheme 3) The cesium carbonate-mediated reaction of 2-bromoallyl sulfones 2a,b with o-hydroxychalcones 7a-i proceeded uneventfully to afford the corresponding 2-methyl-3-arylsulfonyl-4H-chromene derivatives 8aa-8ib (Scheme 4). The annulation reaction appears to be general as evident from the results in Scheme 4. The chalcone component can accommodate chloro, bromo and methoxy groups as aromatic substituents. Polycyclic aromatic hydrocarbon frameworks (naphthalene and anthracene rings) as well as a representative heterocyclic ring (furan) may be incorporated into the 4H-chromene skeleton product by using chalcones (7c, 7d, and 7e, respectively) functionalized with these moieties. Disappointingly, attempts to extend the annulation reaction to phenols with other Michael acceptors at the ortho-position (such as unsaturated esters, enals and nitroolefins) were not successful. Additionally, a very low yield (ca. 10%) of the product 8aa was obtained when the chalcone formation (7a) and its annulation reaction with 2a were combined into a one-pot operation (mediated by KOH in ethanol). A plausible mechanistic rationalization of the 4H-chromene formation is presented in Scheme 5. Cesium carbonate mediates the dehydrobromination of 2a to produce the allenyl sulfone 5 (see Scheme 1, path d). Additionally, deprotonation of 7a by Cs 2 CO 3 generates the phenoxide anion 9. A hetero-Michael addition of 5 and 9 results in the formation of a stabilized carbanion which may be represented as the resonance structures 10 or 11. The α-sulfonyl carbanion 11 then undergoes an intramolecular Michael addition to the β-carbon of the enone unit to afford the enolate 12. Isomerization of the exocyclic olefin moiety of 12 into the endocyclic position may be assisted by internal proton transfer. Tautomerization of the resultant enol 13 to its keto form affords the final product 8aa. It may be Beilstein J. Org. Chem. 2016, 12, 16-21. 19 noted that the key carbon-carbon bond forming event (conversion of 11 to 12) here is completely regioselective as the Michael addition of the stabilized carbanion 11 occurs selectively at the α-sulfonyl position (not at the less hindered terminal of the allylic carbanion 11). Conclusion In conclusion, a base-mediated, facile synthesis of 3-sulfonyl-4H-chromenes from o-hydroxychalcones and 2-bromoallyl sulfones was developed. The starting materials are easily available and the reaction conditions are mild. 2-Bromoallyl sulfones Beilstein J. Org. Chem. 2016, 12, 16-21. 20 Scheme 5: A plausible mechanistic rationalization for the formation of 4H-chromene derivative 8aa from 7a and 2a

Number of Nanoparticles per Cell through a Spectrophotometric Method - A key parameter to Assess Nanoparticle-based Cellular Assays

Engineered nanoparticles (eNPs) for biological and biomedical applications are produced from functionalised nanoparticles (NPs) after undergoing multiple handling steps, giving rise to an inevitable loss of NPs. Herein we present a practical method to quantify nanoparticles (NPs) number per volume in an aqueous suspension using standard spectrophotometers and minute amounts of the suspensions (up to 1 μL). This method allows, for the first time, to analyse cellular uptake by reporting NPs number added per cell, as opposed to current methods which are related to solid content (w/V) of NPs. In analogy to the parameter used in viral infective assays (multiplicity of infection), we propose to name this novel parameter as multiplicity of nanofection.JJDM thanks Spanish Ministerio de Economía y Competitividad for a Ramon y Cajal Fellowship and for supporting this work partially by Grant CTQ2012-34778. This research was partially supported by Marie Curie Career Integration Grants within the 7th European Community Framework Programme (FP7-PEOPLE-2011-CIG-Project Number 294142 and FP7-PEOPLE-2012-CIG-Project Number 322276) to RMSM and JJDM, respectively. This research was partially supported by the Consejería de Economía, Innovación y Ciencia de la Junta de Andalucía (BIO-1778) to JJDM. RMSM and JDUB thank CEI Biotic Granada for funding P_BS_54 and mP_BS_37 projects. JDUB thanks Spanish Ministerio de Economía y Competitividad for a Torres Quevedo fellowship (PTQ-13-06046)

Multidrug resistance: Physiological principles and nanomedical solutions

Multidrug resistance (MDR) is a pathophysiological phenomenon employed by cancer cells which limits the prolonged and effective use of chemotherapeutic agents. MDR is primarily based on the over-expression of drug efflux pumps in the cellular membrane. Prominent examples of such efflux pumps, which belong to the ATP-binding cassette (ABC) superfamily of proteins, are Pgp (P-glycoprotein) and MRP (multidrug resistance-associated protein), nowadays officially known as ABCB1 and ABCC1. Over the years, several strategies have been evaluated to overcome MDR, based not only on the use of low-molecular-weight MDR modulators, but also on the implementation of 1–100(0) nm-sized drug delivery systems. In the present manuscript, after introducing the most important physiological principles of MDR, we summarize prototypic nanomedical strategies to overcome multidrug resistance, including the use of carrier materials with intrinsic anti-MDR properties, the use of nanomedicines to modify the mode of cellular uptake, and the co-formulation of chemotherapeutic drugs together with low- and high-molecular-weight MDR inhibitors within a single drug delivery system. While certain challenges still need to be overcome before such constructs and concepts can be widely applied in the clinic, the insights obtained and the progress made strongly suggest that nanomedicine formulations hold significant potential for improving the treatment of multidrug-resistant malignancie

MO-FG-BRA-07: Theranostic Gadolinium-Based AGuIX Nanoparticles for MRI-Guided Radiation Therapy

International audienc

Gadolinium Nanoparticles for Magnetic Resonance Guided Radiation Therapy

International audienc