Defining Known Drug Space Using DFT.

A density functional theory (DFT) study was performed on a collection of clinically approved drugs, or Known Drug Space (KDS), to determine the statistical distribution of four properties: dipole moment (DM), polarisability (POL), ionisation potential (IP) and electron affinity (EA). The DM and POL are linked to cell permeability of drugs whereas IP and EA reflect their redox stability thus ease of metabolism. A benchmarking exercise showed a good correlation between experimental values and their predicted counterparts. It was found that KDS occupies the volume of chemical space defined by: DM≤10 D, POL≤68 Å(3) , IP 6.0-9.0 V and EA-1.5-2.0 eV. Only 16 % of the drugs are outside one or more of these parameters. Three categories based on known oral absorption and bioavailability (low/medium/high) were established and compared. Predominately, drugs designated as 'low' were found outside the established parameters. The properties were compared with mainstream molecular descriptors and a strong correlation was seen for POL to MW (r(2) =0.899), which can explain the success of the latter since POL reflects the ability of molecules to interact with polar and non-polar environments such as water and interior of a membrane.

Real-time cell viability assays using a new anthracycline derivative DRAQ7®.

The exclusion of charged fluorescent dyes by intact cells has become a well-established assay for determining viability of cells. In search for a noninvasive fluorescent probe capable of long-term monitoring of cell death in real-time, we evaluated a new anthracycline derivative DRAQ7. The novel probe does not penetrate the plasma membrane of living cells but when the membrane integrity is compromised, it enters and binds readily to nuclear DNA to report cell death. It proved to be nontoxic to a panel of cancer cell lines grown continuously for up to 72 h and did not induce any detectable DNA damage signaling when analyzed using laser scanning microscopy and flow cytometry. The DRAQ7 provided a sensitive, real-time readout of cell death induced by a variety of stressors such as hypoxia, starvation, and drug-induced cytotoxicity. The overall responses to anticancer agents and resulting pharmacological dose-response profiles were not affected by the growth of tumor cells in the presence DRAQ7. Moreover, we for the first time introduced a near real-time microflow cytometric assay based on combination of DRAQ7 and mitochondrial inner membrane potential (ΔΨ(m) ) sensitive probe TMRM. We provide evidence that this low-dosage, real-time labeling procedure provides multiparameter and kinetic fingerprint of anticancer drug action.

Multivariate analysis of apoptotic markers versus cell cycle phase in living human cancer cells by microfluidic cytometry.

Measurement of apoptotic markers in tumors can be directly correlated with the cell cycle phase using flow cytometry (FCM). The conventional DNA content analysis requires cell permeabilization to stain nuclei with fluorescent probes such as propidium iodide or use of a costly UV-excitation line for Hoechst 33342 probe. The access to FCM is also still limited to centralized core facilities due to its inherent high costs and complex operation. This work describes development and proof-of-concept validation of a portable and user-friendly microfluidic flow cytometer (µFCM) that can perform multivariate real time analysis on live cells using sampling volumes as small as 10 microliters. The µFCM system employs disposable microfluidic cartridges fabricated using injection molding in poly(methylmethacrylate) transparent thermoplastic. Furthermore, the dedicated and miniaturized electronic hardware interface enables up to six parameter detection using a combination of spatially separated solid-state 473 (10 mW) and 640 nm (20 mW) lasers and x-y stage for rapid laser alignment adjustment. We provide new evidence that a simple 2D flow focusing on a chip is sufficient to measure cellular DNA content in live tumor cells using a far-red DNA probe DRAQ5. The feasibility of using the µFCM system for a dose-response profiling of investigational anti-cancer agents on human hematopoietic cancer cells is also demonstrated. The data show that µFCM can provide a viable novel alternative to conventional FCM for multiparameter detection of caspase activation and dissipation of mitochondrial inner membrane potential (ΔΨm) in relation to DNA content (cell cycle phase) in live tumor cells.