We studied steady-state and time-resolved fluorescence properties of an anticancer drug Doxorubicin in a saline buffer and poly-vinyl alcohol (PVA) film. Absorption of Doxorubicin, located at blue-green spectral region, allows a convenient excitation with visible light emitting diodes or laser diodes. Emission of Doxorubicin with maximum near 600nm can be easily detected with photomultipliers and CCD cameras. Both, absorption and fluorescence spectra in polymeric matrix show more pronounced vibronic structures than in solution. Also, the steady-state anisotropy in the polymer film is significantly higher than in the saline solution. In PVA film the fluorescence anisotropy is about 0.30 whereas in the saline buffer only 0.07. Quantum efficiencies of Doxorubicin were compared to a known standard Rhodamine 101 which has fluorescence emission in a similar spectral region. The quantum yield of Doxorubicin in PVA film is more than 10% and about twice higher than in the saline solution. Similarly, the lifetime of doxorubicin in PVA film is about 2 ns whereas in the saline solution only about 1 ns. The fluorescence anisotropy decays show that Doxorubicin molecules are freely rotating in the saline buffer with a correlation time of about 290 ps, and are almost completely immobilized in the PVA film. The spectroscopic investigations presented in this manuscript are important, as they provide answers to changes in molecular properties of Doxorubicin depending changes in the local environment, which is useful when synthesizing nano-particles for Doxorubicin entrapment.

BackgroundThe process of optimization and fabrication of nanoparticle synthesis for preclinical studies can be challenging and time consuming. Traditional small scale laboratory synthesis techniques suffer from batch to batch variability. Additionally, the parameters used in the original formulation must be re-optimized due to differences in fabrication techniques for clinical production. Several low flow microfluidic synthesis processes have been reported in recent years for developing nanoparticles that are a hybrid between polymeric nanoparticles and liposomes. However, use of high flow microfluidic synthetic techniques has not been described for this type of nanoparticle system, which we will term as nanolipomer. In this manuscript, we describe the successful optimization and functional assessment of nanolipomers fabricated using a microfluidic synthesis method under high flow parameters.ResultsThe optimal total flow rate for synthesis of these nanolipomers was found to be 12 ml/min and flow rate ratio 1:1 (organic phase: aqueous phase). The PLGA polymer concentration of 10 mg/ml and a DSPE-PEG lipid concentration of 10% w/v provided optimal size, PDI and stability. Drug loading and encapsulation of a representative hydrophobic small molecule drug, curcumin, was optimized and found that high encapsulation efficiency of 58.8% and drug loading of 4.4% was achieved at 7.5% w/w initial concentration of curcumin/PLGA polymer. The final size and polydispersity index of the optimized nanolipomer was 102.11 nm and 0.126, respectively. Functional assessment of uptake of the nanolipomers in C4-2B prostate cancer cells showed uptake at 1 h and increased uptake at 24 h. The nanolipomer was more effective in the cell viability assay compared to free drug. Finally, assessment of in vivo retention in mice of these nanolipomers revealed retention for up to 2 h and were completely cleared at 24 h.ConclusionsIn this study, we have demonstrated that a nanolipomer formulation can be successfully synthesized and easily scaled up through a high flow microfluidic system with optimal characteristics. The process of developing nanolipomers using this methodology is significant as the same optimized parameters used for small batches could be translated into manufacturing large scale batches for clinical trials through parallel flow systems.

In this paper, we have synthesized BSA protected gold nanoclusters (BSA Au nanocluster) and studied the effect of quencher, protein denaturant, pH and temperature on the fluorescence properties of the tryptophan molecule of the BSA Au nanocluster and native BSA. We have also studied their effect on the peak emission of BSA Au nanoclusters (650 nm). The phtophysical characterization of a newly developed fluorophore in different environments is absolutely necessary to futher develop their biomedical and analytical applications. It was observed from our experiments that the tryptophan in BSA Au nanoclusters is better shielded from the polar environment. Tryptophan in native BSA showed a red shift in its peak emission wavelength position. Tryptophan is a highly polarity sensitive dye and a minimal change in its microenvironment can be easily observed in its photophysical properties.