Nanotech approaches to drug delivery and imaging

Encapsulation of drug nanoparticles in self-assembled macromolecular nanoshells

Layer-by-Layer (LbL) stepwise self-assembly of the polyelectrolytes poly(allylamine hydrochloride) and poly(styrenesulfonate) was used to create a macromolecular nanoshell around drug nanoparticles (approximately 150 nm in diameter). Dexamethasone, a steroid often used in conjugation with chemotherapy, was chosen as a model drug and was formulated into nanoparticles using a modified solvent-evaporation emulsification method. Measurement of the zeta potential (zeta-potential) after each polyelectrolyte layer was electrostatically added confirmed the successful addition of each layer. Additionally, data acquired from X-ray photon spectroscopy (XPS) indicated the presence of peaks representative of each physisorbed polyelectrolyte layer. Surface modification of the nanoshell was performed by covalently attaching poly(ethylene glycol) (PEG) with a molecular weight of 2000 to the outer surface of the nanoshell. Zeta potential measurements and XPS indicated the presence of PEG chains at the surface of the nanoshell. The polymeric nanoshell on the surface of the drug nanoparticle provides a template upon which surface modifications can be made to create a stealth or targeted drug delivery system.

Bacterial multidrug resistance unrelated to multidrug exporters: cell biology insight

Multidrug resistance (MDR) revealed in malignant cell lines was firstly attributed to the activity of multidrug exporters pumping drugs out of the cell. However, mutagenised Escherichia coli develop extraordinary numerous mutants resistant to target inhibitor and we have shown that with mutations mapped around the entire genome most of the mutants were multiple-resistant. In case of one such mutant studied MDR was shown as a sum of individual resistances due to mutations resulted in target and ligand sequestration and induced simultaneously in tightly linked, cassette-like genes. An explanation of local mutagenesis efficiency and the nature of sequestration process is proposed. A cassette-like organization of genes responsible for chemoresistance emergence could promote the local intensity of mutagenesis by a cassette facing the intracellular space and flux and contacting unlike other genes mutagen the first. Target and ligand sequestration could result from clogging the intracellular flux due to cytoplasm geometry alteration attributable to disorder-order transition in natively unfolded proteins affected with mutation.

Lighting up tumors with receptor-specific optical molecular probes

Accurate and rapid detection of tumors is of great importance for interrogating the molecular basis of cancer pathogenesis, preventing the onset of complications, and implementing a tailored therapeutic regimen. In this era of molecular medicine, molecular probes that respond to, or target molecular processes are indispensable. Although numerous imaging modalities have been developed for visualizing pathologic conditions, the high sensitivity and relatively innocuous low energy radiation of optical imaging method makes it attractive for molecular imaging. While many human diseases have been studied successfully by using intrinsic optical properties of normal and pathologic tissues, molecular imaging of the expression of aberrant genes, proteins, and other pathophysiologic processes would be enhanced by the use of highly specific exogenous molecular beacons. This review focuses on the development of receptor-specific molecular probes for optical imaging of tumors. Particularly, bioconjugates of probes that absorb and fluoresce in the near infrared wavelengths between 750 and 900 nm will be reviewed.