Penetration, label efficiency

The control of inverse transition temperatures by sequence manipulation and biocompatibility of ELPs make them useful polymers for drug delivery. Cultured cancer cells and solid tumors in animal models uptake fluorescently labeled ELPs in a thermally responsive manner (48,49). Two major limitations in cancer therapy have been the inability of therapeutic molecules to cross the cell membrane and the target-specificity of the compounds. To overcome these limitations cell-penetrating, peptides (CPP) have been fused with ELPs (CPP-ELP) to develop thermally responsive therapeutics with the ability to translocate the cell membrane (Figure 3B). CPPs can assist in the transportation of hydrophilic compounds (small molecules, oglionucleotides and peptides) across the cell membrane (50). Fusing ELPs to a variety of CPPs have revealed that the peptide sequence of penetratin demonstrates the most efficient cellular uptake (51). Further, these CPP-ELPs have been fused to a c-Myc inhibitory peptide known to target and inhibit cancer. As proof of principle, these fusion proteins inhibits proliferation of cultured cancer cell lines in a thermally responsive manner (52). 

Micromanipulate the tip of the miaopipet into the tissue, and use a pressure injector (e.g., a Picospritzer II) to deposit the dye. Injections are often ma more easily if the pipette is fractionally withdrawn from the fuU depth of the penetration. If you want to label the cut end of a periphaal nerve, depositing the dye onto the cut surface will efficiently label the axons within. 

The simplest method for detection is by direct exposure (autoradiography) produced by intimate contact of the developed plate with a photographic or x-ray film. Direct exposure is useful for all of the beta emitters, with the possible exception of low-level tritium-labeled samples. A variety of films have been examined for use in autoradiography (5,18,19,21-24,29-33). For maximum sensitivity, the film emulsion must be efficiently penetrated and interact with the radioactive emission. Low-energy isotopes, especially tritium, require the use of film that does not have the normal protective emulsion coating, which would prevent the beta emissions from being detected (21,33). 

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