Doctor of Philosophy / Department of Chemistry / Stefan H. Bossmann / This paper describes two methods for utilizing cancer associated proteases for targeting
cancer therapy to the tumor. The first method is designing a drug delivery system based on
liposomes that are sensitive to cancer associated proteases. Upon contact with the protease, the
liposome releases its contents. The second method is designing a prodrug that is based on a
porin isolated from Mycobacterium smegmatis. The porin is modified with protease consensus
sequences, inhibiting its toxicity. Upon contact with the protease, the drug is activated.
Protease sensitive liposomes were synthesized that were sensitive to urokinase
plasminogen activator. This was done by synthesizing a cholesterol-anchored, uPA consensus –
sequence-containing, acrylic acid block copolymer and using it to form a covalently bound
polymer cage around the outside of a hypertonic liposome. Liposomes were synthesized that had
a diameter of 136 nm. Upon addition of the polymer the diameter increased by 2.69 nm,
indicating it had successfully embedded into the liposome membrane. After crosslinking with
either a short peptide containing a lysine (so that it is a diamine) or ethylenediamine, the
diameter increased between 5.33 nm and 14.1 nm (depending on the type and amount of the
crosslinked). Fluorescence release assays showed that the polymer cage could add in excess of
thirty atmospheres of osmotic pressure resistance, and, under isobaric conditions, would prevent
release of much of the liposomal contents. Upon treatment with uPA, the polymer caged
liposomes released a significantly larger amount of their contents making the liposomes protease
sensitive.
MspA was shown to be a very stable protein able to be imaged by AFM. AFM imaging
demonstrated that MspA is able to form native pore structures in membranes making it a good
imitator of the membrane attack complex. MspA was demonstrated to be highly cytotoxic, but
poor at distinguishing between cells. Pro-MspA was synthesized by adding a hydrophilic
peptide to MspA that prevents insertion. A uPA cleavage sequence embedded causes the MspA
to become activated at the cancer site. This was demonstrated in tests against uPA and non-uPA
producing cell lines.
| Identifer | oai:union.ndltd.org:KSU/oai:krex.k-state.edu:2097/14087 |
| Date | January 1900 |
| Creators | Basel, Matthew T. |
| Publisher | Kansas State University |
| Source Sets | K-State Research Exchange |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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