1. 1. Thermoresposive
Poly(N-alkylacrylamide) family, including Poly(N,N-diethylacrylamide) and Poly(N-isopropylacrylamide) display volume phase transitions in aqueous solution at elevated temperatures.

2. What’s been done?
PEG/PNIPAAm or PEG/PDEAAm hydrogels (swelling behaviors)
Poly(NIPAAm-co-HEMA-lactate) with hydrolytically sensitive lactate ester side group (hydrolysis,LCST)
PNIPAAm-b-PEO (phase transition, aggregation)
Etc.

3. Others Poly(VCL-VAC) Poly(vinyl methyl ether)
(VCL: N-vinyl caprolactam; VAC: vinyl acetate)
Gradually become hydrophobic & insoluble 25~35
Poly(vinyl methyl ether)

4. How about making thermoresponsive nanogels using inversed microenmulsion technique?

5. LCST of PNIPAAm is ~32
Hydrophilic PEG (or PEGdiA) will increase the LCST
Manipulate the LCST controlled release?
Feed ratio of the monomers
M.E. composition
Surfactant

6. What else? Size distribution Phase transition/swelling equilibrium
Intraparticle phase transition or interparticle aggregation
Effect of heating rate on phase transition & aggregation
Etc

7. Is it possible to release drugs upon stimuli?
Decrease temperature locally?

8. 2. pH-dependent conformational transition
Poly (N-vinyl pyrrolidone-acrylic acid)-poly
(ethylene glycol)=poly (NVP-AA)-PEG hydrogel, swelling with increasing pH
Poly(2-ethylacrylic acid)=PEAA, undergoing a conformational collapse when pH is depressed.
Thus far, PEAA has been used to create liposomes that respond to pH, temperature, light intensity and concentration of a solute such as glucose.

9. Make nanogels of PEAA etc
In endosome, pH=~4.
Manipulate the transition point : controlled release; prolonged circulation time; and ability to exit the endosome

10. 3. Hydrolytical crosslinking
Not easy to make ester directly in the microemulsion (step-growth polymerization)
Premade hydrolytical macromer as crosslinker ( )m ( )n ( )m

11. 4. Targeting So many ligands targeting kinds of cells, organelles …
Gene therapy: nuclear targeting
NLSs (specific nuclear localization amino acid sequences): short clusters of the basic amino acids lysine and arginine positioned within a protein at sites where they can be recognized by nuclear binding proteins involved in their delivery to nuclear pores for transport into the nucleus.

12. Generic nuclear delivery vector
Binding domain to specific receptor
NLS
Cell membrane translocation domain
Cargo
-Genes
-Antisense oligos
-Enzymes
-Toxins
-Transcription factors

13. Surface modified nanogels with targeting ligand
NH or OH: form H-bonding with phosphate group of DNA
(And /or electrostatic forces)

14. 5. Improving the cytoplasmic delivery
Delivery to cytoplasm and nucleus
PTDs: protein transduction domains
Attachment of PTDs to liposome carriers and their subsequent cellular uptake and cytoplasmic release may have significant implications for the future of both drug and DNA delivery in vitro and in vivo.

15. TAT peptide
Attachment of TAT peptide to a water-soluble synthetic macromolecule will result in cytoplasmic delivery of the conjugate into cytoplasm and nucleus by a TAT facilitated pathway.
HPMA-TAT conjugates
(E.g. P-TAT-FITC)
Delivery of proteins, nanoparticles and liposomes.

16. Attachement of TAT to nanogels

17. COMBO of 1-5