Internally fixed lipid vesicle

1. A method of generating an internally fixed lipid vesicle, comprising:

providing a precursor lipid vesicle that contains an aqueous interior enclosed by a precursor lipid membrane, wherein the precursor lipid membrane of the precursor lipid vesicle is non-permeable to a crosslinker;

permeabilizing the precursor lipid membrane transiently to generate a permeable vesicle;

contacting the permeable vesicle with an inactive activatable crosslinker, whereby the inactive activatable crosslinker enters the permeable vesicle, wherein the inactive activatable crosslinker is a monomer or polymer;

allowing the permeable vesicle to return to a non-permeable vesicle;

removing any extravesicular crosslinker; and

activating the inactive activatable crosslinker to allow crosslinking to occur inside the non-permeable vesicle, whereby an internally fixed lipid vesicle containing a gelated interior is generated, and wherein the internally fixed lipid vesicle has a lipid membrane that is substantially identical to the precursor lipid membrane in one or more of membrane fluidity, membrane protein mobility, sensitivity to a surfactant, membrane permeability, membrane content, surface charge, and biological function.

2. The method of claim 1 , wherein the precursor lipid vesicle is a cell or a virus.

3. The method of claim 2 , wherein the cell is a mammalian cell or non-mammalian cell.

4. The method of claim 2 , wherein the cell is a human cell, non-human cell, antigen presenting cell, bacterial cell, fungal cell, immortalized cell, engineered cell, artificial cell, immune cell, epithelial cell, liver cell, adipose cell, kidney cell, fibroblast, chondrocyte, muscle cell, blood cell, bone cell, secretory cell, stem cell, ear hair cell, brain cell, neuronal cell, lung cell, or cancer cell.

5. The method of claim 1 , wherein the inactive activatable crosslinker is a photo-reactive, thermo-responsive, or chemical-reactive crosslinker.

6. The method of claim 1 , wherein the permeabilizing step is carried out by subjecting the precursor lipid vesicle to freezing and thawing, osmotic shock, sonoporation, electroporation, laser, surfactant-based permeabilization, or shearing.

7. The method of claim 1 , wherein the contact step includes contacting the permeable vesicle with a solution containing 1 wt % to 70 wt % of the inactive activatable crosslinker.

8. The method of claim 5 , wherein the inactive activatable crosslinker is an epoxide, urethane, polyether, polyester, polyacrylamide derivative containing hydrophobic pendant groups, PEG-PLGA-PEG triblock copolymer, hydroxyethyl methacrylate-methyl methacrylate (HEMA-MMA), polyacrylonitrile-polyvinyl chloride (PAN-PVC), poly(N-isopropyl acrylamide) (polyNIPAM), poly(N-vinylcaprolactam), cellulose derivative, polyethyleneglycol diacrylate, ethylene oxide-propylene, or Matrigel.

9. The method of claim 5 , wherein the inactive activatable crosslinker is a photo-reactive crosslinker, and wherein the contacting step further includes contacting the permeable vesicle with a photo-initiator.

10. The method of claim 1 , wherein the internally fixed lipid vesicle is in a suspension, a monolayer culture, or attached to a solid substrate.

11. The method of claim 2 , wherein the precursor lipid vesicle is an isolated cell.

12. The method of claim 11 , wherein the internally fixed lipid vesicle is in a suspension, a monolayer culture, or attached to a solid substrate.

13. The method of claim 11 , wherein the inactive activatable crosslinker is a photo-reactive, thermo-responsive, or chemical-reactive crosslinker.

14. The method of claim 13 , wherein the contact step includes contacting the permeable vesicle with a solution containing 1 wt % to 70 wt % of the inactive activatable crosslinker.

15. The method of claim 13 , wherein the inactive activatable crosslinker is an epoxide, urethane, polyether, polyester, polyacrylamide derivative containing hydrophobic pendant groups, PEG-PLGA-PEG triblock copolymer, hydroxyethyl methacrylate-methyl methacrylate (HEMA-MMA), polyacrylonitrile-polyvinyl chloride (PAN-PVC), poly(N-isopropyl acrylamide) (polyNIPAM), poly(N-vinylcaprolactam), cellulose derivative, polyethyleneglycol diacrylate, ethylene oxide-propylene, or Matrigel.

16. The method of claim 13 , wherein the inactive activatable crosslinker is a photo-reactive crosslinker, and wherein the contacting step further includes contacting the permeable vesicle with a photo-initiator.

17. The method of claim 11 , wherein the precursor lipid vesicle is an antigen-presenting cell, and the method further includes contacting the internally fixed lipid vesicle with an antigen-responsive cell.

18. The method of claim 11 , wherein the precursor lipid vesicle is a culture feeder cell, and the method further includes co-culturing a target cell with the internally fixed lipid vesicle.

19. The method of claim 11 , wherein the precursor lipid vesicle is a cell having a cell surface receptor for a compound or drug candidate, and the method further includes contacting the internally fixed lipid vesicle with the compound or drug candidate.

20. The method of claim 11 , wherein the precursor lipid vesicle is a cell having a cell surface receptor for a pathogen, and the method further includes contacting the internally fixed lipid vesicle with a sample containing or is suspected of containing the pathogen.