Interdisciplinary Topics, Centers and Institutes Degree Level:Graduate
Undergraduate/Graduate Category: Interdisciplinary Topics, Centers and Institutes Degree Level:Graduate Abstract ID#1469 Introduction
Experimental Results
• Liposome is the most common vehicle for targeted drug delivery[1]
Preliminary Solid-Mechanics Model
Liposome geometry before and after fusion
• Constituting lipids must be fine-tuned to specific optimal chemical and mechanical properties to effectively deliver cytotoxin to malignant tissues[2]
Height: 64.4 um
132um
102.7um
Assumptions: a) Boundary conditions: V = constant b) Free of intersurface forces: No adhesion c) Deformed geometry: truncated sphere with planar polar regions d) Mechanical response: F(z, a) reflects mechanical behavior of the liposome deformation-hemifusion-fusion
• Quantitative mechanics of endocytosis or fusion of liposome with a cell or another liposome is rare in literature
160 um
173um
Total Potential Energy Liposome on cantilever
Liposome on mica
Aggregated Configuration:
Fused liposome on mica
Liposome fusion process 400
Experiment Equipment
Second Force-drop
Hemi-fused Configuration:
b
300
Liposome preparation
d a
Microfluidic device for liposome preparation [3]
Applied force, F (nN)
200
d
First Force-drop
b
100
100 𝜇𝑚
a 0 c
e e
-100
Liposome fusion
Compression
c Fusion
-200
Laser
Hemi-fusion
Tension
Pre-fusion
Conclusions and Future Work
-300 0
20
40
60 80 100 Distance from cantilever to mica, D (um)
120
140
160
Characters of distinguished regions
Liposome
mica
Region ab bc cd
Behavior Gradual Instantaneous Gradual
Process Reversible elastic deformation Irreversible Hemi-fusion: fusion of outer lipid layer Reversible deformation as F turns from tensile to compressive
de Beyond e
Instantaneous Gradual
Irreversible fusion (coalescence) of liposomes Reversible elastic deformation
• Liposome composed of lipid with neutral spontaneous curvature cannot fuse spontaneously in 50mM CaCl 2 solution at room temperature • Experiments were repeated for 56 times in identical conditions, liposome fusion was found in 5 of them
microscopy Schematic diagram for liposome fusion equipment
• 5 fusion processes present identical fusion pattern: hemi-fusion, fusion • In failed experiments, liposomes were observed to explode before fusing with external
• Critical forces for DOPC liposome with diameter of 102.7mm hemi-fusion and fusion are 61.9nN and 258.9nN, respectively; critical membrane tension for hemi-fusion is 0.72mN/m based on solid-mechanics model • For the future work, new material will be introduced into DOPC, in order to produce liposome with negative effective spontaneous curvature and critical forces and membrane tensions will be obtained.
Acknowledge • This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. CMMI-#1232046 • Thanks to Yuting Huang from Harvard for suggestions on sample preparation
References [1] Torchilin, VP; “Multifunctional Nanocarriers”; Adv Drug Deliv Rev 2006 Dec; 58 (14): 1532-1555; [2] Jason, HS; Anne, LV; etc. “Enabling Individualized Therapy through Nanotechnology”; Pharmacol Res 2010 Aug; 62(2): 57-89 [3] Laura, RA; Sujit, SD; Shin-Hyun, K; Esther, A; Thomas, EK; Francisco, M; David AW; “ Ultrathin Shell Double Emulsion Templated Giant Unilamellar Lipid Vesicles with Controlled Microdomain Formation”; Small 2014 Oct; 10(5): 950-956;
Experimental Results
• Liposome is the most common vehicle for targeted drug delivery[1]
Preliminary Solid-Mechanics Model
Liposome geometry before and after fusion
• Constituting lipids must be fine-tuned to specific optimal chemical and mechanical properties to effectively deliver cytotoxin to malignant tissues[2]
Height: 64.4 um
132um
102.7um
Assumptions: a) Boundary conditions: V = constant b) Free of intersurface forces: No adhesion c) Deformed geometry: truncated sphere with planar polar regions d) Mechanical response: F(z, a) reflects mechanical behavior of the liposome deformation-hemifusion-fusion
• Quantitative mechanics of endocytosis or fusion of liposome with a cell or another liposome is rare in literature
160 um
173um
Total Potential Energy Liposome on cantilever
Liposome on mica
Aggregated Configuration:
Fused liposome on mica
Liposome fusion process 400
Experiment Equipment
Second Force-drop
Hemi-fused Configuration:
b
300
Liposome preparation
d a
Microfluidic device for liposome preparation [3]
Applied force, F (nN)
200
d
First Force-drop
b
100
100 𝜇𝑚
a 0 c
e e
-100
Liposome fusion
Compression
c Fusion
-200
Laser
Hemi-fusion
Tension
Pre-fusion
Conclusions and Future Work
-300 0
20
40
60 80 100 Distance from cantilever to mica, D (um)
120
140
160
Characters of distinguished regions
Liposome
mica
Region ab bc cd
Behavior Gradual Instantaneous Gradual
Process Reversible elastic deformation Irreversible Hemi-fusion: fusion of outer lipid layer Reversible deformation as F turns from tensile to compressive
de Beyond e
Instantaneous Gradual
Irreversible fusion (coalescence) of liposomes Reversible elastic deformation
• Liposome composed of lipid with neutral spontaneous curvature cannot fuse spontaneously in 50mM CaCl 2 solution at room temperature • Experiments were repeated for 56 times in identical conditions, liposome fusion was found in 5 of them
microscopy Schematic diagram for liposome fusion equipment
• 5 fusion processes present identical fusion pattern: hemi-fusion, fusion • In failed experiments, liposomes were observed to explode before fusing with external
• Critical forces for DOPC liposome with diameter of 102.7mm hemi-fusion and fusion are 61.9nN and 258.9nN, respectively; critical membrane tension for hemi-fusion is 0.72mN/m based on solid-mechanics model • For the future work, new material will be introduced into DOPC, in order to produce liposome with negative effective spontaneous curvature and critical forces and membrane tensions will be obtained.
Acknowledge • This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. CMMI-#1232046 • Thanks to Yuting Huang from Harvard for suggestions on sample preparation
References [1] Torchilin, VP; “Multifunctional Nanocarriers”; Adv Drug Deliv Rev 2006 Dec; 58 (14): 1532-1555; [2] Jason, HS; Anne, LV; etc. “Enabling Individualized Therapy through Nanotechnology”; Pharmacol Res 2010 Aug; 62(2): 57-89 [3] Laura, RA; Sujit, SD; Shin-Hyun, K; Esther, A; Thomas, EK; Francisco, M; David AW; “ Ultrathin Shell Double Emulsion Templated Giant Unilamellar Lipid Vesicles with Controlled Microdomain Formation”; Small 2014 Oct; 10(5): 950-956;
