OBJECTIVE To investigate the biodistribution of lipid nanoparticles(LNPs)with different surface charges and different particle sizes in mice.METHODS LNPs were prepared using microfluidic technology by incorporating positively charged phospholipids,negatively charged phospholipids,ioniz-able phospholipids,and neutral phospholipids into the formulation to create LNPs with corresponding surface charges.The particle size of the LNPs was controlled by polyethylene glycol(PEG)modifica-tion and measured using dynamic light scattering(DLS)and transmission electron microscopy(TEM),while the surface charge was analyzed using a zeta potential analyzer.The LNPs were labeled with a fluorescent dye,and the mice were intravenously injected with 0.625 μmol·kg-1 of LNPs.At 1,4,12 and 24 h post-injection,the brain,heart,livers,spleen,lungs and kidneys were collected.The fluorescence distribution in different organs was detected using an in vivo imaging system to reflect the distribution of LNPs in various organs.RESULTS Particle size analysis showed that,except the ionizable lipid nanoparticles without PEG modification(LNP-MC3),which had a particle size>200 nm,the particle sizes of positively charged LNPs without PEG modification(LNP-Pos),PEG-modified positively charged LNPs(LNP-Pos-P),PEG-modified neutral LNPs(LNP-Neu-P),PEG-modified ionizable LNPs(LNP-MC3-P),and PEG-modified negatively charged LNPs(LNP-Neg-P)were all<200 nm.Zeta potential analysis revealed that the surface charges of the LNPs were the highest in LNP-Pos,followed by LNP-Pos-P,LNP-MC3-P,LNP-Neu-P,LNP-MC3 and LNP-Neg-P.In vivo imaging results indicated that LNP-Pos-P,LNP-Pos and LNP-MC3-P were primarily distributed in the livers,lungs and kidneys,respectively,while LNP-Neu-P and LNP-Neg-P in the livers,kidneys,and lungs,respectively.The distribution of LNP-MC3-P in the brain,heart,spleen and kidneys peaked at 12 h post-injection,but at 24 h in the livers.The distribution of LNP-Pos-P in the lungs peaked at 1 h post-injection.CONCLUSION LNPs are primarily distributed in the livers.Surface charges influence the second most highly-distributed organs.LNP-Pos-P and LNP-MC3-P are the second most highly-distributed in the lungs,and LNP-Neu-P and LNP-Neg-P in the kidneys.

OBJECTIVE To establish skin contamination models with sulfur mustard analogue 1-chloro-2-ethylsulfanyl ethane(CEES),and evaluate the therapeutic efficacy of reactive skin decontamination lotion kit(RSDL).METHODS ①Kunming,BALB/c,BALB/c-nu,and C57BL/6N were contaminted with CEES 75 μL·kg-1 using exposed method and covered method for 10 min on the dorsal skin.Wound healing times and areas were assessed to determine the stock of mice and exposure method.② BALB/c mice were exposed to a gradient of CEES at the doses of 75,150,250,350 and 500 μL·kg-1(10 min)using the covered method.Wound healing times,areas and Kaplan-Meier survival curves were used to determine the optimal dose.③ BALB/c mice were exposed to CEES 150 μL·kg-1 for varying durations(5,10 and 20 min)using the covered method.Wound healing times,areas and Kaplan-Meier survival curves were analyzed to determine the optimal exposure time.④ BALB/c mice were divided into four groups:control(exposed with the covered method at 150 μL·kg-1,10 min),treatment(20 μL RSDL treatment after exposure,as the control group),5 min treatment(20 μL RSDL treatment after 5 min of exposure,followed by 5 min of coverage)and immediate-treatment(exposed with the exposed method at 150 μL·kg-1,immediately treated with 20 μL RSDL,followed by 10 min of coverage).The therapeutic efficacy was evaluated based on the wound area,subcutaneous microvesicle count,epidermal thick-ness,and inflammatory cytokine(IL-6 and TNF-α)expressions.RESULTS ① The covered method caused more severe and prolonged wounds than the exposed method.BALB/c mice exhibited a high sensitivity to CEES with delayed wound healing and were therefore selected as the model animal.② Survival rates in BALB/c mice dropped below 50%at doses of 250,350 and 500 μL·kg-1,whereas an 83.3%survival rate was observed at 150 μL·kg-1.③ The mice exposed to CEES(150 μL·kg-1,20 min)died within 3 days.The wound area was consistently smaller in the 5 min covered group than in the 10 min covered group.④CEES-induced skin injury led to epidermal nuclear pyknosis,follicular disrup-tion,inflammatory infiltration,and microvesicle formation in both treatment and poisoned control groups.As more immediate treatment,the wound area significantly decreased.While the IL-6 expres-sion showed no significant intergroup difference,the TNF-α expression was significantly higher in the treatment group.CONCLUSION A CEES-induced skin contamination model has been established in BALB/c mice using the covered method(150 μL·kg-1,10 min covered).However,RSDL should be ad-ministered in 10 min post-contamination.

OBJECTIVE To investigate the biodistribution of lipid nanoparticles(LNPs)with different surface charges and different particle sizes in mice.METHODS LNPs were prepared using microfluidic technology by incorporating positively charged phospholipids,negatively charged phospholipids,ioniz-able phospholipids,and neutral phospholipids into the formulation to create LNPs with corresponding surface charges.The particle size of the LNPs was controlled by polyethylene glycol(PEG)modifica-tion and measured using dynamic light scattering(DLS)and transmission electron microscopy(TEM),while the surface charge was analyzed using a zeta potential analyzer.The LNPs were labeled with a fluorescent dye,and the mice were intravenously injected with 0.625 μmol·kg-1 of LNPs.At 1,4,12 and 24 h post-injection,the brain,heart,livers,spleen,lungs and kidneys were collected.The fluorescence distribution in different organs was detected using an in vivo imaging system to reflect the distribution of LNPs in various organs.RESULTS Particle size analysis showed that,except the ionizable lipid nanoparticles without PEG modification(LNP-MC3),which had a particle size>200 nm,the particle sizes of positively charged LNPs without PEG modification(LNP-Pos),PEG-modified positively charged LNPs(LNP-Pos-P),PEG-modified neutral LNPs(LNP-Neu-P),PEG-modified ionizable LNPs(LNP-MC3-P),and PEG-modified negatively charged LNPs(LNP-Neg-P)were all<200 nm.Zeta potential analysis revealed that the surface charges of the LNPs were the highest in LNP-Pos,followed by LNP-Pos-P,LNP-MC3-P,LNP-Neu-P,LNP-MC3 and LNP-Neg-P.In vivo imaging results indicated that LNP-Pos-P,LNP-Pos and LNP-MC3-P were primarily distributed in the livers,lungs and kidneys,respectively,while LNP-Neu-P and LNP-Neg-P in the livers,kidneys,and lungs,respectively.The distribution of LNP-MC3-P in the brain,heart,spleen and kidneys peaked at 12 h post-injection,but at 24 h in the livers.The distribution of LNP-Pos-P in the lungs peaked at 1 h post-injection.CONCLUSION LNPs are primarily distributed in the livers.Surface charges influence the second most highly-distributed organs.LNP-Pos-P and LNP-MC3-P are the second most highly-distributed in the lungs,and LNP-Neu-P and LNP-Neg-P in the kidneys.

OBJECTIVE To establish skin contamination models with sulfur mustard analogue 1-chloro-2-ethylsulfanyl ethane(CEES),and evaluate the therapeutic efficacy of reactive skin decontamination lotion kit(RSDL).METHODS ①Kunming,BALB/c,BALB/c-nu,and C57BL/6N were contaminted with CEES 75 μL·kg-1 using exposed method and covered method for 10 min on the dorsal skin.Wound healing times and areas were assessed to determine the stock of mice and exposure method.② BALB/c mice were exposed to a gradient of CEES at the doses of 75,150,250,350 and 500 μL·kg-1(10 min)using the covered method.Wound healing times,areas and Kaplan-Meier survival curves were used to determine the optimal dose.③ BALB/c mice were exposed to CEES 150 μL·kg-1 for varying durations(5,10 and 20 min)using the covered method.Wound healing times,areas and Kaplan-Meier survival curves were analyzed to determine the optimal exposure time.④ BALB/c mice were divided into four groups:control(exposed with the covered method at 150 μL·kg-1,10 min),treatment(20 μL RSDL treatment after exposure,as the control group),5 min treatment(20 μL RSDL treatment after 5 min of exposure,followed by 5 min of coverage)and immediate-treatment(exposed with the exposed method at 150 μL·kg-1,immediately treated with 20 μL RSDL,followed by 10 min of coverage).The therapeutic efficacy was evaluated based on the wound area,subcutaneous microvesicle count,epidermal thick-ness,and inflammatory cytokine(IL-6 and TNF-α)expressions.RESULTS ① The covered method caused more severe and prolonged wounds than the exposed method.BALB/c mice exhibited a high sensitivity to CEES with delayed wound healing and were therefore selected as the model animal.② Survival rates in BALB/c mice dropped below 50%at doses of 250,350 and 500 μL·kg-1,whereas an 83.3%survival rate was observed at 150 μL·kg-1.③ The mice exposed to CEES(150 μL·kg-1,20 min)died within 3 days.The wound area was consistently smaller in the 5 min covered group than in the 10 min covered group.④CEES-induced skin injury led to epidermal nuclear pyknosis,follicular disrup-tion,inflammatory infiltration,and microvesicle formation in both treatment and poisoned control groups.As more immediate treatment,the wound area significantly decreased.While the IL-6 expres-sion showed no significant intergroup difference,the TNF-α expression was significantly higher in the treatment group.CONCLUSION A CEES-induced skin contamination model has been established in BALB/c mice using the covered method(150 μL·kg-1,10 min covered).However,RSDL should be ad-ministered in 10 min post-contamination.