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 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.

BACKGROUND: Chinese anatomical parameters of antedor atlantoaxial transarticular screw fixation have been rarely reported although the technique is a novel method out of China for patients with C1-C2 instability. OBJECTIVE: To provide Chinese anatomical data for anterior C1-C2 transarticular screw fixation. DESIGN, TIME AND SETTING: A measurement experiment was performed at the Department of Anatomy, Southern Medical University and Department of Orthopedics, Wuhan General Hospital, Guangzhou Command of Chinese PLA between September 2006 and April 2008. MATERIALS: A total of 50 sets of dried Chinese adult human C1 and C2 specimens, without regard to gender and age, but no abnormality and breakage, were measured with an electronic digital caliper (precision 0.01 mm) and a goniometer(precision 0.5°) made in China. METHODS: One proper screw was drilled through the atlantoaxial joint respectively in the direction to middle part of laterosuperior angle in the posterior of C1 lateral mass, and the screw point should not break through the superior facet articularsurface of the C1. In the procedure, the screw drilling point was at the junction of the lateral border of C2 body to 4 mm above the inferior border of C2 anterior arch. border of transverse foramen of C2 body and the median line of C2 body, and the distance between the inserting point and the medial border of transverse foramen of C2 body. RESULTS: The data from all specimens were involved in the result analysis. In the sagittal plane, the minimum lateral angulation of the screw tract was (10.80±2.10)°(left) and (10.76±2.40)°(right) respectively, and the maximum lateral angulation was (25.13±3.12)°(left) and (25.12±2.86)°(right), respectively. In the coronal plane, the minimum posterior angulation was (8.85±2.12)° (left) and (9.28±2.65)° (right) respectively, and the maximum posterior angulation was (26.96±3.09)°(left) and (27.49±2.51)°(right), respectively. The left screw tract length was from (17.48±2.10) mm to (25.41±2.59) ram, and the right was from (17.49±2.23) mm to (25.58±2.42) mm. The left distance between the inserting point and the median line of C2 body was (9.84±0.69) mm, and the right was (9.81±0.66) mm. The left distance between the median line of C2 body and medial border of transverse foramen of C2 body was (14.12±1.28) mm, and the right was (14.60±1.36) mm. The left distance between the inserting point and medial border of transverse foramen of C2 body was (6.28±1.38) mm, and the right was (6.79±1.39) mm. CONCLUSION: It is optimal for the anterior C1-C2 transarticular screw fixation to place the antedor screw with a length of 17 to 25 mm in lateral angulation ranging from 10° to 25° and the posterior angulation ranging from 9° to 27°. During the procedure, the dissecting distance from the middle of C2 body to lateral should not exceed 14 mm.

[Objective]To provide Chinese morphological data for anterior C1、2 transarticular screw fixation.[Method]With a digital vernier and a goniometer made in China,the anatomic parameters related to anterior C1、2 transarticular screw fixation were measured from 50 pairs of dried Chinese adult human C1 and C2 vertebrae.[Result]In the anterior transarticular screw fixation,the lateral angulation of the screw tract to the sagittal plane ranged from(10.8?2.10)? to(25.13?3.12)?,the posterior anguation to the coronal plane from(8.85?2.12)? to(26.96?3.09)?,the screw tract length was from(17.48?2.1) mm to(25.4?2.59)mm,the distance from medial part of C2 foramen to the middle of C2 body was(14.12?1.28)mm.[Conclusion]It is optimal for the anterior C1、2 transarticular screw fixation to place the anterior C1、2 transarticular screw with the length of 17 mm to 25 mm in lateral angulation ranged from 10? to 25? and the posterior angulation ranged from 9? to 27?.During the procedure,the dissecting distance from the middle of C2 to lateral should not exceed 14 mm.