Intraocular Pressure Changes: An Important Determinant of the Biocompatibility of Intravitreous Implants Page: 3
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Biocompatibility of Intravitreous Implants
Table 1. Physical properties of nanoparticles used for intravitreous implantation.
Material Type Wettability Degradable Size nm
Buffered Salt Solution Solution Aqueous solution NA NA
Poly (I-lactic) Acid Polymeric Hydrophobic Yes 143
Polystyrene Polymeric Hydrophobic No 100
Hyaluronic Acid Polymeric Hydrophilic Yes 200
Poly N-isopropyl acrylamide Polymeric Hydrogel Hydrophilic No 100
doi:1 0.1371 /journal.pone.0028720.t001
reduction was not known, it is likely that the material property of
particle implants affects their acute ocular compatibility.
Distribution of intra-vitreous injected nanoparticles
To determine the potential interaction between injected
particles with ocular tissues, we first monitored the particle
distribution following intravitreous implantation using FITC-
labeled PNIPAM particles. As shown in the whole ocular section
images, we found that, at 2 hours, implanted particles were only
found in the posterior, but not anterior segment of eye. We also
found uniform fluorescence along the wall of the posterior
segments indicating the even spread of particles over the retinal
tissue (Figure 2A). Interestingly, we found that substantially more
particles accumulated in the trabecular meshwork area even at an
early time point - 2 hours. With increasing amount of time (4 and
24 hours) following implantation, we found that the particle-
associated fluorescence intensities reduced substantially in the
posterior chamber (Figure 2A and B). Interestingly, by 4 hours the
fluorescence intensity at the trabecular meshwork was significantly
higher than the rest of the eye and substantial fluorescent signals
were also found outside the ocular tissue nearby the trabecular
outflow region. Based on the fluorescent intensity measurements
and distribution, noticeably, most of the particles cleared from the
central portion of posterior chambers while majority of the
residual fluorescence intensity was seen in the area of trabecular
meshwork prior to clearance from the posterior cavities shortly
after 24 hours. Quantification of the distribution of fluorescent
particles throughout the ocular tissues further confirmed the
presence of particles in the trabecular meshwork area (Figure 2C).
These results suggest that the particle implants have little or no
contact with corneal and iris tissues. On the other hand, based on
the fluorescence distribution, it is likely that many posterior ocular
tissues, including retina and trabecular meshwork, were exposed to
Effect of material properties on ocular tissue responses
To assess the potential ocular compatibility of particle implants,
various ocular tissues in both anterior and posterior segments were
histologically analyzed. As expected, we found that the intravitreous
injection of particles have no apparent influence on the anatomical
structure of cornea (Figure 3A) and iris (Figure 3B) tissue based on
morphological assessment of tissue thickness (Figures 3C & D).
Although PNIPAM particle-implanted animals showed the lowest
corneal and iris tissue thickness, the differences were not statistically
Figure 1. Assessment of mean intraocular pressure variations after administration of particles made of poly-L lactic acid (PLLA),
polystyrene (PS), hyaluronic acid (HA), and poly N-isopropyl acrylamide (PNIPAM) and Balanced Salt Solution (BSS) in the vitreous.
Data are mean standard deviation. Significance of PLLA, PS, HA, PNIPAM vs. BSS control; * p<0.05.
. PLoS ONE I www.plosone.org 3 December 2011 Volume 6 Issue 12 e28720
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Zou, Ling; Nair, Ashwin; Weng, Hong; Tsai, Yi-Ting; Hu, Zhibing & Tang, Liping. Intraocular Pressure Changes: An Important Determinant of the Biocompatibility of Intravitreous Implants, article, December 14, 2011; [San Francisco, California]. (digital.library.unt.edu/ark:/67531/metadc288003/m1/3/: accessed October 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.