Determining vitreous viscosity using fluorescence recovery after photobleaching

PURPOSE

Vitreous humor is a complex biofluid whose composition determines its structure and function. Vitreous viscosity will affect the delivery, distribution, and half-life of intraocular drugs, and key physiological molecules. The central pig vitreous is thought to closely match human vitreous viscosity. Diffusion is inversely related to viscosity, and diffusion is of fundamental importance for all biochemical reactions. Fluorescence Recovery After Photobleaching (FRAP) may provide a novel means of measuring intravitreal diffusion that could be applied to drugs and physiological macromolecules. It would also provide information about vitreous viscosity, which is relevant to drug elimination, and delivery.

METHODS

Vitreous viscosity and intravitreal macromolecular diffusion of fluorescently labelled macromolecules were investigated in porcine eyes using fluorescence recovery after photobleaching (FRAP). Fluorescein isothiocyanate conjugated (FITC) dextrans and ficolls of varying molecular weights (MWs), and FITC-bovine serum albumin (BSA) were employed using FRAP bleach areas of different diameters.

RESULTS

The mean (±standard deviation) viscosity of porcine vitreous using dextran, ficoll and BSA were 3.54 ± 1.40, 2.86 ± 1.13 and 4.54 ± 0.13 cP respectively, with an average of 3.65 ± 0.60 cP.

CONCLUSIONS

FRAP is a feasible and practical optical method to quantify the diffusion of macromolecules through vitreous.

Factors affecting the outcome of delayed intravenous thrombolysis (>4.5hours)

INTRODUCTION

Evidence of the intravenous tissue plasminogen activator (tPA) efficacy beyond the 4.5hours window is emerging. We aim to study the factors affecting the outcome of delayed thrombolysis in patients of clear onset acute ischemic stroke (AIS).

METHODS

Data of patients with AIS who received intravenous thrombolytic after 4.5hours were reviewed including: demographics, risk factors, clinical, laboratory, investigational and radiological data, evidence of mismatch, treatment type and onset, National Institutes of Health Stroke Scale (NIHSS) score at baseline, 24hours, 7days after thrombolysis and before discharge, and 3 months follow-up modified Rankin Scale (mRS).

RESULTS

We report 136 patients treated by intravenous tPA between 4.53 and 19.75hours with average duration of 5.7h. The ASPECT score of our patients was≥7. Sixty-four cases showed intracranial arterial occlusion. Perfusion mismatch was detected in 117 (84.6%) patients, while clinical imaging mismatch was detected in 19 (15.4%). Early neurological improvement after 24hours occurred in 114 (83.8%) patients. At 90days, 91 patients (67%) achieved good outcome (mRS 0-2), while 45 (33%) had bad outcome (mRS 3-6). Age, endovascular treatment, NIHSS, AF, and HT were significantly higher in the bad outcome group. Age (P=0.001, OR: 1.099, 95% CI: 1.042-1.160) and baseline NIHSS were predictive of the poor outcome (P=0.002, OR: 1.151, 95% CI: 1.055-1.256). The best cutoff value of age was 72.5 with AUC of 0.76, sensitivity 73.3% and specificity 60.4%. While for NIHSS at admission, the cutoff value of 7 showed the best results with AUC of 0.73, sensitivity 71.1% and specificity 63.7%. Combination of age and admission NIHSS raised the sensitivity and specificity to 84.4% and 63.7%, respectively.

CONCLUSION

Increased age and admission NIHSS may adversely affect the outcome of delayed thrombolysis and narrow the eligibility criteria. Age and baseline NIHSS based stratification of the patients may provide further evidence as regards the efficacy of the delayed thrombolysis.

Significance of assay of nucleated RBCs in umbilical cord blood in neonates with meconium-stained amniotic fluid

BACKGROUND

Approximately 8-15% of all infants are born with evidence of meconium-stained amniotic fluid (MSAF). MSAF is a potentially serious sign of fetal compromise and may indicate fetal hypoxia Objectives and aim of the work: The present study was designed to evaluate the relationship between meconium stained amniotic fluid and fetal nucleated red blood cell counts. As well, we aim to evaluate the relationship between the presence of meconium in amniotic fluid and Apgar scores in neonates.

SUBJECTS AND METHODS

A prospectively case-controlled study was performed on 40 women with clear amniotic fluid as control and 40 women with meconium-stained amniotic fluid as the study group. At delivery, 2 ml of umbilical cord blood was collected and analyzed for nucleated red blood cell (NRBC).

RESULTS

The mean NRBC counts in meconium-stained amniotic fluid was significantly higher than the control group (18.35 ± 7.7 and 9.6 ± 4.96), respectively (p < .001). There were statistically significant differences concerning 1- and 5-min Apgar scores with lower values in the MSAF group (p < .001 and .001, respectively).

CONCLUSION

Our results support previous studies which indicate the presence of meconium can be associated with chronic fetal hypoxia as demonstrated by elevated fetal NRBC levels.

PLGA Microparticles Entrapping Chitosan-Based Nanoparticles for the Ocular Delivery of Ranibizumab

Age-related macular degeneration (AMD) is the leading cause of certified vision loss worldwide. The standard treatment for neovascular AMD involves repeated intravitreal injections of therapeutic proteins directed against vascular endothelial growth factor, such as ranibizumab. Biodegradable polymers, such as poly(lactic-co-glycolic acid) (PLGA), form delivery vehicles which can be used to treat posterior segment eye diseases, but suffer from poor protein loading and release. This work describes a "system-within-system", PLGA microparticles incorporating chitosan-based nanoparticles, for improved loading and sustained intravitreal delivery of ranibizumab. Chitosan-N-acetyl-l-cysteine (CNAC) was synthesized and its synthesis confirmed using FT-IR and (1)H NMR. Chitosan-based nanoparticles composed of CNAC, CNAC/tripolyphosphate (CNAC/TPP), chitosan, chitosan/TPP (chit/TPP), or chit/TPP-hyaluronic acid (chit/TPP-HA) were incorporated in PLGA microparticles using a modified w/o/w double emulsion method. Nanoparticles and final nanoparticles-within-microparticles were characterized for their protein-nanoparticle interaction, size, zeta potential, morphology, protein loading, stability, in vitro release, in vivo antiangiogenic activity, and effects on cell viability. The prepared nanoparticles were 17-350 nm in size and had zeta potentials of -1.4 to +12 mV. Microscopic imaging revealed spherical nanoparticles on the surface of PLGA microparticles for preparations containing chit/TPP, CNAC, and CNAC/TPP. Ranibizumab entrapment efficiency in the preparations varied between 13 and 69% and was highest for the PLGA microparticles containing CNAC nanoparticles. This preparation also showed the slowest release with no initial burst release compared to all other preparations. Incorporation of TPP to this formulation increased the rate of protein release and reduced entrapment efficiency. PLGA microparticles containing chit/TPP-HA showed the fastest and near-complete release of ranibizumab. All of the prepared empty particles showed no effect on cell viability up to a concentration of 12.5 mg/mL. Ranibizumab released from all preparations maintained its structural integrity and in vitro activity. The chit/TPP-HA preparation enhanced antiangiogenic activity and may provide a potential biocompatible platform for enhanced antiangiogenic activity in combination with ranibizumab. In conclusion, the PLGA microparticles containing CNAC nanoparticles showed significantly improved ranibizumab loading and release profile. This novel drug delivery system may have potential for improved intravitreal delivery of therapeutic proteins, thereby reducing the frequency, risk, and cost of burdensome intravitreal injections.

Cholesterol-poly(ethylene) glycol nanocarriers for the transscleral delivery of sirolimus

The aim of this study was to prepare and characterize cholesterol-poly(ethylene) glycol (chol-PEG) nanocarriers of two different molecular weights (1 and 5 kDa) and to determine their effect on the transscleral retention and permeation of a lipophilic multi-therapeutic agent, sirolimus (rapamycin), with potential application in angiogenic and immunogenic ocular diseases. Sirolimus-containing nanocarriers were prepared using the thin-film hydration method and characterized for their physicochemical properties including size, drug entrapment (EE) and loading (DL) efficiencies, stability, surface charge, morphology, critical micelle concentration (CMC) and thermal properties. Ussing chambers were used to determine the retention and permeability of sirolimus-containing nanocarriers in porcine sclera followed by ultrastructural tissue examination. Sirolimus-containing nanocarriers had an average size of 11.7 nm (chol-PEG 1 kDa) and 13.8 nm (chol-PEG 5 kDa) and zeta potentials of 0.41 and -1.05, respectively. Both nanocarriers had similar transscleral permeabilities (chol-PEG 1 kDa 6.44 × 10(-7) and 5 kDa 6.16 × 10(-7) cm2 s(-1)), and very high scleral retention compared with a free solution of sirolimus (chol-PEG 1 kDa 16.9 μg/g; chol-PEG 5 kDa 7.48 μg/g; free sirolimus 0.57 μg/g). The DL (EE) for chol-PEG 1 and 5 kDa were 2.93% (77.4%) and 3.10% (81.6%), respectively. The CMC values for the nanocarriers were similar to those previously reported in literature (3.85 × 10(-7) M for chol-PEG 1 kDa; 4.26 × 10(-7) M for chol-PEG 5 kDa). In conclusion, chol-PEG nanocarriers successfully loaded sirolimus and resulted in scleral permeation and high retention, which shows potential utility for the topical delivery of lipophilic ocular drugs.