Hyungwon Moon

Amplified Photoacoustic Performance and Enhanced Photothermal Stability of Reduced Graphene Oxide Coated Gold Nanorods for Sensitive Photoacoustic Imaging

We report a strongly amplified photoacoustic (PA) performance of the new functional hybrid material composed of reduced graphene oxide and gold nanorods. Due to the excellent NIR light absorption properties of the reduced graphene oxide coated gold nanorods (r-GO-AuNRs) and highly efficient heat transfer process through the reduced graphene oxide layer, r-GO-AuNRs exhibit excellent photothermal stability and significantly higher photoacoustic amplitudes than those of bare-AuNRs, nonreduced graphene oxide coated AuNRs (GO-AuNRs), or silica-coated AuNR, as demonstrated in both in vitro and in vivo systems. The linear response of PA amplitude from reduced state controlled GO on AuNR indicates the critical role of GO for a strong photothermal effect of r-GO-AuNRs. Theoretical studies with finite-element-method lab-based simulation reveal that a 4 times higher magnitude of the enhanced electromagnetic field around r-GO-AuNRs can be generated compared with bare AuNRs or GO-AuNRs. Furthermore, the r-GO-AuNRs are expected to be a promising deep-tissue imaging probe because of extraordinarily high PA amplitudes in the 4-11 MHz operating frequency of an ultrasound transducer. Therefore, the r-GO-AuNRs can be a useful imaging probe for highly sensitive photoacoustic images and NIR sensitive therapeutics based on a strong photothermal effect.

The movement of self-assembled amphiphilic polymeric nanoparticles in the vitreous and retina after intravitreal injection

The purpose of this study is to determine the correlation between the distribution of nanoparticles in the vitreous and retina and their surface properties after intravitreal injection. For this purpose, we synthesized seven kinds of nanoparticles through self-assembly of amphiphilic polymer conjugates in aqueous condition. They showed similar size but different surface properties. They were labeled with fluorescent dyes for efficient tracking. After intravitreal injection of these nanoparticles into a rodent eye, their time-dependent distribution in the vitreous and retina was determined in stacking tissue images by confocal microscopy. The results demonstrated that the surface property of nanoparticles is a key factor in determining their distribution in the vitreous and retina after intravitreal injection. In addition, immunohistochemistry and TEM images of retina tissues suggested the important mechanism related with Mülller cells for intravitreally administered nanoparticles to overcome the physical barrier of inner limiting membrane and to penetrate into the deeper retinal structures. Therefore, we expect that this study can provide valuable information for biomedical researchers to develop optimized nanoparticles as drug or gene carriers for retinal and optic nerve disorders such as glaucoma, age-related macular degeneration, and diabetic retinopathy.

Multifunctional theranostic contrast agent for photoacoustics- and ultrasound-based tumor diagnosis and ultrasound-stimulated local tumor therapy.

Biomedical imaging-guided cancer therapy should have capabilities of both accurate tumor diagnosis and high therapeutic efficacy for the personalized treatment. Various biomedical imaging-guided cancer therapies are currently being investigated to overcome current limitations that include low sensitivity of diagnosis and poor drug delivery to the tumor site. Here, we report the development of a multifunctional theranostic contrast agent demonstrating high sensitive photoacoustic and ultrasound imaging and effective local delivery of anticancer drug to a tumor site. A microbubble (porphyrin-MB) was developed using phospholipid-porphyrin conjugates to enhance ultrasound and photoacoustic signal intensities simultaneously. Paclitaxel-loaded human serum albumin nanoparticles (PTX-HSA-NPs) were then conjugated onto the surface of the microbubble. The developed PTX-HSA-NPs conjugated porphyrin-MB (porphyrin-MB-NPs) provided sensitive, dual modal images of a tumor at 700 nm optimal laser wavelength for photoacoustic imaging and 5-14 MHz operating frequency for the ultrasound imaging. In addition, porphyrin-MB-NPs efficiently suppressed tumor growth by ultrasound exposure. Exposure to the focused ultrasound triggered the collapse of porphyrin-MB-NPs, resulting in the local release of PTX-HSA-NPs and enhanced penetration into the tumor site. The increased preferential accumulation and penetration of PTX-HSA-NPs suppressed tumor growth 10-fold more than without exposure to ultrasound. In conclusion, the developed porphyrin-MB-NPs establish a new paradigm in simultaneous bi-functional ultrasound/photoacoustic imaging diagnosis and locally triggered release of nanomedicine and enhanced chemotherapy efficiency.

Photoacoustic-based nanomedicine for cancer diagnosis and therapy.

Photoacoustic imaging is the latest promising diagnostic modality that has various advantages such as high spatial resolution, deep penetration depth, and use of non-ionizing radiation. It also employs a non-invasive imaging technique and optically functionalized imaging. The goal of this study was to develop a nanomedicine for simultaneous cancer therapy and diagnosis based on photoacoustic imaging. Human serum albumin nanoparticles loaded with melanin and paclitaxel (HMP-NPs) were developed using the desolvation technique. The photoacoustic-based diagnostic and chemotherapeutic properties of HMP-NPs were evaluated through in vitro and in vivo experiments. The size and zeta potential of the HMP-NPs were found to be 192.8±21.11nm and -22.2±4.39mV, respectively. In in vitro experiments, HMP-NPs produced increased photoacoustic signal intensity because of the loaded melanin and decreased cellular viability because of the encapsulated paclitaxel, compared to the free human serum albumin nanoparticles (the control). In vivo experiments showed that the HMP-NPs efficiently accumulated inside the tumor, resulting in the enhanced photoacoustic signal intensity in the tumor site, compared to the normal tissues. The in vivo chemotherapy study demonstrated that HMP-NPs had the capability to treat cancer for an extended period. In conclusion, HMP-NPs were simultaneously capable of photoacoustic diagnostic and chemotherapy against cancer.

Neuroprotective Effects of Human Serum Albumin Nanoparticles Loaded With Brimonidine on Retinal Ganglion Cells in Optic Nerve Crush Model

PURPOSE We investigated the neuroprotective effect of human serum albumin nanoparticles (HSA-NPs) and their conjugation with brimonidine (HSA-Br-NPs) on retinal ganglion cells (RGCs) in optic nerve crush (ONC) model. METHODS We fabricated HSA-Br-NPs by ethanol precipitation, including 0.18% brimonidine (Br) and 3.5% human serum albumin (HSA) in HSA-Br-NP solution. We performed ONC and intravitreal injection in Sprague-Dawley rats, which were divided into (1) Normal, (2) balanced salt solution (BSS)-injected ONC, (3) HSA-NP-injected ONC, (4) Br-injected ONC, and (5) HSA-Br-NP-injected ONC groups. Survival of RGC was compared 5 and 14 days after procedures. A cell viability assay evaluated the amyloid-β (Aβ)-associated neuroprotective mechanism of HSA-NP. RESULTS The HSA-Br-NPs showed a narrow size distribution (152.8 ± 51.1 nm) and a negatively charged surface (-29.7 ± 7.5 mV), releasing Br for 5 days. The percentages of RGC survival in the HSA-NP (52.6 ± 3.3%), Br (58.0 ± 4.2%), and HSA-Br-NP (63.5 ± 7.1%) groups relative to Normal (100%) were significantly higher than in the BSS group (29.2 ± 3.3%) 5 days after ONC (P < 0.001). However, the HSA-Br-NP (38.1 ± 3.6%) group showed significantly higher RGC density than the BSS (10.3 ± 5.6%, P < 0.001) or Br (18.6 ± 3.9%, P = 0.006) group at 14 days. The HSA-NP injection reduced Aβ deposition in the RGC layer of ONC model, and a cell viability test showed that HSA-NP can inhibit Aβ-induced RGC death. CONCLUSIONS Human serum albumin nanoparticles showed neuroprotective potential by inhibiting Aβ deposition, and exerted a sustained therapeutic effect with the combined neuroprotective agent. Our results suggest the potential of HSA-Br-NP as a promising neuroprotective agent.

A Novel Center of Mass Method to Measure Fluid Velocity with MRI

Abstract Major obstacles in effective local drug delivery to a target site include non-invasive measurement of the concentration distribution after local administration. Herein, the development of a non-invasive in vitro magnetic resonance imaging (MRI) method is described to quantitatively study the distribution of drug surrogate and to measure fluid flow velocity in the region of interest (ROI). Dynamic contrast enhanced MRI was used to study diffusion–convection transport phenomena of a magnetic resonance contrast agent, Gd-DTPA, in 1% agarose gel. The relationship between the concentration of Gd-DTPA and T1 relaxation time was determined using an inversion recovery MRI technique. The concentration distribution of Gd-DTPA images was estimated from a calibration curve relating T1 relaxation time and the concentration of Gd-DTPA. Using the estimated concentration profiles, center-of-mass points were calculated in a series of time points in order to determine fluid flow velocity, which correlated well with the real volumetric flow velocity at early time points. In this study, we developed a method to analyze MR images quantitatively and to determine fluid flow velocity through a tissue in vivo.