Drug delivery by sonosensitive liposome and microbubble with acoustic-lens attached ultrasound: an in vivo feasibility study in a murine melanoma model.

Conventional chemotherapy methods have adverse off-target effects and low therapeutic efficiencies of drug release in target tumors. In this study, we proposed a combination therapy of doxorubicin (DOX)-loaded ultrasound (US)-sensitive liposomal nanocarriers (IMP301), microbubbles (MBs) under focused US exposure using convex acoustic lens-attached US (LENS) to tumor treatment. The therapeutic effects of each treatment in a murine melanoma model were evaluated using contrast-enhanced US (CEUS) and micro-computed tomography (micro-CT) imaging, bioluminescence and confocal microscopy imaging, and liquid chromatography-mass spectroscopy (LC/MS) analysis. Tumor-bearing mice were randomly assigned to one of the following groups: (1) G1: IMP301 only (n = 9); (2) G2: IMP301 + LENS (n = 9); (3) G3: IMP301 + MB + LENS (n = 9); (4) G4: DOXIL only (n = 9); and (5) G5: IMP301 without DOXIL group as a control group (n = 4). Ten days after tumor injection, tumor-bearing mice were treated according to each treatment strategy on 10th, 12th, and 14th days from the day of tumor injection. The CEUS images of the tumors in the murine melanoma model clearly showed increased echo signal intensity from MBs as resonant US scattering. The relative tumor volume of the G2 and G3 groups on the micro-CT imaging showed inhibited tumor growth than the reference baseline of the G5 group. DOX signals on bioluminescence and confocal microscopy imaging were mainly located at the tumor sites. LC/MS showed prominently higher intratumoral DOX concentration in the G3 group than in other treated groups. Therefore, this study effectively demonstrates the feasibility of the synergistic combination of IMP301, MBs, and LENS-application for tumor-targeted treatment. Thus, this study can enable efficient tumor-targeted treatment by combining therapy such as IMP301 + MBs + LENS-application.

Development of a Polymersome-Based Nanomedicine for Chemotherapeutic and Sonodynamic Combination Therapy.

In anticancer therapy, combination therapy has been suggested as an alternative to the insufficient therapeutic efficacy of single therapy. Among combination therapies, combination chemo- and photodynamic therapy are actively investigated. However, photodynamic therapy shows a limitation in the penetration depth of the laser. Therefore, sonodynamic therapy (SDT), using ultrasound instead of a laser as a trigger, is an upcoming strategy for deep tumors. Additionally, free drugs are easily degraded by enzymes, have difficulty in reaching the target site, and show side effects after systemic administration; therefore, the development of drug delivery systems is desirable for sufficient drug efficacy for combination therapy. However, nanocarriers, such as microbubbles, and albumin nanoparticles, are unstable in the body and show low drug-loading efficiency. Here, we propose polylactide (PLA)-poly (ethylene glycol) (PEG) polymersomes (PLs) with a high drug loading rate of doxorubicin (DOX) and verteporfin (VP) for effective combination therapy in both in vitro and in vivo experiments. The cellular uptake efficiency and cytotoxicity test results of VP-DOX-PLs were higher than that of single therapy. Moreover, in vivo biodistribution showed the accumulation of the VP-DOX-PLs in tumor regions. Therefore, VP-DOX-PLs showed more effective anticancer efficacy than either single therapy in vivo. These results suggest that the combination therapy of SDT and chemotherapy could show novel anticancer effects using VP-DOX-PLs.

Evading Doxorubicin-Induced Systemic Immunosuppression Using Ultrasound-Responsive Liposomes Combined with Focused Ultrasound.

Doxorubicin (DOX) is a representative anticancer drug with a unique ability to induce immunogenic cell death of cancer cells. However, undesired toxicity on immune cells has remained a significant challenge, hindering the usage of DOX in cancer immunotherapy. Here, we report a combined therapy to avoid the off-target toxicity of DOX by adapting ultrasound-responsive liposomal doxorubicin and focused ultrasound exposure. Histological analysis demonstrated that the combined therapy induced less hemosiderosis of splenocytes and improved tumor infiltration of cytotoxic T lymphocytes. Additionally, in vivo therapeutic evaluation results indicate that the combined therapy achieved higher efficacy when combined with PD-1 immune-checkpoint blockade therapy by improving immunogenicity.

Enhanced delivery to brain using sonosensitive liposome and microbubble with focused ultrasound.

Glioblastoma is considered one of the most aggressive and dangerous brain tumors. However, treatment of GBM has been still challenged due to blood-brain barrier (BBB). BBB prevents that the chemotherapeutic molecules are extravasated to brain. In this study, sonosensitive liposome encapsulating doxorubicin (DOX) was developed for enhancement of GBM penetration in combination with focused ultrasound (FUS) and microbubbles. Upon ultrasound (US) irradiation, microbubbles induce cavitation resulting in the tight junction of BBB endothelium to temporarily open. In addition, the composition of sonosensitive liposome was optimized by comparison of sonosensitivity and intracellular uptake to U87MG cells. The optimal sonosensitive liposome, IMP301-DC, resulted 123.9 ± 38.2 nm in size distribution and 98.2 % in loading efficiency. Related to sonosensitivity of IMP301-DC, US-triggered release ratio of doxorubicin was 69.2 ± 12.3 % at 92 W/cm2 of US intensity for 1 min. In the in vivo experiments, the accumulation of DiD fluorescence probe labeled IMP301-DC-shell in the brain through the BBB opening was increased more than two-fold compared to that of Doxil-shell, non-sonosensitive liposome. US exposure significantly increased GBM cytotoxicity of IMP301-DC. In conclusion, this study demonstrated that IMP301-DC could serve as an alternative solution to enhance the penetration to GBM treatment via BBB opening by non-invasive FUS combined with microbubbles.

Ultrasound-Responsive Liposomes for Targeted Drug Delivery Combined with Focused Ultrasound.

Chemotherapeutic drugs are traditionally used for the treatment of cancer. However, chemodrugs generally induce side effects and decrease anticancer effects due to indiscriminate diffusion and poor drug delivery. To overcome these limitations of chemotherapy, in this study, ultrasound-responsive liposomes were fabricated and used as drug carriers for delivering the anticancer drug doxorubicin, which was able to induce cancer cell death. The ultrasound-sensitive liposome demonstrated a size distribution of 81.94 nm, and the entrapment efficiency of doxorubicin was 97.1 ± 1.44%. The release of doxorubicin under the ultrasound irradiation was 60% on continuous wave and 50% by optimizing the focused ultrasound conditions. In vivo fluorescence live imaging was used to visualize the doxorubicin release in the MDA-MB-231 xenografted mouse, and it was demonstrated that liposomal drugs were released in response to ultrasound irradiation of the tissue. The combination of ultrasound and liposomes suppressed tumor growth over 56% more than liposomes without ultrasound exposure and 98% more than the control group. In conclusion, this study provides a potential alternative for overcoming the previous limitations of chemotherapeutics.

Effects of Lipid Shape and Interactions on the Conformation, Dynamics, and Curvature of Ultrasound-Responsive Liposomes.

We perform coarse-grained molecular dynamics simulations of bilayers composed of various lipids and cholesterol at their different ratios. Simulations show that cholesterol-lipid interactions restrict the lateral dynamics of bilayers but also promote bilayer curvature, indicating that these opposite effects simultaneously occur and thus cannot significantly influence bilayer stability. In contrast, lyso-lipids effectively pack the vacancy in the bilayer composed of cone-shaped lipids and thus reduce bilayer dynamics and curvature, showing that bilayers are more significantly stabilized by lyso-lipids than by cholesterol, in agreement with experiments. In particular, the bilayer composed of cone-shaped lipids shows higher dynamics and curvature than does the bilayer composed of cylindrical-shaped lipids. To mimic ultrasound, a high external pressure was applied in the direction of bilayer normal, showing the formation of small pores that are surrounded by hydrophilic lipid headgroups, which can allow the release of drug molecules encapsulated into the liposome. These findings help to explain experimental observations regarding that liposomes are more significantly stabilized by lyso-lipids than by cholesterol, and that the liposome with cone-shaped lipids more effectively releases drug molecules upon applying ultrasound than does the liposome with cylindrical-shaped lipids.

Ultrasound-triggered imaging and drug delivery using microbubble-self-aggregate complexes.

Co-delivery of microbubbles (MBs) with anticancer drugs is a promising theranostic approach that can enhance both the ultrasound contrast and local extravasation of drugs with the sonoporation effect. The simultaneous administration of MBs and hydrophobic drugs, however, is still challenging due to the limitations in drug loading or undesirable stabilization of MBs. In this research, MB-self-aggregate complexes (MB-SAs) were newly fabricated for the encapsulation of hydrophobic drugs, and their theranostic properties are investigated in vitro and in vivo. Glycol chitosan self-aggregates (GC-SAs) loaded with hydrophobic drugs or dyes were chemically conjugated on the surface MBs. Their conjugation ratio was determined to be 73.9%, and GC-SAs on MBs did not affect the stability of MBs. GC-SA attached MBs (GC@MBs) were successfully visualized with low-intensity insonation and showed enhanced cellular uptake via the sonoporation effect. In vivo biodistribution of GC@MBs was examined with tumor-bearing mice, confirming that their accumulation at the tumor site increased by 1.85 times after ultrasound irradiation. The anticancer drug-loaded GC@MBs also exhibited 10% higher cytotoxicity under ultrasound flash. In conclusion, it was expected that GC@MBs could be used both as an ultrasound contrast agent and a drug carrier even with conventional ultrasonic devices.

Early response evaluation of doxorubicin-nanoparticle-microbubble therapy in orthotopic hepatocellular carcinoma rat model using contrast-enhanced ultrasound and intravoxel incoherent motion-diffusion MRI.

PURPOSE: This study aimed to apply doxorubicin-loaded nanoparticle microbubble (Dox-NP-MB) therapy in an orthotopic rat model of hepatocellular carcinoma (HCC) and investigate the utility of contrast-enhanced ultrasound (CEUS) and intravoxel incoherent motion diffusion-weighted magnetic resonance imaging (IVIM-DWI) for response evaluation. METHODS: Twenty-eight N1S1 HCC model rats were treated with either Dox-NP-MB (group [G] 1, n=8), doxorubicin (Dox) alone (G2, n=7), nanoparticle microbubbles alone (G3, n=7), or saline (G4, control, n=6) on days 0 and 7, and were sacrificed on day 11. IVIM-DWI and CEUS were performed before each treatment and before euthanasia. Efficacy was estimated by the percentage of tumor volume growth inhibition compared with control. Toxicity was assessed by body weight changes and blood tests. Post-treatment changes in IVIM-DWI and CEUS parameters were analyzed. RESULTS: Tumor volume growth was inhibited by 48.4% and 90.2% in G1 and G2 compared to G4, respectively. Compared to G2, G1 had a significantly lower degree of body weight change (median, 91.0% [interquartile range, 88.5%-97.0%] vs. 88.0% [82.5%-88.8%], P<0.05) and leukopenia (1.75×103 cells/µL [1.53-2.77] vs. 1.20×103 cells/µL [0.89-1.51], P<0.05). After the first treatment, an increase in peak enhancement, wash-in rate, and wash-in perfusion index on CEUS was observed in G3 and G4 but suppressed in G1 and G2; the apparent diffusion coefficients, true diffusion coefficients, and perfusion fractions significantly increased in G1 and G2 compared to baseline (P<0.05). CONCLUSION: Dox-NP-MB showed reduced Dox toxicity. Early changes in some CEUS and IVIM-DWI parameters correlated with the therapeutic response.

Development and evaluation of an ultrasound-triggered microbubble combined transarterial chemoembolization (TACE) formulation on rabbit VX2 liver cancer model.

Transarterial chemoembolization (TACE) is an image-guided locoregional therapy used for the treatment of patients with primary or secondary liver cancer. However, conventional TACE formulations are rapidly dissociated due to the instability of the emulsion, resulting in insufficient local drug concentrations in the target tumor. Methods: To overcome these limitations, a doxorubicin-loaded albumin nanoparticle-conjugated microbubble complex in an iodized oil emulsion (DOX-NPs-MB complex in Lipiodol) has been developed as a new ultrasound-triggered TACE formulation. Results: (1) Microbubbles enhanced therapeutic efficacy by effectively delivering doxorubicin- loaded nanoparticles into liver tumors via sonoporation under ultrasound irradiation (US+). (2) Microbubbles constituting the complex retained their function as an ultrasound contrast agent in Lipiodol. In a rabbit VX2 liver cancer model, the in vivo study of DOX-NPs-MB complex in Lipiodol (US+) decreased the viability of tumor more than the conventional TACE formulation, and in particular, effectively killed cancer cells in the tumor periphery. Conclusion: Incorporation of doxorubicin-loaded microbubble in the TACE formulation facilitated drug delivery to the tumor with real-time monitoring and enhanced the therapeutic efficacy of TACE. Thus, the enhanced TACE formulation may represent a new treatment strategy against liver cancer.

Combined treatment of sorafenib and doxorubicin-loaded microbubble-albumin nanoparticle complex for hepatocellular carcinoma: A feasibility study.

PURPOSE: To assess the feasibility of the combined sorafenib (SOR) and doxorubicin-loaded microbubble-albumin nanoparticle complex (DOX-MAC) treatment effect in an orthotopic rat model of hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Sixty-two rats with N1-S1 hepatoma were divided into four groups according to the treatment methods, i.e. G1 (SOR and DOX-MAC; n = 12), G2 (SOR; n = 15), G3 (DOX-MAC; n = 12), G4 (DOX; n = 11), and G5 (normal saline; n = 12). We performed the theragnostic, contrast-enhanced ultrasound examination and treatment at the baseline, one-week, and two-weeks. Tumor volume and perfusion parameters were compared at each time point and the differences between all of the groups over time were analyzed using repeated measures ANOVA. We also analyzed the apoptotic index and microvessel density (MVD) per each tumor specimen in all of the groups. RESULTS: The tumors increased from the beginning in all of the groups to the final follow-up, whereas the tumor growth in the G1 group and the G2 group was inhibited during the treatment period compared to the baseline tumor volume (P = 0.016 and P = 0.031). The G1 group resulted in tumor growth inhibition compared to the control group (P = 0.008). The G1 group showed that the peak enhancement and wash-in area under the curve were lower than that of the G4 group (P = 0.010 and 0.022). However, there was no difference in perfusion parameters in the other treated group compared to control group. The MVD of the G1 group tumor was lower than that of the G4 group (P = .016). CONCLUSION: Our results suggest that the combination therapy of SOR and DOX-MAC can cause inhibition of tumor growth after treatment and that this therapy can be adequately monitored using the theragnostic DOX-MAC agent.

PD-L1 Targeting Immune-Microbubble Complex Enhances Therapeutic Index in Murine Colon Cancer Models.

Cancer immunotherapy has revolutionized the way different neoplasms are treated. Among the different variations of cancer immunotherapy, the checkpoint inhibitors targeting the programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) axis have been validated and are currently used in the clinics. Nevertheless, these therapeutic antibodies are associated with significant side effects and are known to induce immune-related toxicities. To address these issues, we have developed an immune-microbubble complex (IMC) which not only reduces the toxicities associated with the antibodies but also enhances the therapeutic efficacy when combined with focused ultrasound. The concept of IMCs could be applied to any type of antibody-based treatment regimens to maximize their therapeutic potential.

Combination Therapy with Doxorubicin-Loaded Reduced Albumin Nanoparticles and Focused Ultrasound in Mouse Breast Cancer Xenografts.

Because chemotherapeutic drugs are often associated with serious side effects, the central topic in modern drug delivery is maximizing the localization of drugs at the target while minimizing non-specific drug interactions at unwanted regions. To address this issue, biocompatible nanoparticles have been developed to enhance the drug half-life while minimizing the associated toxicity. Nevertheless, relying solely on the enhanced half-life and enhanced permeability and retention (EPR) effects has been ineffective, and designing stimulus-sensitive nanoparticles to introduce the precise control of drug release has been desired. In this paper, we introduce a pH-sensitive, reduced albumin nanoparticle in combination with focused ultrasound treatment. Not only did these nanoparticles have superior therapeutic efficacy and toxicity profiles when compared to the free drugs in xenograft mouse models, but we were also able to show that the albumin nanoparticles reported in this paper were more suitable than other types of non-reduced albumin nanoparticles as vehicles for drug delivery. As such, we believe that the albumin nanoparticles presented in this paper with desirable characteristics including the induction of strong anti-tumor response, precise control, and superior safety profiles hold strong potential for preclinical and clinical anticancer therapy.

Antitumor Effects of Intra-Arterial Delivery of Albumin-Doxorubicin Nanoparticle Conjugated Microbubbles Combined with Ultrasound-Targeted Microbubble Activation on VX2 Rabbit Liver Tumors.

Image-guided intra-arterial therapies play a key role in the management of hepatic malignancies. However, limited clinical outcomes suggest the need for new multifunctional drug delivery systems to enhance local drug concentration while reducing systemic adverse reactions. Therefore, we developed the albumin-doxorubicin nanoparticle conjugated microbubble (ADMB) to enhance therapeutic efficiency by sonoporation under exposure to ultrasound. ADMB demonstrated a size distribution of 2.33 ± 1.34 µm and a doxorubicin loading efficiency of 82.7%. The echogenicity of ADMBs was sufficiently generated in the 2-9 MHz frequency range and cavitation depended on the strength of the irradiating ultrasound. In the VX2 rabbit tumor model, ADMB enhanced the therapeutic efficiency under ultrasound exposure, compared to free doxorubicin. The intra-arterial administration of ADMBs sufficiently reduced tumor growth by five times, compared to the control group. Changes in the ADC values and viable tumor fraction supported the fact that the antitumor effect of ADMBs were enhanced by evidence of necrosis ratio (over 70%) and survival tumor cell fraction (20%). Liver toxicity was comparable to that of conventional therapies. In conclusion, this study shows that tumor suppression can be sufficiently maximized by combining ultrasound exposure with intra-arterial ADMB administration.

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.

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-ß (Aß)-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 Aß deposition in the RGC layer of ONC model, and a cell viability test showed that HSA-NP can inhibit Aß-induced RGC death. CONCLUSIONS: Human serum albumin nanoparticles showed neuroprotective potential by inhibiting Aß 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.

Therapeutic Ultrasound Contrast Agents for the Enhancement of Tumor Diagnosis and Tumor Therapy.

The functionality of ultrasound in early cancer detection is limited because of its relatively low contrast resolution. Because it has a high degree of echogenicity, a microbubble contrast agent is often used to overcome this intrinsic limitation of imaging at low-contrast resolution. A targeted and drug-loaded microbubble contrast agent for simultaneous diagnosis and therapy has recently been investigated. However, no optimized theragnosis ultrasound microbubbles have been developed. Paclitaxel (PTX)-encapsulating human serum albumin nanoparticles (PTX-HSA-NPs) were conjugated onto an ultrasound microbubbles (PTX-HSA-NPs-MBs) fabricated in the laboratory to result in a narrow size distribution (1.7 ± 0.7 µm) and an optimal resonance frequency of 3 MHz. After intravenous injection of HSA-NPs-MBs, echogenicity in the tumor xenografted with breast cancer MCF-7 cells was significantly enhanced, showing the possibility of early cancer diagnosis. Mice injected with PTX-HSA-NPs-MBs showed higher survival rates in comparison with control groups, demonstrating the possibility of theragnosis. In the present study, the conjugation of PTX-HSA-NPs onto the ultrasound microbubbles simultaneously provided (1) enhanced ultrasound signal generation, (2) sufficient drug-loading capacity, (3) ability to deliver drugs to a preferred tumor site, and (4) increased stability in blood circulation.

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.

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.

Narrow size distribution of microbubbles for enhancement of harmonic imaging.

An ultrasound microbubble contrast agent is a promising technique in clinical diagnosis because ultrasound in combination with microbubbles enhances the ultrasound backscatter to produce an increased contrast images. In this study, we developed phospholipid-based microbubbles showing a relatively narrow size distribution of 0.8-1.3 microm. The optimal resonance frequency of developed microbubbles was determined to be 2.5-3.0 MHz by measuring echo signals at various frequencies. Ultrasound harmonic imaging was performed in a vessel phantom at the optimal resonance frequencies. Microbubble contrast-enhanced ultrasound images visualized a vessel tube clearly and demonstrated much improved image quality, compared to the control. In conclusion, the ultrasonography in the harmonic mode is capable of maximally resonating micrbubbles with a narrow size distribution at a specific frequency for enhanced ultrasound imaging.

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.