Surfactant-Stripped Semiconducting Polymer Micelles for Tumor Theranostics and Deep Tissue Imaging in the NIR-II Window.

Photoacoustic imaging (PA) in the second near infrared (NIR-II) window presents key advantages for deep tissue imaging owing to reduced light scattering and low background signal from biological structures. Here, a thiadiazoloquinoxaline-based semiconducting polymer (SP) with strong absorption in the NIR-II region is reported. After encapsulation of SP in Pluronic F127 (F127) followed by removal of excess surfactant, a dual functional polymer system named surfactant-stripped semiconductor polymeric micelles (SSS-micelles) are generated with water solubility, storage stability, and high photothermal conversion efficiency, permitting tumor theranostics in a mouse model. SSS-micelles have a wideband absorption in the NIR-II window, allowing for the PA imaging at both 1064 and 1300 nm wavelengths. The PA signal of the SSS-micelles can be detected through 6.5 cm of chicken breast tissue in vitro. In mice or rats, SSS-micelles can be visualized in bladder and intestine overlaid 5 cm (signal to noise ratio, SNR ≈ 17 dB) and 5.8 cm (SNR over 10 dB) chicken breast tissue, respectively. This work demonstrates the SSS-micelles as a nanoplatform for deep tissue theranostics.

Drug-loaded titanium dioxide nanoparticle coated with tumor targeting polymer as a sonodynamic chemotherapeutic agent for anti-cancer therapy.

Sonodynamic therapy utilizes ultrasound (US)-responsive generation of reactive oxygen species (ROS) from sonosensitizer, and it is a powerful strategy for anti-cancer treatment in combination with chemotherapy. Herein, we report a precisely designed sonodynamic chemotherapeutics which exhibits US-responsive drug release via ROS generation from co-loaded sono-sensitizer. Doxorubicin (DOX)-coordinated titanium dioxide nanoparticles (TNPs) were encapsulated with polymeric phenyboronic acid (pPBA) via phenylboronic ester bond between pPBA and DOX. Loaded DOX was readily released under US irradiation due to the ROS-cleavable characteristics of phenylboronic ester bond. The size of nanoparticles was around 200 nm, and DOX was released by ROS generated under US irradiation. Tumor targeting by PBA moiety, intracellular ROS generation, and combined therapeutic effect against tumor cells were confirmed in vitro. Finally, we demonstrated high tumor accumulation and efficient tumor growth inhibition in tumor-bearing mice under US irradiation, which revealed potential as a multi-functional agent for sonodynamic chemotherapy.

Multifunctional Nanodroplets Encapsulating Naphthalocyanine and Perfluorohexane for Bimodal Image-Guided Therapy.

Although nanocarriers containing perfluorocarbon (PFC) have been widely investigated as an ultrasound (US) imaging agent and a high intensity focused ultrasound (HIFU) agent, these carriers have suffered from low stability and biocompatibility limiting their further biomedical applications. Here, we developed surface cross-linked polymer nanodroplets as a HIFU therapeutic agent guided by bimodal photoacoustic (PA) and US imaging. Pluronic F127 was reacted with 4-nitrophenyl chloroformate (NPC) and mixed with naphthalocyanine (Nc) in dichloromethane, which was added into the aqueous solution of amine-functionalized six-arm-branched poly(ethylene glycol) (PEG) to form an oil-in-water emulsion for the cross-linking reaction between the terminal NPC of Pluronic F127 and the primary amine of six-arm PEG. The resulting solution was sonicated with liquid perfluorohexane (PFH) to prepare PEG cross-linked Pluronic F127 nanoparticles encapsulating Nc and PFH (Nc/PFH@PCPN). Nc/PFH@PCPN appeared to be stable without any coalescence or vaporization in the physiological condition. Upon the application of HIFU, Nc/PFH@PCPN was vaporized and showed increased US intensity for 180 min. The Nc dye in the nanodroplets enabled the stable encapsulation of PFH and the bimodal US/PA imaging. In vivo PA/US image-guided HIFU ablation therapy confirmed that the nanodroplets increased the cavitation effect, induced necrosis and apoptosis of tumor cells, and reduced tumor growth significantly for 12 days. Taken together, the multifunctional Nc/PFH@PCPN was successfully developed as a new platform for PA/US image-guided HIFU therapy.

Photoacoustic imaging of dental implants in a porcine jawbone ex vivo.

Currently, x-ray-based imaging is used before and after the dental implant treatment, but the ionizing radiation is potentially harmful to patients and operators. Here, we demonstrate ex vivo photoacoustic imaging of a dental implant embedded in a porcine jawbone. By layering biological tissue over the jawbone to mimic a clinical environment, we demonstrate 10 mm deep imaging. Our results show that photoacoustic imaging can provide jawbone anatomical information, the location of an embedded implant fixture, and the thickness of the soft tissue above the jawbone.

Polypropylene microplastics promote metastatic features in human breast cancer.

Microplastics (MPs) are now a global issue due to increased plastic production and use. Recently, various studies have been performed in response to the human health risk assessment. However, these studies have focused on spherical MPs, which have smooth edges and a spherical shape and account for less than 1% of MPs in nature. Unfortunately, studies on fragment-type MPs are very limited and remain in the initial stages. In this study, we studied the effect that 16.4 µm fragment type polypropylene (PP) MPs, which have an irregular shape and sharp edges and form naturally in the environment, had on breast cancer. The detrimental effects of PPMPs on breast cancer metastasis were examined. Here, 1.6 mg/ml of PPMP, which does not induce cytotoxicity in MDA-MB-231, was used, and at this concentration, PPMP did not induce morphological changes or cellular migrating in the MDA-MB-231 and MCF-7 cells. However, PPMP incubation for 24 hours in the MDA-MB-231 cells significantly altered the level of cell cycle-related transcripts in an RNA-seq analysis. When confirmed by qRT-PCR, the gene expression of TMBIM6, AP2M1, and PTP4A2 was increased, while the transcript level of FTH1 was decreased. Further, secretion of the pro-inflammatory cytokine IL-6 from cancer cells was elevated with the incubation of PPMP for 12 hours. These results suggest that PPMP enhances metastasis-related gene expression and cytokines in breast cancer cells, exacerbating breast cancer metastasis.

3D printed multi-growth factor delivery patches fabricated using dual-crosslinked decellularized extracellular matrix-based hybrid inks to promote cerebral angiogenesis.

Generally, brain angiogenesis is a tightly regulated process, which scarcely occurred in the absence of specific pathological conditions. Delivery of exogenous angiogenic factors enables the induction of desired angiogenesis by stimulating neovasculature formation. However, effective strategies of mimicking the angiogenesis process with exogenous factors have not yet been fully explored. Herein, we develop a 3D printed spatiotemporally compartmentalized cerebral angiogenesis inducing (SCAI) hydrogel patch, releasing dual angiogenic growth factors (GFs), using extracellular matrix-based hybrid inks. We introduce a new hybrid biomaterial-based ink for printing patches through dual crosslinking mechanisms: Chemical crosslinking with aza-Michael addition reaction with combining methacrylated hyaluronic acid (HAMA) and vascular-tissue-derived decellularized extracellular matrix (VdECM), and thermal crosslinking of VdECM. 3D printing technology, a useful approach with fabrication versatility with customizable systems and multiple biomaterials, is adopted to print three-layered hydrogel patch with spatially separated dual GFs as outer- and inner-layers that provide tunable release profiles of multiple GFs and fabrication versatility. Consequently, these layers of the patch spatiotemporally separated with dual GFs induce excellent neovascularization in the brain area, monitored by label-free photoacoustic microscopy in vivo. The developed multi-GFs releasing patch may offer a promising therapeutic approach of spatiotemporal drugs releasing such as cerebral ischemia, ischemic heart diseases, diabetes, and even use as vaccines. STATEMENT OF SIGNIFICANCE: Effective strategies of mimicking the angiogenesis process with exogenous factors have not yet been fully explored. In this study, we develop a 3D printed spatiotemporally compartmentalized cerebral angiogenesis inducing (SCAI) hydrogel patch, releasing dual angiogenic growth factors (GFs) using extracellular matrix-based hybrid inks. We introduce a new hybrid biomaterial-based ink through dual crosslinking mechanisms: Chemical crosslinking with aza-Michael addition, and thermal crosslinking. 3D printing technology is adopted to print three-layered hydrogel patch with spatially separated dual GFs as outer- and inner-layers that provide tunable release profiles of multiple GFs and fabrication versatility. Consequently, these layers of the patch spatiotemporally separated with dual GFs induce excellent neovascularization in the brain area, monitored by photoacoustic microscopy in vivo.

Porphysome nanovesicles generated by porphyrin bilayers for use as multimodal biophotonic contrast agents.

Optically active nanomaterials promise to advance a range of biophotonic techniques through nanoscale optical effects and integration of multiple imaging and therapeutic modalities. Here, we report the development of porphysomes; nanovesicles formed from self-assembled porphyrin bilayers that generated large, tunable extinction coefficients, structure-dependent fluorescence self-quenching and unique photothermal and photoacoustic properties. Porphysomes enabled the sensitive visualization of lymphatic systems using photoacoustic tomography. Near-infrared fluorescence generation could be restored on dissociation, creating opportunities for low-background fluorescence imaging. As a result of their organic nature, porphysomes were enzymatically biodegradable and induced minimal acute toxicity in mice with intravenous doses of 1,000 mg kg(-1). In a similar manner to liposomes, the large aqueous core of porphysomes could be passively or actively loaded. Following systemic administration, porphysomes accumulated in tumours of xenograft-bearing mice and laser irradiation induced photothermal tumour ablation. The optical properties and biocompatibility of porphysomes demonstrate the multimodal potential of organic nanoparticles for biophotonic imaging and therapy.

Convolutional neural network-based metal and streak artifacts reduction in dental CT images with sparse-view sampling scheme.

PURPOSE: Sparse-view sampling has attracted attention for reducing the scan time and radiation dose of dental cone-beam computed tomography (CBCT). Recently, various deep learning-based image reconstruction techniques for sparse-view CT have been employed to produce high-quality image while effectively reducing streak artifacts caused by the lack of projection views. However, most of these methods do not fully consider the effects of metal implants. As sparse-view sampling strengthens the artifacts caused by metal objects, simultaneously reducing both metal and streak artifacts in sparse-view CT images has been challenging. To solve this problem, in this study, we propose a novel framework. METHODS: The proposed method was based on the normalized metal artifact reduction (NMAR) method, and its performance was enhanced using two convolutional neural networks (CNNs). The first network reduced the initial artifacts while preserving the fine details to generate high-quality priors for NMAR processing. Subsequently, the second network was employed to reduce the streak artifacts after NMAR processing of sparse-view CT data. To validate the proposed method, we generated training and test data by computer simulations using both extended cardiac-torso (XCAT) and clinical data sets. RESULTS: Visual inspection and quantitative evaluations demonstrated that the proposed method effectively reduced both metal and streak artifacts while preserving the details of anatomical structures compared with the conventional metal artifact reduction methods. CONCLUSIONS: We propose a framework for reconstructing accurate CT images in metal-inserted sparse-view CT. The proposed method reduces streak artifacts from both metal objects and sparse-view sampling while recovering the anatomical details, indicating the feasibility of fast-scan dental CBCT imaging.

Gold nanocages covered by smart polymers for controlled release with near-infrared light.

Photosensitive caged compounds have enhanced our ability to address the complexity of biological systems by generating effectors with remarkable spatial/temporal resolutions. The caging effect is typically removed by photolysis with ultraviolet light to liberate the bioactive species. Although this technique has been successfully applied to many biological problems, it suffers from a number of intrinsic drawbacks. For example, it requires dedicated efforts to design and synthesize a precursor compound for each effector. The ultraviolet light may cause damage to biological samples and is suitable only for in vitro studies because of its quick attenuation in tissue. Here we address these issues by developing a platform based on the photothermal effect of gold nanocages. Gold nanocages represent a class of nanostructures with hollow interiors and porous walls. They can have strong absorption (for the photothermal effect) in the near-infrared while maintaining a compact size. When the surface of a gold nanocage is covered with a smart polymer, the pre-loaded effector can be released in a controllable fashion using a near-infrared laser. This system works well with various effectors without involving sophisticated syntheses, and is well suited for in vivo studies owing to the high transparency of soft tissue in the near-infrared region.

Deep tissue photoacoustic imaging of nickel(II) dithiolene-containing polymeric nanoparticles in the second near-infrared window.

Photoacoustic imaging is gaining great attention in the medical world due to its significant potential for clinical translation. Light excitation in the second near-infrared (NIR-II) window (1000-1350 nm) has resolution and penetration depth suitable for several clinical applications. However, the significant challenge exists for clinical translation because of the absence of notable intrinsic chromophores in this clinically significant optical range to generate diagnostic images. Methods: We present newly developed a biocompatible nickel dithiolene-based polymeric nanoparticle (NiPNP), which have a strong and sharp absorption peak at 1064 nm, as a photoacoustic contrast agent to boost specific absorbance in the NIR-II window for in vivo deep tissue imaging. Results: We confirm the enhanced PA signal by NiPNP's strong light absorption in the NIR-II window (287% higher than that of NIR-I) and deep tissue imaging capability (~5.1 cm) through in vitro experiment. We have successfully acquired diagnostic-quality in vivo photoacoustic images in deep tissue (~3.4 cm) of sentinel lymph nodes, gastrointestinal tracts, and bladders of live rats by using clinically viable imaging system. Conclusions: Our results prove that with strong absorption in the NIR-II window and with deeper imaging depth, the clinical translation of photoacoustic imaging with NiPNP is feasible for preclinical studies and thus would facilitate further clinical investigations.

Colloidal Porous AuAg Alloyed Nanoparticles for Enhanced Photoacoustic Imaging.

Colloidal porous AuAg alloyed nanoparticles (pAuAgNPs) were synthesized by galvanic replacement reaction from Ag nanocubes. pAuAgNPs have a 50 nm exterior diameter and half of their inner space consists of voids that have a bimodal size distribution with peaks at 21 and 8.3 nm. pAuAgNPs showed a plasmonic peak at 750 nm, which was exploited for photoacoustic (PA) imaging. Gold nanorods (AuNRs) were prepared and used as the control; they have a strong plasmonic peak at 720 nm. In in vitro experiments at respective plasmonic peak excitations, pAuAgNPs gave stronger PA signals than AuNRs by 8.9 times per particle and 11.7 times per dosage by exogenous atom. The high surface area per volume as a result of the inner voids amplified the PA signals by efficient thermoacoustic conversion. In experiments of chicken-tissue phantoms, pAuAgNPs showed PA signals through 4.5 cm thick tissue, whereas AuNRs gave no detectable signal. In whole-body in vivo experiments, pAuAgNPs injected into the body showed 2.7 times stronger PA signals than AuNRs. Coating the pAuAgNPs with a silica layer additionally increased their PA signal by 1.8 times when compared to the uncoated ones.

A Peptide Probe Enables Photoacoustic-Guided Imaging and Drug Delivery to Lung Tumors in K-rasLA2 Mutant Mice.

The lack of molecular targets and targeting probes remains a major drawback for targeted imaging and drug delivery in lung cancer. In this study, we exploited in vivo phage display to identify a novel targeting probe that homes to the tumor in a K-rasLA2 mutant mouse lung cancer model. Compared with other candidate peptides selected from 5 rounds of phage display, the CRQTKN peptide homed to tumor nodules in the lung of mutant mice at higher levels. Photoacoustic tomography of mutant mice detected lung tumors via tumor homing of the near-infrared fluorescence dye-labeled CRQTKN peptide. Ex vivo photoacoustic images of isolated organs further demonstrated tumor homing of the CRQTKN peptide, whereas minimal accumulation was observed in control organs, such as the liver. Compared with untargeted liposomes and doxorubicin, doxorubicin-loaded liposomes whose surface was modified with the CRQTKN peptide more efficiently delivered doxorubicin and reduced the number or size of tumor lesions in K-rasLA2 mutant mice. Analysis of hematologic parameters and liver and kidney function showed no significant systemic side effects by the treatments. Affinity-based identification was used to detect TNF receptor superfamily member 19L (TNFRSF19L), which was upregulated in lung tumors of mutant mice, as the receptor for the CRQTKN peptide. In conclusion, these results suggest that the CRQTKN peptide is a promising targeting probe for photoacoustic-guided detection and drug delivery to lung cancer, and acts by binding to TNFRSF19L. SIGNIFICANCE: These findings present a new tumor-targeting probe for photoacoustic-guided detection and drug delivery.

Two-axis polydimethylsiloxane-based electromagnetic microelectromechanical system scanning mirror for optical coherence tomography.

Compact size and fast imaging abilities are key requirements for the clinical implementation of an optical coherence tomography (OCT) system. Among the various small-sized technology, a microelectromechanical system (MEMS) scanning mirror is widely used in a miniaturized OCT system. However, the complexities of conventional MEMS fabrication processes and relatively high costs have restricted fast clinical translation and commercialization of the OCT systems. To resolve these problems, we developed a two-axis polydimethylsiloxane (PDMS)-based MEMS (2A-PDMS-MEMS) scanning mirror through simple processes with low costs. It had a small size of 15×15×15??mm3, was fast, and had a wide scanning range at a low voltage. The AC/DC responses were measured to evaluate the performance of the 2A-PDMS-MEMS scanning mirror. The maximum scanning angles were measured as ±16.6??deg and ±11.6??deg along the X and Y axes, respectively, and the corresponding field of view was 29.8??mm×20.5??mm with an optical focal length of 50 mm. The resonance frequencies were 82 and 57 Hz along the X and Y axes, respectively. Finally, in vivo B-scan and volumetric OCT images of human fingertips and palms were successfully acquired using the developed SD-OCT system based on the 2A-PDMS-MEMS scanning mirror.

Biodegradable Photonic Melanoidin for Theranostic Applications.

Light-absorbing nanoparticles for localized heat generation in tissues have various biomedical applications in diagnostic imaging, surgery, and therapies. Although numerous plasmonic and carbon-based nanoparticles with strong optical absorption have been developed, their clearance, potential cytotoxicity, and long-term safety issues remain unresolved. Here, we show that "generally regarded as safe (GRAS)" melanoidins prepared from glucose and amino acid offer a high light-to-heat conversion efficiency, biocompatibility, biodegradability, nonmutagenicity, and efficient renal clearance, as well as a low cost for synthesis. We exhibit a wide range of biomedical photonic applications of melanoidins, including in vivo photoacoustic mapping of sentinel lymph nodes, photoacoustic tracking of gastrointestinal tracts, photothermal cancer therapy, and photothermal lipolysis. The biodegradation rate and renal clearance of melanoidins are controllable by design. Our results confirm the feasibility of biodegradable melanoidins for various photonic applications to theranostic nanomedicines.

Hexamodal imaging with porphyrin-phospholipid-coated upconversion nanoparticles.

Hexamodal imaging using simple nanoparticles is demonstrated. Porphyrin-phospholipids are used to coat upconversion nanoparticles in order to generate a new biocompatible material. The nanoparticles are characterized in vitro and in vivo for imaging via fluorescence, upconversion, positron emission tomography, computed tomography, Cerenkov luminescence, and photoacoustic tomography.

Multifunctional microbubbles and nanobubbles for photoacoustic and ultrasound imaging.

We develop a novel dual-modal contrast agent-encapsulated-ink poly(lactic-co-glycolic acid) (PLGA) microbubbles and nanobubbles-for photoacoustic and ultrasound imaging. Soft gelatin phantoms with embedded tumor simulators of encapsulated-ink PLGA microbubbles and nanobubbles in various concentrations are clearly shown in both photoacoustic and ultrasound images. In addition, using photoacoustic imaging, we successfully image the samples positioned below 1.8-cm-thick chicken breast tissues. Potentially, simultaneous photoacoustic and ultrasound imaging enhanced by encapsulated-dye PLGA microbubbles or nanobubbles can be a valuable tool for intraoperative assessment of tumor boundaries and therapeutic margins.

Chronic label-free volumetric photoacoustic microscopy of melanoma cells in three-dimensional porous scaffolds.

Visualizing cells in three-dimensional (3D) scaffolds has been one of the major challenges in tissue engineering. Most current imaging modalities either suffer from poor penetration depth or require exogenous contrast agents. Here, we demonstrate photoacoustic microscopy (PAM) of the spatial distribution and temporal proliferation of cells inside three-dimensional porous scaffolds with thicknesses over 1 mm. Specifically, we evaluated the effects of seeding and culture methods on the spatial distribution of melanoma cells. Spatial distribution of the cells in the scaffold was well-resolved in PAM images. Moreover, the number of cells in the scaffold was quantitatively measured from the as-obtained volumetric information. The cell proliferation profile obtained from PAM correlated well with what was obtained using the traditional 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.

Effect of hydroxyapatite on bone integration in a rabbit tibial defect model.

BACKGROUND: The aim of the present study was to prepare hydroxyapatite (HA) and then characterize its effect on bone integration in a rabbit tibial defect model. The bone formation with different designs of HA was compared and the bony integration of several graft materials was investigated qualitatively by radiologic and histologic study. METHODS: Ten rabbits were included in this study; two holes were drilled bilaterally across the near cortex and the four holes in each rabbit were divided into four treatment groups (HAP, hydroxyapatite powder; HAC, hydroxyapatite cylinder; HA/TCP, hydroxyapatite/tri-calcium phosphate cylinder, and titanium cylinder). The volume of bone ingrowth and the change of bone mineral density were statistically calculated by computed tomography five times for each treatment group at 0, 2, 4, 6, and 8 weeks after grafting. Histologic analysis was performed at 8 weeks after grafting. RESULTS: The HAP group showed the most pronounced effect on the bone ingrowth surface area, which seen at 4, 6, and 8 weeks after graft (p < 0.05). On comparing the change of bone mineral density the bone ingrowth surface area among the 4 groups, there were no statistically significant differences among the groups found for any period (p > 0.05). On histological examination, the HAP group revealed well-recovered cortical bone, but the bone was irregularly thickened and haphazardly admixed with powder. The HAC group showed similar histological features to those of the HA/TCP group; the cortical surface of the newly developed bone was smooth and the bone matrix on the surface of the cylinder was regularly arranged. CONCLUSIONS: We concluded that both the hydroxyapatite powder and cylinder models investigated in our study may be suitable as a bone substitute in the rabbit tibial defect model, but their characteristic properties are quite different. In contrast to hydroxyapatite powder, which showed better results for the bone ingrowth surface, the hydroxyapatite cylinder showed better results for the sustained morphology.