Molecular contrast of EGFR expression using gold nanoparticles as a reflectance-based imaging probe

Optical Microscopy Systems for the Detection of Unlabeled Nanoparticles

Label-free detection of nanoparticles is essential for a thorough evaluation of their cellular effects. In particular, nanoparticles intended for medical applications must be carefully analyzed in terms of their interactions with cells, tissues, and organs. Since the labeling causes a strong change in the physicochemical properties and thus also alters the interactions of the particles with the surrounding tissue, the use of fluorescently labeled particles is inadequate to characterize the effects of unlabeled particles. Further, labeling may affect cellular uptake and biocompatibility of nanoparticles. Thus, label-free techniques have been recently developed and implemented to ensure a reliable characterization of nanoparticles.

This review provides an overview of frequently used label-free visualization techniques and highlights recent studies on the development and usage of microscopy systems based on reflectance, darkfield, differential interference contrast, optical coherence, photothermal, holographic, photoacoustic, total internal reflection, surface plasmon resonance, Rayleigh light scattering, hyperspectral and reflectance structured illumination imaging. Using these imaging modalities, there is a strong enhancement in the reliability of experiments concerning cellular uptake and biocompatibility of nanoparticles, which is crucial for preclinical evaluations and future medical applications.

EGFR targeting for cancer therapy: Pharmacology and immunoconjugates with drugs and nanoparticles

The epidermal growth factor receptor (EGFR) belongs to the tyrosine kinase receptors family and is present in the epithelial cell membrane. Its endogenous activation occurs through the binding of different endogenous ligands, including the epidermal growth factor (EGF), leading to signaling cascades able to maintain normal cellular functions. Although involved in the development and maintenance of tissues in normal conditions, when EGFR is overexpressed, it stimulates the growth and progression of tumors, resulting in angiogenesis, invasion and metastasis, through some main cascades such as Ras/Raf/MAPK, PIK-3/AKT, PLC-PKC and STAT. Besides, considering the limitations of conventional chemotherapy that result in high toxicity and low tumor specificity, EGFR is currently considered an important target. As a result, several monoclonal antibodies are currently approved for use in cancer treatment, such as cetuximab (CTX), panitumumab, nimotuzumab, necitumumab and others are in clinical trials. Aiming to combine the chemotherapeutic agent toxicity and specific targeting to EGFR overexpressing tumor tissues, two main strategies will be discussed in this review: antibody-drug conjugates (ADCs) and antibody-nanoparticle conjugates (ANCs). Briefly, ADCs consist of antibodies covalently linked through a spacer to the cytotoxic drug. Upon administration, binding to EGFR and endocytosis, ADCs suffer chemical and enzymatic reactions leading to the release and accumulation of the drug. Instead, ANCs consist of nanotechnology-based formulations, such as lipid, polymeric and inorganic nanoparticles able to protect the drug against inactivation, allowing controlled release and also passive accumulation in tumor tissues by the enhanced permeability and retention effect (EPR). Furthermore, ANCs undergo active targeting through EGFR receptor-mediated endocytosis, leading to the formation of lysosomes and drug release into the cytosol. Herein, we will present and discuss some important aspects regarding EGFR structure, its role on internal signaling pathways and downregulation aspects. Then, considering that EGFR is a potential therapeutic target for cancer therapy, the monoclonal antibodies able to target this receptor will be presented and discussed. Finally, ADCs and ANCs state of the art will be reviewed and recent studies and clinical progresses will be highlighted. To the best of our knowledge, this is the first review paper to address specifically the EGFR target and its application on ADCs and ANCs.

A comparative study on generating hydroxyl radicals by single and two-frequency ultrasound with gold nanoparticles and protoporphyrin IX

Sonodynamic therapy (SDT) is a new manner of killing cancer cells based on the cytotoxic interactions of ultrasound with sonosensitizing agents. It is shown that gold nanoparticles (GNPs) increase the efficiency of cavitation activity of ultrasound. In this study the influence of a single and/or two frequencies of ultrasound waves to generate hydroxyl radicals (^·OH) was assessed in the presence of protoporphyrin IX (PpIX) and/or GNPs. Ultrasound cavitation activity was determined by recording fluorescence signals from chemical terephthalic acid (TA) dosimeters with or without PpIX and/or GNPs at the frequencies of 0.8 and 2.4 MHz individually and aggregately. To study hydroxyl radicals, experiments were performed with and without hydroxyl radical scavengers mannitol, histidine, and sodium azide. Cavitation activity was amplified by increasing ultrasound intensity and exposure time. The cavitation activity induced by dual ultrasound frequency was remarkably higher than the summation of effects produced by individual frequencies. All three scavengers reduced the fluorescence signal level. The effect of GNPs on intensifying cavitation activity at higher frequency was greater than that of lower frequency. PpIX showed a more effective sonosensitizing property at the lower frequency. Also, estimated synergism at dual frequency irradiation was improved in the presence of GNPs. We found that GNPs increased hydroxyl radical production at 2.4 MHz and that PpIX increased hydroxyl radical production at 0.8 MHz. Dual frequency exposure was more effective than single frequency exposure. PpIX at low frequency and gold nanoparticles at high frequency both enhance sonodynamic treatment efficacy.

Effect of gold nanoparticle size on acoustic cavitation using chemical dosimetry method

When a liquid is irradiated with high intensities of ultrasound irradiation, acoustic cavitation occurs. Acoustic cavitation generates free radicals from the breakdown of water and other molecules. Cavitation can be fatal to cells and is utilized to destroy cancer tumors. The existence of particles in liquid provides nucleation sites for cavitation bubbles and leads to decrease the ultrasonic intensity threshold needed for cavitation onset. In the present investigation, the effect of gold nanoparticles with appropriate amount and size on the acoustic cavitation activity has been shown by determining hydroxyl radicals in terephthalic acid solutions containing 15, 20, 28 and 35nm gold nanoparticles sizes by using 1MHz low level ultrasound. The effect of sonication intensity in hydroxyl radical production was considered. The recorded fluorescence signal in terephthalic acid solutions containing gold nanoparticles was considerably higher than the terephthalic acid solutions without gold nanoparticles at different intensities of ultrasound irradiation. Also, the results showed that the recorded fluorescence signal intensity in terephthalic acid solution containing finer size of gold nanoparticles was lower than the terephthalic acid solutions containing larger size of gold nanoparticles. Acoustic cavitation in the presence of gold nanoparticles can be used as a way for improving therapeutic effects on the tumors.

3D multiplexed immunoplasmonics microscopy

Selective labelling, identification and spatial distribution of cell surface biomarkers can provide important clinical information, such as distinction between healthy and diseased cells, evolution of a disease and selection of the optimal patient-specific treatment. Immunofluorescence is the gold standard for efficient detection of biomarkers expressed by cells. However, antibodies (Abs) conjugated to fluorescent dyes remain limited by their photobleaching, high sensitivity to the environment, low light intensity, and wide absorption and emission spectra. Immunoplasmonics is a novel microscopy method based on the visualization of Abs-functionalized plasmonic nanoparticles (fNPs) targeting cell surface biomarkers. Tunable fNPs should provide higher multiplexing capacity than immunofluorescence since NPs are photostable over time, strongly scatter light at their plasmon peak wavelengths and can be easily functionalized. In this article, we experimentally demonstrate accurate multiplexed detection based on the immunoplasmonics approach. First, we achieve the selective labelling of three targeted cell surface biomarkers (cluster of differentiation 44 (CD44), epidermal growth factor receptor (EGFR) and voltage-gated K(+) channel subunit KV1.1) on human cancer CD44(+) EGFR(+) KV1.1(+) MDA-MB-231 cells and reference CD44(-) EGFR(-) KV1.1(+) 661W cells. The labelling efficiency with three stable specific immunoplasmonics labels (functionalized silver nanospheres (CD44-AgNSs), gold (Au) NSs (EGFR-AuNSs) and Au nanorods (KV1.1-AuNRs)) detected by reflected light microscopy (RLM) is similar to the one with immunofluorescence. Second, we introduce an improved method for 3D localization and spectral identification of fNPs based on fast z-scanning by RLM with three spectral filters corresponding to the plasmon peak wavelengths of the immunoplasmonics labels in the cellular environment (500 nm for 80 nm AgNSs, 580 nm for 100 nm AuNSs and 700 nm for 40 nm × 92 nm AuNRs). Third, the developed technology is simple and compatible with standard epi-fluorescence microscopes used in biological and clinical laboratories. Thus, 3D multiplexed immunoplasmonics microscopy is ready for clinical applications as a cost-efficient alternative to immunofluorescence.

Advances in imaging probes and optical microendoscopic imaging techniques for early in vivo cancer assessment

A new chapter in the history of medical diagnosis happened when the first X-ray technology was invented in the late 1800s. Since then, many non-invasive and minimally invasive imaging techniques have been invented for clinical diagnosis to research in cellular biology, drug discovery, and disease monitoring. These imaging modalities have leveraged the benefits of significant advances in computer, electronics, and information technology and, more recently, targeted molecular imaging. The development of targeted contrast agents such as fluorescent and nanoparticle probes coupled with optical imaging techniques has made it possible to selectively view specific biological events and processes in both in vivo and ex vivo systems with great sensitivity and selectivity. Thus, the combination of targeted molecular imaging probes and optical imaging techniques have become a mainstay in modern medicinal and biological research. Many promising results have demonstrated great potentials to translate to clinical applications. In this review, we describe a discussion of employing imaging probes and optical microendoscopic imaging techniques for cancer diagnosis.

Antibody-functionalized nanoparticles for imaging cancer: influence of conjugation to gold nanoparticles on the biodistribution of 89Zr-labeled cetuximab in mice

Antibody-labeled gold nanoparticles represent a promising novel tool regarding cancer imaging and therapy. Nevertheless, the characterization of biodistribution of such immunonanocarriers has been poorly documented. In this study, the biodistribution of (89)Zr-labeled cetuximab before and after the coupling reaction to gold nanoparticles (AuNPs) was compared and the quantitative imaging performance of (89)Zr immuno-PET was evaluated. Cetuximab was functionalized with the desferal moiety and labeled with (89)Zr ((89)Zr-Df-Bz-NCS-cetuximab). AuNPs with a mean diameter of 5 nm were synthesized according a new method developed in the laboratory, and conjugated to (89)Zr-Df-Bz-NCS-cetuximab using carbodiimide chemistry (AuNPs-PPAA-cetuximab-(89)Zr). The two tracers were injected in A431 xenograft-bearing mice. Tumor and liver uptakes were assessed at different times after injection using quantitative PET imaging. The in vivo specificity of the binding was investigated using a saturating dose of unlabeled cetuximab. Radiolabeled cetuximab was conjugated to AuNPs with a coupling reaction yield >75%. All conjugates were stable in vitro and to a lesser extent in plasma. In vivo distribution studies revealed no significant difference in tumor uptake for cetuximab conjugated to nanoparticles up to 72 h after injection, compared with unconjugated cetuximab. Immuno-PET studies showed that AuNPs-PPAA-cetuximab-(89)Zr provided high tumor-to-background ratio. The liver uptake of AuNPs-PPAA-cetuximab-(89)Zr was higher, compared with (89)Zr-Df-Bz-NCS-cetuximab. In vivo blocking experiments demonstrated selective tumor targeting after coupling reaction. This study showed that the conjugation of AuNPs to cetuximab did not affect its tumor accumulation and that the efficacy of EGFR-targeted nanoparticles was unaltered. The (89)Zr-labeled cetuximab-targeted gold nanoparticles could be a valuable tool for theranostic purposes.

Gold nanoparticle delivery-enhanced proteasome inhibitor effect in adenocarcinoma cells

BACKGROUND

Proteasome inhibition is a current therapeutic strategy used in the treatment of multiple myeloma. Drugs controlling proteasome activity are ideally suited for unidirectional manipulation of cellular pathways such as apoptosis. The first proteasome inhibitor approved in clinics was bortezomib. This drug is currently used in combination with other anticancer agents.

OBJECTIVES

In this study, the enhancement of bortezomib activity was evaluated using gold nanoparticles coated with poly(ethylene glycol). The uptake mechanism of the gold nanoparticles in pancreatic cell lines, S2-013 and hTERT-HPNE, was assessed by laser scanning confocal microscopy (LSCM).

RESULTS

Pancreatic cancer cells internalized the nanoparticles together with the drug in few minutes through the formation of endocytic vesicles. This rapid uptake leads to an increase in the concentration and diffusion of bortezomib in the cytoplasm yielding an increased toxicity on the cells when compared to the drug alone.

CONCLUSION

Gold nanoparticles can be used as effective delivery systems to increasing the permeation and retention of drugs in cancer cells.

Detection of sonoluminescence signals in a gel phantom in the presence of Protoporphyrin IX conjugated to gold nanoparticles

The particles in a liquid decrease the ultrasonic intensity threshold required for cavitation onset. In this study, a new nanoconjugate composed of Protoporphyrin IX and gold nanoparticles (Au-PpIX) was used as a nucleation site for cavitation. The nonradiative relaxation time of Protoporphyrin IX in the presence of gold nanoparticles is longer than the similar time without gold nanoparticles. The acoustic cavitation activity was investigated via recording of the integrated sonoluminescence signal in the wavelength range of 220-700nm in a gel phantom by a cooled charge coupled device (CCD) at different intensities of 1MHz ultrasound. In order to confirm these results, a chemical dosimetric method was utilized, too. The recorded sonoluminescence signal in the gel phantom containing Au-PpIX was higher than the other phantoms. These records have been confirmed by the chemical dosimetric data. Therefore, we anticipate that a new nanoconjugate composed of Protoporphyrin IX and gold nanoparticles can act as an efficient sonoluminescence agent and could be introduced as a novel sonosensitizer for sonodynamic therapy.

Protein analytical assays for diagnosing, monitoring, and choosing treatment for cancer patients

Cancer treatment is often hindered by inadequate methods for diagnosing the disease or insufficient predictive capacity regarding therapeutic efficacy. Targeted cancer treatments, including Bcr-Abl and EGFR kinase inhibitors, have increased survival for some cancer patients but are ineffective in other patients. In addition, many patients who initially respond to targeted inhibitor therapy develop resistance during the course of treatment. Molecular analysis of cancer cells has emerged as a means to tailor treatment to particular patients. While DNA analysis can provide important diagnostic information, protein analysis is particularly valuable because proteins are more direct mediators of normal and diseased cellular processes. In this review article, we discuss current and emerging protein assays for improving cancer treatment, including trends toward assay miniaturization and measurement of protein activity.

FGF1-gold nanoparticle conjugates targeting FGFR efficiently decrease cell viability upon NIR irradiation

Fibroblast growth factor receptors (FGFRs) are overexpressed in a wide variety of tumors, such as breast, bladder, and prostate cancer, and therefore they are attractive targets for different types of anticancer therapies. In this study, we designed, constructed, and characterized FGFR-targeted gold nanoconjugates suitable for infrared-induced thermal ablation (localized heating leading to cancer cell death) based on gold nanoparticles (AuNPs). We showed that a recombinant ligand of all FGFRs, human fibroblast growth factor 1 (FGF1), can be used as an agent targeting covalently bound AuNPs to cancer cells overexpressing FGFRs. To assure thermal stability, protease resistance, and prolonged half-life of the targeting protein, we employed highly stable FGF1 variant that retains the biological activities of the wild type FGF1. Novel FGF1 variant, AuNP conjugates are specifically internalized only by the cells expressing FGFRs, and they significantly reduce their viability after irradiation with near-infrared light (down to 40% of control cell viability), whereas the proliferation potential of cells lacking FGFRs is not affected. These results demonstrate the feasibility of FGF1-coated AuNPs for targeted cancer therapy.

pH-controlled delivery of luminescent europium coated nanoparticles into platelets

Water soluble, luminescent gold nanoparticles are delivered into human platelets via a rapid, pH-controlled mechanism using a pH low insertion peptide, pHLIP. The approach introduces cocoating of gold nanoparticles with a europium luminescent complex, EuL and the pHLIP peptide to give pHLIP•EuL•Au. The 13-nm diameter gold nanoparticles act as a scaffold for the attachment of both the luminescent probe and the peptide to target delivery. Their size allows delivery of approximately 640 lanthanide probes per nanoparticle to be internalized in human platelets, which are not susceptible to transfection or microinjection. The internalization of pHLIP•EuL•Au in platelets, which takes just minutes, was studied with a variety of imaging modalities including luminescence, confocal reflection, and transmission electron microscopy. The results show that pHLIP•EuL•Au only enters the platelets in low pH conditions, pH 6.5, mediated by the pHLIP translocation across the membrane, and not at pH 7.4. Luminescence microscopy images of the treated platelets show clearly the red luminescence signal from the europium probe and confocal reflection microscopy confirms the presence of the gold particles. Furthermore, transmission electron microscopy gives a detailed insight of the internalization and spatial localization of the gold nanoparticles in the platelets. Thus, we demonstrate the potential of the design to translocate multimodal nanoparticle probes into cells in a pH dependent manner.

Cancer detection using nanoparticle-based sensors

This tutorial review surveys the latest achievements in the use of nanoparticles to detect cancer biomarkers and cancer cells with a focus on optical and electrochemical techniques. Nanoparticle based cancer diagnostics are becoming an increasingly relevant alternative to traditional techniques. Although some drawbacks exist in relation to the obtained sensitivity the use of nanoparticle-based sensors in biomarker detection or cancer cell detection offers some advantages in comparison to conventional methods. The developed techniques can be interesting and relevant for their use in point-of-care of cancer diagnostics. The methods can be of low cost and in addition easy to be incorporated into user-friendly sensing platforms.

A visual tutorial on the synthesis of gold nanoparticles

Many papers have been written on the synthesis of gold nanoparticles but very few included pictures of the process, and none of them used video to show the whole process of synthesis. This paper records the process of synthesis of gold nanoparticles using video clips. Every process from cleaning of glassware, an important step in the synthesis of metallic nanoparticles, to the dialysis process is shown. It also includes the preparation of aqua regia and the actual synthesis of gold nanoparticles. In some papers, the dialysis process was omitted, but in this paper, it is included to complete the whole process as it is being used for purification.

Control of optical contrast using gold nanoshells for optical coherence tomography imaging of mouse xenograft tumor model in vivo

The control of image contrast is essential toward optimizing a contrast enhancement procedure in optical coherence tomography (OCT). In this study, the in vivo control of optical contrast in a mouse tumor model with gold nanoshells as a contrast agent is examined. Gold nanoshells are administered into mice, with the injected dosage and particle surface parameters varied and its concentration in the tumor under each condition is determined using a noninvasive theoretical OCT modeling technique. The results show that too high a concentration of gold nanoshells in the tumor only enhances the OCT signal near the tissue surface, while significantly attenuating the signal deeper into the tissue. With an appropriate dosage, IV delivery of gold nanoshells allows a moderate concentration of 6.2 x 10(9) particles/ml in tumor to achieve a good OCT signal enhancement with minimal signal attenuation with depth. An increase in the IV dosage of gold nanoshells reveals a corresponding nonlinear increase in their tumor concentration, as well as a nonlinear reduction in the fractional concentration of injected gold nanoshells. Furthermore, this fractional concentration is improved with the use of antiepodermal growth factor receptor (EGFR) surface functionalization, which also reduces the time required for tumor delivery from 6 to 2 h.

Shuttling gold nanoparticles into tumoral cells with an amphipathic proline-rich peptide

Cell-penetrating peptides (CPPs) are a potential tool for intracellular delivery of different kinds of cargoes. Because of their growing use in nanobiomedicine, both for diagnostics and for treatment, metal nanoparticles are an interesting cargo for CPPs. Here, gold nanoparticles (AuNps) and the amphipathic proline-rich peptide SAP have been used. Conjugation of the peptide onto the AuNps was achieved by addition of a cysteine to the SAP sequence for thiol chemisorption on gold, and the attachment was confirmed by visible spectroscopy, dynamic light scattering (DLS), zeta-potential (ZP), stability towards ionic strength (as high as 1 M NaCl), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR-TEM) coupled to electron energy loss spectroscopy (EELS). AuNp-C-SAP internalization in HeLa cells was observed by three different microscopy techniques-TEM, confocal laser scanning microscopy (CLSM) and transmission X-ray microscopy (TXM)-and all of them have confirmed the effective intracellular delivery of AuNps by SAP.

Silica-gold nanoshells as potential intraoperative molecular probes for HER2-overexpression in ex vivo breast tissue using near-infrared reflectance confocal microscopy

Obtaining negative margins is critical for breast cancer patients undergoing conservation therapy in order to reduce the reemergence of the original cancer. Currently, breast cancer tumor margins are examined in a pathology lab either while the patient is anesthetized or after the surgical procedure has been terminated. These current methods often result in cancer cells present at the surgical resection margin due to inadequate margin assessment at the point of care. Due to such limitations evident in current diagnoses, tools for increasing the accuracy and speed of tumor margin detection directly in the operating room are still needed. We are exploring the potential of using a nano-biophotonics system to facilitate intraoperative tumor margin assessment ex vivo at the cellular level. By combining bioconjugated silica-based gold nanoshells, which scatter light in the near-infrared, with a portable FDA-approved reflectance confocal microscope, we first validate the use of gold nanoshells as effective reflectance-based imaging probes by evaluating the contrast enhancement of three different HER2-overexpressing cell lines. Additionally, we demonstrate the ability to detect HER2-overexpressing cells in human tissue sections within 5 min of incubation time. This work supports the use of targeted silica-based gold nanoshells as potential real-time molecular probes for HER2-overexpression in human tissue.