Multimodal drug delivery using gold nanoparticles

Nanotechnology-based intelligent drug design for cancer metastasis treatment

Traditional chemotherapy used today at clinics is mainly inherited from the thinking and designs made four decades ago when the Cancer War was declared. The potency of those chemotherapy drugs on in-vitro cancer cells is clearly demonstrated at even nanomolar levels. However, due to their non-specific effects in the body on normal tissues, these drugs cause toxicity, deteriorate patient's life quality, weaken the host immunosurveillance system, and result in an irreversible damage to human's own recovery power. Owing to their unique physical and biological properties, nanotechnology-based chemotherapies seem to have an ability to specifically and safely reach tumor foci with enhanced efficacy and low toxicity. Herein, we comprehensively examine the current nanotechnology-based pharmaceutical platforms and strategies for intelligent design of new nanomedicines based on targeted drug delivery system (TDDS) for cancer metastasis treatment, analyze the pros and cons of nanomedicines versus traditional chemotherapy, and evaluate the importance that nanomaterials can bring in to significantly improve cancer metastasis treatment.

Drug-loaded nanoparticle systems and adult stem cells: a potential marriage for the treatment of malignant glioma?

Despite all recent advances in malignant glioma research, only modest progress has been achieved in improving patient prognosis and quality of life. Such a clinical scenario underscores the importance of investing in new therapeutic approaches that, when combined with conventional therapies, are able to effectively eradicate glioma infiltration and target distant tumor foci. Nanoparticle-loaded delivery systems have recently arisen as an exciting alternative to improve targeted anti-glioma drug delivery. As drug carriers, they are able to efficiently protect the therapeutic agent and allow for sustained drug release. In addition, their surface can be easily manipulated with the addition of special ligands, which are responsible for enhancing tumor-specific nanoparticle permeability. However, their inefficient intratumoral distribution and failure to target disseminated tumor burden still pose a big challenge for their implementation as a therapeutic option in the clinical setting. Stem cell-based delivery of drug-loaded nanoparticles offers an interesting option to overcome such issues. Their ability to incorporate nanoparticles and migrate throughout interstitial barriers, together with their inherent tumor-tropic properties and synergistic anti-tumor effects make these stem cell carriers a good fit for such combined therapy. In this review, we will describe the main nanoparticle delivery systems that are presently available in preclinical and clinical studies. We will discuss their mechanisms of targeting, current delivery methods, attractive features and pitfalls. We will also debate the potential applications of stem cell carriers loaded with therapeutic nanoparticles in anticancer therapy and why such an attractive combined approach has not yet reached clinical trials.

Resveratrol stabilized gold nanoparticles enable surface loading of doxorubicin and anticancer activity

The green synthesis of gold nanoparticles was achieved by exploiting the antioxidant property of resveratrol (R). The formation of resveratrol stabilized gold nanoparticles (R-GNPs) was confirmed by the observation of the surface plasmon resonance band at 537 nm. The average size of R-GNPs produced in resveratrol medium was ~35nm. The geometrical shape and zeta potential of the gold nanoparticles were spherical and -21.2 mV, respectively. R-GNPs showed excellent stability in saline and other buffers mimicking the physiological pH. The MTT assay using fibroblast cells from explants tissue revealed the biocompatibility of R-GNPs. The cytotoxic activity of doxorubicin loaded R-GNPs against glioma carcinoma cell line (LN 229), showed the suitability of R-GNPs as a carrier for anticancer drugs.

Non-mammalian vertebrate embryos as models in nanomedicine

Various in vivo biological models have been proposed for studying the interactions of nano-materials in biological systems. Unfortunately, the widely used small mammalian animal models (rodents) are costly and labor intensive and generate ethical issues and antagonism from the anti-vivisectionist movement. Recently, there has been increasing interest in the scientific community in the interactions between nano-materials and non-mammalian developmental organisms, which are now being recognized as valid models for the study of human disease. This review examines and discusses the biomedical applications and the interaction of nano-materials with embryonic systems, focusing on non-mammalian vertebrate models, such as chicken, zebrafish and Xenopus.

FROM THE CLINICAL EDITOR

Animal models are critical components of preclinical biomedical research. This review discusses the feasibility and potential applications of non-mammalian vertebral animals, such as zebrafish, xenopus, and chicken as animal models in nanomedicine research.

A noncovalent, fluoroalkyl coating monomer for phosphonate-covered nanoparticles

Gadolinium-containing phosphonate-coated gold nanoparticles were prepared and then non-covalently coated with an amphiphilic fluorous monomer. The monomer spontaneously self-assembles into a non-covalent monolayer shell around the particle. The binding of the shell utilizes a guanidinium-phosphonate interaction analogous to the one exploited by the Wender molecular transporter system. Particle-shell binding was characterized by a 27% decrease in 19F T1 of the fluorous shell upon exposure to the paramagnetic gadolinium in the particle and a corresponding increase in hydrodynamic diameter from 3 nm to 4 nm. Interestingly, a much smaller modulation of 19F T1 is observed when the shell monomer is treated with a phosphonate-free particle. By contrast, the phosphonate-free particle is a much more relaxive 1H T1 agent for water. Together, these observations show that the fluoroalkylguanidinium shell binds selectively to the phosphonate-covered particle. The system's relaxivity and selectivity give it potential for use in 19F based nanotheranostic agents.

Replenishable dendrimer-nanoparticle hybrid membranes for sustained release of therapeutics

We report a versatile hybrid membrane for sustained release therapeutic delivery systems. Chemically-directed assembly of a hybrid membrane of nanoparticles and dendrimers was integrated with a fluidic delivery device and a refillable drug reservoir, providing continuous sustained release.

Chitosan-coated triangular silver nanoparticles as a novel class of biocompatible, highly sensitive plasmonic platforms for intracellular SERS sensing and imaging

There is a need for new strategies for noninvasive imaging of pathological conditions within the human body. The approach of combining the unique physical properties of noble-metal nanoparticles with their chemical specificity and an easy way of conjugation open up new routes toward building bio-nano-objects for biomedical tracking and imaging. This work reports the design and assessment of a novel class of biocompatible, highly sensitive SERS nanotags based on chitosan-coated silver nanotriangles (Chit-AgNTs) labeled with para-aminothiophenol (p-ATP). The triangular nanoparticles are used as Raman scattering enhancers and have proved to yield a reproducible and strong SERS signal. When tested inside lung cancer cells (A549) this class of SERS nanotags presents low in vitro toxicity, without interfering with cell proliferation. Easily internalized by the cells, as demonstrated by imaging using both reflected bright-light optical microscopy and SERS spectroscopy, the particles are proved to be detectable inside cells under a wide window of excitation wavelengths, ranging from visible to near infrared (NIR). Their high sensitivity and NIR availability make this class of SERS nanotags a promising candidate for noninvasive imaging of cancer cells.

From atoms to layers: in situ gold cluster growth kinetics during sputter deposition

The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction of morphological real space parameters, such as cluster size and shape, correlation distance, layer porosity and surface coverage, directly from reciprocal space scattering data. This approach enables a large variety of future investigations of the influence of different process parameters on the thin metal film morphology. Furthermore, our study allows for deducing the wetting behavior of gold cluster films on solid substrates and provides a better understanding of the growth kinetics in general, which is essential for optimization of manufacturing parameters, saving energy and resources.

Release of Nile red from thermoresponsive gold nanocomposites by heating a solution and the addition of glutathione

Thermoresponsive gold nanocomposites encapsulating Nile red were fabricated by the conjugation of gold nanoparticles containing Nile red with a thermoresponsive polymer, poly(N-isopropylacrylamide(90 mol%)-co-N-acryloyldiethylenetriamine(10 mol%)). They were then examined as a model of drug delivery carriers and colloidal fluorescence sensors. Nile red, as a fluorophore to be released, was introduced to the surface of gold nanoparticles prior to conjugation with thermoresponsive polymers. Heating a solution at 90°C resulted in shrinkage of the thermoresponsive polymers, which facilitated disassembly of the gold nanocomposites in the presence of glutathione. This disassembly caused a replacement of Nile red with glutathione at the surface of the gold nanoparticles, followed by the release of Nile red from the gold nanocomposites. Nile red liberated from the gold surface recovered its inherent fluorescence properties that had been quenched by gold nanoparticles through fluorescence resonance energy transfer. The fluorescence intensity of the liberated Nile red increased linearly as the glutathione concentration increased up to 1.0 × 10(-5) mol/L, demonstrating that thermoresponsive gold nanocomposites can be used as colloidal sensors or drug delivery carriers that can be manipulated by the concentration of glutathione and the solution temperature. The applicability of the thermoresponsive gold nanocomposites to colloidal fluorescence probes was also checked by assay of glutathione in tablets.

Imaging inward and outward trafficking of gold nanoparticles in whole animals

Gold nanoparticles have emerged as novel safe and biocompatible tools for manifold applications, including biological imaging, clinical diagnostics, and therapeutics. The understanding of the mechanisms governing their interaction with living systems may help the design and development of new platforms for nanomedicine. Here we characterized the dynamics and kinetics of the events underlying the interaction of gold nanoparticles with a living organism, from the first interaction nanoparticle/cell membrane, to the intracellular trafficking and final extracellular clearance. By treating a simple water invertebrate (the cnidarian Hydra polyp) with functionalized gold nanoparticles, multiple inward and outward routes were imaged by ultrastructural analyses, including exosomes as novel undescribed carriers to shuttle the nanoparticles in and out the cells. From the time course imaging a highly dynamic picture emerged in which nanoparticles are rapidly internalized (from 30 min onward), recruited into vacuoles/endosome (24 h onward), which then fuse, compact and sort out the internalized material either to storage vacuoles or to late-endosome/lysosomes, determining almost complete clearance within 48 h from challenging. Beside classical routes, new portals of entry/exit were captured, including exosome-like structures as novel undescribed nanoparticle shuttles. The conservation of the endocytic/secretory machinery through evolution extends the value of our finding to mammalian systems providing dynamics and kinetics clues to take into account when designing nanomaterials to interface with biological entities.

Surface functionalities of gold nanoparticles impact embryonic gene expression responses

Incorporation of gold nanoparticles (AuNPs) into consumer products is increasing; however, there is a gap in available toxicological data to determine the safety of AuNPs. In this study, we utilised the embryonic zebrafish to investigate how surface functionalisation and charge influence molecular responses. Precisely engineered AuNPs with 1.5 nm cores were synthesised and functionalized with three ligands: 2-mercaptoethanesulfonic acid (MES), N,N,N-trimethylammoniumethanethiol (TMAT), or 2-(2-(2-mercaptoethoxy)ethoxy)ethanol. Developmental assessments revealed differential biological responses when embryos were exposed to the functionalised AuNPs at the same concentration. Using inductively coupled plasma-mass spectrometry, AuNP uptake was confirmed in exposed embryos. Following exposure to MES- and TMAT-AuNPs from 6 to 24 or 6 to 48 h post fertilisation, pathways involved in inflammation and immune response were perturbed. Additionally, transport mechanisms were misregulated after exposure to TMAT and MES-AuNPs, demonstrating that surface functionalisation influences many molecular pathways.

Multifunctional gold nanoparticles for diagnosis and therapy of disease

Gold nanoparticles (AuNPs) have a number of physical properties that make them appealing for medical applications. For example, the attenuation of X-rays by gold nanoparticles has led to their use in computed tomography imaging and as adjuvants for radiotherapy. AuNPs have numerous other applications in imaging, therapy and diagnostic systems. The advanced state of synthetic chemistry of gold nanoparticles offers precise control over physicochemical and optical properties. Furthermore gold cores are inert and are considered to be biocompatible and nontoxic. The surface of gold nanoparticles can easily be modified for a specific application, and ligands for targeting, drugs or biocompatible coatings can be introduced. AuNPs can be incorporated into larger structures such as polymeric nanoparticles or liposomes that deliver large payloads for enhanced diagnostic applications, efficiently encapsulate drugs for concurrent therapy or add additional imaging labels. This array of features has led to the aforementioned applications in biomedical fields, but more recently in approaches where multifunctional gold nanoparticles are used for multiple methods, such as concurrent diagnosis and therapy, so-called theranostics. This review covers basic principles and recent findings in gold nanoparticle applications for imaging, therapy and diagnostics, with a focus on reports of multifunctional AuNPs.

A solution to the PEG dilemma: efficient bioconjugation of large gold nanoparticles for biodiagnostic applications using mixed layers

Gold nanoparticles are of high interest in the biodiagnostic and bioimaging field owing to their unique optical properties such as localized surface plasmon resonance (LSPR) and high Rayleigh scattering efficiency in the visible range. Although biofunctionalization is a prerequirement prior to their integration in diagnostic procedures, aggregation-free conjugation of biomacromolecules to large gold nanoparticle is not trivial. Here, a robust and simple method based on commercially available reactants is reported for the efficient biofunctionalization of gold nanoparticles with sizes ranging from 15 to 175 nm. It is demonstrated that mixed poly(ethylene glycol) (PEG) layers, prepared using specific ratios of low- and high-molecular-weight PEG chains, can be conjugated to proteins and monoclonal antibodies using standard carbodiimide chemistry without detectable aggregation. The properties of the mixed PEG interlayer modified gold nanoparticles were investigated using UV-vis spectrometer, dynamic light scattering, and X-ray photoelectron spectroscopy, which demonstrated the importance of controlling biointerfacial properties. Using the epithelial cell adhesion molecule (EpCAM) as a model target antigen, the benefit of the mixed PEG layers over coatings prepared using high-molecular-weight PEG chains only is demonstrated in vitro using bright field microscopy and reflectance confocal microscopy. Very high binding affinity to breast cancer cells was obtained for the mixed PEG layers. This robust procedure demonstrates that, under optimal conditions, a compromise can be achieved between the excellent steric protection provided by thick PEG adlayers and the high bioconjugation yields afforded by adlayers from low-molecular-weight tethers.

Nanomechanical characterization of chemical interaction between gold nanoparticles and chemical functional groups

We report on how to quantify the binding affinity between a nanoparticle and chemical functional group using various experimental methods such as cantilever assay, PeakForce quantitative nanomechanical property mapping, and lateral force microscopy. For the immobilization of Au nanoparticles (AuNPs) onto a microscale silicon substrate, we have considered two different chemical functional molecules of amine and catecholamine (here, dopamine was used). It is found that catecholamine-modified surface is more effective for the functionalization of AuNPs onto the surface than the amine-modified surface, which has been shown from our various experiments. The dimensionless parameter (i.e., ratio of binding affinity) introduced in this work from such experiments is useful in quantitatively depicting such binding affinity, indicating that the binding affinity and stability between AuNPs and catecholamine is approximately 1.5 times stronger than that between amine and AuNPs. Our study sheds light on the experiment-based quantitative characterization of the binding affinity between nanomaterial and chemical groups, which will eventually provide an insight into how to effectively design the functional material using chemical groups.

INTRACELLULAR LOCALIZATION AND KINETICS OF UPTAKE AND CLEARANCE OF GOLD NANOPARTICLES IN PRIMARY HEPATIC CELLS

Gold nanoparticles (AuNPs) used for therapeutic applications preferentially accumulate in the liver following exposure. However, uptake and clearance by hepatic cells are not well understood. Time-dependent intracellular localization, uptake and clearance of 30 nm AuNPs were monitored in primary rat hepatocytes and liver sinusoidal endothelial cells (LSECs). Confocal Raman microscopy studies demonstrated the differences in the localization of AuNPs in hepatic cells over a 24 h period. The uptake of unmodified AuNPs over 24 h was 17% and 55% for hepatocytes and LSECs. The uptake of poly(ethylene glycol)-coated AuNPs was 3% and 1% over 24 h in hepatocytes and LSECs, respectively. Both cell types expelled approximately 60–70% of intracellular AuNPs within seven days. AuNP accumulation resulted in the disruption of the pericanalicular actin between adjoining hepatocytes. These trends suggest that AuNPs may affect actin organization, which could impair hepatic function long term.

Physical basis and biological mechanisms of gold nanoparticle radiosensitization

The unique properties of nanomaterials, in particular gold nanoparticles (GNPs) have applications for a wide range of biomedical applications. GNPs have been proposed as novel radiosensitizing agents due to their strong photoelectric absorption coefficient. Experimental evidence supporting the application of GNPs as radiosensitizing agents has been provided from extensive in vitro investigation and a relatively limited number of in vivo studies. Whilst these studies provide experimental evidence for the use of GNPs in combination with ionising radiation, there is an apparent disparity between the observed experimental findings and the level of radiosensitization predicted by mass energy absorption and GNP concentration. This review summarises experimental findings and attempts to highlight potential underlying biological mechanisms of response in GNP radiosensitization.

Gold nanoparticles in theranostic oncology: current state-of-the-art

INTRODUCTION

In recent years, extensive multidisciplinary investigations have been carried out in the area of cancer nanotechnology. Gold nanoparticles (GNPs) have emerged as promising carrier for delivery of various pay-loads into their target. In view of their unique physicochemical and optical properties, GNPs have been exploited for multimodality imaging, tumor targeting, and as transporter of various therapeutics. Additionally, GNPs have been used as photothermal therapeutics against cancer.

AREAS COVERED

This review will focus on recent progress in the field of gold nanomaterials in cancer therapy and diagnosis. Moreover, concern about the toxicity of gold nanomaterials is addressed.

EXPERT OPINION

GNPs present versatile scaffolds for efficient delivery of cancer chemotherapeutics. Tuneable chemistry of the GNPs contributes to their ever increasing use in oncology research. The promises of a functional cancer therapy using GNPs have been extensively demonstrated, although the materials are still in their infancy stage and not surfaced to meet clinical standards.

Enhanced delivery of gold nanoparticles with therapeutic potential into the brain using MRI-guided focused ultrasound

The blood brain barrier (BBB) is a major impediment to the delivery of therapeutics into the central nervous system (CNS). Gold nanoparticles (AuNPs) have been successfully employed in multiple potential therapeutic and diagnostic applications outside the CNS. However, AuNPs have very limited biodistribution within the CNS following intravenous administration. Magnetic resonance imaging guided focused ultrasound (MRgFUS) is a novel technique that can transiently increase BBB permeability allowing delivery of therapeutics into the CNS. MRgFUS has not been previously employed for delivery of AuNPs into the CNS. This work represents the first demonstration of focal enhanced delivery of AuNPs into the CNS using MRgFUS in a rat model both safely and effectively. Histologic visualization and analytical quantification of AuNPs within the brain parenchyma suggest BBB transgression. These results suggest a role for MRgFUS in the delivery of AuNPs with therapeutic potential into the CNS for targeting neurological diseases.

FROM THE CLINICAL EDITOR

Gold nanoparticles have been successfully utilized in experimental diagnostic and therapeutic applications; however, the blood-brain barrier (BBB) is not permeable to these particles. In this paper, the authors demonstrated that MRI guided focused ultrasound is capable to transiently open the BBB thereby enabling CNS access.

Electrochemically controlled assembly and logic gates operations of gold nanoparticle arrays

The reversible assembly of β-cyclodextrin-functionalized gold NPs (β-CD Au NPs) is studied on mixed self-assembled monolayer (SAM), formed by coadsorption of redox-active ferrocenylalkylthiols and n-alkanethiols on gold surfaces. The surface coverage and spatial distribution of the β-CD Au NPs monolayer on the gold substrate are tuned by the self-assembled monolayer composition. The binding and release of β-CD Au NPs to and from the SAMs modified surface are followed by surface plasmon resonance (SPR) spectroscopy. The redox state of the tethered ferrocene in binary SAMs controls the formation of the supramolecular interaction between ferrocene moieties and β-CD-capped Au NPs. As a result, the potential-induced uptake and release of β-CD Au NPs to and from the surface is accomplished. The competitive binding of β-CD Au NPs with guest molecules in solution shifted the equilibrium of the complexation-decomplexation process involving the supramolecular interaction with the Fc-functionalized surface. The dual controlled assembly of β-CD Au NPs on the surface enabled to use two stimuli as inputs for logic gate activation; the coupling between the localized surface plasmon, associated with the Au NP, and the surface plasmon wave, associated with the thin metal surface, is implemented as readout signal for "AND" logic gate operations.

Monolayer coated gold nanoparticles for delivery applications

Gold nanoparticles (AuNPs) provide attractive vehicles for delivery of drugs, genetic materials, proteins, and small molecules. AuNPs feature low core toxicity coupled with the ability to parametrically control particle size and surface properties. In this review, we focus on engineering of the AuNP surface monolayer, highlighting recent advances in tuning monolayer structures for efficient delivery of drugs and biomolecules. This review covers two broad categories of particle functionalization, organic monolayers and biomolecule coatings, and discusses their applications in drug, DNA/RNA, protein and small molecule delivery.

Multiphoton molecular photorelease in click-chemistry-functionalized gold nanoparticles

Yellow-green controlled photorelease: probes click-linked to peptide-coated gold nanospheres by a triazole ring can be released in living cells under a focused 561 nm laser at low power. Photocleaving follows a three-photon event stimulated by the excitation of the localized surface plasmon resonance.

Toxicology and clinical potential of nanoparticles

In recent years, nanoparticles (NPs) have increasingly found practical applications in technology, research and medicine. The small particle size coupled to their unique chemical and physical properties is thought to underlie their exploitable biomedical activities. Here, we review current toxicity studies of NPs with clinical potential. Mechanisms of cytotoxicity are discussed and the problem of extrapolating knowledge gained from cell-based studies into a human scenario is highlighted. The so-called 'proof-of-principle' approach, whereby ultra-high NP concentrations are used to ensure cytotoxicity, is evaluated on the basis of two considerations; firstly, from a scientific perspective, the concentrations used are in no way related to the actual doses required which, in many instances, discourages further vital investigations. Secondly, these inaccurate results cast doubt on the science of nanomedicine and thus, quite dangerously, encourage unnecessary alarm in the public. In this context, the discrepancies between in vitro and in vivo results are described along with the need for a unifying protocol for reliable and realistic toxicity reports.

Gold nanoparticles in biomedical applications: recent advances and perspectives

Gold nanoparticles (GNPs) with controlled geometrical, optical, and surface chemical properties are the subject of intensive studies and applications in biology and medicine. To date, the ever increasing diversity of published examples has included genomics and biosensorics, immunoassays and clinical chemistry, photothermolysis of cancer cells and tumors, targeted delivery of drugs and antigens, and optical bioimaging of cells and tissues with state-of-the-art nanophotonic detection systems. This critical review is focused on the application of GNP conjugates to biomedical diagnostics and analytics, photothermal and photodynamic therapies, and delivery of target molecules. Distinct from other published reviews, we present a summary of the immunological properties of GNPs. For each of the above topics, the basic principles, recent advances, and current challenges are discussed (508 references).

Towards new therapeutic approaches for malignant melanoma

Recent progress in understanding the molecular mechanisms of the initiation and progression of melanoma has created new opportunities for developing novel therapeutic modalities to manage this potentially lethal disease. Although at first glance, melanoma carcinogenesis appears to be a chaotic system, it is indeed, arguably, a deterministic multistep process involving sequential alterations of proto-oncogenes, tumour suppressors and miRNA genes. The scope of this article is to discuss the most recent and significant advances in melanoma molecular therapeutics. It is apparent that using single agents targeting solely individual melanoma pathways might be insufficient for long-term survival. However, the outstanding results on melanoma survival observed with novel selective inhibitors of B-RAF, such as PLX4032 give hope that melanoma can be cured. The fact that melanoma develops acquired resistance to PLX4032 emphasises the importance of simultaneously targeting several pathways. Because the most striking feature of melanoma is its unsurpassed ability to metastasise, it is important to implement newer systems for drug delivery adapted from research on stem cells and nanotechnology.

Modulating pharmacokinetics, tumor uptake and biodistribution by engineered nanoparticles

Background

Inorganic nanoparticles provide promising tools for biomedical applications including detection, diagnosis and therapy. While surface properties such as charge are expected to play an important role in their in vivo behavior, very little is known how the surface chemistry of nanoparticles influences their pharmacokinetics, tumor uptake, and biodistribution.

Method/Principal Findings

Using a family of structurally homologous nanoparticles we have investigated how pharmacological properties including tumor uptake and biodistribution are influenced by surface charge using neutral (TEGOH), zwitterionic (Tzwit), negative (TCOOH) and positive (TTMA) nanoparticles. Nanoparticles were injected into mice (normal and athymic) either in the tail vein or into the peritoneum.

Conclusion

Neutral and zwitterionic nanoparticles demonstrated longer circulation time via both IP and IV administration, whereas negatively and positively charged nanoparticles possessed relatively short half-lives. These pharmacological characteristics were reflected on the tumor uptake and biodistribution of the respective nanoparticles, with enhanced tumor uptake by neutral and zwitterionic nanoparticles via passive targeting.

Nano meets biology: structure and function at the nanoparticle interface

Understanding the interactions of nanomaterials with biosystems is a critical goal in both biomedicine and environmental science. Engineered nanoparticles provide excellent tools for probing this interface. In this feature article, we will summarize one of the themes presented in our recent Langmuir lecture discussing the use of monolayer design to understand and control the interactions of nanoparticles with biomolecules and cells.

Gold nanoparticles in cancer therapy

The rapid advancement of nanotechnology in recent years has fuelled a burgeoning interest in the field of nanoparticle research, in particular, its application in the medical arena. A constantly expanding knowledge based on a better understanding of the properties of gold nanoparticles (AuNPs) coupled with relentless experimentation means that the frontiers of nanotechnology are constantly being challenged. At present, there seems to be heightened interest in the application of AuNPs to the management of cancer, encompassing diagnosis, monitoring and treatment of the disease. These efforts are undertaken in the hope of revolutionizing current methods of treatment and treatment strategies for a multifactorial disease such as cancer. This review will focus on the current applications of AuNPs in cancer management.

Beauty is skin deep: a surface monolayer perspective on nanoparticle interactions with cells and bio-macromolecules

Surface recognition of biosystems is a critical component in the development of novel biosensors and delivery vehicles, and for the therapeutic regulation of biological processes. Monolayer-protected nanoparticles present a highly versatile scaffold for selective interaction with bio-macromolecules and cells. Through the engineering of the monolayer surface, nanoparticles can be tailored for surface recognition of biomolecules and cells. This review highlights recent progress in nanoparticle-bio-macromolecule/cellular interactions, emphasizing the effect of the surface monolayer structure on the interactions with proteins, DNA, and cell surfaces. The extension of these tailored interactions to hybrid nanomaterials, biosensing platforms, and delivery vehicles is also discussed.

Probing DNA's interstrand orientation with gold nanoparticles

The interstrand orientation of a DNA duplex plays a pivotal role in its biological and chemical functions. Therefore, developing an efficient way to determine (control and monitor) the parallel or antiparallel conformation of a DNA duplex is of great significance, which, however, remains a big challenge under some circumstances. In this work, we demonstrate that gold nanoparticles tagged on DNA are especially useful in trapping and detecting a special interstrand orientation of a DNA double helix, based on inherent electrostatic and steric repulsions between nanoparticles which will affect their self-assembly into a large structure. More importantly, some of the conformations revealed by the gold nanoparticle assay may even not be thermodynamically preferred and thus will be hard to detect using currently available methods. This simple, straightforward, and efficient methodology capable of dictating and probing a special DNA duplex structure provides a useful tool for conformational analyses and functional explorations of biomolecules as well as biophysical and nanobiomedical research.

Anti-cancer studies of noble metal nanoparticles synthesized using different plant extracts

Biofunctionalized gold and silver nanoparticles synthesized using different plant extracts of guava and clove in vitro anti-cancer efficacy against four different cancer cell lines human colorectal adenocarcinoma, human kidney, human chronic myelogenous, leukemia, bone marrow, and human cervix have been studied and reported. The present experimental study suggests that flavonoids functionalized gold nanoparticles synthesized using aqueous clove buds extract are more potential than guava leaf extract towards anti-cancer activities. The microscopic and 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide (XTT) assay infer that the functionalized irregular shaped gold nanoparticles synthesized with aqueous clove bud extract showed a satisfactory anti-cancer effect on all the cell lines. The silver nanoparticles synthesized using same extracts are devoid of anti-cancer activity. The XTT assay revealed dose-dependent cytotoxicity to cancer cell lines. The study revealed that the free radicals generated by gold nanoparticles are responsible for anti-cancer effect. To confirm the free-radical scavenging efficacy of gold nanoparticle, nitric oxide assay is followed. We observed that the gold nanoparticles swabbed the free radicals in dose-dependent manner. With continued improvements, these nanoparticles may prove to be potential anti-cancer agents.

Single-step biofriendly synthesis of surface modifiable, near-spherical gold nanoparticles for applications in biological detection and catalysis

There is an increased interest in understanding the toxicity and rational design of gold nanoparticles (GNPs) for biomedical applications in recent years. Such efforts warrant reliable, viable, and biofriendly synthetic methodology for GNPs with homogeneous sizes and shapes, particularly sizes above 30 nm, which is currently challenging. In the present study, an environmentally benign, biofriendly, single-step/single-phase synthetic method using dextrose as a reducing and capping agent in a buffered aqueous solution at moderate temperature is introduced. The resulting GNPs are near-spherical, stable, catalytically active, place exchangeable, and water-soluble within the size range of 10-120 nm. The added advantage of the biologically friendly reaction medium employed in this new synthetic approach provides a method for the direct embedment/integration of GNPs into biological systems such as the E. coli bacterium without additional capping ligand or surface modification processes.

Visualizing gold nanoparticle uptake in live cells with liquid scanning transmission electron microscopy

The intracellular uptake of 30 nm diameter gold nanoparticles (Au-NPs) was studied at the nanoscale in pristine eukaryotic cells. Live COS-7 cells were maintained in a microfluidic chamber and imaged using scanning transmission electron microscopy. A quantitative image analysis showed that Au-NPs bound to the membranes of vesicles, possibly lysosomes, and occupied 67% of the available surface area. The vesicles accumulated to form a micrometer-sized cluster after 24 h of incubation. Two clusters were analyzed and found to consist of 117 ± 9 and 164 ± 4 NP-filled vesicles.