Seven challenges for nanomedicine

Polymeric nanoparticles: the future of nanomedicine

Polymeric nanoparticles (NPs) are one of the most studied organic strategies for nanomedicine. Intense interest lies in the potential of polymeric NPs to revolutionize modern medicine. To determine the ideal nanosystem for more effective and distinctly targeted delivery of therapeutic applications, particle size, morphology, material choice, and processing techniques are all research areas of interest. Utilizations of polymeric NPs include drug delivery techniques such as conjugation and entrapment of drugs, prodrugs, stimuli-responsive systems, imaging modalities, and theranostics. Cancer, neurodegenerative disorders, and cardiovascular diseases are fields impacted by NP technologies that push scientific boundaries to the leading edge of transformative advances for nanomedicine.

Nanotechnology in the war against cancer: new arms against an old enemy – a clinical view

ABSTRACT 

Clinical oncology is facing a paradigm shift. A new treatment philosophy is emerging and new targets are appearing that require new active agents. The medical use of nanotechnology – nanomedicine – holds several promising possibilities in the war against cancer. Some of these include: new formats for old drugs, that is, increasing efficacy while diminishing side effects; and new administration routes – that is, dermal, oral and pulmonary. In this overview, we describe some nanoparticles and their medical uses as well as highlight advantages of nanoparticles compared with conventional pharmaceuticals. We also point to some of the many technical challenges and potential risks with using nanotechnology for oncological applications.

Ultrasmall [(64)Cu]Cu nanoclusters for targeting orthotopic lung tumors using accurate positron emission tomography imaging

Positron emission tomography (PET) imaging has received special attention owing to its higher sensitivity, temporal resolution, and unlimited tissue penetration. The development of tracers that target specific molecules is therefore essential for the development and utility of clinically relevant PET procedures. However, (64)Cu as a PET imaging agent generally has been introduced into biomaterials through macrocyclic chelators, which may lead to the misinterpretation of PET imaging results due to the detachment and transchelation of (64)Cu. In this study, we have developed ultrasmall chelator-free radioactive [(64)Cu]Cu nanoclusters using bovine serum albumin (BSA) as a scaffold for PET imaging in an orthotopic lung cancer model. We preconjugated the tumor target peptide luteinizing hormone releasing hormone (LHRH) to BSA molecules to prepare [(64)Cu]CuNC@BSA-LHRH. The prepared [(64)Cu]Cu nanoclusters showed high radiolabeling stability, ultrasmall size, and rapid deposition and diffusion into tumor, as well as predominantly renal clearance. [(64)Cu]CuNC@BSA-LHRH showed 4 times higher tumor uptake compared with that of [(64)Cu]CuNC@BSA by analyzing the (64)Cu radioactivity of tissues via gamma counting. The PET imaging using [(64)Cu]Cu nanoclusters as tracers showed more sensitive, accurate, and deep penetration imaging of orthotopic lung cancer in vivo compared with near-infrared fluorescence imaging. The nanoclusters provide biomedical research tools for PET molecular imaging.

Pharmacokinetics of quercetin-loaded nanodroplets with ultrasound activation and their use for bioimaging

Bubble formulations have both diagnostic and therapeutic applications. However, research on nanobubbles/nanodroplets remains in the initial stages. In this study, a nanodroplet formulation was prepared and loaded with a novel class of chemotherapeutic drug, ie, quercetin, to observe its pharmacokinetic properties and ultrasonic bioimaging of specific sites, namely the abdominal vein and bladder. Four parallel groups were designed to investigate the effects of ultrasound and nanodroplets on the pharmacokinetics of quercetin. These groups were quercetin alone, quercetin triggered with ultrasound, quercetin-encapsulated in nanodroplets, and quercetin encapsulated in nanodroplets triggered with ultrasound. Spherical vesicles with a mean diameter of 280 nm were formed, and quercetin was completely encapsulated within. In vivo ultrasonic imaging confirmed that the nanodroplets could be treated by ultrasound. The results indicate that the initial 5-minute serum concentration, area under the concentration–time curve, elimination half-life, and clearance of quercetin were significantly enhanced by nanodroplets with or without ultrasound.

Protein binding for detection of small changes on a nanoparticle surface

Protein adsorption on nanoparticles is closely associated with the physicochemical properties of particles, in particular, their surface properties. We synthesized two batches of polyacrylic acid-coated nanoparticles under almost identical conditions except for the heating duration and found differences in the head-group structure of the polyacrylic acid. The structure change was confirmed by NMR and MS. The two batches of particles had varied binding affinities to a selected group of proteins. Computational work confirmed that the head group of the polymer on the surface of a nanoparticle could directly interact with a protein, and small structural changes in the head group were sufficient to result in a significant difference in the free energy of binding. Our results demonstrate that protein adsorption is so sensitive to the surface properties of particles that it can reveal even small variations in the structure of a nanoparticle surface ligand, and should be useful for quick assessment of nanoparticle properties.

PEG-b-AGE Polymer Coated Magnetic Nanoparticle Probes with Facile Functionalization and Anti-fouling Properties for Reducing Non-specific Uptake and Improving Biomarker Targeting

Non-specific surface adsorption of bio-macromolecules (e.g. proteins) on nanoparticles, known as biofouling, and the uptake of nanoparticles by the mononuclear phagocyte system (MPS) and reticuloendothelial system (RES) lead to substantial reduction in the efficiency of target-directed imaging and delivery in biomedical applications of engineered nanomaterials in vitro and in vivo. In this work, a novel copolymer consisting of blocks of poly ethylene glycol and allyl glycidyl ether (PEG-b-AGE) was developed for coating magnetic iron oxide nanoparticles (IONPs) to reduce non-specific protein adhesion that leads to formation of "protein corona" and uptake by macrophages. The facile surface functionalization was demonstrated by using targeting ligands of a small peptide of RGD or a whole protein of transferrin (Tf). The PEG-b-AGE coated IONPs exhibited anti-biofouling properties with significantly reduced protein corona formation and non-specific uptake by macrophages before and after the surface functionalization, thus improving targeting of RGD-conjugated PEG-b-AGE coated IONPs to integrins in U87MG glioblastoma and MDA-MB-231 breast cancer cells that overexpress α_vβ₃ integrins, and Tf-conjugated PEG-b-AGE coated IONPs to transferrin receptor (TfR) in D556 and Daoy medulloblastoma cancer cells with high overexpression of transferrin receptor, compared to respective control cell lines. Magnetic resonance imaging (MRI) of cancer cells treated with targeted IONPs with or without anti-biofouling PEG-b-AGE coating polymers demonstrated the target specific MRI contrast change using anti-biofouling PEG-b-AGE coated IONP with minimal off-targeted background compared to the IONPs without anti-biofouling coating, promising the highly efficient active targeting of nanoparticle imaging probes and drug delivery systems and potential applications of imaging quantification of targeted biomarkers.

Amphiphilic p-sulfonatocalix[4]arene as "drug chaperone" for escorting anticancer drugs

Supramolecularly constructing multifunctional platform for drug delivery is a challenging task. In this work, we propose a novel supramolecular strategy “drug chaperone”, in which macrocyclic amphiphiles directly coassemble with cationic drugs into a multifunctional platform and its surface is further decorated with targeting ligands through host–guest recognition. The coassembling and hierarchical decoration processes were monitored by optical transmittance measurements, and the size and morphology of amphiphilic coassemblies were identified by dynamic light scattering and high-resolution transmission electron microscopy. In cell experiments to validate the drug chaperone strategy, the anticancer activities of free drugs were pronouncedly improved by coassembling with amphiphilic chaperone and further functionalization with targeting ligand.

Monocyte-mediated delivery of polymeric backpacks to inflamed tissues: a generalized strategy to deliver drugs to treat inflammation

Targeted delivery of drugs and imaging agents to inflamed tissues, as in the cases of cancer, Alzheimer's disease, Parkinson's disease, and arthritis, represents one of the major challenges in drug delivery. Monocytes possess a unique ability to target and penetrate into sites of inflammation. Here, we describe a broad approach to take advantage of the natural ability of monocytes to target and deliver flat polymeric particles ("Cellular Backpacks") to inflamed tissues. Cellular backpacks attach strongly to the surface of monocytes but do not undergo phagocytosis due to backpack's size, disk-like shape and flexibility. Following attachment of backpacks, monocytes retain important cellular functions including transmigration through an endothelial monolayer and differentiation into macrophages. In two separate in vivo inflammation models, backpack-laden monocytes exhibit increased targeting to inflamed tissues. Cellular backpacks, and their abilities to attach to monocytes without impairing monocyte functions and 'hitchhike' to a variety of inflamed tissues, offer a new platform for both cell-mediated therapies and broad targeting of inflamed tissues.

Platelet-like nanoparticles: mimicking shape, flexibility, and surface biology of platelets to target vascular injuries

Targeted delivery of therapeutic and imaging agents in the vascular compartment represents a significant hurdle in using nanomedicine for treating hemorrhage, thrombosis, and atherosclerosis. While several types of nanoparticles have been developed to meet this goal, their utility is limited by poor circulation, limited margination, and minimal targeting. Platelets have an innate ability to marginate to the vascular wall and specifically interact with vascular injury sites. These platelet functions are mediated by their shape, flexibility, and complex surface interactions. Inspired by this, we report the design and evaluation of nanoparticles that exhibit platelet-like functions including vascular injury site-directed margination, site-specific adhesion, and amplification of injury site-specific aggregation. Our nanoparticles mimic four key attributes of platelets, (i) discoidal morphology, (ii) mechanical flexibility, (iii) biophysically and biochemically mediated aggregation, and (iv) heteromultivalent presentation of ligands that mediate adhesion to both von Willebrand Factor and collagen, as well as specific clustering to activated platelets. Platelet-like nanoparticles (PLNs) exhibit enhanced surface-binding compared to spherical and rigid discoidal counterparts and site-selective adhesive and platelet-aggregatory properties under physiological flow conditions in vitro. In vivo studies in a mouse model demonstrated that PLNs accumulate at the wound site and induce ∼65% reduction in bleeding time, effectively mimicking and improving the hemostatic functions of natural platelets. We show that both the biochemical and biophysical design parameters of PLNs are essential in mimicking platelets and their hemostatic functions. PLNs offer a nanoscale technology that integrates platelet-mimetic biophysical and biochemical properties for potential applications in injectable synthetic hemostats and vascularly targeted payload delivery.

Nanoassembly of probucol enables novel therapeutic efficacy in the suppression of lung metastasis of breast cancer

Metastasis is one of the major obstacles hindering the success of cancer therapy. The directed nanoassembly of probucol results in the "DNP" system, which greatly improves the oral delivery of probucol and subsequently leads to a novel therapeutic efficacy of probucol in the suppression of lung metastasis of breast cancer. DNP is formed by employing the intermolecular hydrophobic interactions between probucol and polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether (also known as Triton X-100). After oral administration, the probucol concentration in the intestines is surprisingly about 200 times higher if it is applied as DNP rather than free probucol; it can be absorbed into intestinal enterocytes via clathrin-mediated endocytosis and transported into the systemic circulation through the lymphatic pathway. Moreover, the oral bioavailability of probucol is significantly higher-13.55 times higher-when applied as DNP in place of free probucol. The drug concentration in major organs is also significantly increased. The in vitro measurements show that the migration and invasion abilities of 4T1 cells are obviously inhibited by DNP. In particular, in an orthotopic metastatic breast cancer model, the notable suppression of lung metastasis from DNP is observed, but no effect is seen from the free-probucol suspension. As a result, the directed drug nanoassembly may open a new route for enhancing oral drug delivery and enable new therapeutic abilities for probucol against cancer metastasis.

Tenfibgen ligand nanoencapsulation delivers bi-functional anti-CK2 RNAi oligomer to key sites for prostate cancer targeting using human xenograft tumors in mice

Protected and specific delivery of nucleic acids to malignant cells remains a highly desirable approach for cancer therapy. Here we present data on the physical and chemical characteristics, mechanism of action, and pilot therapeutic efficacy of a tenfibgen (TBG)-shell nanocapsule technology for tumor-directed delivery of single stranded DNA/RNA chimeric oligomers targeting CK2αα' to xenograft tumors in mice. The sub-50 nm size TBG nanocapsule (s50-TBG) is a slightly negatively charged, uniform particle of 15 - 20 nm size which confers protection to the nucleic acid cargo. The DNA/RNA chimeric oligomer (RNAi-CK2) functions to decrease CK2αα' expression levels via both siRNA and antisense mechanisms. Systemic delivery of s50-TBG-RNAi-CK2 specifically targets malignant cells, including tumor cells in bone, and at low doses reduces size and CK2-related signals in orthotopic primary and metastatic xenograft prostate cancer tumors. In conclusion, the s50-TBG nanoencapsulation technology together with the chimeric oligomer targeting CK2αα' offer significant promise for systemic treatment of prostate malignancy.

A novel hydrolysis-resistant lipophilic folate derivative enables stable delivery of targeted liposomes in vivo

Instability of targeting ligand is a roadblock towards successful development of folate targeted liposomes. Folate ligands have been linked to polyethylene glycol (PEG) and cholesterol by an amide bond to form folate-CONH-PEG-CONH-Cholesterol (F-CONH-PEG-CONH-Chol), which is subject to hydrolysis. To increase the stability of folate ligands and promote the long circulation and targeting effects, we synthesized a chemically stable lipophilic folate derivative, folate-CONH-PEG-NH-Cholesterol (F-CONH-PEG-NH-Chol), where the amide bond was replaced by a C-N bond, to deliver liposomal doxorubicin (Dox). Its physical stability, cellular uptake, cellular toxicity, pharmacokinetics, distribution, anti-tumor efficacy, and cardiac toxicity were investigated. Our results indicate that F-CONH-PEG-NH-Chol conjugated liposomes are taken up selectively by folate receptor-positive HeLa and KB cells. Compared with F-CONH-PEG-CONH-Chol with two carbonate linkages, F-CONH-PEG-NH-Chol better retained its drug entrapment efficiency and folate receptor-targeting activity during prolonged circulation. F-CONH-PEG-NH-Chol thus represents a physically stable and effective ligand for delivering folate receptor-targeted liposomes, with prolonged circulation time and efficient tissue distribution, as well as higher efficacy and less cardiac toxicity. Collectively, these results suggest that this novel conjugate can serve as a promising derivative for the delivery of anti-tumor therapeutic agents.

Co-delivery of doxorubicin and Bmi1 siRNA by folate receptor targeted liposomes exhibits enhanced anti-tumor effects in vitro and in vivo

Bmi1 gene overexpression is found in various human tumors and has been shown as a potential target for gene treatment. However, siRNA-based treatments targeting Bmi1 gene have been restricted to limited delivery, low bioavailability and hence relatively reduced efficacy. To overcome these barriers, we developed a folate receptor targeted co-delivery system folate-doxorubicin/Bmi1 siRNA liposome (FA-DOX/siRNA-L). The FA-DOX/siRNA-L was prepared through electrostatic interaction between folate doxorubicin liposome (FA-DOX-L) and Bmi1 siRNA. In vitro and in vivo studies showed that FA-DOX/siRNA-L inhibited tumor growth by combinatory role of Bmi1 siRNA and doxorubicin (DOX). Co-delivery of Bmi1 siRNA and DOX by FA-DOX/siRNA-L showed significantly higher efficacy than sole delivery of either DOX or Bmi1 siRNA. Real-time PCR and western blot analysis showed that FA-DOX/siRNA-L silenced the expression of Bmi1 gene. In addition, higher accumulation of the siRNA and DOX in tumor cells indicated that folate ligand displayed tumor targeting effect. These results suggest that Bmi1 is an effective therapeutic target for siRNA based cancer treatment that can be further improved by co-delivery of DOX through targeted liposomes.

A modular labeling strategy for in vivo PET and near-infrared fluorescence imaging of nanoparticle tumor targeting

Advances in preclinical molecular imaging have generated new opportunities to noninvasively visualize the biodistribution and tumor targeting of nanoparticle therapeutics. Capitalizing on recent achievements in this area, we sought to develop an (89)Zr-based labeling strategy for liposomal nanoparticles that accumulate in tumors via passive targeting mechanisms.

METHODS

(89)Zr-labeled liposomes were prepared using 2 different approaches: click labeling and surface chelation. Pharmacokinetic and biodistribution studies, as well as PET/CT imaging of the radiolabeled nanoparticles, were performed on a mouse model of breast cancer. In addition, a dual PET/optical probe was prepared by incorporation of a near-infrared fluorophore and tested in vivo by PET and near-infrared fluorescence imaging.

RESULTS

The surface chelation approach proved to be superior in terms of radiochemical yield and stability, as well as in vivo performance. Accumulation of these liposomes in tumor peaked at 24 h after injection and was measured to be 13.7 ± 1.8 percentage injected dose per gram. The in vivo performance of this probe was not essentially perturbed by the incorporation of a near-infrared fluorophore.

CONCLUSION

We have developed a highly modular and efficient strategy for the labeling of liposomal nanoparticles with (89)Zr. In xenograft and orthotopic mouse models of breast cancer, we demonstrated that the biodistribution of these nanoparticles can be visualized by PET imaging. In combination with a near-infrared dye, these liposomal nanoparticles can serve as bimodal PET/optical imaging agents. The liposomes target malignant growth, and their bimodal features may be useful for simultaneous PET and intraoperative imaging.

Convergence of nanotechnology and cancer prevention: are we there yet?

Nanotechnology is emerging as a promising modality for cancer treatment; however, in the realm of cancer prevention, its full utility has yet to be determined. Here, we discuss the potential of integrating nanotechnology in cancer prevention to augment early diagnosis, precision targeting, and controlled release of chemopreventive agents, reduced toxicity, risk/response assessment, and personalized point-of-care monitoring. Cancer is a multistep, progressive disease; the functional and acquired characteristics of the early precancer phenotype are intrinsically different from those of a more advanced anaplastic or invasive malignancy. Therefore, applying nanotechnology to precancers is likely to be far more challenging than applying it to established disease. Frank cancers are more readily identifiable through imaging and biomarker and histopathologic assessment than their precancerous precursors. In addition, prevention subjects routinely have more rigorous intervention criteria than therapy subjects. Any nanopreventive agent developed to prevent sporadic cancers found in the general population must exhibit a very low risk of serious side effects. In contrast, a greater risk of side effects might be more acceptable in subjects at high risk for cancer. Using nanotechnology to prevent cancer is an aspirational goal, but clearly identifying the intermediate objectives and potential barriers is an essential first step in this exciting journey.

Multifunctional theranostic red blood cells for magnetic-field-enhanced in vivo combination therapy of cancer

Red blood cells are attached to iron oxide nanoparticles pre-coated with chlorine e6, a photosensitizer, and then loaded with a chemotherapeutic drug, doxorubicin, to enable imaging-guided combined photodynamic and chemotherapy of cancer, achieving excellent synergistic therapeutic effects in an animal tumor model. This work highlights the great promise of integrating cell-based drug-delivery systems with nanotechnology as a biocompatible multifunctional platform for applications in cancer theranostics.

Positron emission tomography image-guided drug delivery: current status and future perspectives

Positron emission tomography (PET) is an important modality in the field of molecular imaging, which is gradually impacting patient care by providing safe, fast, and reliable techniques that help to alter the course of patient care by revealing invasive, de facto procedures to be unnecessary or rendering them obsolete. Also, PET provides a key connection between the molecular mechanisms involved in the pathophysiology of disease and the according targeted therapies. Recently, PET imaging is also gaining ground in the field of drug delivery. Current drug delivery research is focused on developing novel drug delivery systems with emphasis on precise targeting, accurate dose delivery, and minimal toxicity in order to achieve maximum therapeutic efficacy. At the intersection between PET imaging and controlled drug delivery, interest has grown in combining both these paradigms into clinically effective formulations. PET image-guided drug delivery has great potential to revolutionize patient care by in vivo assessment of drug biodistribution and accumulation at the target site and real-time monitoring of the therapeutic outcome. The expected end point of this approach is to provide fundamental support for the optimization of innovative diagnostic and therapeutic strategies that could contribute to emerging concepts in the field of “personalized medicine”. This review focuses on the recent developments in PET image-guided drug delivery and discusses intriguing opportunities for future development. The preclinical data reported to date are quite promising, and it is evident that such strategies in cancer management hold promise for clinically translatable advances that can positively impact the overall diagnostic and therapeutic processes and result in enhanced quality of life for cancer patients.

Magnetic resonance guided high-intensity focused ultrasound for image-guided temperature-induced drug delivery

Magnetic resonance guided high-intensity focused ultrasound (MR-HIFU) is a versatile technology platform for noninvasive thermal therapies in oncology. Since MR-HIFU allows heating of deep-seated tissue to well-defined temperatures under MR image guidance, this novel technology has great potential for local heat-mediated drug delivery from temperature-sensitive liposomes (TSLs). In particular, MR provides the ability for image guidance of the drug delivery when an MRI contrast agent is co-encapsulated with the drug in the aqueous lumen of the liposomes. Monitoring of the tumor drug coverage offers possibilities for a personalized thermal treatment in oncology. This review focuses on MR-HIFU as a noninvasive technology platform, temperature-sensitive liposomal formulations for drug delivery and image-guided drug delivery, and the effect of HIFU-induced hyperthermia on the TSL and drug distribution. Finally, the opportunities and challenges of localized MR-HIFU-mediated drug delivery from temperature-sensitive liposomes in oncology are discussed.

Computational nanomedicine: modeling of nanoparticle-mediated hyperthermal cancer therapy

Nanoparticle-mediated hyperthermia for cancer therapy is a growing area of cancer nanomedicine because of the potential for localized and targeted destruction of cancer cells. Localized hyperthermal effects are dependent on many factors, including nanoparticle size and shape, excitation wavelength and power, and tissue properties. Computational modeling is an important tool for investigating and optimizing these parameters. In this review, we focus on computational modeling of magnetic and gold nanoparticle-mediated hyperthermia, followed by a discussion of new opportunities and challenges.

Margination of micro- and nano-particles in blood flow and its effect on drug delivery

Drug delivery by micro- and nano-carriers enables controlled transport of pharmaceuticals to targeted sites. Even though carrier fabrication has made much progress recently, the delivery including controlled particle distribution and adhesion within the body remains a great challenge. The adhesion of carriers is strongly affected by their margination properties (migration toward walls) in the microvasculature. To investigate margination characteristics of carriers of different shapes and sizes and to elucidate the relevant physical mechanisms, we employ mesoscopic hydrodynamic simulations of blood flow. Particle margination is studied for a wide range of hematocrit values, vessel sizes, and flow rates, using two- and three-dimensional models. The simulations show that the margination properties of particles improve with increasing carrier size. Spherical particles yield slightly better margination than ellipsoidal carriers; however, ellipsoidal particles exhibit a slower rotational dynamics near a wall favoring their adhesion. In conclusion, micron-sized ellipsoidal particles are favorable for drug delivery in comparison with sub-micron spherical particles.

Etoposide-loaded immunoliposomes as active targeting agents for GD2-positive malignancies

Systemic chemotherapeutics remain the standard of care for most malignancies even though they frequently suffer from narrow therapeutic index, poor serum solubility, and off-target effects. In this study, we have encapsulated etoposide, a topoisomerase inhibitor effective against a wide range of cancers, in surface-modified liposomes decorated with anti-GD2 antibodies. We characterized the properties of the liposomes using a variety of methods including dynamic light scattering, electron microscopy, and Fourier transformed infrared spectroscopy. We examined whether these immunoliposomes were able to target cell lines expressing varying levels of surface GD2 and affect cellular proliferation. Anti-GD2 liposomes were generally targeted in a manner that correlated with GD2 expression and inhibited proliferation in cell lines to which they were efficiently targeted. The mechanism by which the immunoliposomes entered targeted cells appeared to be via clathrin-dependent uptake as demonstrated using flow cytometry and confocal microscopy. These studies suggest that anti-GD2-targeted, etoposide-loaded liposomes represent a potential strategy for more effective delivery of anti-cancer drugs that could be used for GD2 positive tumors.

Membrane monolayer protrusion mediates a new nanoparticle wrapping pathway

Understanding how nanoparticles (NPs) interact with the lipid membrane is of importance for their potential applications in biomedicine and cytotoxic effects. In this paper, with the aid of computer simulation techniques, we report that NPs can be wrapped by lipid membranes in a pathway different from the conventional endocytic pathway. Our simulation results show that under the conditions of strong NP-membrane adhesion and low membrane tension, NPs can be wrapped by membranes with a pathway regulated by membrane monolayer protrusion. We also find that in the monolayer protrusion mediated wrapping pathway NPs are first trapped in the membrane and the subsequent NP internalization can be achieved by several means, including decreasing the membrane tension, breaking the membrane symmetry between upper and lower leaflets, and exerting an external force on the NPs. The findings from our simulations are well supported by the free energy analysis.

Probing lipid coating dynamics of quantum dot core micelles via Förster resonance energy transfer

Lipid coated nanocrystal assemblies are among the most extensively investigated nanoparticle platforms for biomedical imaging and therapeutic purposes. However, very few efforts have been addressed to the lipid coating exchange dynamics in such systems, which is key to our understanding of the nanoparticles' coating stability and their interactions with the environment. Here, we apply the Förster resonance energy transfer (FRET) from quantum dot (QD) core to Cy5.5 dye labeled lipids at the surface to monitor the lipid exchange dynamics in situ and to study its dependence on concentration, temperature and solvent. A kinetic model is developed to describe the experimental data, allowing the rate constants and the activation energy for lipid exchange to be determined. The activation energy for lipid exchange on QD micelles is 155 kJ/mol in saline environment and 130 kJ/mol in pure water. The findings presented here provide basic knowledge on these self-assembled structures and contribute to understanding their performance and to further design of nanomedicine.

Perturbation of physiological systems by nanoparticles

Nanotechnology is having a tremendous impact on our society. However, societal concerns about human safety under nanoparticle exposure may derail the broad application of this promising technology. Nanoparticles may enter the human body via various routes, including respiratory pathways, the digestive tract, skin contact, intravenous injection, and implantation. After absorption, nanoparticles are carried to distal organs by the bloodstream and the lymphatic system. During this process, they interact with biological molecules and perturb physiological systems. Although some ingested or absorbed nanoparticles are eliminated, others remain in the body for a long time. The human body is composed of multiple systems that work together to maintain physiological homeostasis. The unexpected invasion of these systems by nanoparticles disturbs normal cell signaling, impairs cell and organ functions, and may even cause pathological disorders. This review examines the comprehensive health risks of exposure to nanoparticles by discussing how nanoparticles perturb various physiological systems as revealed by animal studies. The potential toxicity of nanoparticles to each physiological system and the implications of disrupting the balance among systems are emphasized.

In vivo enhancement of anticancer therapy using bare or chemotherapeutic drug-bearing nanodiamond particles

Background

This study investigated the use of nanodiamond particles (NDs) as a promising material for drug delivery in vivo and in vitro.

Methods

HepG2 cells (a human hepatic carcinoma cell line) were used to determine the characteristics of a nanodiamond-doxorubicin complex (ND-DOX) when taken up by cells in vitro using laser scanning confocal microscopy and dialysis experiments. We also compared the survival rate and histopathology of tumor-bearing mice after treatment with NDs or ND-DOX in vivo.

Results

In vitro investigation showed that ND-DOX has slow and sustained drug release characteristics compared with free doxorubicin. In vivo, the survival rate of tumor-bearing mice treated with ND-DOX was four times greater than that of mice treated with free doxorubicin. Interestingly, the survival rate in mice treated with NDs alone was close to that of mice treated with free doxorubicin. This indicates that treatment with ND-DOX can prolong the lifespan of tumor-bearing mice significantly compared with conventional doxorubicin and that NDs can have this effect as well. Histopathological analysis showed that neither the NDs nor ND-DOX were toxic to the kidney, liver, or spleen in contrast with the well-known toxic effects of free doxorubicin on the kidney and liver. Further, both the bare NDs and ND-DOX could suppress tumor growth effectively.

Conclusion

NDs can potentially prolong survival, and ND-DOX may act as a nanodrug with promising chemotherapeutic efficacy and safety.

Nanobody: the "magic bullet" for molecular imaging?

Molecular imaging involves the non-invasive investigation of biological processes in vivo at the cellular and molecular level, which can play diverse roles in better understanding and treatment of various diseases. Recently, single domain antigen-binding fragments known as 'nanobodies' were bioengineered and tested for molecular imaging applications. Small molecular size (~15 kDa) and suitable configuration of the complementarity determining regions (CDRs) of nanobodies offer many desirable features suitable for imaging applications, such as rapid targeting and fast blood clearance, high solubility, high stability, easy cloning, modular nature, and the capability of binding to cavities and difficult-to-access antigens. Using nanobody-based probes, several imaging techniques such as radionuclide-based, optical and ultrasound have been employed for visualization of target expression in various disease models. This review summarizes the recent developments in the use of nanobody-based probes for molecular imaging applications. The preclinical data reported to date are quite promising, and it is expected that nanobody-based molecular imaging agents will play an important role in the diagnosis and management of various diseases.

Probing nanoparticle translocation across the permeable endothelium in experimental atherosclerosis

Therapeutic and diagnostic nanomaterials are being intensely studied for several diseases, including cancer and atherosclerosis. However, the exact mechanism by which nanomedicines accumulate at targeted sites remains a topic of investigation, especially in the context of atherosclerotic disease. Models to accurately predict transvascular permeation of nanomedicines are needed to aid in design optimization. Here we show that an endothelialized microchip with controllable permeability can be used to probe nanoparticle translocation across an endothelial cell layer. To validate our in vitro model, we studied nanoparticle translocation in an in vivo rabbit model of atherosclerosis using a variety of preclinical and clinical imaging methods. Our results reveal that the translocation of lipid-polymer hybrid nanoparticles across the atherosclerotic endothelium is dependent on microvascular permeability. These results were mimicked with our microfluidic chip, demonstrating the potential utility of the model system.

Prospects for magnetic nanoparticles in systemic administration: synthesis and quantitative detection

Methods for the quantitative determination of magnetic nanoparticles in biological matrices, in the frame of biomedical applications, are required to evaluate the particles biodistribution after systemic administration.

Nanomaterials: impact on cells and cell organelles

Colloidal nanoparticles designed for the interactions with cells are very small, nanoscale objects usually consisting of inorganic cores and organic shells that are dispersed in a buffer or biological medium. By tuning the material properties of the nanoparticles a number of different biological applications of nanomaterials are enabled i.e. targeting, labelling, drug delivery, use as diagnostic tools or therapy. For all biological applications of nanoparticles, it is important to understand their interactions with the surrounding biological environment in order to predict their biological impact, in particular when designing the nanoparticles for diagnostic and therapeutic purpose. Due to the high surface-to-volume ratio, the surface of nanomaterials is very reactive. When exposed to biological fluids, the proteins and biomolecules present therein tend to associate with the nanoparticles' surface. This phenomenon is defined as biomolecular corona formation. The biomolecular corona plays a key role in the interaction between nanoparticles and biological systems, impacting on how these particles interact with biological systems on a cellular and molecular level. This book chapter describes the nature of the interactions at the bio-nano interface, shows the design strategy of nanoparticles for nanomedicine, and defines the concepts of biomolecular corona and biological identity of nanoparticles. Moreover, it describes the interaction of functionalised nanomaterials with cell organelles and intracellular fate of nanoparticles and it shows therapeutic application of gold nanoparticles as dose enhancers in radiotherapy.

Serum biomarkers for personalization of nanotherapeutics-based therapy in different tumor and organ microenvironments

Enhanced permeation and retention (EPR) effect, the mechanism by which nanotherapeutics accumulate in tumors, varies in patients based on differences in the tumor and organ microenvironment. Surrogate biomarkers for the EPR effect will aid in selecting patients who will accumulate higher amounts of nanotherapeutics and show better therapeutic efficacy. Our data suggest that the differences in the vascular permeability and pegylated liposomal doxorubicin (PLD) accumulation are tumor type as well as organ-specific and significantly correlated with the relative ratio of MMP-9 to TIMP-1 in the circulation, supporting development of these molecules as biomarkers for the personalization of nanoparticle-based therapy.

Delivering nanoparticles to lungs while avoiding liver and spleen through adsorption on red blood cells

Nanoparticulate drug delivery systems are one of the most widely investigated approaches for developing novel therapies for a variety of diseases. However, rapid clearance and poor targeting limit their clinical utility. Here, we describe an approach to harness the flexibility, circulation, and vascular mobility of red blood cells (RBCs) to simultaneously overcome these limitations (cellular hitchhiking). A noncovalent attachment of nanoparticles to RBCs simultaneously increases their level in blood over a 24 h period and allows transient accumulation in the lungs, while reducing their uptake by liver and spleen. RBC-adsorbed nanoparticles exhibited ∼3-fold increase in blood persistence and ∼7-fold higher accumulation in lungs. RBC-adsorbed nanoparticles improved lung/liver and lung/spleen nanoparticle accumulation by over 15-fold and 10-fold, respectively. Accumulation in lungs is attributed to mechanical transfer of particles from the RBC surface to lung endothelium. Independent tracing of both nanoparticles and RBCs in vivo confirmed that RBCs themselves do not accumulate in lungs. Attachment of anti-ICAM-1 antibody to the exposed surface of NPs that were attached to RBCs led to further increase in lung targeting and retention over 24 h. Cellular hitchhiking onto RBCs provides a new platform for improving the blood pharmacokinetics and vascular delivery of nanoparticles while simultaneously avoiding uptake by liver and spleen, thus opening the door for new applications.

Bioorthogonal, two-component delivery systems based on antibody and drug-loaded nanocarriers for enhanced internalization of nanotherapeutics

Nanocarriers play an important role in targeted cancer chemotherapy. The optimal nanocarrier delivery system should provide efficient and highly specific recognition of the target cells and rapid internalization of the therapeutic cargo to reduce systemic toxicity as well as to increase the cytotoxicity to cancer cells. To this end, we developed a two-step, two-component targeted delivery system based on antibody and drug-loaded nanocarrier that uses bioorthogonal click reactions for specific internalization of nanotherapeutics. The pretargeting component, anti-HER2 humanized monoclonal antibody, trastuzumab, functionalized with azide groups labels cancer cells that overexpress HER2 surface receptors. The drug carrier component, dibenzylcyclooctyne substituted albumin conjugated with paclitaxel, reacts specifically with the pretargeting component. These two components form cross-linked clusters on the cell surface, which facilitates the internalization of the complex. This strategy demonstrated substantial cellular internalization of clusters consisted of HER2 receptors, modified trastuzumab and paclitaxel-loaded albumin nanocarriers, and subsequent significant cytotoxicity in HER2-positive BT-474 breast cancer cells. Our results show high efficacy of this strategy for targeted nanotherapeutics. We foresee to broaden the applications of this strategy using agents such as radionuclides, toxins, and interfering RNA.

Myoglobin on silica: a case study of the impact of adsorption on protein structure and dynamics

If protein structure and function changes upon adsorption are well documented, modification of adsorbed protein dynamics remains a blind spot, despite its importance in biological processes. The adsorption of metmyoglobin on a silica surface was studied by isotherm measurements, microcalorimetry, circular dichroïsm, and UV-visible spectroscopy to determine the thermodynamic parameters of protein adsorption and consequent structure modifications. The mean square displacement and the vibrational densities of states of the adsorbed protein were measured by elastic and inelastic neutron scattering experiments. A decrease of protein flexibility and depletion in low frequency modes of myoglobin after adsorption on silica was observed. Our results suggest that the structure loss itself is not the entropic driving force of adsorption.

Gold nanoparticle-protein agglomerates as versatile nanocarriers for drug delivery

The fabrication of a versatile nanocarrier based on agglomerated structures of gold nanoparticle (Au NP)-lysozyme (Lyz) in aqueous medium is reported. The carriers exhibit efficient loading capacities for both hydrophilic (doxorubicin) and hydrophobic (pyrene) molecules. The nanocarriers are finally coated with an albumin layer to render them stable and also facilitate their uptake by cancer cells. The interaction between agglomerated structures and the payloads is non-covalent. Cell viability assay in vitro showed that the nanocarriers by themselves are non-cytotoxic, whereas the doxorubicin-loaded ones are cytotoxic, with efficiencies higher than that of the free drug. Transmission electron microscopy and fluorescence microscopy along with flow cytometry analysis confirm the uptake of the drug-loaded nanocarriers by a human cervical cancer HeLa cell line. Field-emission scanning electron microscopy reveals the formation of apoptotic bodies leading to cell death, confirming the release of the payloads from the nanocarriers into the cell. Overall, the findings suggest the fabrication of novel Au NP-protein agglomerate-based nanocarriers with efficient drug-loading and -releasing capabilities, enabling them to act as multimodal drug-delivery vehicles.

Prevention and treatment of biofilms by hybrid- and nanotechnologies

Bacteria growing as adherent biofilms are difficult to treat and frequently develop resistance to antimicrobial agents. To counter biofilms, various approaches, including prevention of bacterial surface adherence, application of device applicators, and assimilation of antimicrobials in targeted drug delivery machinery, have been utilized. These methods are also combined to achieve synergistic bacterial killing. This review discusses various multimodal technologies, presents general concepts, and describes therapies relying on the principles of electrical energy, ultrasound, photodynamics, and targeted drug delivery for prevention and treatment of biofilms.

Engineering multi-stage nanovectors for controlled degradation and tunable release kinetics

Nanovectors hold substantial promise in abating the off-target effects of therapeutics by providing a means to selectively accumulate payloads at the target lesion, resulting in an increase in the therapeutic index. A sophisticated understanding of the factors that govern the degradation and release dynamics of these nanovectors is imperative to achieve these ambitious goals. In this work, we elucidate the relationship that exists between variations in pore size and the impact on the degradation, loading, and release of multistage nanovectors. Larger pored vectors displayed faster degradation and higher loading of nanoparticles, while exhibiting the slowest release rate. The degradation of these particles was characterized to occur in a multi-step progression where they initially decreased in size leaving the porous core isolated, while the pores gradually increased in size. Empirical loading and release studies of nanoparticles along with diffusion modeling revealed that this prolonged release was modulated by the penetration within the porous core of the vectors regulated by their pore size.

Magnetic and photoresponsive theranosomes: translating cell-released vesicles into smart nanovectors for cancer therapy

Cell-released vesicles are natural carriers that circulate in body fluids and transport biological agents to distal cells. As nature uses vesicles in cell communication to promote tumor progression, we propose to harness their unique properties and exploit these biogenic carriers as Trojan horses to deliver therapeutic payloads to cancer cells. In a theranostic approach, cell-released vesicles were engineered by a top-down procedure from precursor cells, previously loaded with a photosensitizer and magnetic nanoparticles. The double exogenous cargo provided vesicles with magnetic and optical responsiveness allowing therapeutic and imaging functions. This new class of cell-derived smart nanovectors was named "theranosomes". Theranosomes enabled efficient photodynamic tumor therapy in a murine cancer model in vivo. Moreover the distribution of this biogenic vector could be monitored by dual-mode imaging, combining fluorescence and MRI. This study reports the first success in translating a cell communication mediator into a smart theranostic nanovector.

Coupled Particulate and Continuum Model for Nanoparticle Targeted Delivery

Prediction of nanoparticle (NP) distribution in a vasculature involves transport phenomena at various scales and is crucial for the evaluation of NP delivery efficiency. A combined particulate and continuum model is developed to model NP transport and delivery processes. In the particulate model ligand-receptor binding kinetics is coupled with Brownian dynamics to study NP binding on a microscale. An analytical formula is derived to link molecular level binding parameters to particulate level adhesion and detachment rates. The obtained NP adhesion rates are then coupled with a convection-diffusion-reaction model to study NP transport and delivery at macroscale. The binding results of the continuum model agree well with those from the particulate model. The effects of shear rate, particle size and vascular geometry on NP adhesion are investigated. Attachment rates predicted by the analytical formula also agree reasonably well with the experimental data reported in literature. The developed coupled model that links ligand-receptor binding dynamics to NP adhesion rate along with macroscale transport and delivery processes may serve as a faster evaluation and prediction tool to determine NP distribution in complex vascular networks.

Atomic force microscopy images label-free, drug encapsulated nanoparticles in vivo and detects difference in tissue mechanical properties of treated and untreated: a tip for nanotoxicology

Overcoming the intractable challenge of imaging of label-free, drug encapsulated nanoparticles in tissues in vivo would directly address associated regulatory concerns over 'nanotoxicology'. Here we demonstrate the utility of Atomic Force Microscopy (AFM) for visualising label-free, drug encapsulated polyester particles of ∼280 nm distributed within tissues following their intravenous or peroral administration to rodents. A surprising phenomenon, in which the tissues' mechanical stiffness was directly measured (also by AFM) and related to the number of embedded nanoparticles, was utilised to generate quantitative data sets for nanoparticles localisation. By coupling the normal determination of a drug's pharmacokinetics/pharmacodynamics with post-sacrifice measurement of nanoparticle localisation and number, we present for the first time an experimental design in which a single in vivo study relates the PK/PD of a nanomedicine to its toxicokinetics.

Silicon micro- and nanofabrication for medicine

This manuscript constitutes a review of several innovative biomedical technologies fabricated using the precision and accuracy of silicon micro- and nanofabrication. The technologies to be reviewed are subcutaneous nanochannel drug delivery implants for the continuous tunable zero-order release of therapeutics, multi-stage logic embedded vectors for the targeted systemic distribution of both therapeutic and imaging contrast agents, silicon and porous silicon nanowires for investigating cellular interactions and processes as well as for molecular and drug delivery applications, porous silicon (pSi) as inclusions into biocomposites for tissue engineering, especially as it applies to bone repair and regrowth, and porous silica chips for proteomic profiling. In the case of the biocomposites, the specifically designed pSi inclusions not only add to the structural robustness, but can also promote tissue and bone regrowth, fight infection, and reduce pain by releasing stimulating factors and other therapeutic agents stored within their porous network. The common material thread throughout all of these constructs, silicon and its associated dielectrics (silicon dioxide, silicon nitride, etc.), can be precisely and accurately machined using the same scalable micro- and nanofabrication protocols that are ubiquitous within the semiconductor industry. These techniques lend themselves to the high throughput production of exquisitely defined and monodispersed nanoscale features that should eliminate architectural randomness as a source of experimental variation thereby potentially leading to more rapid clinical translation.