Toward a magic or imaginary bullet? Ligands for drug targeting to cancer cells: principles, hopes, and challenges

Artificial viruses: A nanotechnology based approach

OBJECTIVES

The main objective of this work was to review and summarise the detailed literature available on viral nanoparticle and the strategies utilised for their manufacture along with their applications as therapeutic agents.

DATA ACQUISITION

The reported literature related to development and application of virus nanoparticles have been collected from electronic data bases like ScienceDirect, google scholar, PubMed by using key words like "viral nanoparticles", "targeted drug delivery" and "vaccines" and related combinations.

RESULT

From the detailed literature survey, virus nanoparticles were identified as carriers for the targeted delivery. Due to the presence of nanostructures in virus nanoparticles, these protect the drugs from the degradation in the gastrointestinal tract and in case of the delivery of gene medicine, they carry the nucleic acids to the target/susceptible host cells. Thus, artificial viruses are utilised for targeted delivery to specific organ in biomedical and biotechnological areas.

CONCLUSION

Thus, virus nanoparticles can be considered as viable option as drug/gene carrier in various healthcare sectors especially drug delivery and vaccine and can be explored further in future for the development of better drug delivery techniques.

New opportunities for RGD-engineered metal nanoparticles in cancer

The advent of nanotechnology has opened new possibilities for bioimaging. Metal nanoparticles (such as gold, silver, iron, copper, etc.) hold tremendous potential and offer enormous opportunities for imaging and diagnostics due to their broad optical characteristics, ease of manufacturing technique, and simple surface modification. The arginine-glycine-aspartate (RGD) peptide is a three-amino acid sequence that seems to have a considerably greater ability to adhere to integrin adhesion molecules that exclusively express on tumour cells. RGD peptides act as the efficient tailoring ligand with a variety of benefits including non-toxicity, greater precision, rapid clearance, etc. This review focuses on the possibility of non-invasive cancer imaging using metal nanoparticles with RGD assistance.

EGFR-Targeted Photodynamic Therapy

The epidermal growth factor receptor (EGFR) plays a pivotal role in the proliferation and metastatization of cancer cells. Aberrancies in the expression and activation of EGFR are hallmarks of many human malignancies. As such, EGFR-targeted therapies hold significant potential for the cure of cancers. In recent years, photodynamic therapy (PDT) has gained increased interest as a non-invasive cancer treatment. In PDT, a photosensitizer is excited by light to produce reactive oxygen species, resulting in local cytotoxicity. One of the critical aspects of PDT is to selectively transport enough photosensitizers to the tumors environment. Accordingly, an increasing number of strategies have been devised to foster EGFR-targeted PDT. Herein, we review the recent nanobiotechnological advancements that combine the promise of PDT with EGFR-targeted molecular cancer therapy. We recapitulate the chemistry of the sensitizers and their modes of action in PDT, and summarize the advantages and pitfalls of different targeting moieties, highlighting future perspectives for EGFR-targeted photodynamic treatment of cancer.

Biomedical Applications of Iron Oxide Nanoparticles: Current Insights Progress and Perspectives

The enormous development of nanomaterials technology and the immediate response of many areas of science, research, and practice to their possible application has led to the publication of thousands of scientific papers, books, and reports. This vast amount of information requires careful classification and order, especially for specifically targeted practical needs. Therefore, the present review aims to summarize to some extent the role of iron oxide nanoparticles in biomedical research. Summarizing the fundamental properties of the magnetic iron oxide nanoparticles, the review's next focus was to classify research studies related to applying these particles for cancer diagnostics and therapy (similar to photothermal therapy, hyperthermia), in nano theranostics, multimodal therapy. Special attention is paid to research studies dealing with the opportunities of combining different nanomaterials to achieve optimal systems for biomedical application. In this regard, original data about the synthesis and characterization of nanolipidic magnetic hybrid systems are included as an example. The last section of the review is dedicated to the capacities of magnetite-based magnetic nanoparticles for the management of oncological diseases.

Polyethyleneimine-Based Lipopolyplexes as Carriers in Anticancer Gene Therapies

Recent years have witnessed rapidly growing interest in application of gene therapies for cancer treatment. However, this strategy requires nucleic acid carriers that are both effective and safe. In this context, non-viral vectors have advantages over their viral counterparts. In particular, lipopolyplexes—nanocomplexes consisting of nucleic acids condensed with polyvalent molecules and enclosed in lipid vesicles—currently offer great promise. In this article, we briefly review the major aspects of developing such non-viral vectors based on polyethyleneimine and outline their properties in light of anticancer therapeutic strategies. Finally, examples of current in vivo studies involving such lipopolyplexes and possibilities for their future development are presented.

Lipid Nanoparticles─From Liposomes to mRNA Vaccine Delivery, a Landscape of Research Diversity and Advancement

Lipid nanoparticles (LNPs) have emerged across the pharmaceutical industry as promising vehicles to deliver a variety of therapeutics. Currently in the spotlight as vital components of the COVID-19 mRNA vaccines, LNPs play a key role in effectively protecting and transporting mRNA to cells. Liposomes, an early version of LNPs, are a versatile nanomedicine delivery platform. A number of liposomal drugs have been approved and applied to medical practice. Subsequent generations of lipid nanocarriers, such as solid lipid nanoparticles, nanostructured lipid carriers, and cationic lipid-nucleic acid complexes, exhibit more complex architectures and enhanced physical stabilities. With their ability to encapsulate and deliver therapeutics to specific locations within the body and to release their contents at a desired time, LNPs provide a valuable platform for treatment of a variety of diseases. Here, we present a landscape of LNP-related scientific publications, including patents and journal articles, based on analysis of the CAS Content Collection, the largest human-curated collection of published scientific knowledge. Rising trends are identified, such as nanostructured lipid carriers and solid lipid nanoparticles becoming the preferred platforms for numerous formulations. Recent advancements in LNP formulations as drug delivery platforms, such as antitumor and nucleic acid therapeutics and vaccine delivery systems, are discussed. Challenges and growth opportunities are also evaluated in other areas, such as medical imaging, cosmetics, nutrition, and agrochemicals. This report is intended to serve as a useful resource for those interested in LNP nanotechnologies, their applications, and the global research effort for their development.

Peanut-Shaped Gold Nanoparticles with Shells of Ceragenin CSA-131 Display the Ability to Inhibit Ovarian Cancer Growth In Vitro and in a Tumor Xenograft Model

Simple Summary

Despite a spectrum of therapeutics available for the treatment of ovarian tumors, there is a constant need to develop novel treatment options, particularly due to a high incidence of drug resistant tumors and low 5-year survival of patients diagnosed with ovarian carcinomas. In this study, we employed a nanotechnology-based approach to present a novel nanosystem based on ceragenin CSA-131 attached to the surface of a peanut-shaped gold nanoparticle. We demonstrate that such a prepared nanoformulation was highly effective against ovarian cancer cells in in vitro settings and, with limited toxicity, was able to prevent the growth of ovarian tumors in treated animals. Based on obtained data we suggest that ceragenin-containing nanosystems should be considered and further tested as potential therapeutics for ovarian malignancy.

Abstract

Gold nanoparticles-assisted delivery of antineoplastics into cancerous cells is presented as an effective approach for overcoming the limitations of systemic chemotherapy. Although ceragenins show great potential as anti-cancer agents, in some tumors, effective inhibition of cancer cells proliferation requires application of ceragenins at doses within their hemolytic range. For the purpose of toxicity/efficiency ratio control, peanut-shaped gold nanoparticles (AuP NPs) were functionalized with a shell of ceragenin CSA-131 and the cytotoxicity of AuP@CSA-131 against ovarian cancer SKOV-3 cells and were then analyzed. In vivo efficiency of intravenously and intratumorally administered CSA-131 and AuP@CSA-131 was examined using a xenograft ovarian cancer model. Serum parameters were estimated using ELISA methods. Comparative analysis revealed that AuP@CSA-131 exerted stronger anti-cancer effects than free ceragenin, which was determined by enhanced ability to induce caspase-dependent apoptosis and autophagy processes via reactive oxygen species (ROS)-mediated pathways. In an animal study, AuP@CSA-131 was characterized by delayed clearance and prolonged blood circulation when compared with free ceragenin, as well as enhanced anti-tumor efficiency, particularly when applied intratumorally. Administration of CSA-131 and AuP@CSA-131 prevented the inflammatory response associated with cancer development. These results present the possibility of employing non-spherical gold nanoparticles as an effective nanoplatform for the delivery of antineoplastics for the treatment of ovarian malignancy.

Advances in Nano-Enabled Platforms for the Treatment of Depression

Nanotechnology has aided in the advancement of drug delivery for the treatment of several neurological disorders including depression. Depression is a relatively common mental disorder which is characterized by a severe imbalance of neurotransmitters. Several current therapeutic regimens against depression display drawbacks which include low bioavailability, delayed therapeutic outcome, undesirable side effects and drug toxicity due to high doses. The blood–brain barrier limits the entry of the drugs into the brain matrix, resulting in low bioavailability and tissue damage due to drug accumulation. Due to their size and physico-chemical properties, nanotechnological drug delivery systems present a promising strategy to enhance the delivery of nanomedicines into the brain matrix, thereby improving bioavailability and limiting toxicity. Furthermore, ligand-complexed nanocarriers can improve drug specificity and antidepressant efficacy and reduce drug toxicity. Biopolymers and nanocarriers can also be employed to enhance controlled drug release and reduce the hepatic first-pass effect, hence reducing the dosing frequency. This manuscript reviews recent advances in different biopolymers, such as polysaccharides and other nanocarriers, for targeted antidepressant drug delivery to the brain. It probes nano-based strategies that can be employed to enhance the therapeutic efficacy of antidepressants through the oral, intranasal, and parenteral routes of administration.

Synthesis of Poly(Malic Acid) Derivatives End-Functionalized with Peptides and Preparation of Biocompatible Nanoparticles to Target Hepatoma Cells

Recently, short synthetic peptides have gained interest as targeting agents in the design of site-specific nanomedicines. In this context, our work aimed at developing new tools for the diagnosis and/or therapy of hepatocellular carcinoma (HCC) by grafting the hepatotropic George Baker (GB) virus A (GBVA10-9) and Plasmodium circumsporozoite protein (CPB)-derived peptides to the biocompatible poly(benzyl malate), PMLABe. We successfully synthesized PMLABe derivatives end-functionalized with peptides GBVA10-9, CPB, and their corresponding scrambled peptides through a thiol/maleimide reaction. The corresponding nanoparticles (NPs), varying by the nature of the peptide (GBVA10-9, CPB, and their scrambled peptides) and the absence or presence of poly(ethylene glycol) were also successfully formulated using nanoprecipitation technique. NPs were further characterized by dynamic light scattering (DLS), electrophoretic light scattering (ELS) and transmission electron microscopy (TEM), highlighting a diameter lower than 150 nm, a negative surface charge, and a more or less spherical shape. Moreover, a fluorescent probe (DiD Oil) has been encapsulated during the nanoprecipitation process. Finally, preliminary in vitro internalisation assays using HepaRG hepatoma cells demonstrated that CPB peptide-functionalized PMLABe NPs were efficiently internalized by endocytosis, and that such nanoobjects may be promising drug delivery systems for the theranostics of HCC.

Viral Mimicry as a Design Template for Nucleic Acid Nanocarriers

Therapeutic nucleic acids hold immense potential in combating undruggable, gene-based diseases owing to their high programmability and relative ease of synthesis. While the delivery of this class of therapeutics has successfully entered the clinical setting, extrahepatic targeting, endosomal escape efficiency, and subcellular localization. On the other hand, viruses serve as natural carriers of nucleic acids and have acquired a plethora of structures and mechanisms that confer remarkable transfection efficiency. Thus, understanding the structure and mechanism of viruses can guide the design of synthetic nucleic acid vectors. This review revisits relevant structural and mechanistic features of viruses as design considerations for efficient nucleic acid delivery systems. This article explores how viral ligand display and a metastable structure are central to the molecular mechanisms of attachment, entry, and viral genome release. For comparison, accounted for are details on the design and intracellular fate of existing nucleic acid carriers and nanostructures that share similar and essential features to viruses. The review, thus, highlights unifying themes of viruses and nucleic acid delivery systems such as genome protection, target specificity, and controlled release. Sophisticated viral mechanisms that are yet to be exploited in oligonucleotide delivery are also identified as they could further the development of next-generation nonviral nucleic acid vectors.

Building Blocks to Design Liposomal Delivery Systems

The flexibility of liposomal carriers does not just simply rely on their capability to encapsulate various types of therapeutic substances, but also on the large array of components used for designing liposome-based nanoformulations. Each of their components plays a very specific role in the formulation and can be easily replaced whenever a different therapeutic effect is desired. It is tempting to describe this by an analogy to Lego blocks, since a whole set of structures, differing in their features, can be designed using a certain pool of blocks. In this review, we focus on different design strategies, where a broad variety of liposomal components facilitates the attainment of straightforward control over targeting and drug release, which leads to the design of the most promising systems for drug delivery. The key aspects of this block-based architecture became evident after its implementation in our recent works on liposomal carriers of antisense oligonucleotides and statins, which are described in the last chapter of this review.

In vitro Targetability Validation of Peptide-Functionalized Mesoporous Silica Nanoparticles in the Presence of Serum Proteins

Demonstration of receptor-mediated targeting of nanoparticles to specific organs and/or cell types is an integral aim in many bionanomedicine development projects. However, engagement of targeted receptors with ligands on nanocarriers, which is the cornerstone of the active targeting concept, is challenging to study under biologically relevant conditions and thus often stays overlooked. In this work, we utilize an in-house established bioassay for in vitro targetability validation of mesoporous silica nanoparticles (MSNs), functionalized with high-affinity peptide ligands to somatostatin receptors via protective group chemistry, ensuring the correct orientation of the peptide's pharmacophore. We demonstrate that targeted nanoparticles, but not scrambled peptide-decorated counterparts, specifically engage the targeted receptors in living cells in culture media containing serum protein. The importance of being able to exclude false positives originating from the premature detachment of targeting peptides from the MSNs is highlighted.

Natural compound catechol induces DNA damage, apoptosis, and G1 cell cycle arrest in breast cancer cells

Targeting cell cycle and inducing DNA damage by activating cell death pathways are considered as effective therapeutic strategy for combating breast cancer progression. Many of the naturally known small molecules target these signaling pathways and are effective against resistant and/or aggressive types of breast cancers. Here, we investigated the effect of catechol, a naturally occurring plant compound, for its specificity and chemotherapeutic efficacies in breast cancer (MCF-7 and MDA-MB-231) cells. Catechol treatment showed concentration-dependent cytotoxicity and antiproliferative growth in both MCF-7 and MDA-MB-231 cells while sparing minimal effects on noncancerous (F-180 and HK2) cells. Catechol modulated differential DNA damage effects by activating ATM/ATR pathways and showed enhanced γ-H2AX expression, as an indicator for DNA double-stranded breaks. MCF-7 cells showed G1 cell cycle arrest by regulating p21-mediated cyclin E/Cdk2 inhibition. Furthermore, activation of p53 triggered a caspase-mediated cell death mechanism by inhibiting regulatory proteins such as DNMT1, p-BRCA1, MCL-1, and PDCD6 with an increased Bax/Bcl-2 ratio. Overall, our results showed that catechol possesses favorable safety profile for noncancerous cells while specifically targeting multiple signaling cascades to inhibit proliferation in breast cancer cells.

Radiosynthesis, Biological Evaluation, and Preclinical Study of a 68Ga-Labeled Cyclic RGD Peptide as an Early Diagnostic Agent for Overexpressed α v β 3 Integrin Receptors in Non-Small-Cell Lung Cancer

The α_vβ₃ integrin receptors have high expression on proliferating growing tumor cells of different origins including non-small-cell lung cancer. RGD-containing peptides target the extracellular domain of integrin receptors. This specific targeting makes these short sequences a suitable nominee for theranostic application. DOTA-E(cRGDfK)₂ was radiolabeled with ⁶⁸Ga efficiently. The in vivo and in vitro stability was examined in different buffer systems. Metabolic stability was assessed in mice urine. In vitro specific binding, cellular uptake, and internalization were determined. The tumor-targeting potential of [⁶⁸Ga]Ga-DOTA-E(cRGDfK)₂ in a lung cancer mouse model was studied. Besides, the very early diagnostic potential of the ⁶⁸Ga-labeled RGD peptide was evaluated. The acquisition and reconstruction of the PET-CT image data were also carried out. Radiochemical and radionuclide purity for [⁶⁸Ga]Ga-DOTA-E(cRGDfK)₂ was >%98 and >%99, respectively. Radiotracer showed high in vivo, in vitro, and metabolic stability which was determined by ITLC. The dissociation constant (K_d) of [⁶⁸Ga]Ga-DOTA-E(cRGDfK)₂ was 15.28 nM. On average, more than 95% of the radioactivity was specific binding (internalized + surface-bound) to A549 cells. Biodistribution data showed that radiolabeled peptides were accumulated significantly in A549 tumor and excreted rapidly by the renal system. Tumor uptake peaks were at 1-hour postinjection for [⁶⁸Ga]Ga-DOTA-E(cRGDfK)₂. The tumor was clearly visualized in all images. [⁶⁸Ga]Ga-DOTA-E(cRGDfK)₂ can be used as a peptide-based imaging agent allowing very early detection of different cancers overexpressing α_vβ₃ integrin receptors and can be a potential candidate in clinical peptide-based imaging for lung cancer.

Editorial focus: understanding off-target effects as the key to successful RNAi therapy

With the first RNA interference (RNAi) drug (ONPATTRO (patisiran)) on the market, we witness the RNAi therapy field reaching a critical turning point, when further improvements in drug candidate design and delivery pipelines should enable fast delivery of novel life changing treatments to patients. Nevertheless, ignoring parallel development of RNAi dedicated in vitro pharmacological profiling aiming to identify undesirable off-target activity may slow down or halt progress in the RNAi field. Since academic research is currently fueling the RNAi development pipeline with new therapeutic options, the objective of this article is to briefly summarize the basics of RNAi therapy, as well as to discuss how to translate basic research into better understanding of related drug candidate safety profiles early in the process.

Insights into Active Targeting of Nanoparticles in Drug Delivery: Advances in Clinical Studies and Design Considerations for Cancer Nanomedicine

Nanomedicine is a promising strategy for improving clinical outcomes for cancer therapies, by improving drug efficacy through enhanced delivery to disease sites. It is of importance for ultimate clinical success to consider the contributing factors to achieving this goal, such as size, chemistry, and functionality of nanoparticle delivery systems, and how these parameters influence tumor localization and uptake. This Topical Review will first discuss the evolution and progress of nanoparticles for cancer drug delivery and the current challenges that remain to be addressed. Strategies for overcoming the limitations of passive targeting through active targeting approaches, and the current state of such nanomedicines in the clinic will be highlighted. Finally, novel approaches toward the design of active targeted nanoparticles building on our growing understanding of nanobio interactions are considered, in order to shed light on future design considerations for accelerating clinical translation of nanomedicines.

[Is there a magic bullet for sarcomas? : Personalised treatment for maligant tumours of bone and soft tissue]

BACKGROUND

Personalised tumour therapies aim to selectively target pathways and structures to which a tumour shows an oncogenic addiction.

OBJECTIVE AND METHOD

This article aims to provide an overview of relevant genetic alterations in bone and soft-tissue tumours, which might serve as potential therapeutic targets for personalised medicines in the future. Recent approaches towards a personalised treatment of various tumours of bone and soft tissues are reviewed.

RESULTS

Molecular diagnosis has become an essential tool for the characterisation of bone and soft-tissue tumours. Currently, no targeted therapies are routinely available for bone sarcomas. Denosumab is merely a symptomatic treatment for giant cell tumours of the bone. Imatinib has become the paradigm of a targeted treatment for subgroups of malignant gastrointestinal stromal tumours (GISTs) and dermatofibrosarcoma protuberans. Antiangiogenic multikinase inhibitors, various other tyrosine kinase inhibitors (TKIs) and monoclonal antibodies are currently being evaluated in several (sub-)types of soft-tissue sarcomas. Sorafenib showed promising results in the treatment of aggressive desmoid-type fibromatosis. Histology-tailored chemotherapies did not yield superior results in a prospective randomised multicentre trial.

CONCLUSION

More in-depth knowledge is required for many sarcomas to link their genetic alterations to tumorigenesis in order to develop efficient personalised treatment strategies. Clinical trial designs need to be adapted to evaluate new therapeutic strategies in these ultra-rare tumours and their various sub-types more efficaciously.

Targeting Cancer Via Resveratrol-Loaded Nanoparticles Administration: Focusing on In Vivo Evidence

Resveratrol (RSV) is a polyphenol endowed with potential therapeutic effects in chronic diseases, particularly in cancer, the second leading cause of death worldwide in the twenty-first century. The advent of nanotechnology application in the field of drug delivery allows to overcome the constrains associated with the conventional anticancer treatments, in particular chemotherapy, reducing its adverse side effects, off target risks and surpassing cancer multidrug chemoresistance. Moreover, the use of nanotechnology-based carriers in the delivery of plant-derived anticancer agents, such as RSV, has already demonstrated to surpass the poor water solubility, instability and reduced bioavailability associated with phytochemicals, improving their therapeutic activity, thus prompting pharmaceutical developments. This review highlights the in vivo anticancer potential of RSV achieved by nanotherapeutic approaches. First, RSV physicochemical, stability and pharmacokinetic features are described. Thereupon, the chemotherapeutic and chemopreventive properties of RSV are underlined, emphasizing the RSV numerous cancer molecular targets. Lastly, a comprehensive analysis of the RSV-loaded nanoparticles (RSV-NPs) developed and administered in different in vivo cancer models to date is presented. Nanoparticles (NPs) have shown to improve RSV solubility, stability, pharmacokinetics and biodistribution in cancer tissues, enhancing markedly its in vivo anticancer activity. RSV-NPs are, thus, considered a potential nanomedicine-based strategy to fight cancer; however, further studies are still necessary to allow RSV-NP clinical translation.

Free radical-mediated targeting and immobilization of coupled payloads

Targeted drug delivery is a promising approach to enhance the accumulation of therapies in diseased tissues while limiting off-site effects. Ligand-receptor interactions are traditionally identified to deliver therapies, and although specific, this can be costly and often suffers from limited sensitivity. An emerging approach is to target intermediary species that modulate disease progression. Here, we propose novel methods of targeting therapies by using native free radicals as a homing signal. Elevated concentrations of free radicals are a characteristic comorbidity of many different diseases. In polymer chemistry, free radicals are frequently used to initiate crosslinking reactions. We proposed that free radicals elevated in injury sites are capable of inducing crosslinking of acrylate groups on polymer chains. Coupling payloads to the polymer then allow for specific targeting of therapies to areas with elevated free radicals. We demonstrate in vitro proof-of-principle of this approach. Reactive oxygen species (ROS) initiated crosslinking of acrylated PEGs, which immobilized a fluorescent payload within tissue mimics. The cross-linking efficiency and immobilization potential varied with the polymer chain length, suggesting that a tuneable platform can be achieved. Together these results provide promising proof-of-concept for using free radicals to specifically target and sustain nearly endless payloads to disease sites.

Immunoliposomes with Simvastatin as a Potential Therapeutic in Treatment of Breast Cancer Cells Overexpressing HER2-An In Vitro Study

Lipophilic statins are promising candidates for breast cancer treatment. However, anticancer therapy requires much higher doses of statins than can be delivered orally, and such high doses are known to exert more adverse effects. The main objective of our study was to design a targeted, therapeutic liposomal carrier of simvastatin characterised by high stability and specificity towards breast cancer cells. We chose SKBR3, the cell line that showed the highest sensitivity for simvastatin and liposomal simvastatin treatment. Additionally, SKBR3 has a notably high expression level of human epidermal growth factor receptor 2 (HER2), which we used as a target for our immunoliposomes. To do so we attached humanized anti-HER2 antibody to the envelope of liposomes. We tested the stability and selectivity of the proposed formulation along with the toxicity, ability to induce apoptosis and the effect on signalling pathways involving Akt and Erk kinases. The immunoliposomal formulation of simvastatin is characterized by long-term stability, high selectivity towards HER2-overexpressing breast cancer cells, low non-specific cytotoxicity and effective inhibition of the growth of target cells, presumably by inhibition of signalling pathways and induction of apoptosis. Hence, for the first time, we propose the use of immunoliposomes with simvastatin, targeted directly towards breast cancer cells overexpressing HER2. The prepared immunoliposomes may become a proof of concept in developing new anticancer therapy.

Targeting Somatostatin Receptors By Functionalized Mesoporous Silica Nanoparticles - Are We Striking Home?

The concept of delivering nanoformulations to desired tissues by means of targeting membrane receptors of high local abundance by ligands anchored to the nanocarrier has gained a lot of attention over the last decade. Currently, there is no unanimous opinion on whether surface functionalization of nanocarriers by targeting ligands translates into any real benefit in terms of pharmacokinetics or treatment outcomes. Having examined the published nanocarriers designed to engage with somatostatin receptors, we realized that in the majority of cases targetability claims were not supported by solid evidence of targeting ligand-targeted receptor coupling, which is the very crux of a targetability concept. Here, we present an approach to characterize targetability of mesoporous silica-based nanocarriers functionalized with ligands of somatostatin receptors. The targetability proof in our case comes from a functional assay based on a genetically-encoded cAMP probe, which allows for real-time capture of receptor activation in living cells, triggered by targeting ligands on nanoparticles. We elaborate on the development and validation of the assay, highlighting the power of proper functional tests in the characterization pipeline of targeted nanoformulations.

Unintended effects of drug carriers: Big issues of small particles

Humoral and cellular host defense mechanisms including diverse phagocytes, leukocytes, and immune cells have evolved over millions of years to protect the body from microbes and other external and internal threats. These policing forces recognize engineered sub-micron drug delivery systems (DDS) as such a threat, and react accordingly. This leads to impediment of the therapeutic action, extensively studied and discussed in the literature. Here, we focus on side effects of DDS interactions with host defenses. We argue that for nanomedicine to reach its clinical potential, the field must redouble its efforts in understanding the interaction between drug delivery systems and the host defenses, so that we can engineer safer interventions with the greatest potential for clinical success.

Dendrimer and dendrimer–conjugate protein complexes and protein coronas

Dendrimers and dendrimer conjugates are widely employed for biological applications such as bio-imaging and drug delivery. Understanding the interaction between dendrimers and their biological environment is key to evaluating the efficacy and safety of these materials. Proteins can form an adsorbed layer, termed a “protein corona”, on dendrimers in either a non-specific or specific fashion. A tight-binding, non-exchangeable corona is defined as a “hard” corona, whereas a loosely bound, highly exchangeable corona is called a “soft” corona. Recent research indicates that small molecules conjugated to the polymer surface can induce protein structural change, leading to tighter protein–dendrimer binding and further protein aggregation. This “triggered” corona formation on dendrimer and dendrimer conjugates is reviewed and discussed along with the existing hard or soft corona model. This review describes the triggered corona model to further the understanding of protein corona formation.

In vivo Biocompatibility, Biodistribution and Therapeutic Efficiency of Titania Coated Upconversion Nanoparticles for Photodynamic Therapy of Solid Oral Cancers

Despite the advantages of using photodynamic therapy (PDT) for the treatment of head and neck tumors, it can only be used to treat early stage flat lesions due to the limited tissue penetration ability of the visible light. Here, we developed near-infrared (NIR) excitable upconversion nanoparticle (UCN) based PDT agent that can specifically target epithelial growth factor receptor (EGFR) overexpressing oral cancer cells, in a bid to widen the application of PDT against thick and solid advanced or recurrent head and neck cancers. In vivo studies using the synthesized anti-EGFR-PEG-TiO2-UCNs following systemic administration displayed no major sub-acute or long term toxic effects in terms of blood biochemical, hematological or histopathological changes at a concentration of 50 mg/kg. NIR-PDT even in the presence of a 10 mm tissue phantom placed over the xenograft tumor, showed significant delay in tumor growth and improved survival rate compared to conventional chlorin-e6 (Ce6) PDT using 665 nm red light. Our work, one of the longest study till date in terms of safety (120 d), PDT efficacy (35 d) and survival (60 d), demonstrates the usefulness of UCN based PDT technology for targeted treatment of thick and bulky head and neck tumors.

Aminoflavone-loaded EGFR-targeted unimolecular micelle nanoparticles exhibit anti-cancer effects in triple negative breast cancer

Triple negative breast cancer (TNBC) is an aggressive subtype of breast cancer for which there is no available targeted therapy. TNBC cases contribute disproportionately to breast cancer-related mortality, thus the need for novel and effective therapeutic methods is urgent. We have previously shown that a National Cancer Institute (NCI) investigational drug aminoflavone (AF) exhibits strong growth inhibitory effects in TNBC cells. However, in vivo pulmonary toxicity resulted in withdrawal or termination of several human clinical trials for AF. Herein we report the in vivo efficacy of a nanoformulation of AF that enhances the therapeutic index of AF in TNBC. We engineered a unique unimolecular micelle nanoparticle (NP) loaded with AF and conjugated with GE11, a 12 amino acid peptide targeting epidermal growth factor receptor (EGFR), since EGFR amplification is frequently observed in TNBC tumors. These unimolecular micelles possessed excellent stability and preferentially released drug payload at endosomal pH levels rather than blood pH levels. Use of the GE11 targeting peptide resulted in enhanced cellular uptake and strong growth inhibitory effects in TNBC cells. Further, AF-loaded, GE11-conjugated (targeted) unimolecular micelle NPs significantly inhibit orthotopic TNBC tumor growth in a xenograft model, compared to treatment with AF-loaded, GE11-lacking (non-targeted) unimolecular micelle NPs or free AF. Interestingly, the animals treated with AF-loaded, targeted NPs had the highest plasma and tumor level of AF among different treatment groups yet exhibited no increase in plasma aspartate aminotransferase (AST) activity level or observable tissue damage at the time of sacrifice. Together, these results highlight AF-loaded, EGFR-targeted unimolecular micelle NPs as an effective therapeutic option for EGFR-overexpressing TNBC.

Design, synthesis, and evaluation of cisplatin-containing EGFR targeting bioconjugates as potential therapeutic agents for brain tumors

The aim of this study was to evaluate four different platinated bioconjugates containing a cisplatin (cis-diamminedichloroplatinum [cis-DDP]) fragment and epidermal growth factor receptor (EGFR)-targeting moieties as potential therapeutic agents for the treatment of brain tumors using a human EGFR-expressing transfectant of the F98 rat glioma (F98_EGFR) to assess their efficacy. The first two bioconjugates employed the monoclonal antibody cetuximab (C225 or Erbitux^®) as the targeting moiety, and the second two used genetically engineered EGF peptides. C225-G₅-Pt was produced by reacting cis-DDP with a fifth-generation polyamidoamine dendrimer (G₅) and then linking it to C225 by means of two heterobifunctional reagents. The second bioconjugate (C225-PG-Pt) employed the same methodology except that polyglutamic acid was used as the carrier. The third and fourth bioconjugates used two different EGF peptides, PEP382 and PEP455, with direct coordination to the Pt center of the cis-DDP fragment. In vivo studies with C225-G₅-Pt failed to demonstrate therapeutic activity following intracerebral (ic) convection-enhanced delivery (CED) to F98_EGFR glioma-bearing rats. The second bioconjugate, C225-PG-Pt, failed to show in vitro cytotoxicity. Furthermore, because of its high molecular weight, we decided that lower molecular weight peptides might provide better targeting and microdistribution within the tumor. Both PEP382-Pt and PEP455-Pt bioconjugates were cytotoxic in vitro and, based on this, a pilot study was initiated using PEP455-Pt. The end point for this study was tumor size at 6 weeks following tumor cell implantation and 4 weeks following ic CED of PEP455-Pt to F98 glioma-bearing rats. Neuropathologic examination revealed that five of seven rats were either tumor-free or only had microscopic tumors at 42 days following tumor implantation compared to a mean survival time of 20.5 and 26.3 days for untreated controls. In conclusion, we have succeeded in reformatting the toxicity profile of cis-DDP and demonstrated the therapeutic efficacy of the PEP455-Pt bioconjugate in F98 glioma-bearing rats.

NANOMEDICINE: will it offer possibilities to overcome multiple drug resistance in cancer?

This review is written with the purpose to review the current nanomedicine literature and provide an outlook on the developments in utilizing nanoscale drug constructs in treatment of solid cancers as well as in the potential treatment of multi-drug resistant cancers. No specific design principles for this review have been utilized apart from our active choice to avoid results only based on in vitro studies. Few drugs based on nanotechnology have progressed to clinical trials, since most are based only on in vitro experiments which do not give the necessary data for the research to progress towards pre-clinical studies. The area of nanomedicine has indeed spark much attention and holds promise for improved future therapeutics in the treatment of solid cancers. However, despite much investment few targeted therapeutics have successfully progressed to early clinical trials, indicating yet again that the human body is complicated and that much more understanding of the fundamentals of receptor interactions, physics of nanomedical constructs and their circulation in the body is indeed needed. We believe that nanomedical therapeutics can allow for more efficient treatments of resistant cancers, and may well be a cornerstone for RNA based therapeutics in the future given their general need for shielding from the harsh environment in the blood stream.

Current development of targeted oligonucleotide-based cancer therapies: Perspective on HER2-positive breast cancer treatment

This Review discusses the various types of non-coding oligonucleotides, which have garnered extensive interest as new alternatives for targeted cancer therapies over small molecule inhibitors and monoclonal antibodies. These oligonucleotides can target any hallmark of cancer, no longer limited to so-called "druggable" targets. Thus, any identified gene that plays a key role in cancer progression or drug resistance can be exploited with oligonucleotides. Among them, small-interfering RNAs (siRNAs) are frequently utilized for gene silencing due to the robust and well established mechanism of RNA interference. Despite promising advantages, clinical translation of siRNAs is hindered by the lack of effective delivery platforms. This Review provides general criteria and consideration of nanoparticle development for systemic siRNA delivery. Different classes of nanoparticle candidates for siRNA delivery are discussed, and the progress in clinical trials for systemic cancer treatment is reviewed. Lastly, this Review presents HER2 (human epidermal growth factor receptor type 2)-positive breast cancer as one example that could benefit significantly from siRNA technology. How siRNA-based therapeutics can overcome cancer resistance to such therapies is discussed.

Effects of silver nanoparticles on neonatal testis development in mice

Background

Metal nanoparticles (MNPs) play an important role in consumer products. An increasing use of MNPs has raised concerns about potential risks for human health. Therefore, in vivo tests of MNPs are urgently required. Using mice as a model animal, the aim of the present study was designed to investigate the effect of biologically synthesized silver nanoparticles (AgNPs) on spermatogenesis in neonatal mice.

Methods

AgNPs were synthesized using Bacillus funiculus. The prepared nanoparticles were characterized using various analytical techniques such as UV–visible spectroscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, and transmission electron microscopy. The prepared AgNPs were used to investigate testis development in neonatal mice. Institute of Cancer Research neonatal male mice were used in all experiments and were treated with different doses (0, 1, and 5 mg/kg) of AgNPs five times (interval of 3 days from postnatal day [PND] 8–21) by abdominal subcutaneous injection.

Results

The results showed that the sperm abnormalities such as quality and quantity were significantly increased by the synthesized AgNPs. The diameter of the convoluted tubules shrank significantly in mice treated with AgNPs on PND28 and PND42. The results of reverse transcription-quantitative polymerase chain reaction indicated that the E1f1ay, Gsta4, and Fdx1 genes were up-regulated, and the Amh, Cx43, and Claudin-11 genes were down-regulated in response to AgNPs exposure on PND28; however, these genes recovered at PND60. AgNPs had no effect on the recombination levels of chromosomes in germ cells.

Conclusion

These results demonstrated the adverse effects of AgNPs on the male reproductive tract, particularly spermatogenesis and the quality of sperm. This study suggests that the development of nanomaterials should be safer and non-toxic to the living organisms and the potential reprotoxicity of AgNPs should be investigated more carefully.

Genetically-encoded tools for cAMP probing and modulation in living systems

Intracellular 3′-5′-cyclic adenosine monophosphate (cAMP) is one of the principal second messengers downstream of a manifold of signal transduction pathways, including the ones triggered by G protein-coupled receptors. Not surprisingly, biochemical assays for cAMP have been instrumental for basic research and drug discovery for decades, providing insights into cellular physiology and guiding pharmaceutical industry. However, despite impressive track record, the majority of conventional biochemical tools for cAMP probing share the same fundamental shortcoming—all the measurements require sample disruption for cAMP liberation. This common bottleneck, together with inherently low spatial resolution of measurements (as cAMP is typically analyzed in lysates of thousands of cells), underpin the ensuing limitations of the conventional cAMP assays: (1) genuine kinetic measurements of cAMP levels over time in a single given sample are unfeasible; (2) inability to obtain precise information on cAMP spatial distribution and transfer at subcellular levels, let alone the attempts to pinpoint dynamic interactions of cAMP and its effectors. At the same time, tremendous progress in synthetic biology over the recent years culminated in drastic refinement of our toolbox, allowing us not only to bypass the limitations of conventional assays, but to put intracellular cAMP life-span under tight control—something, that seemed scarcely attainable before. In this review article we discuss the main classes of modern genetically-encoded tools tailored for cAMP probing and modulation in living systems. We examine the capabilities and weaknesses of these different tools in the context of their operational characteristics and applicability to various experimental set-ups involving living cells, providing the guidance for rational selection of the best tools for particular needs.