Towards targeted Cas9 (CRISPR-Cas) delivery: Preparation of IgG antibody-Cas9 conjugates using a split intein

The CRISPR-Cas9 system has revolutionized the field of genetic engineering, but targeted cellular delivery remains a central problem. The delivery of the preformed ribonuclease-protein (RNP) complex has the advantages of fewer side effects and avoidance of potential permanent effects. We reasoned that an internalizing IgG antibody as a targeting device could address the delivery of Cas9-RNP. We opted for protein trans-splicing mediated by a split intein to facilitate posttranslational conjugation of the two large protein entities. We recently described the cysteine-less CL split intein that efficiently performs under oxidizing conditions and does not interfere with disulfide bonds or thiol bioconjugation chemistries. Using the CL split intein, we report for the first time the ligation of monoclonal IgG antibody precursors, expressed in mammalian cells, and a Cas9 precursor, obtained from bacterial expression. A purified IgG-Cas9 conjugate was loaded with sgRNA to form the active RNP complex and introduced a double-strand break in its target DNA in vitro. Furthermore, a synthetic peptide variant of the short N-terminal split intein precursor proved useful for chemical modification of Cas9. The split intein ligation procedure reported here for IgG-Cas9 provides the first step towards a novel CRISPR-Cas9 targeting approach involving the preformed RNP complex.

Phase-Separated Lipid-Based Nanoparticles: Selective Behavior at the Nano-Bio Interface

The membrane-protein interface on lipid-based nanoparticles influences their in vivo behavior. Better understanding may evolve current drug delivery methods toward effective targeted nanomedicine. Previously, the cell-selective accumulation of a liposome formulation in vivo is demonstrated, through the recognition of lipid phase-separation by triglyceride lipases. This exemplified how liposome morphology and composition can determine nanoparticle-protein interactions. Here, the lipase-induced compositional and morphological changes of phase-separated liposomes-which bear a lipid droplet in their bilayer- are investigated, and the mechanism upon which lipases recognize and bind to the particles is unravelled. The selective lipolytic degradation of the phase-separated lipid droplet is observed, while nanoparticle integrity remains intact. Next, the Tryptophan-rich loop of the lipase is identified as the region with which the enzymes bind to the particles. This preferential binding is due to lipid packing defects induced on the liposome surface by phase separation. In parallel, the existing knowledge that phase separation leads to in vivo selectivity, is utilized to generate phase-separated mRNA-LNPs that target cell-subsets in zebrafish embryos, with subsequent mRNA delivery and protein expression. Together, these findings can expand the current knowledge on selective nanoparticle-protein communications and in vivo behavior, aspects that will assist to gain control of lipid-based nanoparticles.

BRAIDing receptors for cell-specific targeting

Systemic toxicity is a major challenge in the development of therapeutics. Consequently, cell-type-specific targeting is needed to improve on-target efficacy while reducing off-target toxicity. Here, we describe a cell-targeting system we have termed BRAID (BRidged Activation by Intra/intermolecular Division) whereby an active molecule is divided into two inactive or less active parts that are subsequently brought together via a so-called 'bridging receptor' on the target cell. This concept was validated using the WNT/β-catenin signaling system, demonstrating that a multivalent WNT agonist molecule divided into two inactive components assembled from different epitopes via the hepatocyte receptor βKlotho induces signaling specifically on hepatocytes. These data provide proof of concept for this cell-specific targeting strategy, and in principle, this may also allow activation of multiple signaling pathways where desirable. This approach has broad application potential for other receptor systems.

Biomarkers and targeted therapy for cancer stem cells

Cancer stem cells (CSCs) are a small subpopulation of cancer cells with capabilities of self-renewal, differentiation, and tumorigenicity, and play a critical role in driving tumor heterogeneity that evolves insensitivity to therapeutics. For these reasons, extensive efforts have been made to identify and target CSCs to potentially improve the antitumor efficacy of therapeutics. While progress has been made to uncover certain CSC-associated biomarkers, the identification of CSC-specific markers, especially the targetable ones, remains a significant challenge. Here we provide an overview of the unique signaling and metabolic pathways of CSCs, summarize existing CSC biomarkers and CSC-targeted therapies, and discuss strategies to further differentiate CSCs from non-stem cancer cells and healthy cells for the development of enhanced CSC-targeted therapies.

Cell-targeted vaccines: implications for adaptive immunity

Recent advancements in immunology and chemistry have facilitated advancements in targeted vaccine technology. Targeting specific cell types, tissue locations, or receptors can allow for modulation of the adaptive immune response to vaccines. This review provides an overview of cellular targets of vaccines, suggests methods of targeting and downstream effects on immune responses, and summarizes general trends in the literature. Understanding the relationships between vaccine targets and subsequent adaptive immune responses is critical for effective vaccine design. This knowledge could facilitate design of more effective, disease-specialized vaccines.

Extracellular vesicles: The next generation in gene therapy delivery

Extracellular vesicles (EVs) are esteemed as a promising delivery vehicle for various genetic therapeutics. They are relatively inert, non-immunogenic, biodegradable, and biocompatible. At least in rodents, they can even transit challenging bodily hurdles such as the blood-brain barrier. Constitutively shed by all cells and with the potential to interact specifically with neighboring and distant targets, EVs can be engineered to carry and deliver therapeutic molecules such as proteins and RNAs. EVs are thus emerging as an elegant in vivo gene therapy vector. Deeper understanding of basic EV biology-including cellular production, EV loading, systemic distribution, and cell delivery-is still needed for effective harnessing of these endogenous cellular nanoparticles as next-generation nanodelivery tools. However, even a perfect EV product will be challenging to produce at clinical scale. In this regard, we propose that vector transduction technologies can be used to convert cells either ex vivo or directly in vivo into EV factories for stable, safe modulation of gene expression and function. Here, we extrapolate from the current EV state of the art to a bright potential future using EVs to treat genetic diseases that are refractory to current therapeutics.

Targeting Mucin Protein Enables Rapid and Efficient Ovarian Cancer Cell Capture: Role of Nanoparticle Properties in Efficient Capture and Culture

The development of specific and sensitive immunomagnetic cell separation nanotechnologies is central to enhancing the diagnostic relevance of circulating tumor cells (CTCs) and improving cancer patient outcomes. The limited number of specific biomarkers used to enrich a phenotypically diverse set of CTCs from liquid biopsies has limited CTC yields and purity. The ultra-high molecular weight mucin, mucin16 (MUC16) is shown to physically shield key membrane proteins responsible for activating immune responses against ovarian cancer cells and may interfere with the binding of magnetic nanoparticles to popular immunomagnetic cell capture antigens. MUC16 is expressed in ≈90% of ovarian cancers and is almost universal in High Grade Serous Epithelial Ovarian Cancer. This work demonstrates that cell bound MUC16 is an effective target for rapid immunomagnetic extraction of expressor cells with near quantitative yield, high purity and viability from serum. The results provide a mechanistic insight into the effects of nanoparticle physical properties and immunomagnetic labeling on the efficiency of immunomagnetic cell isolation. The growth of these cells has also been studied after separation, demonstrating that nanoparticle size impacts cell-particle behavior and growth rate. These results present the successful isolation of "masked" CTCs enabling new strategies for the detection of cancer recurrence and select and monitor chemotherapy.

Chitosan Surface-Modified PLGA Nanoparticles Loaded with Cranberry Powder Extract as a Potential Oral Delivery Platform for Targeting Colon Cancer Cells

Nutraceutical cranberry powder extract (CBPE) has distinct polyphenols inhibiting colon cancer growth and proliferation. However, its oral therapeutic efficacy is hindered because of its low permeability. This study aims to formulate chitosan surface-modified PLGA nanoparticles (CS-PLGA NPs) for encapsulating CBPE and modulating its release rate, permeation, cell targeting, and, therefore, its cytotoxicity. A full 2³ factorial design is employed to scrutinize the effect of lactide/glycolide ratio, PLGA weight, and stabilizer concentrations on entrapment efficiency percentage (EE%), particle size (PS), polydispersity index (PDI), and zeta potential (ZP). The optimum formula (F4) shows spherical particles with a relatively high EE% (72.30 ± 2.86%), an appropriate size of 370.10 ± 10.31 nm, PDI; 0.398 ± 0.001, and ZP; -5.40 ± 0.21 mV. Alongside the ATR-FTIR outcomes, the chitosan surface-modified formula (CS-F4) demonstrates a significant increase in particle size (417.67 ± 6.77 nm) and a shift from negative to positive zeta potential (+21.63 ± 2.46 mV), confirming the efficiency of surface modification with chitosan. The intestinal permeability of F4 and CS-F4 is significantly increased by 2.19- and 3.10-fold, respectively, compared to the CBPE solution, with the permeability coefficient (P_app) being 2.05 × 10^-4 cm/min and 2.91 × 10^-4 cm/min, for F4 and CS-F4, respectively, compared to the CBPE solution, 9.36 × 10^-5 cm/min. Moreover, CS-F4 evidences significant caspase-3 protein level expression stimulation and significant inhibition of vascular endothelial growth factor (VEGF) and signal transducer and activator of transcription-3 (STAT-3) protein expression levels, confirming the superiority of CS-F4 for targeting HT-29 cells. Briefly, CS-PLGA NPs could be regarded as a prosperous delivery system of CBPE with enhanced permeation, cell targeting, and antitumor efficacy.

Drug delivery targets and strategies to address mast cell diseases

INTRODUCTION

Current and developing mast cell therapeutics are reliant on small molecule drugs and biologics, but few are truly selective for mast cells. Most have cellular and disease-specific limitations that require innovation to overcome longstanding challenges to selectively targeting and modulating mast cell behavior. This review is designed to serve as a frame of reference for new approaches that utilize nanotechnology or combine different drugs to increase mast cell selectivity and therapeutic efficacy.

AREAS COVERED

Mast cell diseases include allergy and related conditions as well as malignancies. Here, we discuss the targets of existing and developing therapies used to treat these disease pathologies, classifying them into cell surface, intracellular, and extracellular categories. For each target discussed, we discuss drugs that are either the current standard of care, under development, or have indications for potential use. Finally, we discuss how novel technologies and tools can be used to take existing therapeutics to a new level of selectivity and potency against mast cells.

EXPERT OPINION

There are many broadly and very few selectively targeted therapeutics for mast cells in allergy and malignant disease. Combining existing targeting strategies with technology like nanoparticles will provide novel platforms to treat mast cell disease more selectively.

Oral Cell-Targeted Delivery Systems Constructed of Edible Materials: Advantages and Challenges

Cell-targeted delivery is an advanced strategy which can effectively solve health problems. However, the presence of synthetic materials in delivery systems may trigger side effects. Therefore, it is necessary to develop cell-targeted delivery systems with excellent biosafety. Edible materials not only exhibit biosafety, but also can be used to construct cell-targeted delivery systems such as ligands, carriers, and nutraceuticals. Moreover, oral administration is the appropriate route for cell-targeted delivery systems constructed of edible materials (CDSEMs), which is the same as the pattern of food intake, resulting in good patient compliance. In this review, relevant studies of oral CDSEMs are collected to summarize the construction method, action mechanism, and health impact. The gastrointestinal stability of delivery systems can be improved by anti-digestible materials. The design of the surface structure, shape, and size of carrier is beneficial to overcoming the mucosal barrier. Additionally, some edible materials show dual functions of a ligand and carrier, which is conductive to simplifying the design of CDSEMs. This review can provide a better understanding and prospect for oral CDSEMs and promote their application in the health field.

helixCAM: A platform for programmable cellular assembly in bacteria and human cells

Interactions between cells are indispensable for signaling and creating structure. The ability to direct precise cell-cell interactions would be powerful for engineering tissues, understanding signaling pathways, and directing immune cell targeting. In humans, intercellular interactions are mediated by cell adhesion molecules (CAMs). However, endogenous CAMs are natively expressed by many cells and tend to have cross-reactivity, making them unsuitable for programming specific interactions. Here, we showcase "helixCAM," a platform for engineering synthetic CAMs by presenting coiled-coil peptides on the cell surface. helixCAMs were able to create specific cell-cell interactions and direct patterned aggregate formation in bacteria and human cells. Based on coiled-coil interaction principles, we built a set of rationally designed helixCAM libraries, which led to the discovery of additional high-performance helixCAM pairs. We applied this helixCAM toolkit for various multicellular engineering applications, such as spherical layering, adherent cell targeting, and surface patterning.

Protein Cages Engineered for Interaction-Driven Selective Encapsulation of Biomolecules

Hollow protein cages have become attractive drug delivery vehicles with high biocompatibility and precise functional/structural manipulability. However, difficulties in effective cargo loading inside the cages have been limiting further development of protein cage-based drug carriers. Here, we developed a specific interaction-driven encapsulation and cellular delivery strategy for various biomolecules by engineering a porous protein cage. The computationally designed hyperstable mi3 protein cage was circularly permuted to fuse the cancer targeting RGD tripeptide to the cage surface and SpyTag (ST), which forms a covalent bond with SpyCatcher (SC), to the cage inner cavity. SC-fused proteins with different sizes and charges could be stably and actively encapsulated in the engineered nanocage via the ST/SC reaction. Cargo protein encapsulation inside the cage was directly confirmed by cryo-electron microscopy (EM) structure determination. In addition, SC-fused monomeric avidin was added to the nanocage to encapsulate various biotinylated (nonprotein) cargos such as oligonucleotides and the anticancer drug doxorubicin. All cargo molecules loaded onto the engineered mi3 were effectively delivered to cells. This work introduces a highly versatile cargo loading/delivery strategy, where loading/delivery interactions, cargo molecules, and cell targeting moieties can be further varied for optimal cellular drug delivery.

Biocomposite-based nanostructured delivery systems for treatment and control of inflammatory lung diseases

Diseases related to the lungs are among the most prevalent medical problems threatening human life. The treatment options and therapeutics available for these diseases are hindered by inadequate drug concentrations at pathological sites, a dearth of cell-specific targeting and different biological barriers in the alveoli or conducting airways. Nanostructured delivery systems for lung drug delivery have been significant in addressing these issues. The strategies used include surface engineering by altering the material structure or incorporation of specific ligands to reach prespecified targets. The unique characteristics of nanoparticles, such as controlled size and distribution, surface functional groups and therapeutic release triggering capabilities, are tailored to specific requirements to overcome the major therapeutic barriers in pulmonary diseases. In the present review, the authors intend to deliver significant up-to-date research in nanostructured therapies in inflammatory lung diseases with an emphasis on biocomposite-based nanoparticles.

Extracellular Vesicles Tropism: A Comparative Study between Passive Innate Tropism and the Active Engineered Targeting Capability of Lymphocyte-Derived EVs

Cellular communications take place thanks to a well-connected network of chemical–physical signals, biomolecules, growth factors, and vesicular messengers that travel inside or between cells. A deep knowledge of the extracellular vesicle (EV) system allows for a better understanding of the whole series of phenomena responsible for cell proliferation and death. To this purpose, here, a thorough immuno-phenotypic characterization of B-cell EV membranes is presented. Furthermore, the cellular membrane of B lymphocytes, Burkitt lymphoma, and human myeloid leukemic cells were characterized through cytofluorimetry assays and fluorescent microscopy analysis. Through cytotoxicity and internalization tests, the tropism of B lymphocyte-derived EVs was investigated toward the parental cell line and two different cancer cell lines. In this study, an innate capability of passive targeting of the native EVs was distinguished from the active targeting capability of monoclonal antibody-engineered EVs, able to selectively drive the vesicles, enhancing their internalization into the target cancer cells. In particular, the specific targeting ability of anti-CD20 engineered EVs towards Daudi cells, highly expressing CD20 marker on their cell membrane, was proved, while almost no internalization events were observed in HL60 cells, since they did not express an appreciable amount of the CD20 marker on their plasma membranes.

CRISPA: A Non-viral, Transient Cas9 Delivery System Based on Reengineered Anthrax Toxin

Translating the CRISPR/Cas9 genome editing technology into clinics is still hampered by rather unspecific, unsafe and/or inconvenient approaches for the delivery of its main components - the Cas9 endonuclease and a guide RNA - into cells. Here, we describe the development of a novel transient and non-viral Cas9 delivery strategy based on the translocation machinery of the Bacillus anthracis anthrax toxin, PA (protective antigen). We show that Cas9 variants fused to the N-terminus of the lethal factor or to a hexahistidine tag are shuttled through channels formed by PA into the cytosol of human cells. As proof-of-principle, we applied our new approach, denoted as CRISPA, to knock out lipolysis-stimulated lipoprotein receptor (LSR) in the human colon cancer cell line HCT116 and green-fluorescent protein (GFP) in human embryonic kidney 293T cells stably expressing GFP. Notably, we confirmed that the transporter PA can be adapted to recognize specific host cell-surface receptor proteins and may be optimized for cell type-selective delivery of Cas9. Altogether, CRISPA provides a novel, transient and non-viral way to deliver Cas9 into specific cells. Thus, this system is an additional step towards safe translation of the CRISPR/Cas9 technology into clinics.

Neutrophils and Macrophages as Targets for Development of Nanotherapeutics in Inflammatory Diseases

Neutrophils and macrophages are major components of innate systems, playing central roles in inflammation responses to infections and tissue injury. If they are out of control, inflammation responses can cause the pathogenesis of a wide range of diseases, such as inflammatory disorders and autoimmune diseases. Precisely regulating the functions of neutrophils and macrophages in vivo is a potential strategy to develop immunotherapies to treat inflammatory diseases. Advances in nanotechnology have enabled us to design nanoparticles capable of targeting neutrophils or macrophages in vivo. This review discusses the current status of how nanoparticles specifically target neutrophils or macrophages and how they manipulate leukocyte functions to inhibit their activation for inflammation resolution or to restore their defense ability for pathogen clearance. Finally, we present a novel concept of hijacking leukocytes to deliver nanotherapeutics across the blood vessel barrier. This review highlights the challenges and opportunities in developing nanotherapeutics to target leukocytes for improved treatment of inflammatory diseases.

Folic Acid-Functionalized Composite Scaffolds of Gelatin and Gold Nanoparticles for Photothermal Ablation of Breast Cancer Cells

Photothermal therapy (PTT) has been developed as a useful therapeutic method for cancer treatment. Localization of PTT agents in cancer sites and targeting capacity are required to further increase therapeutic efficacy. In this study, gold nanoparticles (AuNPs) and gelatin were functionalized with folic acid (FA) and hybridized to prepare FA-functionalized gelatin-AuNPs composite scaffolds. AuNPs with rod and star shapes of three sizes (40, 70, and 110 nm) were used for the hybridization to investigate the influence of AuNPs shape and size. The composite scaffolds showed porous structures with good interconnectivity. Modification with FA increased capture capacity of the composite scaffolds. Hybridization with AuNPs rendered the composite scaffold a good photothermal conversion property under near-infrared (NIR) laser irradiation. Temperature change during laser irradiation increased with the laser power intensity and irradiation time. The shape and size of AuNPs also affected their photothermal conversion property. The composite scaffold of gold nanorods 70 (FA-G/R70) had the highest photothermal conversion capacity. Breast cancer cells cultured in the FA-G/R70 composite scaffold were killed under NIR laser irradiation. Mouse subcutaneous implantation further demonstrated the excellent photothermal ablation capability of FA-G/R70 composite scaffold to breast cancer cells. The FA-functionalized composite scaffolds were demonstrated a high potential for local PPT of breast cancer.

Ternary Polypeptide Nanoparticles with Improved Encapsulation, Sustained Release, and Enhanced In Vitro Efficacy of Carfilzomib

PURPOSE

To develop a new nanoparticle formulation for a proteasome inhibitor Carfilzomib (CFZ) to improve its stability and efficacy for future in vivo applications.

METHODS

CFZ-loaded ternary polypeptide nanoparticles (CFZ/tPNPs) were prepared by using heptakis(6-amino-6-deoxy)-β-cyclodextrin(hepta-hydrochloride) (HaβCD) and azido-poly(ethylene glycol)-block-poly(L-glutamic acid sodium salt) (N₃-PEG-PLE). The process involved ternary (hydrophobic/ionic/supramolecular) interactions in three steps: 1) CFZ was entrapped in the cavity of HaβCD by hydrophobic interaction, 2) the drug-cyclodextrin inclusion complexes were mixed with N₃-PEG-PLE to form polyion complex nanoparticles, and 3) the nanoparticles were modified with fluorescent dyes (AFDye 647) for imaging and/or epithelial cell adhesion molecule (EpCAM) antibodies for cancer cell targeting. CFZ/tPNPs were characterized for particle size, surface charge, drug release, stability, intracellular uptake, proteasome inhibition, and in vitro cytotoxicity.

RESULTS

tPNPs maintained an average particle size of 50 nm after CFZ entrapment, EpCAM conjugation, and freeze drying. tPNPs achieved high aqueous solubility of CFZ (>1 mg/mL), sustained drug release (t_1/2 = 6.46 h), and EpCAM-mediated cell targeting, which resulted in increased intracellular drug accumulation, prolonged proteasome inhibition, and enhanced cytotoxicity of CFZ in drug-resistant DLD-1 colorectal cancer cells.

CONCLUSIONS

tPNPs improved stability and efficacy of CFZ in vitro, and these results potentiate effective cancer treatment using CFZ/tPNPs in future vivo studies.

Neuroinflammation Treatment via Targeted Delivery of Nanoparticles

The lack of effective treatments for most neurological diseases has prompted the search for novel therapeutic options. Interestingly, neuroinflammation is emerging as a common feature to target in most CNS pathologies. Recent studies suggest that targeted delivery of small molecules to reduce neuroinflammation can be beneficial. However, suboptimal drug delivery to the CNS is a major barrier to modulate inflammation because neurotherapeutic compounds are currently being delivered systemically without spatial or temporal control. Emerging nanomaterial technologies are providing promising and superior tools to effectively access neuropathological tissue in a controlled manner. Here we highlight recent advances in nanomaterial technologies for drug delivery to the CNS. We propose that state-of-the-art nanoparticle drug delivery platforms can significantly impact local CNS bioavailability of pharmacological compounds and treat neurological diseases.

Multivalency Beats Complexity: A Study on the Cell Uptake of Carbohydrate Functionalized Nanocarriers to Dendritic Cells

Herein, we report the synthesis of carbohydrate and glycodendron structures for dendritic cell targeting, which were subsequently bound to hydroxyethyl starch (HES) nanocapsules prepared by the inverse miniemulsion technique. The uptake of the carbohydrate-functionalized HES nanocapsules into immature human dendritic cells (hDCs) revealed a strong dependence on the used carbohydrate. A multivalent mannose-terminated dendron was found to be far superior in uptake compared to the structurally more complex oligosaccharides used.

The intersectional genetics landscape for humans

BACKGROUND

The human body is made up of hundreds-perhaps thousands-of cell types and states, most of which are currently inaccessible genetically. Intersectional genetic approaches can increase the number of genetically accessible cells, but the scope and safety of these approaches have not been systematically assessed. A typical intersectional method acts like an "AND" logic gate by converting the input of 2 or more active, yet unspecific, regulatory elements (REs) into a single cell type specific synthetic output.

RESULTS

Here, we systematically assessed the intersectional genetics landscape of the human genome using a subset of cells from a large RE usage atlas (Functional ANnoTation Of the Mammalian genome 5 consortium, FANTOM5) obtained by cap analysis of gene expression sequencing (CAGE-seq). We developed the heuristics and algorithms to retrieve and quality-rank "AND" gate intersections. Of the 154 primary cell types surveyed, >90% can be distinguished from each other with as few as 3 to 4 active REs, with quantifiable safety and robustness. We call these minimal intersections of active REs with cell-type diagnostic potential "versatile entry codes" (VEnCodes). Each of the 158 cancer cell types surveyed could also be distinguished from the healthy primary cell types with small VEnCodes, most of which were robust to intra- and interindividual variation. Methods for the cross-validation of CAGE-seq-derived VEnCodes and for the extraction of VEnCodes from pooled single-cell sequencing data are also presented.

CONCLUSIONS

Our work provides a systematic view of the intersectional genetics landscape in humans and demonstrates the potential of these approaches for future gene delivery technologies.

Particle-Size-Dependent Delivery of Antitumoral miRNA Using Targeted Mesoporous Silica Nanoparticles

Multifunctional core-shell mesoporous silica nanoparticles (MSN) were tailored in size ranging from 60 to 160 nm as delivery agents for antitumoral microRNA (miRNA). The positively charged particle core with a pore diameter of about 5 nm and a stellate pore morphology allowed for an internal, protective adsorption of the fragile miRNA cargo. A negatively charged particle surface enabled the association of a deliberately designed block copolymer with the MSN shell by charge-matching, simultaneously acting as a capping as well as endosomal release agent. Furthermore, the copolymer was functionalized with the peptide ligand GE11 targeting the epidermal growth factor receptor, EGFR. These multifunctional nanoparticles showed an enhanced uptake into EGFR-overexpressing T24 bladder cancer cells through receptor-mediated cellular internalization. A luciferase gene knock-down of up to 65% and additional antitumoral effects such as a decreased cell migration as well as changes in cell cycle were observed. We demonstrate that nanoparticles with a diameter of 160 nm show the fastest cellular internalization after a very short incubation time of 45 min and produce the highest level of gene knock-down.

Multimeric Presentation of RGD Peptidomimetics Enhances Integrin Binding and Tumor Cell Uptake

The use of multimeric ligands is considered as a promising strategy to improve tumor targeting for diagnosis and therapy. Herein, tetrameric RGD (Arg-Gly-Asp) peptidomimetics were designed to target α_v β₃ integrin-expressing tumor cells. These compounds were prepared by an oxime chemoselective assembly of cyclo(DKP-RGD) ligands and a cyclodecapeptide scaffold, which allows a tetrameric presentation. The resulting tetrameric RGD peptidomimetics were shown to improve α_v β₃ integrin binding compared with the monomeric form. Interestingly, these compounds were also able to enhance tumor cell endocytosis in the same way as tetrameric RGD peptides. Altogether, the results show the potential of the tetrameric cyclo(DKP-RGD) ligands for in vivo imaging and drug delivery.

Nanoparticle Beacons: Supersensitive Smart Materials with On/Off-Switchable Affinity to Biomedical Targets

Smart materials that can switch between different states under the influence of chemical triggers are highly demanded in biomedicine, where specific responsiveness to biomarkers is imperative for precise diagnostics and therapy. Superior selectivity of drug delivery to malignant cells may be achieved with the nanoagents that stay "inert" until "activation" by the characteristic profile of microenvironment cues (e.g., tumor metabolites, angiogenesis factors, microRNA/DNA, etc.). However, despite a wide variety and functional complexity of smart material designs, their real-life applications are hindered by very limited sensitivity to inputs. Here, we present ultrasensitive smart nanoagents with input-dependent On/Off switchable affinity to a biomedical target based on a combination of gold nanoparticles with low-energy polymer structures. In the proposed method, a nanoparticle-based agent is surface coated with a custom designed flexible polymer chain, which has an input-switchable structure that regulates accessibility of the terminal receptor for target binding. Implementation of the concept with a DNA-model of such polymer has yielded nanoagents that have input-dependent cell-targeting capabilities and responsiveness to as little as 30 fM of DNA input in 15 min lateral flow assay. Thus, we show that surface phenomena can augment nanoagents with capability for switchable affinity without compromising the sensitivity to inputs. The proposed approach is promising for development of next-generation theranostic agents and ultrasensitive nanosensors for point-of-care diagnostics.

Antifouling and pH-Responsive Poly(Carboxybetaine)-Based Nanoparticles for Tumor Cell Targeting

Nanocarriers with responsibility and surface functionality of targeting molecules have been widely used to improve therapeutic efficiency. Hence, we report the assembly of pH-responsive and targeted polymer nanoparticles (NPs) composed of poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) as the core and poly(carboxybetaine methacrylate) (PCBMA) as the shell, functionalized with cyclic peptides containing Arginine-Glycine-Aspartic acid-D-Phenylalanine-Lysine (RGD). The resulting polymer NPs (PDPA@PCBMA-RGD NPs) can maintain the pH-responsivity of PDPA (pKa ~6.5) and low-fouling property of PCBMA that significantly resist non-specific interactions with RAW 264.7 and HeLa cells. Meanwhile, PDPA@PCBMA-RGD NPs could specifically target αvβ3 integrin-expressed human glioblastoma (U87) cells. The pH-responsiveness and low-fouling properties of PDPA@PCBMA NPs are comparable to PDPA@poly(ethylene glycol) (PDPA@PEG) NPs, which indicates that PCBMA is an alternative to PEG for low-fouling coatings. The advantage of PDPA@PCBMA NPs lies in the presence of carboxyl groups on their surfaces for further modification (e.g., RGD functionalization for cell targeting). The reported polymer NPs represent a new carrier that have the potential for targeted therapeutic delivery.

Cellular Targeting of Bispecific Antibody-Functionalized Poly(ethylene glycol) Capsules: Do Shape and Size Matter?

In the present study, a capsule system that consists of a stealth carrier based on poly(ethylene glycol) (PEG) and functionalized with bispecific antibodies (BsAbs) is introduced to examine the influence of the capsule shape and size on cellular targeting. Hollow spherical and rod-shaped PEG capsules with tunable aspect ratios (ARs) of 1, 7, and 18 were synthesized and subsequently functionalized with BsAbs that exhibit dual specificities to PEG and epidermal growth factor receptor (EGFR). Dosimetry (variation between the concentrations of capsules present and capsules that reach the cell surface) was controlled through "dynamic" incubation (i.e., continuously mixing the incubation medium). The results obtained were compared with those obtained from the "static" incubation experiments. Regardless of the incubation method and the capsule shape and size studied, BsAb-functionalized PEG capsules showed >90% specific cellular association to EGFR-positive human breast cancer cells MDA-MB-468 and negligible association with both control cell lines (EGFR negative Chinese hamster ovary cells CHO-K1 and murine macrophages RAW 264.7) after incubation for 5 h. When dosimetry was controlled and the dose concentration was normalized to the capsule surface area, the size or shape had a minimal influence on the cell association behavior of the capsules. However, different cellular internalization behaviors were observed, and the capsules with ARs 7 and 18 were, respectively, the least and most optimal shape for achieving high cell internalization under both dynamic and static conditions. Dynamic incubation showed a greater impact on the internalization of rod-shaped capsules (∼58-67% change) than on the spherical capsules (∼24-29% change). The BsAb-functionalized PEG capsules reported provide a versatile particle platform for the evaluation and comparison of cellular targeting performance of capsules with different sizes and shapes in vitro.

Aptamer-Mediated Polymeric Vehicles for Enhanced Cell-Targeted Drug Delivery

BACKGROUND

The search for smart delivery systems for enhanced pre-clinical and clinical pharmaceutical delivery and cell targeting continues to be a major biomedical research endeavor owing to differences in the physicochemical characteristics and physiological effects of drug molecules, and this affects the delivery mechanisms to elicit maximum therapeutic effects. Targeted drug delivery is a smart evolution essential to address major challenges associated with conventional drug delivery systems. These challenges mostly result in poor pharmacokinetics due to the inability of the active pharmaceutical ingredients to specifically act on malignant cells thus, causing poor therapeutic index and toxicity to surrounding normal cells. Aptamers are oligonucleotides with engineered affinities to bind specifically to their cognate targets. Aptamers have gained significant interests as effective targeting elements for enhanced therapeutic delivery as they can be generated to specifically bind to wide range of targets including proteins, peptides, ions, cells and tissues. Notwithstanding, effective delivery of aptamers as therapeutic vehicles is challenged by cell membrane electrostatic repulsion, endonuclease degradation, low pH cleavage, and binding conformation stability.

OBJECTIVE

The application of molecularly engineered biodegradable and biocompatible polymeric particles with tunable features such as surface area and chemistry, particulate size distribution and toxicity creates opportunities to develop smart aptamer-mediated delivery systems for controlled drug release.

RESULTS

This article discusses opportunities for particulate aptamer-drug formulations to advance current drug delivery modalities by navigating active ingredients through cellular and biomolecular traffic to target sites for sustained and controlled release at effective therapeutic dosages while minimizing systemic cytotoxic effects.

CONCLUSION

A proposal for a novel drug-polymer-aptamer-polymer (DPAP) design of aptamer-drug formulation with stage-wise delivery mechanism is presented to illustrate the potential efficacy of aptamer- polymer cargos for enhanced cell targeting and drug delivery.

Modulating Targeting of Poly(ethylene glycol) Particles to Tumor Cells Using Bispecific Antibodies

Low-fouling or "stealth" particles composed of poly(ethylene glycol) (PEG) display a striking ability to evade phagocytic cell uptake. However, functionalizing them for specific targeting is challenging. To address this challenge, stealth PEG particles prepared by a mesoporous silica templating method are functionalized with bispecific antibodies (BsAbs) to obtain PEG-BsAb particles via a one-step binding strategy for cell and tumor targeting. The dual specificity of the BsAbs-one arm binds to the PEG particles while the other targets a cell antigen (epidermal growth factor receptor, EGFR)-is exploited to modulate the number of targeting ligands per particle. Increasing the BsAb incubation concentration increases the amount of BsAb tethered to the PEG particles and enhances targeting and internalization into breast cancer cells overexpressing EGFR. The degree of BsAb functionalization does not significantly reduce the stealth properties of the PEG particles ex vivo, as assessed by their interactions with primary human blood granulocytes and monocytes. Although increasing the BsAb amount on PEG particles does not lead to the expected improvement in tumor accumulation in vivo, BsAb functionalization facilitates tumor cell uptake of PEG particles. This work highlights strategies to balance evading nonspecific clearance pathways, while improving tumor targeting and accumulation.

Delivering DNA origami to cells

DNA nanotechnology research has long-held promise as a means of developing functional molecules capable of delivery to cells. Recent advances in DNA origami have begun to realize this potential but is still at the earliest stage and a number of hurdles remain. This review focuses on progress in addressing these hurdles and considers some of the challenges still outstanding. These include stability of such structures necessary to reach target cells after administration; methods of cell targeting and uptake; strategies to avoid or escape endosomes and techniques for achieving specific subcellular localization. Finally, the functionality that can be expected once DNA origami structures reach their final intracellular targets will be considered.

Polydopamine/Transferrin Hybrid Nanoparticles for Targeted Cell-Killing

Polydopamine can form biocompatible particles that convert light into heat. Recently, a protocol has been optimized to synthesize polydopamine/protein hybrid nanoparticles that retain the biological function of proteins, and combine it with the stimuli-induced heat generation of polydopamine. We have utilized this novel system to form polydopamine particles, containing transferrin (PDA/Tf). Mouse melanoma cells, which strongly express the transferrin receptor, were exposed to PDA/Tf nanoparticles (NPs) and, subsequently, were irradiated with a UV laser. The cell death rate was monitored in real-time. When irradiated, the melanoma cells exposed to PDA/Tf NPs underwent apoptosis, faster than the control cells, pointing towards the ability of PDA/Tf to mediate UV-light-induced cell death. The system was also validated in an organotypic, 3D-printed tumor spheroid model, comprising mouse melanoma cells, and the exposure and subsequent irradiation with UV-light, yielded similar results to the 2D cell culture. The process of apoptosis was found to be targeted and mediated by the lysosomal membrane permeabilization. Therefore, the herein presented polydopamine/protein NPs constitute a versatile and stable system for cancer cell-targeting and photothermal apoptosis induction.

Multivalent activation of GLP-1 and sulfonylurea receptors modulates β-cell second-messenger signaling and insulin secretion

Linking two pharmacophores that bind different cell surface receptors into a single molecule can enhance cell-targeting specificity to cells that express the complementary receptor pair. In this report, we developed and tested a synthetic multivalent ligand consisting of glucagon-like peptide-1 (GLP-1) linked to glibenclamide (Glb) (GLP-1/Glb) for signaling efficacy in β-cells. Expression of receptors for these ligands, as a combination, is relatively specific to the β-cell in the pancreas. The multivalent GLP-1/Glb increased both intracellular cAMP and Ca²⁺, although Ca²⁺ responses were significantly depressed compared with the monomeric Glb. Moreover, GLP-1/Glb increased glucose-stimulated insulin secretion in a dose-dependent manner. However, unlike the combined monomers, GLP-1/Glb did not augment insulin secretion at nonstimulatory glucose concentrations in INS 832/13 β-cells or human islets of Langerhans. These data suggest that linking two binding elements, such as GLP-1 and Glb, into a single bivalent ligand can provide a unique functional agent targeted to β-cells.

Synthesis and photophysical studies of a multivalent photoreactive RuII-calix[4]arene complex bearing RGD-containing cyclopentapeptides

Photoactive ruthenium-based complexes are actively studied for their biological applications as potential theragnostic agents against cancer. One major issue of these inorganic complexes is to penetrate inside cells in order to fulfil their function, either sensing the internal cell environment or exert a photocytotoxic activity. The use of lipophilic ligands allows the corresponding ruthenium complexes to passively diffuse inside cells but limits their structural and photophysical properties. Moreover, this strategy does not provide any cell selectivity. This limitation is also faced by complexes anchored on cell-penetrating peptides. In order to provide a selective cell targeting, we developed a multivalent system composed of a photoreactive ruthenium(II) complex tethered to a calix[4]arene platform bearing multiple RGD-containing cyclopentapeptides. Extensive photophysical and photochemical characterizations of this Ru(II)–calixarene conjugate as well as the study of its photoreactivity in the presence of guanosine monophosphate have been achieved. The results show that the ruthenium complex should be able to perform efficiently its photoinduced cytotoxic activity, once incorporated into targeted cancer cells thanks to the multivalent platform.

Enhanced Photogeneration of Reactive Oxygen Species and Targeted Photothermal Therapy of C6 Glioma Brain Cancer Cells by Folate-Conjugated Gold-Photoactive Polymer Nanoparticles

Tumor-selective photodynamic therapy is a successful method for ablation of malignant and cancerous cells. Herein, we introduce the design and preparation of functionalized acrylic copolymer nanoparticles with spiropyran (SP) and imidazole groups through a facile semicontinuous emulsion polymerization. Then, Au³⁺ ions were immobilized and reduced on their surface to obtain photoresponsive gold-decorated polymer nanoparticles (PGPNPs). The prepared PGPNPs were surface-modified with folic acid as a site-specific tumor cell targeting agent and improve intracellular uptake via endocytosis. Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy analyses, UV-vis spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy images were employed to characterize their spectral and morphological properties. Fluorescence microscopy images and inductively coupled plasma analysis demonstrated the cell line labeling capability and improved targeting efficiency of folate-conjugated PGPNPs (FA-PGPNPs) toward rat brain cancer cells (C6 glioma) with 71.8% cell uptake in comparison with 28.8% for the nonconjugated ones. Nonpolar SP groups are converted to zwitterionic merocyanine isomers under UV irradiation at 365 nm and their conjugation with Au nanoparticles exhibited enhanced photogeneration of reactive oxygen species (ROS). These were confirmed by intracellular ROS analysis and cytotoxicity evaluation on malignant C6 glioma cells. Owing to the strong surface plasmon resonance absorption of gold nanoparticles, FA-PGPNPs provided elevated local photothermal efficiency under near-IR irradiation at 808 nm. The prepared multifunctional FA-PGPNPs with a comprehensive integration of prospective materials introduced promising nanoprobes with targeting ability, enhanced tumor photodynamic therapy, cell tracking, and photothermal therapy.

Targeting Accessories to the Crime: Nanoparticle Nucleic Acid Delivery to the Tumor Microenvironment

Nucleic acid delivery for cancer holds extraordinary promise. Increasing expression of tumor suppressor genes or inhibition of oncogenes in cancer cells has important therapeutic potential. However, several barriers impair progress in cancer gene delivery. These include effective delivery to cancer cells and relevant intracellular compartments. Although viral gene delivery can be effective, it has the disadvantages of being immuno-stimulatory, potentially mutagenic and lacking temporal control. Various nanoparticle (NP) platforms have been developed to overcome nucleic acid delivery hurdles, but several challenges still exist. One such challenge has been the accumulation of NPs in non-cancer cells within the tumor microenvironment (TME) as well as the circulation. While uptake by these cancer-associated cells is considered to be an off-target effect in some contexts, several strategies have now emerged to utilize NP-mediated gene delivery to intentionally alter the TME. For example, the similarity of NPs in shape and size to pathogens promotes uptake by antigen presenting cells, which can be used to increase immune stimulation and promote tumor killing by T-lymphocytes. In the era of immunotherapy, boosting the ability of the immune system to eliminate cancer cells has proven to be an exciting new area in cancer nanotechnology. Given the importance of cancer-associated cells in tumor growth and metastasis, targeting these cells in the TME opens up new therapeutic applications for NPs. This review will cover evidence for non-cancer cell accumulation of NPs in animal models and patients, summarize characteristics that promote NP delivery to different cell types, and describe several therapeutic strategies for gene modification within the TME.

Aptamer Cell-Based Selection: Overview and Advances

Aptamers are high affinity single-stranded DNA/RNA molecules, produced by a combinatorial procedure named SELEX (Systematic Evolution of Ligands by Exponential enrichment), that are emerging as promising diagnostic and therapeutic tools. Among selection strategies, procedures using living cells as complex targets (referred as "cell-SELEX") have been developed as an effective mean to generate aptamers for heavily modified cell surface proteins, assuring the binding of the target in its native conformation. Here we give an up-to-date overview on cell-SELEX technology, discussing the most recent advances with a particular focus on cancer cell targeting. Examples of the different protocol applications and post-SELEX strategies will be briefly outlined.

A New Spin on Antibody-Drug Conjugates: Trastuzumab-Fulvestrant Colloidal Drug Aggregates Target HER2-Positive Cells

While the formation of colloidal aggregates leads to artifacts in early drug discovery, their composition makes them attractive as nanoparticle formulations for targeted drug delivery as the entire nanoparticle is composed of drug. The typical transient stability of colloidal aggregates has inhibited exploiting this property. To overcome this limitation, we investigated a series of proteins to stabilize colloidal aggregates of the chemotherapeutic, fulvestrant, including the following: bovine serum albumin, a generic human immunoglobulin G, and trastuzumab, a therapeutic human epidermal growth factor receptor 2 antibody. Protein coronas reduced colloid size to <300 nm and improved their stability to over 48 h in both buffered saline and media containing serum protein. Unlike colloids stabilized with other proteins, trastuzumab-fulvestrant colloids were taken up by HER2 overexpressing cells and were cytotoxic. This new targeted formulation reimagines antibody-drug conjugates, delivering mM concentrations of drug to a cell.

Doxorubicin-loaded cell-derived nanovesicles: an alternative targeted approach for anti-tumor therapy

Cell-derived nanovesicles (CDNs) are an emerging class of biological drug delivery systems (DDS) that retain the characteristics of the cells they were derived from, without the need for further surface functionalization. CDNs are also biocompatible, being derived from natural sources and also take advantage of the enhanced permeability and retention effect due to their nanodimensions. Furthermore, CDNs derived from monocytes were shown to have an in vivo targeting effect, accumulating at the tumor site in a previous study conducted in a mouse tumor model. Here, we report a systematic approach pertaining to various loading methods of the chemotherapeutic drug doxorubicin into our CDNs and examine the differential cellular uptake of drug-loaded CDNs in cancerous (HeLa) and healthy (HEK293) cell lines. Lastly, we proved that the addition of doxorubicin-loaded CDNs to the HeLa and HEK293 co-cultures showed a clear discrimination toward cancer cells at the cellular level. Our results further reinforce the intriguing potential of CDNs as an alternative targeted strategy for anticancer therapy.

Size-Dependent Facilitation of Cancer Cell Targeting by Proteins Adsorbed on Nanoparticles

Understandings of how biomolecules modify nanoparticles in a biological context and how these exchanges impact nano-biointeractions are fundamental to nanomedicine and nanotoxicology research. In this work, cancer-targeting gold nanoparticles (TGNPs) with different sizes (5, 15, and 40 nm) were designed and synthesized. These nanoparticles spontaneously adsorbed proteins in complete cell culture medium (Dulbecco's modified Eagle's medium with 10% human serum). Although the targeting ligands on the surface of nanoparticles were likely to be shielded by adsorbed proteins, the targeting capability of nanoparticles was maintained due to the highly dynamic nature of protein adsorption. By regulating the size and surface curvature of nanoparticles, we found that smaller TGNPs (5 nm, large surface curvature) recognize folate receptors on HeLa cells mainly through one-on-one bindings, and adsorbed proteins partially interfered with their binding, inducing a reduction of cell uptake by ∼30%. Larger TGNPs (40 nm, small surface curvature) bound to cell surface receptors through multivalent interactions, and their binding affinity was, in contrast, enhanced by adsorbed proteins, resulting in an increased cell uptake by ∼13%. Computational modeling further corroborated our experimental findings. The compelling findings from this work demonstrated how nanoparticle's size controlled its biological activity and provided key design principles for nanomedicine agents.

Improving Targeting of Metal-Phenolic Capsules by the Presence of Protein Coronas

Particles adsorb proteins when they enter a physiological environment; this results in a surface coating termed a "protein corona". A protein corona can affect both the properties and functionalities of engineered particles. Here, we prepared hyaluronic acid (HA)-based capsules through the assembly of metal-phenolic networks (MPNs) and engineered their targeting ability in the absence and presence of protein coronas by varying the HA molecular weight. The targeting ability of the capsules was HA molecular weight dependent, and a high HA molecular weight (>50 kDa) was required for efficient targeting. The specific interactions between high molecular weight HA capsules and receptor-expressing cancer cells were negligibly affected by the presence of protein coronas, whereas nonspecific capsule-cell interactions were significantly reduced in the presence of a protein corona derived from human serum. Consequently, the targeting specificity of HA-based MPN capsules was enhanced due to the formation of a protein corona. This study highlights the significant and complex roles of a protein corona in biointeractions and demonstrates how protein coronas can be used to improve the targeting specificity of engineered particles.

Surface Modified Multifunctional and Stimuli Responsive Nanoparticles for Drug Targeting: Current Status and Uses

Nanocarriers, due to their unique features, are of increased interest among researchers working with pharmaceutical formulations. Polymeric nanoparticles and nanocapsules, involving non-toxic biodegradable polymers, liposomes, solid lipid nanoparticles, and inorganic-organic nanomaterials, are among the most used carriers for drugs for a broad spectrum of targeted diseases. In fact, oral, injectable, transdermal-dermal and ocular formulations mainly consist of the aforementioned nanomaterials demonstrating promising characteristics such as long circulation, specific targeting, high drug loading capacity, enhanced intracellular penetration, and so on. Over the last decade, huge advances in the development of novel, safer and less toxic nanocarriers with amended properties have been made. In addition, multifunctional nanocarriers combining chemical substances, vitamins and peptides via coupling chemistry, inorganic particles coated by biocompatible materials seem to play a key role considering that functionalization can enhance characteristics such as biocompatibility, targetability, environmental friendliness, and intracellular penetration while also have limited side effects. This review aims to summarize the "state of the art" of drug delivery carriers in nanosize, paying attention to their surface functionalization with ligands and other small or polymeric compounds so as to upgrade active and passive targeting, different release patterns as well as cell targeting and stimuli responsibility. Lastly, future aspects and potential uses of nanoparticulated drug systems are outlined.

Multifunctional Transmembrane Protein Ligands for Cell-Specific Targeting of Plasma Membrane-Derived Vesicles

Liposomes and nanoparticles that bind selectively to cell-surface receptors can target specific populations of cells. However, chemical conjugation of ligands to these particles is difficult to control, frequently limiting ligand uniformity and complexity. In contrast, the surfaces of living cells are decorated with highly uniform populations of sophisticated transmembrane proteins. Toward harnessing cellular capabilities, here it is demonstrated that plasma membrane vesicles (PMVs) derived from donor cells can display engineered transmembrane protein ligands that precisely target cells on the basis of receptor expression. These multifunctional targeting proteins incorporate (i) a protein ligand, (ii) an intrinsically disordered protein spacer to make the ligand sterically accessible, and (iii) a fluorescent protein domain that enables quantification of the ligand density on the PMV surface. PMVs that display targeting proteins with affinity for the epidermal growth factor receptor (EGFR) bind at increasing concentrations to breast cancer cells that express increasing levels of EGFR. Further, as an example of the generality of this approach, PMVs expressing a single-domain antibody against green fluorescence protein (eGFP) bind to cells expressing eGFP-tagged receptors with a selectivity of ≈50:1. The results demonstrate the versatility of PMVs as cell targeting systems, suggesting diverse applications from drug delivery to tissue engineering.

Autonomous magnetic labelling of functional mesenchymal stem cells for improved traceability and spatial control in cell therapy applications

Mesenchymal stem cells (MSCs) represent a valuable resource for regenerative medicine treatments for orthopaedic repair and beyond. Following developments in isolation, expansion and differentiation protocols, efforts to promote clinical translation of emerging cellular strategies now seek to improve cell delivery and targeting. This study shows efficient live MSC labelling using silica‐coated magnetic particles (MPs), which enables 3D tracking and guidance of stem cells. A procedure developed for the efficient and unassisted particle uptake was shown to support MSC viability and integrity, while surface marker expression and MSC differentiation capability were also maintained. In vitro, MSCs showed a progressive decrease in labelling over increasing culture time, which appeared to be linked to the dilution effect of cell division, rather than to particle release, and did not lead to detectable secondary particle uptake. Labelled MSC populations demonstrated magnetic responsiveness in vitro through directed migration in culture and, when seeded onto a scaffold, supporting MP‐based approaches to cell targeting. The potential of these silica‐coated MPs for MRI cell tracking of MSC populations was validated in 2D and in a cartilage repair model following cell delivery. These results highlight silica‐coated magnetic particles as a simple, safe and effective resource to enhance MSC targeting for therapeutic applications and improve patient outcomes. © 2016 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.

Automatic Echographic Detection of Halloysite Clay Nanotubes in a Low Concentration Range

Aim of this work was to investigate the automatic echographic detection of an experimental drug delivery agent, halloysite clay nanotubes (HNTs), by employing an innovative method based on advanced spectral analysis of the corresponding "raw" radiofrequency backscatter signals. Different HNT concentrations in a low range (5.5-66 × 1010 part/mL, equivalent to 0.25-3.00 mg/mL) were dispersed in custom-designed tissue-mimicking phantoms and imaged through a clinically-available echographic device at a conventional ultrasound diagnostic frequency (10 MHz). The most effective response (sensitivity = 60%, specificity = 95%), was found at a concentration of 33 × 1010 part/mL (1.5 mg/mL), representing a kind of best compromise between the need of enough particles to introduce detectable spectral modifications in the backscattered signal and the necessity to avoid the losses of spectral peculiarity associated to higher HNT concentrations. Based on theoretical considerations and quantitative comparisons with literature-available results, this concentration could also represent an optimal concentration level for the automatic echographic detection of different solid nanoparticles when employing a similar ultrasound frequency. Future dedicated studies will assess the actual clinical usefulness of the proposed approach and the potential of HNTs for effective theranostic applications.

A High-Sensitivity and Low-Power Theranostic Nanosystem for Cell SERS Imaging and Selectively Photothermal Therapy Using Anti-EGFR-Conjugated Reduced Graphene Oxide/Mesoporous Silica/AuNPs Nanosheets

A high-sensitivity and low-power theranostic nanosystem that combines with synergistic photothermal therapy and surface-enhanced Raman scattering (SERS) mapping is constructed by mesoporous silica self-assembly on the reduced graphene oxide (rGO) nanosheets with nanogap-aligned gold nanoparticles (AuNPs) encapsulated and arranged inside the nanochannels of the mesoporous silica layer. Rhodamine 6G (R6G) as a Raman reporter is then encapsulated into the nanochannels and anti-epidermal growth factor receptor (EGFR) is conjugated on the nanocomposite surface, defined as anti-EGFR-PEG-rGO@CPSS-Au-R6G, where PEG is polyethylene glycol and CPSS is carbon porous silica nanosheets. SERS spectra results show that rGO@CPSS-Au-R6G enhances 5 × 10(6) magnification of the Raman signals and thus can be applied in the noninvasive cell tracking. Furthermore, it displays high sensitivity (detection limits: 10(-8) m R6G solution) due to the "hot spots" effects by the arrangements of AuNPs in the nanochannels of mesoporous silica. The highly selective targeting of overexpressing EGFR lung cancer cells (A549) is observed in the anti-EGFR-PEG-rGO@CPSS-Au-R6G, in contrast to normal cells (MRC-5). High photothermal therapy efficiency with a low power density (0.5 W cm(-2) ) of near-infrared laser can be achieved because of the synergistic effect by conjugated AuNPs and rGO nanosheets. These results demonstrate that the anti-EGFR-PEG-rGO@CPSS-Au-R6G is an excellent new theranostic nanosystem with cell targeting, cell tracking, and photothermal therapy capabilities.

High number of transplanted stem cells improves myocardial recovery after AMI in a porcine model

OBJECTIVE

The clinical data considering the bone marrow mononuclear cell (BMMNC) therapy in treatment for acute myocardial infarction (AMI) are controversial and the mechanisms remain unknown. Our objective was to study the cardiac function and changes in cytokine levels after administration of BMMNC in experimental AMI model.

DESIGN

Unlabeled or Super-Paramagnetic-Iron-Oxide-labeled BMMNCs or saline was injected into myocardium of 31 pigs after circumflex artery occlusion. Ejection fraction (EF) was measured preoperatively, postoperatively and at 21 days by echocardiography. Cardiac MRI was performed postoperatively and after 21 days in 7 BMMNC animals. Serum cytokine levels were measured at baseline, 24 h and 21 days. Cellular homing was evaluated comparing MRI and histology.

RESULTS

From baseline to 21 days EF decreased less in BMMNC group (EF mean control -19 SD 12 vs. BMMNC -4 SD 15 percentage points p = 0.02). Cytokine concentrations showed high variability between the animals. MRI correlated with histology in cell detection and revealed BMMNCs in the infarction area. By MRI, EF improved 11 percentage points. The improvement in EF was associated with the number of transplanted BMMNCs detected in the myocardium.

CONCLUSION

BMMNC injection after AMI improved cardiac function. Quantity of transplanted BMMNCs correlated with the improvement in cardiac function after AMI.

Detection of PLGA-based nanoparticles at a single-cell level by synchrotron radiation FTIR spectromicroscopy and correlation with X-ray fluorescence microscopy

Poly-lactide-co-glycolide (PLGA) is one of the few polymers approved by the US Food and Drug Administration as a carrier for drug administration in humans; therefore, it is one of the most used materials in the formulation of polymeric nanoparticles (NPs) for therapeutic purposes. Because the cellular uptake of polymeric NPs is a hot topic in the nanomedicine field, the development of techniques able to ensure incontrovertible evidence of the presence of NPs in the cells plays a key role in gaining understanding of their therapeutic potential. On the strength of this premise, this article aims to evaluate the application of synchrotron radiation-based Fourier transform infrared spectroscopy (SR-FTIR) spectromicroscopy and SR X-ray fluorescence (SR-XRF) microscopy in the study of the in vitro interaction of PLGA NPs with cells. To reach this goal, we used PLGA NPs, sized around 200 nm and loaded with superparamagnetic iron oxide NPs (PLGA-IO-NPs; Fe₃O₄; size, 10-15 nm). After exposing human mesothelial (MeT5A) cells to PLGA-IO-NPs (0.1 mg/mL), the cells were analyzed after fixation both by SR-FTIR spectromicroscopy and SR-XRF microscopy setups. SR-FTIR-SM enabled the detection of PLGA NPs at single-cell level, allowing polymer detection inside the biological matrix by the characteristic band in the 1,700-2,000 cm(-1) region. The precise PLGA IR-signature (1,750 cm(-1) centered pick) also was clearly evident within an area of high amide density. SR-XRF microscopy performed on the same cells investigated under SR-FTIR microscopy allowed us to put in evidence the Fe presence in the cells and to emphasize the intracellular localization of the PLGA-IO-NPs. These findings suggest that SR-FTIR and SR-XRF techniques could be two valuable tools to follow the PLGA NPs' fate in in vitro studies on cell cultures.

Poly(3-hydroxybutyrate-co-R-3-hydroxyhexanoate) nanoparticles with polyethylenimine coat as simple, safe, and versatile vehicles for cell targeting: population characteristics, cell uptake, and intracellular trafficking

A simple and highly safe poly(3-hydroxybutyrate-co-R-3-hydroxyhexanoate) nanoparticulate delivery system that targets different cell types is developed. A sub-cytotoxic level of polyethylenimine coat mediates universal cell targeting. Internalized nanoparticles traffic along endolysosomal compartments, endoplasmic reticulum and the Golgi complex. Nanoparticles have no detrimental effects on cell morphology and respiration.

Polyethylene glycol backfilling mitigates the negative impact of the protein corona on nanoparticle cell targeting

In protein-rich environments such as the blood, the formation of a protein corona on receptor-targeting nanoparticles prevents target recognition. As a result, the ability of targeted nanoparticles to selectively bind to diseased cells is drastically inhibited. Backfilling the surface of a targeted nanoparticle with polyethylene glycol (PEG) molecules is demonstrated to reduce the formation of the protein corona and re-establishes specific binding. The length of the backfilled PEG molecules must be less than the length of the ligand linker; otherwise, PEG interferes with the binding of the targeting ligand to its corresponding cellular receptor.

Nanostructured porous Si-based nanoparticles for targeted drug delivery

One of the backbones in nanomedicine is to deliver drugs specifically to unhealthy cells. Drug nanocarriers can cross physiological barriers and access different tissues, which after proper surface biofunctionalization can enhance cell specificity for cancer therapy. Recent developments have highlighted the potential of mesoporous silica (PSiO₂) and silicon (PSi) nanoparticles for targeted drug delivery. In this review, we outline and discuss the most recent advances on the applications and developments of cancer therapies by means of PSiO₂ and PSi nanomaterials. Bio-engineering and fine tuning of anti-cancer drug vehicles, high flexibility and potential for sophisticated release mechanisms make these nanostructures promising candidates for “smart” cancer therapies. As a result of their physicochemical properties they can be controllably loaded with large amounts of drugs and coupled to homing molecules to facilitate active targeting. The main emphasis of this review will be on the in vitro and in vivo studies.

NF-κB inhibitor targeted to activated endothelium demonstrates a critical role of endothelial NF-κB in immune-mediated diseases

Activation of the nuclear transcription factor κB (NF-κB) regulates the expression of inflammatory genes crucially involved in the pathogenesis of inflammatory diseases. NF-κB governs the expression of adhesion molecules that play a pivotal role in leukocyte-endothelium interactions. We uncovered the crucial role of NF-κB activation within endothelial cells in models of immune-mediated diseases using a "sneaking ligand construct" (SLC) selectively inhibiting NF-κB in the activated endothelium. The recombinant SLC1 consists of three modules: (i) an E-selectin targeting domain, (ii) a Pseudomonas exotoxin A translocation domain, and (iii) a NF-κB Essential Modifier-binding effector domain interfering with NF-κB activation. The E-selectin-specific SLC1 inhibited NF-κB by interfering with endothelial IκB kinase 2 activity in vitro and in vivo. In murine experimental peritonitis, the application of SLC1 drastically reduced the extravasation of inflammatory cells. Furthermore, SLC1 treatment significantly ameliorated the disease course in murine models of rheumatoid arthritis. Our data establish that endothelial NF-κB activation is critically involved in the pathogenesis of arthritis and can be selectively inhibited in a cell type- and activation stage-dependent manner by the SLC approach. Moreover, our strategy is applicable to delineating other pathogenic signaling pathways in a cell type-specific manner and enables selective targeting of distinct cell populations to improve effectiveness and risk-benefit ratios of therapeutic interventions.