Targosomes: Anti-HER2 PLGA nanocarriers for bioimaging, chemotherapy and local photothermal treatment of tumors and remote metastases

Developing combined cancer therapy strategies is of utmost importance as it can enhance treatment efficacy, overcome drug resistance, and ultimately improve patient outcomes by targeting multiple pathways and mechanisms involved in cancer growth and progression. Specifically, the potential of developing a combination chemo&photothermal therapy using targeted polymer nanoparticles as nanocarriers offers a promising approach for synergistic cancer treatment by combining the benefits of both therapies, such as targeted drug delivery and localized hyperthermia. Here, we report the first targeted anti-HER2 PLGA nanocarriers, called targosomes, that simultaneously possess photothermal, chemotherapeutic and diagnostic properties using only molecular payloads. Biocompatible poly(lactic-co-glycolic acid), PLGA, nanoparticles were loaded with photosensitizer phthalocyanine, diagnostic dye Nile Blue, and chemotherapeutic drug irinotecan, which was chosen as a result of screening a panel of theragnostic nanoparticles. The targeted delivery to cell surface oncomarker HER2 was ensured by nanoparticle modification with the anti-HER2 monoclonal antibody, trastuzumab, using the one-pot synthesis method without chemical conjugation. The irradiation tests revealed prominent photothermal properties of nanoparticles, namely heating by 35 °C in 10 min. Nanoparticles exhibited a 7-fold increase in binding and nearly an 18-fold increase in cytotoxicity for HER2-overexpressing cells compared to cells lacking HER2 expression. This enhancement of cytotoxicity was further amplified by >20-fold under NIR light irradiation. In vivo studies proved the efficacy of nanoparticles for bioimaging of primary tumor and metastasis sites and demonstrated 93% tumor growth inhibition, making these nanoparticles excellent candidates for translation into theragnostic applications.

Targeted PLGA-Chitosan Nanoparticles for NIR-Triggered Phototherapy and Imaging of HER2-Positive Tumors

Targeted medicine uses the distinctive features of cancer cells to find and destroy tumors. We present human epidermal growth factor receptor 2 (HER2)-targeted PLGA-chitosan nanoparticles for cancer therapy and visualization. Loading with two near-infrared (NIR) dyes provides imaging in the NIR transparency window and phototherapy triggered by 808 nm light. Nile Blue (NB) is a biocompatible solvatochromic NIR dye that serves as an imaging agent. Laser irradiation of IR-780 dye leads to a temperature rise and the generation of reactive oxygen species (ROS). Resonance energy transfer between two dyes allows visualization of tumors in a wide range of visible and IR wavelengths. The combination of two NIR dyes enables the use of nanoparticles for diagnostics only or theranostics. Modification of poly(lactic-co-glycolic acid) (PLGA)-chitosan nanoparticles with trastuzumab provides an efficient nanoparticle uptake by tumor cells and promotes more than sixfold specificity towards HER2-positive cells, leading to a synergistic anticancer effect. We demonstrate optical imaging of the HER2-positive mouse mammary tumor and tumor-specific accumulation of PLGA-IR-780-NB nanoparticles in vivo after intravenous administration. We managed to achieve almost complete suppression of the proliferative activity of cells in vitro by irradiation with an 808 nm laser with a power of 0.27 W for 1 min at a concentration at which nanoparticles are nontoxic to cells in the dark.

Topological Darkness: How to Design a Metamaterial for Optical Biosensing with Ultrahigh Sensitivity

Due to the absence of labels and fast analyses, optical biosensors promise major advances in biomedical diagnostics, security, environmental, and food safety applications. However, the sensitivity of the most advanced plasmonic biosensor implementations has a fundamental limitation caused by losses in the system and/or geometry of biochips. Here, we report a "scissor effect" in topologically dark metamaterials which is capable of providing ultrahigh-amplitude sensitivity to biosensing events, thus solving the bottleneck sensitivity limitation problem. We explain how the "scissor effect" can be realized via the proper design of topologically dark metamaterials and describe strategies for their fabrication. To validate the applicability of this effect in biosensing, we demonstrate the detection of folic acid (vitamin important for human health) in a wide 3-log linear dynamic range with a limit of detection of 0.22 nM, which is orders of magnitude better than those previously reported for all optical counterparts. Our work provides possibilities for designing and realizing plasmonic, semiconductor, and dielectric metamaterials with ultrasensitivity to binding events.

Surface Characteristics Affect the Properties of PLGA Nanoparticles as Photothermal Agents

Photothermal therapy is one of the most promising and rapidly developing fields in modern oncology due to its high efficiency, localized action, and minimal invasiveness. Polymeric nanoparticles (NPs) incorporating low molecular-weight photothermal dyes are capable of delivering therapeutic agents to the tumor site, releasing them in a controlled manner, and providing tumor treatment under external light irradiation. The nanoparticle synthesis components are critically important factors that influence the therapeutically significant characteristics of polymeric NPs. Here, we show the impact of stabilizers and solvents used for synthesis on the properties of PLGA NPs for photothermal therapy. We synthesized PLGA nanocarriers using the microemulsion method and varied the nature of the solvent and the concentration of the stabilizer-namely, chitosan oligosaccharide lactate. A phthalocyanine-based photosensitizer, which absorbs light in the NIR window, was encapsulated in the PLGA NPs. When mQ water was used as a solvent and chitosan oligosaccharide lactate was used at a concentration of 1 g/L, the PLGA NPs exhibited highly promising photothermal properties. The final composite of the nanocarriers demonstrated photoinduced cytotoxicity against EMT6/P cells under NIR laser irradiation in vitro and was suitable for bioimaging.

Comparative Study of Nanoparticle Blood Circulation after Forced Clearance of Own Erythrocytes (Mononuclear Phagocyte System-Cytoblockade) or Administration of Cytotoxic Doxorubicin- or Clodronate-Loaded Liposomes

Recent developments in the field of nanomedicine have introduced a wide variety of nanomaterials that are capable of recognizing and killing tumor cells with increased specificity. A major limitation preventing the widespread introduction of nanomaterials into the clinical setting is their fast clearance from the bloodstream via the mononuclear phagocyte system (MPS). One of the most promising methods used to overcome this limitation is the MPS-cytoblockade, which forces the MPS to intensify the clearance of erythrocytes by injecting allogeneic anti-erythrocyte antibodies and, thus, significantly prolongs the circulation of nanoagents in the blood. However, on the way to the clinical application of this approach, the question arises whether the induced suppression of macrophage phagocytosis via the MPS-cytoblockade could pose health risks. Here, we show that highly cytotoxic doxorubicin- or clodronate-loaded liposomes, which are widely used for cancer therapy and biomedical research, induce a similar increase in the nanoparticle blood circulation half-life in mice as the MPS-cytoblockade, which only gently and temporarily saturates the macrophages with the organism's own erythrocytes. This result suggests that from the point of view of in vivo macrophage suppression, the MPS-cytoblockade should be less detrimental than the liposomal anti-cancer drugs that are already approved for clinical application while allowing for the substantial improvement in the nanoagent effectiveness.

Ratiometric i-Motif-Based Sensor for Precise Long-Term Monitoring of pH Micro Alterations in the Nucleoplasm and Interchromatin Granules

DNA-intercalated motifs (iMs) are facile scaffolds for the design of various pH-responsive nanomachines, including biocompatible pH sensors. First, DNA pH sensors relied on complex intermolecular scaffolds. Here, we used a simple unimolecular dual-labeled iM scaffold and minimized it by replacing the redundant loop nucleosides with abasic or alkyl linkers. These modifications improved the thermal stability of the iM and increased the rates of its pH-induced conformational transitions. The best effects were obtained upon the replacement of all three native loops with short and flexible linkers, such as the propyl one. The resulting sensor showed a pH transition value equal to 6.9 ± 0.1 and responded rapidly to minor acidification (tau_1/2 <1 s for 7.2 → 6.6 pH jump). We demonstrated the applicability of this sensor for pH measurements in the nuclei of human lung adenocarcinoma cells (pH = 7.4 ± 0.2) and immortalized embryonic kidney cells (pH = 7.0 ± 0.2). The sensor stained diffusely the nucleoplasm and piled up in interchromatin granules. These findings highlight the prospects of iMs in the studies of normal and pathological pH-dependent processes in the nucleus, including the formation of biomolecular condensates.

Barnase-barstar Specific Interaction Regulates Car-T Cells Cytotoxic Activity toward Malignancy

The development of CAR-T specific therapy made a revolution in modern oncology. Despite the pronounced therapeutic effects, this novel approach displayed several crucial limitations caused by the complications in pharmacokinetics and pharmacodynamics controls. The presence of the several severe medical complications of CAR-T therapy initiated a set of attempts aimed to regulate their activity in vivo. We propose to apply the barnase-barstar system to control the cytotoxic antitumor activity of CAR-T cells. To menage the regulation targeting effect of the system we propose to use barstar-modified CAR-T cells together with barnase-based molecules. Barnase was fused with designed ankyrin repeat proteins (DARPins) specific to tumor antigens HER2 (human epidermal growth factor receptor 2) The application of the system demonstrates the pronounced regulatory effects of CAR-T targeting.

Genetically Encoded Self-Assembling Protein Nanoparticles for the Targeted Delivery In Vitro and In Vivo

Targeted nanoparticles of different origins are considered as new-generation diagnostic and therapeutic tools. However, there are no targeted drug formulations within the composition of nanoparticles approved by the FDA for use in the clinic, which is associated with the insufficient effectiveness of the developed candidates, the difficulties of their biotechnological production, and inadequate batch-to-batch reproducibility. Targeted protein self-assembling nanoparticles circumvent this problem since proteins are encoded in DNA and the final protein product is produced in only one possible way. We believe that the combination of the endless biomedical potential of protein carriers as nanoparticles and the standardized protein purification protocols will make significant progress in "magic bullet" creation possible, bringing modern biomedicine to a new level. In this review, we are focused on the currently existing platforms for targeted self-assembling protein nanoparticles based on transferrin, lactoferrin, casein, lumazine synthase, albumin, ferritin, and encapsulin proteins, as well as on proteins from magnetosomes and virus-like particles. The applications of these self-assembling proteins for targeted delivery in vitro and in vivo are thoroughly discussed, including bioimaging applications and different therapeutic approaches, such as chemotherapy, gene delivery, and photodynamic and photothermal therapy. A critical assessment of these protein platforms' efficacy in biomedicine is provided and possible problems associated with their further development are described.

Lectin-Modified Magnetic Nano-PLGA for Photodynamic Therapy In Vivo

The extreme aggressiveness and lethality of many cancer types appeal to the problem of the development of new-generation treatment strategies based on smart materials with a mechanism of action that differs from standard treatment approaches. The targeted delivery of nanoparticles to specific cancer cell receptors is believed to be such a strategy; however, there are no targeted nano-drugs that have successfully completed clinical trials to date. To meet the challenge, we designed an alternative way to eliminate tumors in vivo. Here, we show for the first time that the targeting of lectin-equipped polymer nanoparticles to the glycosylation profile of cancer cells, followed by photodynamic therapy (PDT), is a promising strategy for the treatment of aggressive tumors. We synthesized polymer nanoparticles loaded with magnetite and a PDT agent, IR775 dye (mPLGA/IR775). The magnetite incorporation into the PLGA particle structure allows for the quantitative tracking of their accumulation in different organs and the performing of magnetic-assisted delivery, while IR775 makes fluorescent in vivo bioimaging as well as light-induced PDT possible, thus realizing the theranostics concept. To equip PLGA nanoparticles with targeting modality, the particles were conjugated with lectins of different origins, and the flow cytometry screening revealed that the most effective candidate for breast cancer cell labeling is ConA, a lectin from Canavalia ensiformis. In vivo experiments showed that after i.v. administration, mPLGA/IR775-ConA nanoparticles efficiently accumulated in the allograft tumors under the external magnetic field; produced a bright fluorescent signal for in vivo bioimaging; and led to 100% tumor growth inhibition after the single session of PDT, even for large solid tumors of more than 200 mm³ in BALB/c mice. The obtained results indicate that the mPLGA/IR775 nanostructure has great potential to become a highly effective oncotheranostic agent.

Fluorescent Magnetic Nanoparticles for Bioimaging through Biomimetic Surface Modification

Nanostructured materials and systems find various applications in biomedical fields. Hybrid organo-inorganic nanomaterials are intensively studied in a wide range of areas, from visualization to drug delivery or tissue engineering. One of the recent trends in material science is biomimetic approaches toward the synthesis or modification of functional nanosystems. Here, we describe an approach toward multifunctional nanomaterials through the biomimetic polymerization of dopamine derivatives. Magnetite nanoparticles were modified with a combination of dopamine conjugates to give multifunctional magneto-fluorescent nanocomposites in one synthetic step. The obtained material showed excellent biocompatibility at concentrations up to 200 μg/mL and an in vivo biodistribution profile typical for nanosized formulations. The synthesized systems were conjugated with antibodies against HER2 to improve their selectivity toward HER2-positive cancer cells. The produced material can be used for dual magneto-optical in vivo studies or targeted drug delivery. The applied synthetic strategy can be used for the creation of various multifunctional hybrid nanomaterials in mild conditions.

Switchable targeting of solid tumors by BsCAR T cells

The development of chimeric antigen receptor (CAR) T cell therapy has become a critical milestone in modern oncotherapy. Despite the remarkable in vitro effectiveness, the problem of safety and efficacy of CAR T cell therapy against solid tumors is challenged by the lack of tumor-specific antigens required to avoid on-target off-tumor effects. Spatially separating the cytotoxic function of CAR T cells from tumor antigen recognition provided by protein mediators allows for the precise control of CAR T cell cytotoxicity. Here, the high affinity and capability of the bacterial toxin-antitoxin barnase-barstar system were adopted to guide CAR T cells to solid tumors. The complementary modules based on (1) ankyrin repeat (DARPin)-barnase proteins and (2) barstar-based CAR (BsCAR) were designed to provide switchable targeting to tumor cells. The alteration of the DARPin-barnase switches enabled the targeting of different tumor antigens with a single BsCAR. A gradual increase in cytokine release and tunable BsCAR T cell cytotoxicity was achieved by varying DARPin-barnase loads. Switchable BsCAR T cell therapy was able to eradicate the HER2⁺ ductal carcinoma in vivo. Guiding BsCAR T cells by DARPin-barnase switches provides a universal approach for a controlled multitargeted adoptive immunotherapy.

Effect of Surface Modification of Multifunctional Nanocomposite Drug Delivery Carriers with DARPin on Their Biodistribution In Vitro and In Vivo

We present a targeted drug delivery system for therapy and diagnostics that is based on a combination of contrasting, cytotoxic, and cancer-cell-targeting properties of multifunctional carriers. The system uses multilayered polymer microcapsules loaded with magnetite and doxorubicin. Loading of magnetite nanoparticles into the polymer shell by freezing-induced loading (FIL) allowed the loading efficiency to be increased 5-fold, compared with the widely used layer-by-layer (LBL) assembly. FIL also improved the photoacoustic signal and particle mobility in a magnetic field gradient, a result unachievable by the LBL alone. For targeted delivery of the carriers to cancer cells, the carrier surface was modified with a designed ankyrin repeat protein (DARPin) directed toward the epithelial cell adhesion molecule (EpCAM). Flow cytometry measurements showed that the DARPin-coated capsules specifically interacted with the surface of EpCAM-overexpressing human cancer cells such as MCF7. In vivo and ex vivo biodistribution studies in FvB mice showed that the carrier surface modification with DARPin changed the biodistribution of the capsules toward epithelial cells. In particular, the capsules accumulated substantially in the lungs─a result that can be effectively used in targeted lung cancer therapy. The results of this work may aid in the further development of the "magic bullet" concept and may bring the quality of personalized medicine to another level.

Photothermal Therapy with HER2-Targeted Silver Nanoparticles Leading to Cancer Remission

Nanoparticles exhibiting the localized surface plasmon resonance (LSPR) phenomenon are promising tools for diagnostics and cancer treatment. Among widely used metal nanoparticles, silver nanoparticles (Ag NPs) possess the strongest light scattering and surface plasmon strength. However, the therapeutic potential of Ag NPs has until now been underestimated. Here we show targeted photothermal therapy of solid tumors with 35 nm HER2-targeted Ag NPs, which were produced by the green synthesis using an aqueous extract of Lavandula angustifolia Mill. Light irradiation tests demonstrated effective hyperthermic properties of these NPs, namely heating by 10 °C in 10 min. To mediate targeted cancer therapy, Ag NPs were conjugated to the scaffold polypeptide, affibody ZHER2:342, which recognizes a clinically relevant oncomarker HER2. The conjugation was mediated by the PEG linker to obtain Ag-PEG-HER2 nanoparticles. Flow cytometry tests showed that Ag-PEG-HER2 particles successfully bind to HER2-overexpressing cells with a specificity comparable to that of full-size anti-HER2 IgGs. A confocal microscopy study showed efficient internalization of Ag-PEG-HER2 into cells in less than 2 h of incubation. Cytotoxicity assays demonstrated effective cell death upon exposure to Ag-PEG-HER2 and irradiation, caused by the production of reactive oxygen species. Xenograft tumor therapy with Ag-PEG-HER2 particles in vivo resulted in full primary tumor regression and the prevention of metastatic spread. Thus, for the first time, we have shown that HER2-directed plasmonic Ag nanoparticles are effective sensitizers for targeted photothermal oncotherapy.

Genetically encoded BRET-activated photodynamic therapy for the treatment of deep-seated tumors

Photodynamic therapy (PDT) is one of the most appealing photonic modalities for cancer treatment based on anticancer activity of light-induced photosensitizer-mediated reactive oxygen species (ROS), but a limited depth of light penetration into tissues does not make possible the treatment of deep-seated neoplasms and thus complicates its widespread clinical adoption. Here, we introduce the concept of genetically encoded bioluminescence resonance energy transfer (BRET)-activated PDT, which combines an internal light source and a photosensitizer (PS) in a single-genetic construct, which can be delivered to tumors seated at virtually unlimited depth and then triggered by the injection of a substrate to initiate their treatment. To illustrate the concept, we engineered genetic NanoLuc-miniSOG BRET pair, combining NanoLuc luciferase flashlight and phototoxic flavoprotein miniSOG, which generates ROS under luciferase-substrate injection. We prove the concept feasibility in mice bearing NanoLuc-miniSOG expressing tumor, followed by its elimination under the luciferase-substrate administration. Then, we demonstrate a targeted delivery of NanoLuc-miniSOG gene, via tumor-specific lentiviral particles, into a tumor, followed by its successful elimination, with tumor-growth inhibition (TGI) coefficient exceeding 67%, which confirms a great therapeutic potential of the proposed concept. In conclusion, this study provides proof-of-concept for deep-tissue "photodynamic" therapy without external light source that can be considered as an alternative for traditional PDT.

Barnase encapsulation into submicron porous CaCO3 particles: studies of loading and enzyme activity

The present study focuses on the immobilization of the bacterial ribonuclease barnase (Bn) into submicron porous calcium carbonate (CaCO₃) particles. For encapsulation, we apply adsorption, freezing-induced loading and co-precipitation methods and study the effects of adsorption time, enzyme concentration and anionic polyelectrolytes on the encapsulation efficiency of Bn. We show that the use of negatively charged dextran sulfate (DS) and ribonucleic acid from yeast (RNA) increases the loading capacity (LC) of the enzyme on CaCO₃ particles by about 3-fold as compared to the particles with Bn itself. The ribonuclease (RNase) activity of encapsulated enzyme depends on the LC of the particles and transformation of metastable vaterite to stable calcite, as studied by the assessment of enzyme activities in particles.

DARPin_9-29-Targeted Gold Nanorods Selectively Suppress HER2-Positive Tumor Growth in Mice

Simple Summary

Breast cancer is one of the main causes of cancer-related death in women all around the world. The disease becomes largely incurable and lethal after metastasis to distant organs. High level of HER2, a tyrosine kinase receptor, is associated with more aggressive clinical behavior and poor prognosis for breast cancer patients. In this paper, we developed a novel nano-biomaterial for selective photothermal therapy of HER2-positive breast cancers. We demonstrate that bovine serum albumin (BSA)-coated mini gold nanorods (GNRs) chemically conjugated with a HER2-specific designed ankyrin repeat protein, DARPin_9-29, selectively accumulate in HER2-positive xenograft tumors in mice and lead to a strong reduction in the tumor size when being illuminated with near-infrared light.

Abstract

Near-infrared phototherapy has great therapeutic potential for cancer treatment. However, for efficient application, in vivo photothermal agents should demonstrate excellent stability in blood and targeted delivery to pathological tissue. Here, we demonstrated that stable bovine serum albumin-coated gold mini nanorods conjugated to a HER2-specific designed ankyrin repeat protein, DARPin_9-29, selectively accumulate in HER2-positive xenograft tumors in mice and lead to a strong reduction in the tumor size when being illuminated with near-infrared light. The results pave the way for the development of novel DARPin-based targeted photothermal therapy of cancer.

Comparative Evaluation of Engineered Polypeptide Scaffolds in HER2-Targeting Magnetic Nanocarrier Delivery

Targeted drug delivery is one of the most intriguing and challenging issues in modern biomedicine. For active targeting, full-size IgG molecules (150 kDa) are usually used. Recent studies have revealed that small artificial polypeptide scaffolds such as DARPins (14 kDa) and affibodies (8 kDa) are much more promising tools for drug delivery due to their small size, artificial nature, low immunogenicity, and many other properties. However, there is no comparative information on the targeting abilities of scaffold polypeptides, which should be taken into account when developing drug delivery systems (DDSs). The present work is the first comprehensive study on the comparison of the effectiveness of different HER2-targeting proteins within the architecture of nanoparticles. Namely, we synthesized trimodal nanoparticles: magnetic, fluorescent, and directed toward HER2 oncomarker on cancer cells. The magnetic particles (MPs) were covalently modified with (i) full-size IgG, 150 kDa, (ii) DARPin_G3, 14 kDa, and (iii) affibody Z_HER2:342, 8 kDa. We showed that the number of DARPin_G3 and affibody Z_HER2:342 molecules conjugated to the nanoparticle surface are 10 and 40 times higher, respectively, than the corresponding value for trastuzumab. Using the methods of magnetic particle quantification (MPQ)-cytometry and confocal microscopy, we showed that all types of the obtained magnetic conjugates specifically labeled HER2-overexpressing cells. Namely, we demonstrated that particle binding to HER2-positive cells is 1113 ± 39 fg/cell for MP*trastuzumab, 1431 ± 186 fg/cell for MP*Z_HER2:342, and 625±21 fg/cell for MP*DARPin_G3, which are 2.77, 2.75, and 2.30 times higher than the corresponding values for control HER2-negative cells. Thus, we showed that the smallest HER2-recognizing polypeptide affibody Z_HER2:342 is more effective in terms of specificity and selectivity in nanoparticle-mediated cell labeling.

Laser-synthesized TiN nanoparticles for biomedical applications: Evaluation of safety, biodistribution and pharmacokinetics

Having plasmonic absorption within the biological transparency window, titanium nitride (TiN) nanoparticles (NPs) can potentially outperform gold counterparts in phototheranostic applications, but characteristics of available TiN NPs are still far from required parameters. Recently emerged laser-ablative synthesis opens up opportunities to match these parameters as it makes possible the production of ultrapure low size-dispersed spherical TiN NPs, capable of generating a strong phototherapy effect under 750-800 nm excitation. This study presents the first assessment of toxicity, biodistribution and pharmacokinetics of laser-synthesized TiN NPs. Tests in vitro using 8 cell lines from different tissues evidenced safety of both as-synthesized and PEG-coated NPs (TiN-PEG NPs). After systemic administration in mice, they mainly accumulated in liver and spleen, but did not cause any sign of toxicity or organ damage up to concentration of 6 mg kg^-1, which was confirmed by the invariability of blood biochemical parameters, weight and hemotoxicity examination. The NPs demonstrated efficient passive accumulation in EMT6/P mammary tumor, while concentration of TiN-PEG NPs was 2.2-fold higher due to "stealth" effect yielding 7-times longer circulation in blood. The obtained results evidence high safety of laser-synthesized TiN NPs for biological systems, which promises a major advancement of phototheranostic modalities on their basis.

Dual Regioselective Targeting the Same Receptor in Nanoparticle-Mediated Combination Immuno/Chemotherapy for Enhanced Image-Guided Cancer Treatment

When combined with immunotherapy, image-guided targeted delivery of chemotherapeutic agents is a promising direction for combination cancer theranostics, but this approach has so far produced only limited success due to a lack of molecular targets on the cell surface and low therapeutic index of conventional chemotherapy drugs. Here, we demonstrate a synergistic strategy of combination immuno/chemotherapy in conditions of dual regioselective targeting, implying vectoring of two distinct binding sites of a single oncomarker (here, HER2) with theranostic compounds having a different mechanism of action. We use: (i) PLGA nanoformulation, loaded with an imaging diagnostic fluorescent dye (Nile Red) and a chemotherapeutic drug (doxorubicin), and functionalized with affibody Z_HER2:342 (8 kDa); (ii) bifunctional genetically engineered DARP-LoPE (42 kDa) immunotoxin comprising of a low-immunogenic modification of therapeutic Pseudomonas exotoxin A (LoPE) and a scaffold targeting protein, DARPin9.29 (14 kDa). According to the proposed strategy, the first chemotherapeutic nanoagent is targeted by the affibody to subdomain III and IV of HER2 with 60-fold specificity compared with nontargeted particles, while the second immunotoxin is effectively targeted by DARPin molecule to subdomain I of HER2. We demonstrate that this dual targeting strategy can enhance anticancer therapy of HER2-positive cells with a very strong synergy, which made possible 1000-fold decrease of effective drug concentration in vitro and a significant enhancement of HER2 cancer therapy compared to monotherapy in vivo. Moreover, this therapeutic combination prevented the appearance of secondary tumor nodes. Thus, the suggested synergistic strategy utilizing dual targeting of the same oncomarker could give rise to efficient methods for aggressive tumors treatment.

Plants with genetically encoded autoluminescence

Autoluminescent plants engineered to express a bacterial bioluminescence gene cluster in plastids have not been widely adopted because of low light output. We engineered tobacco plants with a fungal bioluminescence system that converts caffeic acid (present in all plants) into luciferin and report self-sustained luminescence that is visible to the naked eye. Our findings could underpin development of a suite of imaging tools for plants.

Author Correction: Plants with genetically encoded autoluminescence

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Enhancement of the blood-circulation time and performance of nanomedicines via the forced clearance of erythrocytes

The rapid elimination of nanoparticles from the bloodstream by the mononuclear phagocyte system limits the activity of many nanoparticle formulations. Here, we show that inducing a slight and transient depletion of erythrocytes in mice (~5% decrease in haematocrit) by administrating a low dose (1.25 mg kg^-1) of allogeneic anti-erythrocyte antibodies increases the circulation half-life of a range of short-circulating and long-circulating nanoparticle formulations by up to 32-fold. Treatment of the animals with anti-erythrocyte antibodies significantly improved the targeting of CD4⁺ cells in vivo with fluorescent anti-CD4-antibody-conjugated nanoparticles, the magnetically guided delivery of ferrofluid nanoparticles to subcutaneous tumour allografts and xenografts, and the treatment of subcutaneous tumour allografts with magnetically guided liposomes loaded with doxorubicin and magnetite or with clinically approved 'stealthy' doxorubicin liposomes. The transient and partial blocking of the mononuclear phagocyte system may enhance the performance of a wide variety of nanoparticle drugs.

Chemotherapeutic Agents Sensitize Resistant Cancer Cells to the DR5-Specific Variant DR5-B more Efficiently than to TRAIL by Modulating the Surface Expression of Death and Decoy Receptors

TRAIL is considered a promising antitumor agent because it causes apoptosis of transformed cells without affecting normal cells. However, many types of tumors are cytokine resistant, and combination therapy with various chemotherapeutic drugs is being developed to overcome the resistance. We have demonstrated that the combination of TRAIL with doxorubicin, bortezomib, and panobinostat dramatically reduced the viability of TRAIL-resistant A549 and HT-29 cells. Chemotherapy even more efficiently sensitized cells to the DR5-specific mutant variant of TRAIL DR5-B, which does not have an affinity for decoy receptors. Bortezomib and doxorubicin greatly enhanced the surface expression of the death receptors DR5 and DR4, while panobinostat increased expression of DR5 and suppressed expression of DR4 in both cell lines. All drugs increased surface expression of the decoy receptors DcR1 and DcR2. Unlike the combined treatment, if the cells were pretreated with chemotherapy for 24 h, the cytotoxic activity of TRAIL was less pronounced, while sequential treatment of cells enhanced the effectiveness of DR5-B. The same results were obtained with agonistic anti-DR5 antibodies. Thus, the effectiveness of TRAIL was rather limited due to changes in the ratio of death and decoy receptors and DR5-specific agonists may be preferred in combination antitumor therapy regimens.

Nanoparticle-based drug delivery via RBC-hitchhiking for the inhibition of lung metastases growth

Delivery of particle-based theranostic agents via their transportation on the surfaces of red blood cells, commonly referred to as RBC-hitchhiking, has historically been developed as a promising strategy for increasing the extremely poor blood circulation lifetime, primarily, of the large-sized sub-micron agents. Here, we show for the first time that RBC-hitchhiking can be extremely efficient for nanoparticle delivery and tumor treatment even in those cases when no circulation prolongation is observed. Specifically, we demonstrate that RBC-hitchhiking of certain small 100 nm particles, unlike that of the conventional sub-micron ones, can boost the delivery of non-targeted particles to lungs up to a record high value of 120-fold (and up to 40% of the injected dose). To achieve this remarkable result, we screened sub-200 nm nanoparticles of different sizes, polymer coatings and ζ-potentials and identified particles with the optimal RBC adsorption/desorption behavior. Furthermore, we demonstrated that such RBC-mediated rerouting of particles to lungs can be used to fight pulmonary metastases of aggressive melanoma B16-F1. Our findings could change the general paradigm of drug delivery for cancer treatment with RBC-hitchhiking. It is not the blood circulation lifetime that is the key factor for nanoparticle efficiency, but rather the complexation of nanoparticles with the RBC. The demonstrated technology could become a valuable tool for development of new strategies based on small nanoparticles for the treatment of aggressive and small-cell types of cancer as well as other lung diseases.

Data on characterization of magnetic nanoparticles stabilized with fusion protein of Barstar and C-term part of Mms6

Mms6 is a protein that plays crucial role in the biomineralization and formation of magnetosomes in magnetotactic bacteria Magnetospirillum magneticum (strain AMB-1). We developed a fusion protein of C-term part of Mms6 and Barstar (natural inhibitor of ribonuclease Barnase), namely, Bs-C-Mms6. This protein successfully stabilized uncoated monocrystalline Fe₃O₄ magnetite nanoparticles in buffered solutions. Here, we present data regarding the synthesis and characterization of magnetite nanoparticles stabilized with Bs-C-Mms6. For further interpretation of the data presented in this article, please see the research article 'Self-assembling nanoparticles biofunctionalized with magnetite-binding protein for the targeted delivery to HER2/neu overexpressing cancer cells' (Shipunova et al., 2018) [1].

Synthesis of Magnetic Nanoparticles Stabilized by Magnetite-Binding Protein for Targeted Delivery to Cancer Cells

A new method for obtaining biomodified magnetite nanoparticles for targeted delivery to cells was developed. The method is based on the use of the C-terminal fragment of the Mms6 protein, which is involved in the magnetite biomineralization during the synthesis of magnetosomes in magnetotactic bacteria Magnetospirillum magneticum AMB-1, and the barnase*barstar high-affinity protein pair. The Mms6 protein fragment is required for stabilizing magnetite, and the barnase*barstar pair mediates the interaction between nanoparticles and the component for modification. The efficiency of this method was confirmed in the synthesis of magnetite nanoparticles recognizing the HER2/neu tumor marker and in the selective labeling of HER2/neu with these nanoparticles on the surface of cancer cells.

Versatile Platform for Nanoparticle Surface Bioengineering Based on SiO2-Binding Peptide and Proteinaceous Barnase*Barstar Interface

Nanoparticle surface engineering can change its chemical identity to enable surface coupling with functional biomolecules. However, common surface coupling methods such as physical adsorption or chemical conjugation often suffer from the low coupling yield, poorly controllable orientation of biomolecules, and steric hindrance during target binding. These issues limit the application scope of nanostructures for theranostics and personalized medicine. To address these shortfalls, we developed a rapid and versatile method of nanoparticle biomodification. The method is based on a SiO₂-binding peptide that binds to the nanoparticle surface and a protein adaptor system, Barnase*Barstar protein pair, serving as a "molecular glue" between the peptide and the attached biomolecule. The biomodification procedure shortens to several minutes, preserves the orientation and functions of biomolecules, and enables control over the number and ratio of attached molecules. The capabilities of the proposed biomodification platform were demonstrated by coupling different types of nanoparticles with DARPin9.29 and 4D5scFv-molecules that recognize the human epidermal growth factor receptor 2 (HER2/neu) oncomarker-and by subsequent highly selective immunotargeting of the modified nanoparticles to different HER2/neu-overexpressing cancer cells in one-step or two-step (by pretargeting with HER2/neu-recognizing molecule) modes. The method preserved the biological activity of the DARPin9.29 molecules attached to a nanoparticle, whereas the state-of-the-art carbodiimide 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/ N-hydroxysulfosuccinimide method of conjugation led to a complete loss of the functional activity of the DARPin9.29 nanoparticle-protein complex. Moreover, the method allowed surface design of nanoparticles that selectively interacted with antigens in complex biological fluids, such as whole blood. The demonstrated capabilities show this method to be a promising alternative to commonly used chemical conjugation techniques in nanobiotechnology, theranostics, and clinical applications.

MPQ-cytometry: a magnetism-based method for quantification of nanoparticle-cell interactions

Precise quantification of interactions between nanoparticles and living cells is among the imperative tasks for research in nanobiotechnology, nanotoxicology and biomedicine. To meet the challenge, a rapid method called MPQ-cytometry is developed, which measures the integral non-linear response produced by magnetically labeled nanoparticles in a cell sample with an original magnetic particle quantification (MPQ) technique. MPQ-cytometry provides a sensitivity limit 0.33 ng of nanoparticles and is devoid of a background signal present in many label-based assays. Each measurement takes only a few seconds, and no complicated sample preparation or data processing is required. The capabilities of the method have been demonstrated by quantification of interactions of iron oxide nanoparticles with eukaryotic cells. The total amount of targeted nanoparticles that specifically recognized the HER2/neu oncomarker on the human cancer cell surface was successfully measured, the specificity of interaction permitting the detection of HER2/neu positive cells in a cell mixture. Moreover, it has been shown that MPQ-cytometry analysis of a HER2/neu-specific iron oxide nanoparticle interaction with six cell lines of different tissue origins quantitatively reflects the HER2/neu status of the cells. High correlation of MPQ-cytometry data with those obtained by three other commonly used in molecular and cell biology methods supports consideration of this method as a prospective alternative for both quantifying cell-bound nanoparticles and estimating the expression level of cell surface antigens. The proposed method does not require expensive sophisticated equipment or highly skilled personnel and it can be easily applied for rapid diagnostics, especially under field conditions.

A comprehensive study of interactions between lectins and glycoproteins for the development of effective theranostic nanoagents

A comprehensive study of the interactions between lectins and glycoproteins possessing different glycosylation profiles in the composition of nanoparticles was carried out in order to find specifically interacting protein pairs for the creation of novel classes of multifunctional nanoagets that based on protein-assisted selfassembly. We obtained information about specific interactions of certain lectins with selected glycoproteins as well as about the ability of certain monosaccharides to competitively inhibit binding of glycoproteins with lectins. These protein-mediated interactions may be involved in the formulation of self-assembled nanoparticles for therapy and diagnostics of various diseases.

Biocomputing based on particle disassembly

Nanoparticles with biocomputing capabilities could potentially be used to create sophisticated robotic devices with a variety of biomedical applications, including intelligent sensors and theranostic agents. DNA/RNA-based computing techniques have already been developed that can offer a complete set of Boolean logic functions and have been used, for example, to analyse cells and deliver molecular payloads. However, the computing potential of particle-based systems remains relatively unexplored. Here, we show that almost any type of nanoparticle or microparticle can be transformed into autonomous biocomputing structures that are capable of implementing a functionally complete set of Boolean logic gates (YES, NOT, AND and OR) and binding to a target as result of a computation. The logic-gating functionality is incorporated into self-assembled particle/biomolecule interfaces (demonstrated here with proteins) and the logic gating is achieved through input-induced disassembly of the structures. To illustrate the capabilities of the approach, we show that the structures can be used for logic-gated cell targeting and advanced immunoassays.