Artificial Scaffold Polypeptides As an Efficient Tool for the Targeted Delivery of Nanostructures In Vitro and In Vivo

Surface-functionalised polymeric nanoparticles for breast cancer treatment: processes and advances

The World Health Organization (WHO) reported that of all the non-communicable diseases, cancer is considered the second cause of death worldwide. This has driven the big pharma companies to prioritise anticancer products in their pipeline. In addition, research has focused on exploration of new anticancer molecules and design of suitable dosage forms to achieve effective drug delivery to the tumour site. Nanotechnology is a valuable tool to build nano delivery systems with controlled and targeted drug release properties. Nanoparticles can be fabricated by robust, scalable and economic techniques using various polymers. Moreover, specific functional groups can be introduced to the surface of nanoparticles enabling targeting to a specific tissue; besides, they exhibit versatile drug release patterns according to the rate of polymer degradation. This review outlines the processes and advances in surface functionalisation of nanoparticles employed for treatment of breast cancer. The therapeutic molecules, the polymers used to fabricate nanoparticles, the techniques used to prepare the nanoparticles have been reviewed with a focus on the processes employed to functionalise these nanoparticles with suitable ligands to target different types of breast cancer.

Luminescent polypeptides

Polypeptides, as biomacromolecules, hold immense potential in various biological applications such as tissue engineering, immunomodulating agents, and target binding. Among these applications, the attention towards luminescent polypeptides has grown significantly, due to their ability to visualize biological processes effectively. In this perspective, we have compiled information on three distinct types of luminescent polypeptides: natural fluorescent proteins, luminophores-bioconjugated polypeptides, and synthesized polypeptides with clusteroluminescence. Last, we shed light on the significance and prospects of clusteroluminescent polypeptides, which are expected to emerge as crucial new-generation bioluminophores, offering high emission efficiency and tunable emission wavelengths.

Quantitative Description of the N-Protein of the SARS-CoV-2 Virus Degradation in Cells Stably Expressing It under the Influence of New Modular Nanotransporters

Two eukaryotic cell lines, A549 and A431, with stable expression of the nucleocapsid protein (N-protein) of the SARS-CoV-2 virus fused with the red fluorescent protein mRuby3 were obtained. Using microscopy, the volumes of the cytoplasm and nucleus were determined for these cells. Using quantitative immunoblotting techniques, the concentrations of the N-mRuby3 fusion protein in their cytoplasm were assessed. They were 19 and 9 μM for A549 and A431 cells, respectively. Using these concentrations, the initial rate of N-protein degradation in the studied cells was estimated from the decrease in cell fluorescence. In A549 and A431 cells, it was the same (84 nM per hour). The approach of quantitatively describing the degradation process can be applied to analyze the effectiveness of a wide class of antiviral drugs that cause degradation of viral proteins.

Modular Nanotransporters Capable of Causing Intracellular Degradation of the N-Protein of the SARS-CoV-2 Virus in A549 Cells with Temporary Expression of This Protein Fused with a Fluorescent Protein mRuby3

Modular nanotransporters (MNTs) containing an antibody-like molecule, monobody, to the N‑protein of the SARS-CoV-2 virus, as well as an amino acid sequence that recruits the Keap1 E3 ligase (E3BP) were created. This MNT also included a site for cleavage of the E3BP monobody from the MNT in acidic endocytic compartments. It was shown that this cleavage by the endosomal protease cathepsin B leads to a 2.7-fold increase in the affinity of the E3BP monobody for the N-protein. Using A549 cells with transient expression of the N-protein fused with the fluorescent protein mRuby3, it was shown that incubation with MNT leads to a significant decrease in mRuby3 fluorescence. It is assumed that the developed MNTs can serve as a basis for the creation of new antiviral drugs against the SARS-CoV-2 virus.

Non-Immunoglobulin Synthetic Binding Proteins for Oncology

Extensive application of technologies like phage display in screening peptide and protein combinatorial libraries has not only facilitated creation of new recombinant antibodies but has also significantly enriched repertoire of the protein binders that have polypeptide scaffolds without homology to immunoglobulins. These innovative synthetic binding protein (SBP) platforms have grown in number and now encompass monobodies/adnectins, DARPins, lipocalins/anticalins, and a variety of miniproteins such as affibodies and knottins, among others. They serve as versatile modules for developing complex affinity tools that hold promise in both diagnostic and therapeutic settings. An optimal scaffold typically has low molecular weight, minimal immunogenicity, and demonstrates resistance against various challenging conditions, including proteolysis - making it potentially suitable for peroral administration. Retaining functionality under reducing intracellular milieu is also advantageous. However, paramount to its functionality is the scaffold's ability to tolerate mutations across numerous positions, allowing for the formation of a sufficiently large target binding region. This is achieved through the library construction, screening, and subsequent expression in an appropriate system. Scaffolds that exhibit high thermodynamic stability are especially coveted by the developers of new SBPs. These are steadily making their way into clinical settings, notably as antagonists of oncoproteins in signaling pathways. This review surveys the diverse landscape of SBPs, placing particular emphasis on the inhibitors targeting the oncoprotein KRAS, and highlights groundbreaking opportunities for SBPs in oncology.

Intracellular Delivery of an Antibody-Like Molecule Capable of Inhibiting c-Myc

A modular nanotransporter (MNT) carrying the sequence of an antibody-like molecule, anti-c-Myc nanobody, was synthesized and characterized. It was demonstrated that the created MNT is able to interact with the target protein, c-Myc oncogene, with a dissociation constant of 46 ± 14 nM, internalize into target cells, change Myc-dependent expression, and exert an antiproliferative effect.

Prospects of Using Protein Engineering for Selective Drug Delivery into a Specific Compartment of Target Cells

A large number of proteins are successfully used to treat various diseases. These include natural polypeptide hormones, their synthetic analogues, antibodies, antibody mimetics, enzymes, and other drugs based on them. Many of them are demanded in clinical settings and commercially successful, mainly for cancer treatment. The targets for most of the aforementioned drugs are located at the cell surface. Meanwhile, the vast majority of therapeutic targets, which are usually regulatory macromolecules, are located inside the cell. Traditional low molecular weight drugs freely penetrate all cells, causing side effects in non-target cells. In addition, it is often difficult to elaborate a small molecule that can specifically affect protein interactions. Modern technologies make it possible to obtain proteins capable of interacting with almost any target. However, proteins, like other macromolecules, cannot, as a rule, freely penetrate into the desired cellular compartment. Recent studies allow us to design multifunctional proteins that solve these problems. This review considers the scope of application of such artificial constructs for the targeted delivery of both protein-based and traditional low molecular weight drugs, the obstacles met on the way of their transport to the specified intracellular compartment of the target cells after their systemic bloodstream administration, and the means to overcome those difficulties.

Targeted Two-Step Delivery of Oncotheranostic Nano-PLGA for HER2-Positive Tumor Imaging and Therapy In Vivo: Improved Effectiveness Compared to One-Step Strategy

Therapy for aggressive metastatic breast cancer remains a great challenge for modern biomedicine. Biocompatible polymer nanoparticles have been successfully used in clinic and are seen as a potential solution. Specifically, researchers are exploring the development of chemotherapeutic nanoagents targeting the membrane-associated receptors of cancer cells, such as HER2. However, there are no targeting nanomedications that have been approved for human cancer therapy. Novel strategies are being developed to alter the architecture of agents and optimize their systemic administration. Here, we describe a combination of these approaches, namely, the design of a targeted polymer nanocarrier and a method for its systemic delivery to the tumor site. Namely, PLGA nanocapsules loaded with a diagnostic dye, Nile Blue, and a chemotherapeutic compound, doxorubicin, are used for two-step targeted delivery using the concept of tumor pre-targeting through the barnase/barstar protein “bacterial superglue”. The first pre-targeting component consists of an anti-HER2 scaffold protein, DARPin9_29 fused with barstar, Bs-DARPin9_29, and the second component comprises chemotherapeutic PLGA nanocapsules conjugated to barnase, PLGA-Bn. The efficacy of this system was evaluated in vivo. To this aim, we developed an immunocompetent BALB/c mouse tumor model with a stable expression of human HER2 oncomarkers to test the potential of two-step delivery of oncotheranostic nano-PLGA. In vitro and ex vivo studies confirmed HER2 receptor stable expression in the tumor, making it a feasible tool for HER2-targeted drug evaluation. We demonstrated that two-step delivery was more effective than one-step delivery for both imaging and tumor therapy: two-step delivery had higher imaging capabilities than one-step and a tumor growth inhibition of 94.9% in comparison to 68.4% for the one-step strategy. The barnase*barstar protein pair has been proven to possess excellent biocompatibility, as evidenced by the successful completion of biosafety tests assessing immunogenicity and hemotoxicity. This renders the protein pair a highly versatile tool for pre-targeting tumors with various molecular profiles, thereby enabling the development of personalized medicine.

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.

Minibody-Based and scFv-Based Antibody Fragment-Drug Conjugates Selectively Eliminate GD2-Positive Tumor Cells

Ganglioside GD2 is a well-established target expressed on multiple solid tumors, many of which are characterized by low treatment efficiency. Antibody-drug conjugates (ADCs) have demonstrated marked success in a number of solid tumors, and GD2-directed drug conjugates may also hold strong therapeutic potential. In a recent study, we showed that ADCs based on the approved antibody dinutuximab and the drugs monomethyl auristatin E (MMAE) or F (MMAF) manifested potent and selective cytotoxicity in a panel of tumor cell lines and strongly inhibited solid tumor growth in GD2-positive mouse cancer models. Here, we employed two different GD2-binding moieties-minibodies and scFv fragments that carry variable antibody domains identical to those of dinutuximab, and site-directly conjugated them to MMAE or MMAF by thiol-maleimide chemistry with drug-to-antibody ratios (DAR) of 2 and 1, respectively. Specific binding of the antibody fragment-drug conjugates (FDCs) to GD2 was confirmed in direct ELISA, flow cytometry, and confocal microscopy. Selective cytotoxic and cytostatic effects of the conjugates were observed in GD2-positive but not GD2-negative neuroblastoma and melanoma cell lines. Minibody-based FDCs demonstrated more pronounced cytotoxic effects and stronger antigen binding compared to scFv-based FDCs. The developed molecules may offer considerable practical benefit, since antibody fragment-drug conjugates are capable of enhancing therapeutic efficacy of ADCs by improving their pharmacokinetic characteristics and reducing side effects.

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.

Two-Step Targeted Drug Delivery via Proteinaceous Barnase-Barstar Interface and Doxorubicin-Loaded Nano-PLGA Outperforms One-Step Strategy for Targeted Delivery to HER2-Overexpressing Cells

Nanoparticle-based chemotherapy is considered to be an effective approach to cancer diagnostics and therapy in modern biomedicine. However, efficient tumor targeting remains a great challenge due to the lack of specificity, selectivity, and high dosage of chemotherapeutic drugs required. A two-step targeted drug delivery strategy (DDS), involving cancer cell pre-targeting, first with a first nontoxic module and subsequent targeting with a second complementary toxic module, is a solution for decreasing doses for administration and lowering systemic toxicity. To prove two-step DDS efficiency, we performed a direct comparison of one-step and two-step DDS based on chemotherapy loaded PLGA nanoparticles and barnase*barstar interface. Namely, we developed and thoroughly characterized the two-step targeting strategy of HER2-overexpressing cancer cells. The first targeting block consists of anti-HER2 scaffold polypeptide DARPin9_29 fused with barstar. Barstar exhibits an extremely effective binding to ribonuclease barnase with K_aff = 10¹⁴ M^-1, thus making the barnase*barstar protein pair one of the strongest known protein*protein complexes. A therapeutic PLGA-based nanocarrier coupled to barnase was used as a second targeting block. The PLGA nanoparticles were loaded with diagnostic dye, Nile Blue, and a chemotherapeutic drug, doxorubicin. We showed that the two-step DDS increases the performance of chemotherapy-loaded nanocarriers: IC50 of doxorubicin delivered via two-step DDS was more than 100 times lower than that for one-step DDS: IC50 = 43 ± 3 nM for two-step DDS vs. IC50 = 4972 ± 1965 nM for one-step DDS. The obtained results demonstrate the significant efficiency of two-step DDS over the classical one-step one. We believe that the obtained data will significantly change the direction of research in developing targeted anti-cancer drugs and promote the creation of new generation cancer treatment strategies.

Subpopulation Heterogeneity of NK Cells during the Genetic Modification for Subsequent Use in Targeted Therapy

Obtaining genetically engineered NK cells is a developing area of immunotherapy. In this work, we analyzed the subset heterogeneity of NK cells subjected to retroviral transduction, taking into account the content of adaptive NK cell progenitors. It was shown that subsets KIR2DL2/DL3⁺, as well as CD57^-KIR2DL2/DL3⁺NKG2C⁺, can be modified with greater efficiency than the corresponding subsets that do not carry the KIR2DL2/DL3 and NKG2C markers. After genetic modification, the CD57^-KIR2DL2/DL3⁺NKG2C⁺ cells began to express CD57 de novo, acquiring the adaptive NK cell phenotype.

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.

The Evolution of Targeted Radionuclide Diagnosis of HER2-Positive Breast Cancer

This review examines the evolution of the radionuclide diagnosis of HER2-positive breast cancer using various compounds as a targeting module in clinical practice: from full-length antibodies to a new group of small synthetic proteins called alternative scaffold proteins. This topic is of especial relevance today in view of the problems attendant to the detection of breast cancer with HER2/neu overexpression, which, in most cases, introduce errors in the treatment of patients. The results of clinical studies of radiopharmaceuticals based on affibody molecules, ADAPTs, and DARPins for SPECT and PET have demonstrated good tolerability of the compounds, their rapid excretion from the body, and the possibility to differentiate tumor sites depending on the HER2/neu status. This indicates that targeted radionuclide diagnosis holds promise and the need to continue research in this direction.