Biotin-decorated anti-cancer nucleotide theranostic conjugate of human serum albumin: Where the seed meets the soil?

Nano-therapeutics: The upcoming nanomedicine to treat cancer

Nanotechnology is considered a successful approach for cancer diagnosis and treatment. Preferentially, cancer cell recognition and drug targeting via nano-delivery system include the penetration of anticancer agents into the cell membrane to damage the cancer cell by protein modification, DNA oxidation, or mitochondrial dysfunction. The past research on nano-delivery systems and their target has proven the beneficial achievement in a malignant tumor. Modern perceptions using inventive nanomaterials for cancer management have been offered by a multifunctional platform based on various nano-carriers with the probability of imaging and cancer therapy simultaneously. Emerging nano-delivery systems in cancer therapy still lack knowledge of the biological functions behind the interaction between nanoparticles and cancer cells. Since the potential of engineered nanoparticles addresses the various challenges, limiting the success of cancer therapy subsequently, it is a must to review the molecular targeting of a nano-delivery system to enhance the therapeutic efficacy of cancer. This review focuses on using a nano-delivery system, an imaging system, and encapsulated nanoparticles for cancer therapy.

Recent Advancements and Strategies for Overcoming the Blood-Brain Barrier Using Albumin-Based Drug Delivery Systems to Treat Brain Cancer, with a Focus on Glioblastoma

Glioblastoma multiforme (GBM) is a highly aggressive malignant tumor, and the most prevalent primary malignant tumor affecting the brain and central nervous system. Recent research indicates that the genetic profile of GBM makes it resistant to drugs and radiation. However, the main obstacle in treating GBM is transporting drugs through the blood-brain barrier (BBB). Albumin is a versatile biomaterial for the synthesis of nanoparticles. The efficiency of albumin-based delivery systems is determined by their ability to improve tumor targeting and accumulation. In this review, we will discuss the prevalence of human glioblastoma and the currently adopted treatment, as well as the structure and some essential functions of the BBB, to transport drugs through this barrier. We will also mention some aspects related to the blood-tumor brain barrier (BTBB) that lead to poor treatment efficacy. The properties and structure of serum albumin were highlighted, such as its role in targeting brain tumors, as well as the progress made until now regarding the techniques for obtaining albumin nanoparticles and their functionalization, in order to overcome the BBB and treat cancer, especially human glioblastoma. The albumin drug delivery nanosystems mentioned in this paper have improved properties and can overcome the BBB to target brain tumors.

Advanced theranostic nanoplatforms for hypericin delivery in the cancer treatment

Biomodified coated-lipid vesicles were obtained using the DPPC lipid (L) and F127 copolymer linked covalently with spermine (SN), biotin (BT), and folic acid (FA), resulting in LF127-SN, LF127-BT, and LF127-FA nanoplatforms. The photosensitizer hypericin (HY) was incorporated into the nanosystem by a thin-film method and characterized by dynamic light scattering, zeta potential, encapsulation efficiency, and transmission electronic microscopy. The results provided a good level of stability for all nanoplatforms for at least 5 days as an aqueous dispersion. The in vitro serum stability showed that the HY-loaded LF127-SN has a lower tendency to form complexes with BSA protein than with its analogs. LF127-SN was the most stable HY formulation, followed by LF127-BT and LF127-FA, confirmed by the association constant (Kd) values: 600 μmol L-1, 1100 μmol L-1, 515 μmol L-1, and 378 μmol L-1 for LF127, LF127 FA, LF127-BT, and LF127-SN, respectively. The photodynamic potential of HY was accessed by cytotoxicity assays using Caco-2, B16-F10, L-929, and HaCat cells. HY-loaded LF127-SN revealed a significant increase in the selectivity compared to other nanoplatforms. HY-loaded in LF127-BT and LF127-SN showed distinct uptake and biodistribution after 2 h of intravenous application. All biomodified coated-lipids showed satisfactory metabolism within 72 h after application, without significant accumulation or residue in any vital organ. These results suggest that incorporating HY-loaded in these nanosystems may be a promising strategy for future applications, even with a small amount of binders to the coating copolymer (0.02% w/v). Furthermore, these results indicate that the LF127-SN showed remarkable superiority compared to other evaluated systems, being the most distinct for future photodynamic therapy and theranostic applications.

Design of the New Closo-Dodecarborate-Containing Gemcitabine Analogue for the Albumin-Based Theranostics Composition

Combination therapy is becoming an increasingly important treatment strategy because multi-drugs can maximize therapeutic effect and overcome potential mechanisms of drug resistance. A new albumin-based theranostic containing gemcitabine closo-dodecaborate analogue has been developed for combining boron neutron capture therapy (BNCT) and chemotheraphy. An exo-heterocyclic amino group of gemcitabine was used to introduce closo-dodecaborate, and a 5′-hydroxy group was used to tether maleimide moiety through an acid-labile phosphamide linker. The N-trifluoroacylated homocysteine thiolactone was used to attach the gemcitabine analogue to human serum albumin (HSA) bearing Cy5 or Cy7 fluorescent dyes. The half-maximal inhibitory concentration (IC50) of the designed theranostic relative to T98G cells was 0.47 mM with the correlation coefficient R = 0.82. BNCT experiments resulted in a decrease in the viability of T98G cells, and the survival fraction was ≈ 0.4.

pH-Responsible Doxorubicin-Loaded Fe3O4@CaCO3 Nanocomposites for Cancer Treatment

A magnetic nanocomposite (MNC) is an integrated nanoplatform that combines a set of functions of two types of materials. A successful combination can give rise to a completely new material with unique physical, chemical, and biological properties. The magnetic core of MNC provides the possibility of magnetic resonance or magnetic particle imaging, magnetic field-influenced targeted delivery, hyperthermia, and other outstanding applications. Recently, MNC gained attention for external magnetic field-guided specific delivery to cancer tissue. Further, drug loading enhancement, construction stability, and biocompatibility improvement may lead to high progress in the area. Herein, the novel method for nanoscale Fe3O4@CaCO3 composites synthesis was proposed. For the procedure, oleic acid-modified Fe3O4 nanoparticles were coated with porous CaCO3 using an ion coprecipitation technique. PEG-2000, Tween 20, and DMEM cell media was successfully used as a stabilization agent and template for Fe3O4@CaCO3 synthesis. Transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and dynamic light scattering (DLS) data were used for the Fe3O4@CaCO3 MNC’s characterization. To improve the nanocomposite properties, the concentration of the magnetic core was varied, yielding optimal size, polydispersity, and aggregation ability. The resulting Fe3O4@CaCO3 had a size of 135 nm with narrow size distributions, which is suitable for biomedical applications. The stability experiment in various pH, cell media, and fetal bovine serum was also evaluated. The material showed low cytotoxicity and high biocompatibility. An excellent anticancer drug doxorubicin (DOX) loading of up to 1900 µg/mg (DOX/MNC) was demonstrated. The Fe3O4@CaCO3/DOX displayed high stability at neutral pH and efficient acid-responsive drug release. The series of DOX-loaded Fe3O4@CaCO3 MNCs indicated effective inhibition of Hela and MCF-7 cell lines, and the IC 50 values were calculated. Moreover, 1.5 μg of the DOX-loaded Fe3O4@CaCO3 nanocomposite is sufficient to inhibit 50% of Hela cells, which shows a high prospect for cancer treatment. The stability experiments for DOX-loaded Fe3O4@CaCO3 in human serum albumin solution indicated the drug release due to the formation of a protein corona. The presented experiment showed the “pitfalls” of DOX-loaded nanocomposites and provided step-by-step guidance on efficient, smart, anticancer nanoconstruction fabrication. Thus, the Fe3O4@CaCO3 nanoplatform exhibits good performance in the cancer treatment area.

Fluorinated Human Serum Albumin as Potential 19F Magnetic Resonance Imaging Probe

Fluorinated human serum albumin conjugates were prepared and tested as potential metal-free probes for ¹⁹F magnetic resonance imaging (MRI). Each protein molecule was modified by several fluorine-containing compounds via the N-substituted natural acylating reagent homocysteine thiolactone. Albumin conjugates retain the protein's physical and biological properties, such as its 3D dimensional structure, aggregation ability, good solubility, proteolysis efficiency, biocompatibility, and low cytotoxicity. A dual-labeled with cyanine 7 fluorescence dye and fluorine reporter group albumin were synthesized for simultaneous fluorescence imaging and ¹⁹F MRI. The preliminary in vitro studies show the prospects of albumin carriers for multimodal imaging.

Multifunctional Nanoparticles as High-Efficient Targeted Hypericin System for Theranostic Melanoma

Biotin, spermine, and folic acid were covalently linked to the F127 copolymer to obtain a new drug delivery system designed for HY-loaded PDT treatment against B₁₆F₁₀ cells. Chemical structures and binders quantification were performed by spectroscopy and spectrophotometric techniques (¹NMR, HABA/Avidin reagent, fluorescamine assay). Critical micelle concentration, critical micelle temperature, size, polydispersity, and zeta potential indicate the hydrophobicity of the binders can influence the physicochemical parameters. Spermine-modified micelles showed fewer changes in their physical and chemical parameters than the F127 micelles without modification. Furthermore, zeta potential measurements suggest an increase in the physical stability of these carrier systems. The phototherapeutic potential was demonstrated using hypericin-loaded formulation against B₁₆F₁₀ cells, which shows that the combination of the binders on F127 copolymer micelles enhances the photosensitizer uptake and potentializes the photodynamic activity.

Serum Albumin for Magnetic Nanoparticles Coating

Magnetic nanoparticles (MNPs) have great potential in biochemistry and medical science. In particular, iron oxide nanoparticles have demonstrated a promising effect in various biomedical applications due to their high magnetic properties, large surface area, stability, and easy functionalization. However, colloidal stability, biocompatibility, and potential toxicity of MNPs in physiological environments are crucial for their in vivo application. In this context, many research articles focused on the possible procedures for MNPs coating to improve their physic-chemical and biological properties. This review highlights one viable fabrication strategy of biocompatible iron oxide nanoparticles using human serum albumin (HSA). HSA is mainly a transport protein with many functions in various fundamental processes. As it is one of the most abundant plasma proteins, not a single drug in the blood passes without its strength test. It influences the stability, pharmacokinetics, and biodistribution of different drug-delivery systems by binding or forming its protein corona on the surface. The development of albumin-based drug carriers is gaining increasing importance in the targeted delivery of cancer therapy. Considering this, HSA is a highly potential candidate for nanoparticles coating and theranostics area and can provide biocompatibility, prolonged blood circulation, and possibly resolve the drug-resistance cancer problem.

Human Serum Albumin Labelling with a New BODIPY Dye Having a Large Stokes Shift

BODIPY dyes are photostable neutral derivatives of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene. These are widely used as chemosensors, laser materials, and molecular probes. At the same time, BODIPY dyes have small or moderate Stokes shifts like most other fluorophores. Large Stokes shifts are preferred for fluorophores because of higher sensitivity of such probes and sensors. The new boron containing BODIPY dye was designed and synthesized. We succeeded to perform an annulation of pyrrole ring with coumarin heterocyclic system and achieved a remarkable difference in absorption and emission maximum of obtained fluorophore up to 100 nm. This BODIPY dye was equipped with linker arm and was functionalized with a maleimide residue specifically reactive towards thiol groups of proteins. BODIPY residue equipped with a suitable targeting protein core can be used as a suitable imaging probe and agent for Boron Neutron Capture Therapy (BNCT). As the most abundant protein with a variety of physiological functions, human serum albumin (HSA) has been used extensively for the delivery and improvement of therapeutic molecules. Thiolactone chemistry provides a powerful tool to prepare albumin-based multimodal constructions. The released sulfhydryl groups of the homocysteine functional handle in thiolactone modified HSA were labeled with BODIPY dye to prepare a labeled albumin-BODIPY dye conjugate confirmed by MALDI-TOF-MS, UV-vis, and fluorescent emission spectra. Cytotoxicity of the resulting conjugate was investigated. This study is the basis for a novel BODIPY dye-albumin theranostic for BNCT. The results provide further impetus to develop derivatives of HSA for delivery of boron to cancer cells.

Rational Design of Albumin Theranostic Conjugates for Gold Nanoparticles Anticancer Drugs: Where the Seed Meets the Soil?

Multifunctional gold nanoparticles (AuNPs) may serve as a scaffold to integrate diagnostic and therapeutic functions into one theranostic system, thereby simultaneously facilitating diagnosis and therapy and monitoring therapeutic responses. Herein, albumin-AuNP theranostic agents have been obtained by conjugation of an anticancer nucleotide trifluorothymidine (TFT) or a boron-neutron capture therapy drug undecahydro-closo-dodecaborate (B12H12) to bimodal human serum albumin (HSA) followed by reacting of the albumin conjugates with AuNPs. In vitro studies have revealed a stronger cytotoxicity by the AuNPs decorated with the TFT-tagged bimodal HSA than by the boronated albumin conjugates. Despite long circulation time, lack of the significant accumulation in the tumor was observed for the AuNP theranostic conjugates. Our unique labelling strategy allows for monitoring of spatial distribution of the AuNPs theranostic in vivo in real time with high sensitivity, thus reducing the number of animals required for testing and optimizing new nanosystems as chemotherapeutic agents and boron-neutron capture therapy drug candidates.

Human Serum Albumin Labelled with Sterically-Hindered Nitroxides as Potential MRI Contrast Agents

Four albumin-nitroxide conjugates were prepared and tested as metal-free organic radical contrast agents (ORCAs) for magnetic resonance imaging (MRI). Each human serum albumin (HSA) carrier bears multiple nitroxides conjugated via homocysteine thiolactones. These molecular conjugates retain important physical and biological properties of their HSA component, and the resistance of their nitroxide groups to bioreduction was retained or enhanced. The relaxivities are similar for these four conjugates and are much greater than those of their individual components: the HSA or the small nitroxide molecules. This new family of conjugates has excellent prospects for optimization as ORCAs.

Protein modification by thiolactone homocysteine chemistry: a multifunctionalized human serum albumin theranostic

As the most abundant protein with a variety of physiological functions, albumin has been used extensively for the delivery of therapeutic molecules. Thiolactone chemistry provides a powerful tool to prepare spin-labeled albumin-based multimodal imaging probes and therapeutic agents. We report the synthesis of a tamoxifen homocysteine thiolactone derivative and its use in thiol-'click' chemistry to prepare multi-functionalized serum albumin. The released sulfhydryl group of the homocysteine functional handle was labeled with a nitroxide reagent to prepare a spin-labeled albumin-tamoxifen conjugate confirmed by MALDI-TOF-MS, EPR spectroscopy, UV-vis and fluorescent emission spectra. This is the basis for a novel multimodal tamoxifen-albumin theranostic with a significant (dose-dependent) inhibitory effect on the proliferation of malignant cells. The response of human glioblastoma multiforme T98G cells and breast cancer MCF-7 cells to tamoxifen and its albumin conjugates was different in tumor cells with different expression level of ERα in our experiments. These results provide further impetus to develop a serum protein for delivery of tamoxifen to cancer cells.

Methanethiosulfonate Derivative of OX063 Trityl: A Promising and Efficient Reagent for Side-Directed Spin Labeling of Proteins

Trityl radicals (TAMs) have recently appeared as an alternative source of spin labels for measuring long distances in biological systems. Finland trityl radical (FTAM) served as the basis for this new generation of spin labels, but FTAM is rather lipophilic and susceptible to self-aggregation, noncovalent binding with lipophilic sites of proteins, and noncovalent docking at the termini of duplex DNA. In this paper the very hydrophilic OX063 TAM with very low toxicity and little tendency for aggregation is used as the basis for a spin label. Human serum albumin (HSA) labeled with OX063 has an intense narrow line typical of TAM radicals in solution, whereas HSA labeled with FTAM shows broad lines and extensive aggregation. In pulse EPR measurements, the measured phase memory time T_M for HSA labeled with OX063 is 6.3 μs at 50 K, the longest yet obtained with a TAM-based spin label. The lowered lipophilicity also decreases side products in the labeling reaction.