RGD Peptide as a Targeting Moiety for Theranostic Purpose: An Update Study

Development of 5-Fluorouracil/pH-Responsive Adjuvant-Embedded Extracellular Vesicles for Targeting αvβ3 Integrin Receptors in Tumors

To selectively target and treat murine melanoma B16BL6 tumors expressing αvβ3 integrin receptors, we engineered tumor-specific functional extracellular vesicles (EVs) tailored for the targeted delivery of antitumor drugs. This objective was achieved through the incorporation of a pH-responsive adjuvant, cyclic arginine-glycine-aspartic acid peptide (cRGD, serving as a tumor-targeting ligand), and 5-fluorouracil (5-FU, employed as a model antitumor drug). The pH-responsive adjuvant, essential for modulating drug release, was synthesized by chemically conjugating 3-(diethylamino)propylamine (DEAP) to deoxycholic acid (DOCA, a lipophilic substance capable of integrating into EVs' membranes), denoted as DEAP-DOCA. The DOCA, preactivated using N-(2-aminoethyl)maleimide (AEM), was chemically coupled with the thiol group of the cRGD-DOCA through the thiol-maleimide click reaction, resulting in the formation of cRGD-DOCA. Subsequently, DEAP-DOCA, cRGD-DOCA, and 5-FU were efficiently incorporated into EVs using a sonication method. The resulting tumor-targeting EVs, expressing cRGD ligands, demonstrated enhanced in vitro/in vivo cellular uptake specifically for B16BL6 tumors expressing αvβ3 integrin receptors. The ionization characteristics of the DEAP in DEAP-DOCA induced destabilization of the EVs membrane at pH 6.5 through protonation of the DEAP substance, thereby expediting 5-FU release. Consequently, an improvement in the in vivo antitumor efficacy was observed for B16BL6 tumors. Based on these comprehensive in vitro/in vivo findings, we anticipate that this EV system holds substantial promise as an exceptionally effective platform for antitumor therapeutic delivery.

Theranostic applications of peptide-based nanoformulations for growth factor defective cancers

Growth factors play a pivotal role in orchestrating cellular growth and division by binding to specific cell surface receptors. Dysregulation of growth factor production or activity can contribute to the uncontrolled cell proliferation observed in cancer. Peptide-based nanoformulations (PNFs) have emerged as promising therapeutic strategies for growth factor-deficient cancers. PNFs offer multifaceted capabilities including targeted delivery, imaging modalities, combination therapies, resistance modulation, and personalized medicine approaches. Nevertheless, several challenges remain, including limited specificity, stability, pharmacokinetics, tissue penetration, toxicity, and immunogenicity. To address these challenges and optimize PNFs for clinical translation, in-depth investigations are warranted. Future research should focus on elucidating the intricate interplay between peptides and nanoparticles, developing robust spectroscopic and computational methodologies, and establishing a comprehensive understanding of the structure-activity relationship governing peptide-nanoparticle interactions. Bridging these knowledge gaps will propel the translation of peptide-nanoparticle therapies from bench to bedside. While a few peptide-nanoparticle drugs have obtained FDA approval for cancer treatment, the integration of nanostructured platforms with peptide-based medications holds tremendous potential to expedite the implementation of innovative anticancer interventions. Therefore, growth factor-deficient cancers present both challenges and opportunities for targeted therapeutic interventions, with peptide-based nanoformulations positioned as a promising avenue. Nonetheless, concerted research and development endeavors are essential to optimize the specificity, stability, and safety profiles of PNFs, thereby advancing the field of peptide-based nanotherapeutics in the realm of oncology research.

Design of manganese-based nanomaterials for pharmaceutical and biomedical applications

In the past few years, manganese-based nanostructures have been extensively investigated in the biomedical field particularly to design highly biocompatible theranostics, which can not only act as efficient diagnostic imaging contrast agents but also deliver the drugs to the target sites. The nanoscale size, large surface area-to-volume ratio, availability of cheap precursors, flexibility to synthesize nanostructures with reproducible properties and high yield, and easy scale up are the major reasons for the attraction towards manganese nanostructures. Along with these properties, the nontoxic nature, pH-sensitive degradation, and easy surface functionalization are additional benefits for the use of manganese nanostructures in biomedical and pharmaceutical sciences. Therefore, in this review, we discuss the recent progress made in the synthesis of manganese nanostructures, describe the attempts made to modify their surfaces to impart biocompatibility and stability in biological fluids, and critically discuss their use in magnetic resonance imaging, drug and gene delivery, hyperthermia, photothermal/photodynamic, immunotherapy, biosensing and tumor diagnosis.

Water-soluble chromenylium dyes for shortwave infrared imaging in mice

In vivo imaging using shortwave infrared light (SWIR, 1000-2000 nm) benefits from deeper penetration and higher resolution compared to using visible and near-infrared wavelengths. However, the development of biocompatible SWIR contrast agents remains challenging. Despite recent advancements, small molecule SWIR fluorophores are often hindered by their significant hydrophobicity. We report a platform for generating a panel of soluble and functional dyes for SWIR imaging by late-stage functionalization of a versatile fluorophore intermediate, affording water-soluble dyes with bright SWIR fluorescence in serum. Specifically, a tetra-sulfonate derivative enables clear video-rate imaging of vasculature with only 0.05 nmol dye, and a tetra-ammonium dye shows strong cellular retention for tracking of tumor growth. Additionally, incorporation of phosphonate functionality enables imaging of bone in awake mice. This modular design provides insights for facile derivatization of existing SWIR fluorophores to introduce both solubility and bioactivity towards in vivo bioimaging.

Ultrasound-triggered release of miR-199a-3p from liposome nanobubbles for enhanced hepatocellular carcinoma treatment

This study was aimed to develop an efficient tumour-targeted liposome nanobubbles (LNBs) system using ultrasound-targeted nanobubble destruction for enhanced release and transfection of miRNA-199a-3p in hepatocellular carcinoma (HCC) therapy. The prepared LNBs comprised a polyethylene glycol-modified liposome shell and a perfluoropentane (PFP) core. MiRNA-199a-3p was attached to the nanocomposite surface via electrostatic adsorption, while RGD peptide functionalized the LNBs surface for enhanced HCC cell targeting, namely PFP@miR-RGD-LNBs. The LNBs were spherical with a narrow size distribution. The gene-loaded LNBs effectively condensed miR-199a-3p and protected it from enzymatic degradation. Low-intensity focused ultrasound (LIFU) promoted a fast release of miR-199a-3p from the prepared LNBs, thereby enhancing therapeutic effects. The combined application of PFP@miR-RGD-LNBs and LIFU exhibited a more potent inhibitory effect on HepG2 cells than the other groups, potentially due to LIFU promoting rapid and efficient gene release at the target site and increasing cell membrane permeability. Quantitative reverse transcription-polymerase chain reaction analysis revealed significantly increased mRNA expression levels of key apoptosis markers (Bad, Bax, Caspase-9 and Caspase-3) in the PFP@miR-RGD-LNBs + LIFU group compared to other groups. These findings suggest that the prepared LNBs are highly likely to be promising candidates for further exploration of HCC gene delivery and therapy.

Tumor-derived systems as novel biomedical tools-turning the enemy into an ally

Cancer is a complex illness that presents significant challenges in its understanding and treatment. The classic definition, "a group of diseases characterized by the uncontrolled growth and spread of abnormal cells in the body," fails to convey the intricate interaction between the many entities involved in cancer. Recent advancements in the field of cancer research have shed light on the role played by individual cancer cells and the tumor microenvironment as a whole in tumor development and progression. This breakthrough enables the utilization of the tumor and its components as biological tools, opening new possibilities. This article delves deeply into the concept of "tumor-derived systems", an umbrella term for tools sourced from the tumor that aid in combatting it. It includes cancer cell membrane-coated nanoparticles (for tumor theranostics), extracellular vesicles (for tumor diagnosis/therapy), tumor cell lysates (for cancer vaccine development), and engineered cancer cells/organoids (for cancer research). This review seeks to offer a complete overview of the tumor-derived materials that are utilized in cancer research, as well as their current stages of development and implementation. It is aimed primarily at researchers working at the interface of cancer biology and biomedical engineering, and it provides vital insights into this fast-growing topic.

Surface engineering of lipid nanoparticles: targeted nucleic acid delivery and beyond

Harnessing surface engineering strategies to functionalize nucleic acid-lipid nanoparticles (LNPs) for improved performance has been a hot research topic since the approval of the first siRNA drug, patisiran, and two mRNA-based COVID-19 vaccines, BNT162b2 and mRNA-1273. Currently, efforts have been mainly made to construct targeted LNPs for organ- or cell-type-specific delivery of nucleic acid drugs by conjugation with various types of ligands. In this review, we describe the surface engineering strategies for nucleic acid-LNPs, considering ligand types, conjugation chemistries, and incorporation methods. We then outline the general purification and characterization techniques that are frequently used following the engineering step and emphasize the specific techniques for certain types of ligands. Next, we comprehensively summarize the currently accessible organs and cell types, as well as the other applications of the engineered LNPs. Finally, we provide considerations for formulating targeted LNPs and discuss the challenges of successfully translating the "proof of concept" from the laboratory into the clinic. We believe that addressing these challenges could accelerate the development of surface-engineered LNPs for targeted nucleic acid delivery and beyond.

Recent progress of targeted nanocarriers in diagnostic, therapeutic, and theranostic applications in colorectal cancer

Cancer at the lower end of the digestive tract, colorectal cancer (CRC), starts with asymptomatic polyps, which can be diagnosed as cancer at a later stage. It is the fourth leading cause of malignancy-associated mortality worldwide. Despite progress in conventional treatment strategies, the possibility to overcome the mortality and morbidity issues with the enhancement of the lifespan of CRC patients is limited. With the advent of nanocarrier-based drug delivery systems, a promising revolution has been made in diagnosis, treatment, and theranostic purposes for cancer management. Herein, we reviewed the progress of miniaturized nanocarriers, such as liposomes, niosomes, solid lipid nanoparticles, micelles, and polymeric nanoparticles, employed in passive and active targeting and their role in theranostic applications in CRC. With this novel scope, the diagnosis and treatment of CRC have proceeded to the forefront of innovation, where specific characteristics of the nanocarriers, such as processability, flexibility in developing precise architecture, improved circulation, site-specific delivery, and rapid response, facilitate the management of cancer patients. Furthermore, surface-engineered technologies for the nanocarriers could involve receptor-mediated deliveries towards the overexpressed receptors on the CRC microenvironment. Moreover, the potential of clinical translation of these targeted miniaturized formulations as well as the possible limitations and barriers that could impact this translation into clinical practice were highlighted. The advancement of these newest developments in clinical research and progress into the commercialization stage gives hope for a better tomorrow.

Light-initiated 1,3-dipolar cycloaddition between dehydroalanines and tetrazoles: application to late-stage peptide and protein modifications

As an easily introduced noncoded amino acid with unique electrophilicity distinct from the 20 natural amino acids, dehydroalanine (Dha) is not only a precise protein post-translational modification (PTM) insertion tool, but also a promising multifunctional labelling site for peptides and proteins. However, achieving a balance between the reaction rate and mild reaction conditions has been a major challenge in developing novel Dha-modified strategies. Rapid, efficient, and mild Dha modification strategies are highly desired. Additionally, catalyst-free photocontrollable reactions for Dha-containing peptide and protein modification have yet to be developed. Here, we report a photoinitiated 1,3-dipolar cycloaddition reaction between Dha and 2,5-diaryl tetrazoles. Under low-power UV lamp irradiation, this reaction is completed within minutes without catalysis, resulting in a fluorescent pyrazoline-modified peptide or protein with excellent chemoselectivity for Dha residues. Notably, this reaction exhibits complete site-specificity in the modification of thiostrepton, a natural antimicrobial peptide containing multiple Dha residues (Dha3, Dha16, and Dha17), within 20 minutes in high yields. This is currently the fastest reaction for modifying the Dha residue in thiostrepton with clear site-specificity towards Dha16. This photoinitiated reaction also provides a chemoselective strategy for precise functionalization of proteins. Additionally, the rapidity and efficiency of the reaction minimize UV light damage to the biological reaction system. Combined with fluorogenic properties, this photo-controllable methodology can be applied to live cell imaging, further broadening the application scope of the Dha modification methodology.

Toward a theranostic device for gliomas

BACKGROUND

In the surgical management of glioblastoma, a highly aggressive and incurable type of brain cancer, identification and treatment of residual tissue is the most common site of disease recurrence. Monitoring and localized treatment are achieved with engineered microbubbles (MBs) by combining ultrasound and fluorescence imaging with actively targeted temozolomide (TMZ) delivery.

METHODS

The MBs were conjugated with a near-infrared fluorescence probe CF790, cyclic pentapeptide bearing the RGD sequence and a carboxyl-temozolomide, TMZA. The efficiency of adhesion to HUVEC cells was assessed in vitro in realistic physiological conditions of shear rate and vascular dimensions. Cytotoxicity of TMZA-loaded MBs on U87 MG cells and IC50 were assessed by MTT tests.

RESULTS

We report on the design of injectable poly(vinyl alcohol) echogenic MBs designed as a platform with active targeting ability to tumor tissues, by tethering on the surface a ligand having the tripeptide sequence, RGD. The biorecognition of RGD-MBs onto HUVEC cells is quantitatively proved. Efficient NIR emission from the CF790-decorated MBs was successfully detected. The conjugation on the MBs surface of a specific drug as TMZ is achieved. The pharmacological activity of the coupled-to-surface drug is preserved by controlling the reaction conditions.

CONCLUSIONS

We present an improved formulation of PVA-MBs to achieve a multifunctional device with adhesion ability, cytotoxicity on glioblastoma cells and supporting imaging.

Synthesis of Novel Carborane-Containing Derivatives of RGD Peptide

Short peptides containing the Arg-Gly-Asp (RGD) fragment can selectively bind to integrins on the surface of tumor cells and are attractive transport molecules for the targeted delivery of therapeutic and diagnostic agents to tumors (for example, glioblastoma). We have demonstrated the possibility of obtaining the N- and C-protected RGD peptide containing 3-amino-closo-carborane and a glutaric acid residue as a linker fragment. The resulting carboranyl derivatives of the protected RGD peptide are of interest as starting compounds in the synthesis of unprotected or selectively protected peptides, as well as building blocks for preparation of boron-containing derivatives of the RGD peptide of a more complex structure.

Proteinoid Polymers and Nanocapsules for Cancer Diagnostics, Therapy and Theranostics: In Vitro and In Vivo Studies

Proteinoids-simple polymers composed of amino acids-were suggested decades ago by Fox and coworkers to form spontaneously by heat. These special polymers may self-assemble in micrometer structures called proteinoid microspheres, presented as the protocells of life on earth. Interest in proteinoids increased in recent years, in particular for nano-biomedicine. They were produced by stepwise polymerization of 3-4 amino acids. Proteinoids based on the RGD motif were prepared for targeting tumors. Nanocapsules form by heating proteinoids in an aqueous solution and slowly cooling to room temperature. Proteinoid polymers and nanocapsules suit many biomedical applications owing to their non-toxicity, biocompatibility and immune safety. Drugs and/or imaging reagents for cancer diagnostic, therapeutic and theranostic applications were encapsulated by dissolving them in aqueous proteinoid solutions. Here, recent in vitro and in vivo studies are reviewed.

Nanoparticles Design for Theranostic Approach in Cancer Disease

Presently, there are no conclusive treatments for many types of cancer, mainly due to the advanced phase of the disease at the time of diagnosis and to the side effects of existing therapies. Present diagnostic and therapeutic procedures need to be improved to supply early detection abilities and perform a more specific therapy with reduced systemic toxicity. In this review, improvements in nanotechnology allowing the design of multifunctional nanoparticles for cancer detection, therapy, and monitoring are reported. Nanoparticles, thanks to the nanomaterials they are made of, can be used as contrast agents for various diagnostic techniques such as MRI, optical imaging, and photoacoustic imaging. Furthermore, when used as drug carriers, they can accumulate in tumor tissues through the passive or/and active targeting, protect encapsulated drugs from degradation, raise tumor exposure to chemotherapeutic agents improving treatment effects. In addition, nanocarriers can simultaneously deliver more than one therapeutic agent enhancing the effectiveness of therapy and can co-deliver imaging and therapy agents to provide integration of diagnostics, therapy, and follow-up. Furthermore, the use of nanocarriers allows to use different therapeutic approaches, such as chemotherapy and hyperthermia to exploit synergistic effects. Theranostic approach to diagnose and treat cancer show a great potential to improve human health, however, despite technological advances in this field, the transfer into clinical practice is still a long way off.

Peptide-based assembled nanostructures that can direct cellular responses

Natural originated materials have been well-studied over the past several decades owing to their higher biocompatibility compared to the traditional polymers. Peptides, consisting of amino acids, are among the most popular programable building blocks, which is becoming a growing interest in nanobiotechnology. Structures assembled using those biomimetic peptides allow the exploration of chemical sequences beyond those been routinely used in biology. In this Review, we discussed the most recent experimental discoveries on the peptide-based assembled nanostructures and their potential application at the cellular level such as drug delivery. In particular, we explored the fundamental principles of peptide self-assembly and the most recent development in improving their interactions with biological systems. We believe that as the fundamental knowledge of the peptide assemblies evolves, the more sophisticated and versatile nanostructures can be built, with promising biomedical applications.

Sortase A-mediated cyclization of novel polycyclic RGD peptides for ανβ3 integrin targeting

Cyclic arginine-glycine-aspartic (RGD) peptides that specifically bind to integrin α_νβ₃ have been developed for drug delivery, tracers, and imaging for tumor diagnosis and treatment. Herein, a series of polycyclic RGD peptides containing dual, tri, and tetra rings were designed and synthesized through sortase A-mediated ligation. An in vitro test on cell adhesion inhibition indicated that the RGD peptide containing tricylic structure exhibited outstanding potency and selectivity for α_νβ₃ integrin.

Peptides to Overcome the Limitations of Current Anticancer and Antimicrobial Nanotherapies

Biomedical research devotes a huge effort to the development of efficient non-viral nanovectors (NV) to improve the effectiveness of standard therapies. NVs should be stable, sustainable and biocompatible and enable controlled and targeted delivery of drugs. With the aim to foster the advancements of such devices, this review reports some recent results applicable to treat two types of pathologies, cancer and microbial infections, aiming to provide guidance in the overall design of personalized nanomedicines and highlight the key role played by peptides in this field. Additionally, future challenges and potential perspectives are illustrated, in the hope of accelerating the translational advances of nanomedicine.

Targeted Molecular Imaging Probes Based on Magnetic Resonance Imaging for Hepatocellular Carcinoma Diagnosis and Treatment

Hepatocellular carcinoma (HCC) is the sixth most commonly malignant tumor and the third leading cause of cancer-related death in the world, and the early diagnosis and treatment of patients with HCC is core in improving its prognosis. The early diagnosis of HCC depends largely on magnetic resonance imaging (MRI). MRI has good soft-tissue resolution, which is the international standard method for the diagnosis of HCC. However, MRI is still insufficient in the diagnosis of some early small HCCs and malignant nodules, resulting in false negative results. With the deepening of research on HCC, researchers have found many specific molecular biomarkers on the surface of HCC cells, which may assist in diagnosis and treatment. On the other hand, molecular imaging has progressed rapidly in recent years, especially in the field of cancer theranostics. Hence, the preparation of molecular imaging probes that can specifically target the biomarkers of HCC, combined with MRI testing in vivo, may achieve the theranostic purpose of HCC in the early stage. Therefore, in this review, taking MR imaging as the basic point, we summarized the recent progress regarding the molecular imaging targeting various types of biomarkers on the surface of HCC cells to improve the theranostic rate of HCC. Lastly, we discussed the existing obstacles and future prospects of developing molecular imaging probes as HCC theranostic nanoplatforms.

Visualizing nitroreductase activity in living cells and tissues under hypoxia and hepatic inflammation

Detecting nitroreductase (NTR) activity in hypoxic cells and tissues in situ represents an important step toward accurate delineation of hypoxic disease loci. However, it remains challenging to develop fluorescent probes with the necessary attributes of selectivity, sensitivity, precise targeting and aqueous solubility. Herein, two kinds of fluorescent probes (NNP and cRGD-NNP) built on a 2-nitroimidazole sensing platform were synthesized for the detection of NTR activity in cell and in vivo models of hypoxia. In the presence of NADH, NNP displayed high selectivity for NTR, a strong fluorescence enhancement (108 fold), and a low detection limit (3.6 ng mL^-1). Benefiting from the hydrophilic structure and tumor-targeting properties of the cRGD cyclopeptide group, the probe cRGD-NNP efficiently detected NTR activity in MCF cancer cells under hypoxia. In addition, the liposome-encapsulated probe was successfully applied to visualize NTR during liver inflammation in mice.

Lipid based nanoparticles as a novel treatment modality for hepatocellular carcinoma: a comprehensive review on targeting and recent advances

Liver cancer is considered one of the deadliest diseases with one of the highest disease burdens worldwide. Among the different types of liver cancer, hepatocellular carcinoma is considered to be the most common type. Multiple conventional approaches are being used in treating hepatocellular carcinoma. Focusing on drug treatment, regular agents in conventional forms fail to achieve the intended clinical outcomes. In order to improve the treatment outcomes, utilizing nanoparticles-specifically lipid based nanoparticles-are considered to be one of the most promising approaches being set in motion. Multiple forms of lipid based nanoparticles exist including liposomes, solid lipid nanoparticles, nanostructured lipid carriers, microemulsion, nanoemulsion, phytosomes, lipid coated nanoparticles, and nanoassemblies. Multiple approaches are used to enhance the tumor uptake as well tumor specificity such as intratumoral injection, passive targeting, active targeting, and stimuli responsive nanoparticles. In this review, the effect of utilizing lipidic nanoparticles is being discussed as well as the different tumor uptake enhancement techniques used.

An injectable self-assembling hydrogel based on RGD peptidomimetic β-sheets as multifunctional biomaterials

Ability of the cells to adhere to an extracellular material is central to successful tissue genesis. Arg-Gly-Asp (RGD) sequences found in extracellular matrix proteins are well known for cell adhesion, however, enzymatic degradation and lack of specificity have limited their widespread use. Besides, a multifunctional material with inherent antimicrobial ability would help in invigorating the practical tissue engineering applications. Here, we report novel modified RGD (M_R) and RGD mimic [R(K)] peptides (M_OH and M_NH2) which were synthesized post-in-silico screening, based on their interactions with integrin protein α_Vβ₃ using HEX 8.0 docking server. These mimics, containing hydrophobic Phe-Phe (FF) moiety which has been specifically introduced to initiate the self-assembling process of β-sheet structures, were characterized thoroughly using various physicochemical and spectroscopic techniques. Under physiological conditions, these mimetics displayed thixotropic behavior rendering them highly suitable as injectable hydrogels having an added advantage of site-specific targeting abilities. Electron microscopy further revealed the formation of nanofibers upon self-assembly of these peptides. Besides, enhanced cell adhesiveness by these peptides compared to the commercial Poly l-lysine coated surfaces as well as the inherent antimicrobial potential against both sensitive and antibiotic-resistant pathogens (Methicillin-resistant Staphylococcus aureus and multi-drug resistant Salmonella enteritidis) substantiated the applicability of these unique injectable hydrogels wherein the porous fibrous framework offered a favorable environment for drug entrapment and 3D cell culture. Altogether, these properties render these novel RGD mimic peptides as promising multifunctional candidates for various tissue regenerative applications.

Protease-Resistant Peptides for Targeting and Intracellular Delivery of Therapeutics

Peptides show high promise in the targeting and intracellular delivery of next-generation bio- and nano-therapeutics. However, the proteolytic susceptibility of peptides is one of the major limitations of their activity in biological environments. Numerous strategies have been devised to chemically enhance the resistance of peptides to proteolysis, ranging from N- and C-termini protection to cyclization, and including backbone modification, incorporation of amino acids with non-canonical side chains and conjugation. Since conjugation of nanocarriers or other cargoes to peptides for targeting and cell penetration may already provide some degree of shielding, the question arises about the relevance of using protease-resistant sequences for these applications. Aiming to answer this question, here we provide a critical review on protease-resistant targeting peptides and cell-penetrating peptides (CPPs). Two main approaches have been used on these classes of peptides: enantio/retro-enantio isomerization and cyclization. On one hand, enantio/retro-enantio isomerization has been shown to provide a clear enhancement in peptide efficiency with respect to parent L-amino acid peptides, especially when applied to peptides for drug delivery to the brain. On the other hand, cyclization also clearly increases peptide transport capacity, although contribution from enhanced protease resistance or affinity is often not dissected. Overall, we conclude that although conjugation often offers some degree of protection to proteolysis in targeting peptides and CPPs, modification of peptide sequences to further enhance protease resistance can greatly increase homing and transport efficiency.

[68Ga]Ga-DFO-c(RGDyK): Synthesis and Evaluation of Its Potential for Tumor Imaging in Mice

Angiogenesis has a pivotal role in tumor growth and the metastatic process. Molecular imaging was shown to be useful for imaging of tumor-induced angiogenesis. A great variety of radiolabeled peptides have been developed to target αvβ3 integrin, a target structure involved in the tumor-induced angiogenic process. The presented study aimed to synthesize deferoxamine (DFO)-based c(RGD) peptide conjugate for radiolabeling with gallium-68 and perform its basic preclinical characterization including testing of its tumor-imaging potential. DFO-c(RGDyK) was labeled with gallium-68 with high radiochemical purity. In vitro characterization including stability, partition coefficient, protein binding determination, tumor cell uptake assays, and ex vivo biodistribution as well as PET/CT imaging was performed. [⁶⁸Ga]Ga-DFO-c(RGDyK) showed hydrophilic properties, high stability in PBS and human serum, and specific uptake in U-87 MG and M21 tumor cell lines in vitro and in vivo. We have shown here that [⁶⁸Ga]Ga-DFO-c(RGDyK) can be used for αvβ3 integrin targeting, allowing imaging of tumor-induced angiogenesis by positron emission tomography.

Two Novel PET Radiopharmaceuticals for Endothelial Vascular Cell Adhesion Molecule-1 (VCAM-1) Targeting

Atherosclerosis is a chronic progressive disease involving inflammatory events, such as the overexpression of adhesion molecules including the endothelial Vascular Cell Adhesion Molecule-1 (VCAM-1). VCAM-1 is rapidly overexpressed in the first stages of atherosclerosis, thus representing a promising target for early atheroma detection. Two novel Positron Emission Tomography (PET) radiopharmaceuticals (MacroP and NAMP), based on the VCAM-1-binding peptide having sequence VHPKQHRGGSKGC, were synthesized and characterized. MacroP is derived from the direct conjugation of a DOTA derivative with the peptide, while NAMP is a biotin derivative conceived to be employed in a three-step pretargeting system, involving the use of a double-chelating derivative of DOTA. The identity of the newly synthesized radiopharmaceuticals was confirmed by mass spectrometry and, after radiolabeling with 68Ga, both showed high radiochemical purity; in vitro tests on human umbilical vein endothelial cells evidenced their VCAM-1 binding ability, with higher radioactive uptake in the case of NAMP. Moreover, NAMP might also be employed in a theranostic approach in association with functionalized biotinylated nanoparticles.

Nanodiamonds and their potential applications in breast cancer therapy: a narrative review

Breast cancer remains the most commonly diagnosed cancer and the leading cause of cancer-related death among women worldwide. With the projected increase in breast cancer cases in recent years, optimising treatment becomes increasingly important. Current treatment modalities in breast cancer present major limitations, including chemoresistance, dose-limiting adverse effects and lack of selectivity in aggressive subtypes of breast cancers such as triple-negative breast cancer. Nanodiamonds have demonstrated promising outcomes in preclinical models from their unique surface characteristics allowing optimised delivery of various therapeutic agents, overcoming some of the significant hurdles in conventional treatment modalities. This review will present an update on preclinical findings of nanodiamond-based drug delivery systems for breast cancer therapy to date, challenges with the use of nanodiamonds along with considerations for future research.

Poly(aspartic acid) in Biomedical Applications: From Polymerization, Modification, Properties, Degradation, and Biocompatibility to Applications

Poly(aspartic acid) (PASP) is an anionic polypeptide that is a highly versatile, biocompatible, and biodegradable polymer that fulfils key requirements for use in a wide variety of biomedical applications. The derivatives of PASP can be readily tailored via the amine-reactive precursor, poly(succinimide) (PSI), which opens up a large window of opportunity for the design and development of novel biomaterials. PASP also has a strong affinity with calcium ions, resulting in complexation, which has been exploited for bone targeting and biomineralization. In addition, recent studies have further verified the biocompatibility and biodegradability of PASP-based polymers, which is attributed to their protein-like structure. In light of growing interest in PASP and its derivatives, this paper presents a comprehensive review on their synthesis, characterization, modification, biodegradation, biocompatibility, and applications in biomedical areas.

Peptide functionalized liposomes for receptor targeted cancer therapy

Most clinically approved cancer therapies are potent and toxic small molecules that are limited by severe off-target toxicities and poor tumor-specific localization. Over the past few decades, attempts have been made to load chemotherapies into liposomes, which act to deliver the therapeutic agent directly to the tumor. Although liposomal encapsulation has been shown to decrease toxicity in human patients, reliance on passive targeting via the enhanced permeability and retention (EPR) effect has left some of these issues unresolved. Recently, investigations into modifying the surface of liposomes via covalent and/or electrostatic functionalization have offered mechanisms for tumor homing and subsequently controlled chemotherapeutic delivery. A wide variety of biomolecules can be utilized to functionalize liposomes such as proteins, carbohydrates, and nucleic acids, which enable multiple directions for cancer cell localization. Importantly, when nanoparticles are modified with such molecules, care must be taken as not to inactivate or denature the ligand. Peptides, which are small proteins with <30 amino acids, have demonstrated the exceptional ability to act as ligands for transmembrane protein receptors overexpressed in many tumor phenotypes. Exploring this strategy offers a method in tumor targeting for cancers such as glioblastoma multiforme, pancreatic, lung, and breast based on the manifold of receptors overexpressed on various tumor cell populations. In this review, we offer a comprehensive summary of peptide-functionalized liposomes for receptor-targeted cancer therapy.

Synthesis of a DOTA-C-glyco bifunctional chelating agent and preliminary in vitro and in vivo study of [68Ga]Ga-DOTA-C-glyco-RGD

The design of bifunctional chelating agents (BFCA) allowing straightforward radiometal labelling of biomolecules is a current challenge. We report herein the development of a bifunctional chelating agent based on a DOTA chelator linked to a C-glycosyl compound, taking advantage of the robustness and hydrophilicity of this type of carbohydrate derivative. This new BFCA was coupled with success by CuAAC with c(RGDfK) for αvβ3 integrin targeting. As attested by in vitro evaluation, the conjugate DOTA-C-glyco-c(RGDfC) demonstrated high affinity for αvβ3 integrins (IC50 of 42 nM). [68Ga]Ga-DOTA-C-glyco-c(RGDfK) was radiosynthesized straightforwardly and showed high hydrophilic property (log D 7.4 = -3.71) and in vitro stability (>120 min). Preliminary in vivo PET study of U87MG engrafted mice gave evidence of an interesting tumor-to-non-target area ratio. All these data indicate that [68Ga]Ga-DOTA-C-glyco-c(RGDfK) allows monitoring of αvβ3 expression and could thus be used for cancer diagnosis. The DOTA-C-glycoside BFCA reported here could also be used with various ligands and chelating other (radio)metals opening a broad scope of applications in imaging modalities and therapy.

Poly(2-ethyl-2-oxazoline-co-ethyleneimine)-block-poly(ε-caprolactone) based micelles: synthesis, characterization, peptide conjugation and cytotoxic activity

Here we present self-assembled polymeric micelles as potential delivery systems for therapeutic agents with highly tunable properties.

Recent Advances on Graphene Quantum Dots as Multifunctional Nanoplatforms for Cancer Treatment

Graphene quantum dots (GQDs), the latest member of the graphene family, have attracted enormous interest in the last few years, due to their exceptional physical, chemical, electrical, optical, and biological properties. Their strong size-dependent photoluminescence and the presence of many reactive groups on the graphene surface allow their multimodal conjugation with therapeutic agents, targeting ligands, polymers, light responsive agents, fluorescent dyes, and functional nanoparticles, making them valuable agents for cancer diagnosis and treatment. In this review, the very recent advances covering the last 3 years on the applications of GQDs as drug delivery systems and theranostic tools for anticancer therapy are discussed, highlighting the relevant factors which regulate their biocompatibility. Among these factors, the size, kind, and degree of surface functionalization have shown to greatly affect their use in biological systems. Toxicity issues, which still represent an open challenge for the clinical development of GQDs based therapeutic agents, are also discussed at cellular and animal levels.

Supramolecular Peptide Assemblies as Antimicrobial Scaffolds

Antimicrobial discovery in the age of antibiotic resistance has demanded the prioritization of non-conventional therapies that act on new targets or employ novel mechanisms. Among these, supramolecular antimicrobial peptide assemblies have emerged as attractive therapeutic platforms, operating as both the bactericidal agent and delivery vector for combinatorial antibiotics. Leveraging their programmable inter- and intra-molecular interactions, peptides can be engineered to form higher ordered monolithic or co-assembled structures, including nano-fibers, -nets, and -tubes, where their unique bifunctionalities often emerge from the supramolecular state. Further advancements have included the formation of macroscopic hydrogels that act as bioresponsive, bactericidal materials. This systematic review covers recent advances in the development of supramolecular antimicrobial peptide technologies and discusses their potential impact on future drug discovery efforts.

c(RGDfK)- and ZnTriMPyP-Bound Polymeric Nanocarriers for Tumor-Targeted Photodynamic Therapy

Active targeting strategies are currently being extensively investigated in order to enhance the selectivity of photodynamic therapy. The aim of the present research was to evaluate whether the external decoration of nanopolymeric carriers with targeting peptides could add more value to a photosensitizer formulation and increase antitumor therapeutic efficacy and selectivity. To this end, we assessed PLGA-PLA-PEG nanoparticles (NPs) covalently attached to a hydrophilic photosensitizer 5-[4-azidophenyl]-10,15,20-tri-(N-methyl-4-pyridinium)porphyrinato zinc (II) trichloride (ZnTriMPyP) and also to c(RGDfK) peptides, in order to target α_v β₃ integrin-expressing cells. In vitro phototoxicity investigations showed that the ZnTriMPyP-PLGA-PLA-PEG-c(RGDfK) nanosystem is effective at submicromolar concentrations, is devoid of dark toxicity, successfully targets α_v β₃ integrin-expressing cells and is 10-fold more potent than related nanosystems where the PS is occluded instead of covalently bound.