Conjugates of Ciprofloxacin and Levofloxacin with Cell-Penetrating Peptide Exhibit Antifungal Activity and Mammalian Cytotoxicity

Evaluating the cytotoxicity mechanism of the cell-penetrating peptide TP10 on Jurkat cells

TP10, a classic cell-penetrating peptide, shows a high degree of similarity to AMPs in structure. Although TP10 has been widely used in drug delivery, the mechanism underlying its cytotoxicity is yet to be elucidated. Herein, we explored the cell-killing mechanism of TP10 against human leukemia Jurkat cells. TP10 induced necrosis in Jurkat cells via rapid disruption of cell membranes, particularly at high concentrations. Although mitochondria in Jurkat cells were damaged by TP10, mitochondria-mediated apoptosis did not occur, possibly due to intracellular ATP depletion. Necroptosis in TP10-treated Jurkat cells became an alternative route of apoptosis. Our results demonstrate that necrosis and necroptosis rather than apoptosis are involved in the cell-killing mechanism of TP10, which contributes to the understanding of its toxicity.

Uptake pathways of cell-penetrating peptides in the context of drug delivery, gene therapy, and vaccine development

Cell-penetrating peptides have been extensively utilized for the purpose of facilitating the intracellular delivery of cargo that is impermeable to the cell membrane. The researchers have exhibited proficient delivery capabilities for oligonucleotides, thereby establishing cell-penetrating peptides as a potent instrument in the field of gene therapy. Furthermore, they have demonstrated a high level of efficiency in delivering several additional payloads. Cell penetrating peptides (CPPs) possess the capability to efficiently transport therapeutic molecules to specific cells, hence offering potential remedies for many illnesses. Hence, their utilization is imperative for the improvement of therapeutic vaccines. In contemporary studies, a plethora of cell-penetrating peptides have been unveiled, each characterized by its own distinct structural attributes and associated mechanisms. Although it is widely acknowledged that there are multiple pathways through which particles might be internalized, a comprehensive understanding of the specific mechanisms by which these particles enter cells has to be fully elucidated. The absorption of cell-penetrating peptides can occur through either direct translocation or endocytosis. However, it is worth noting that categories of cell-penetrating peptides are not commonly linked to specific entrance mechanisms. Furthermore, research has demonstrated that cell-penetrating peptides (CPPs) possess the capacity to enhance antigen uptake by cells and facilitate the traversal of various biological barriers. The primary objective of this work is to examine the mechanisms by which cell-penetrating peptides are internalized by cells and their significance in facilitating the administration of drugs, particularly in the context of gene therapy and vaccine development. The current study investigates the immunostimulatory properties of numerous vaccine components administered using different cell-penetrating peptides (CPPs). This study encompassed a comprehensive discussion on various topics, including the uptake pathways and mechanisms of cell-penetrating peptides (CPPs), the utilization of CPPs as innovative vectors for gene therapy, the role of CPPs in vaccine development, and the potential of CPPs for antigen delivery in the context of vaccine development.

Advancements in Synthetic Strategies and Biological Effects of Ciprofloxacin Derivatives: A Review

Ciprofloxacin is a widely used antibiotic in the fluoroquinolone class. It is widely acknowledged by various researchers worldwide, and it has been documented to have a broad range of other pharmacological activities, such as anticancer, antiviral, antimalarial activities, etc. Researchers have been exploring the synthesis of ciprofloxacin derivatives with enhanced biological activities or tailored capability to target specific pathogens. The various biological activities of some of the most potent and promising ciprofloxacin derivatives, as well as the synthetic strategies used to develop them, are thoroughly reviewed in this paper. Modification of ciprofloxacin via 4-oxo-3-carboxylic acid resulted in derivatives with reduced efficacy against bacterial strains. Hybrid molecules containing ciprofloxacin scaffolds displayed promising biological effects. The current review paper provides reported findings on the development of novel ciprofloxacin-based molecules with enhanced potency and intended therapeutic activities which will be of great interest to medicinal chemists.

Searching for Conjugates as New Structures for Antifungal Therapies

The progressive increase in fungal infections and the decrease in the effectiveness of current therapy explain research on new drugs. The synthesis of compounds with proven antifungal activity, favorable physicochemical and pharmacokinetic properties affecting their pharmaceutical availability and bioavailability, and limiting or eliminating side effects has become the goal of many studies. The publication describes the directions of searching for new compounds with antifungal activity, focusing on conjugates. The described modifications include, among others, azoles or amphotericin B in combination with fatty acids, polysaccharides, proteins, and synthetic polymers. The benefits of these combinations in terms of activity, mechanism of action, and bioavailability were indicated. The possibilities of creating or using nanoparticles, "umbrella" conjugates, siderophores (iron-chelating compounds), and monoclonal antibodies were also presented. Taking into account the role of vaccinations in prevention, the scope of research related to developing a vaccine protecting against fungal infections was also indicated.

Silver ciprofloxacin (CIPAG): a multitargeted metallodrug in the development of breast cancer therapy

The anti-proliferative activity of the known metalloantibiotic {[Ag(CIPH)2]NO3∙0.75MeOH∙1.2H2O} (CIPAG) (CIPH = ciprofloxacin) against the human breast adenocarcinoma cancer cells MCF-7 (hormone dependent (HD)) and MDA-MB-231 (hormone independent (HI)) is evaluated. The in vitro toxicity and genotoxicity of the metalloantibiotic were estimated toward fetal lung fibroblast (MRC-5) cells. The molecular mechanism of the CIPAG activity against MCF-7 cells was clarified by the (i) cell morphology, (ii) cell cycle arrest, (iii) mitochondrial membrane permeabilization, and (iv) by the assessment of the possible differential effect of CIPAG on estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) transcriptional activation, applying luciferase reporter gene assay. Moreover, the ex vivo mechanism of CIPAG was clarified by its binding affinity toward calf thymus (CT-DNA).

Design, Synthesis, and Antitumor Evaluation of an Opioid Growth Factor Bioconjugate Targeting Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) presents a formidable challenge with high lethality and limited effective drug treatments. Its heightened metastatic potential further complicates the prognosis. Owing to the significant toxicity of current chemotherapeutics, compounds like [Met5]-enkephalin, known as opioid growth factor (OGF), have emerged in oncology clinical trials. OGF, an endogenous peptide interacting with the OGF receptor (OGFr), plays a crucial role in inhibiting cell proliferation across various cancer types. This in vitro study explores the potential anticancer efficacy of a newly synthesized OGF bioconjugate in synergy with the classic chemotherapeutic agent, gemcitabine (OGF-Gem). The study delves into assessing the impact of the OGF-Gem conjugate on cell proliferation inhibition, cell cycle regulation, the induction of cellular senescence, and apoptosis. Furthermore, the antimetastatic potential of the OGF-Gem conjugate was demonstrated through evaluations using blood platelets and AsPC-1 cells with a light aggregometer. In summary, this article demonstrates the cytotoxic impact of the innovative OGF-Gem conjugate on pancreatic cancer cells in both 2D and 3D models. We highlight the potential of both the OGF-Gem conjugate and OGF alone in effectively inhibiting the ex vivo pancreatic tumor cell-induced platelet aggregation (TCIPA) process, a phenomenon not observed with Gem alone. Furthermore, the confirmed hemocompatibility of OGF-Gem with platelets reinforces its promising potential. We anticipate that this conjugation strategy will open avenues for the development of potent anticancer agents.

Lactoferricin B Combined with Antibiotics Exhibits Leukemic Selectivity and Antimicrobial Activity

The fusion of penetrating peptides (PPs), e.g., cell penetration peptides (CPPs) or antimicrobial peptides (AMPs), together with antimicrobial agents is an expanding research field. Specific AMPs, such as lactoferricin B (LfcinB), have demonstrated strong antibacterial, antifungal, and antiparasitic activity, as well as valuable anticancer activity, proving beneficial in the development of anticancer conjugates. The resulting conjugates offer potential dual functionality, acting as both an anticancer and an antimicrobial agent. This is especially necessary in cancer treatment, where microbial infections pose a critical risk. Leukemic cells frequently exhibit altered outer lipid membranes compared to healthy cells, making them more sensitive to compounds that interfere with their membrane. In this study, we revisited and reanalyzed our earlier research on LfcinB and its conjugates. Furthermore, we carried out new experiments with a specific focus on cell proliferation, changes in membrane asymmetric phosphatidylserine location, intracellular reactive oxygen species (ROS) generation, mitochondrial functions, and in vitro bacterial topoisomerase inhibition.

Ciprofloxacin and Norfloxacin Hybrid Compounds: Potential Anticancer Agents

BACKGROUND

The concept of utilizing drug repurposing/repositioning in the development of hybrid molecules is an important strategy in drug discovery. Fluoroquinolones, a class of antibiotics, have been reported to exhibit anticancer activities. Although anticancer drug development is achieving some positive outcomes, there is still a need to develop new and effective anticancer drugs. Some limitations associated with most of the available anticancer drugs are drug resistance and toxicity, poor bio-distribution, poor solubility, and lack of specificity, thereby reducing their therapeutic outcomes.

OBJECTIVES

Fluoroquinolones, a known class of antibiotics, have been explored by hybridizing them with other pharmacophores and evaluating their anticancer activity in silico and in vitro. Hence, this review provides an update on new anticancer drugs containing fluoroquinolones moiety, Ciprofloxacin and Norfloxacin between 2020 and 2023, their structural relationship activity, and the future strategies to develop potent chemotherapeutic agents.

METHODS

Fluoroquinolones were mostly hybridized via the N-4 of the piperazine ring on position C-7 with known pharmacophores characterized, followed by biological studies to evaluate their anticancer activity.

RESULTS

The hybrid molecules displayed promising and interesting anticancer activities. Factors such as the nature of the linker, the presence of electron-withdrawing groups, nature, and position of the substituents influenced the anticancer activity of the synthesized compounds.

CONCLUSION

The hybrids were selective towards some cancer cells. However, further in vivo studies are needed to fully understand their mode of action.

Dual-Activity Fluoroquinolone-Transportan 10 Conjugates Offer Alternative Leukemia Therapy during Hematopoietic Cell Transplantation

Hematopoietic cell transplantation (HCT) is often considered a last resort leukemia treatment, fraught with limited success due to microbial infections, a leading cause of mortality in leukemia patients. To address this critical issue, we explored a novel approach by synthesizing antileukemic agents containing antibacterial substances. This innovative strategy involves conjugating fluoroquinolone antibiotics, such as ciprofloxacin (CIP) or levofloxacin (LVX), with the cell-penetrating peptide transportan 10 (TP10). Here, we demonstrate that the resultant compounds display promising biologic activities in preclinical studies. These novel conjugates not only exhibit potent antimicrobial effects but are also selective against leukemia cells. The cytotoxic mechanism involves rapid disruption of cell membrane asymmetry leading to membrane damage. Importantly, these conjugates penetrated mammalian cells, accumulating within the nuclear membrane without significant effect on cellular architecture or mitochondrial function. Molecular simulations elucidated the aggregation tendencies of TP10 conjugates within lipid bilayers, resulting in membrane disruption and permeabilization. Moreover, mass spectrometry analysis confirmed efficient reduction of disulfide bonds within TP10 conjugates, facilitating release and activation of the fluoroquinolone derivatives. Intriguingly, these compounds inhibited human topoisomerases, setting them apart from traditional fluoroquinolones. Remarkably, TP10 conjugates generated lower intracellular levels of reactive oxygen species compared with CIP and LVX. The combination of antibacterial and antileukemic properties, coupled with selective cytostatic effects and minimal toxicity toward healthy cells, positions TP10 derivatives as promising candidates for innovative therapeutic approaches in the context of antileukemic HCT. This study highlights their potential in search of more effective leukemia treatments. SIGNIFICANCE STATEMENT: Fluoroquinolones are commonly used antibiotics, while transportan 10 (TP10) is a cell-penetrating peptide (CPP) with anticancer properties. In HCT, microbial infections are the primary cause of illness and death. Combining TP10 with fluoroquinolones enhanced their effects on different cell types. The dual pharmacological action of these conjugates offers a promising proof-of-concept solution for leukemic patients undergoing HCT. Strategically designed therapeutics, incorporating CPPs with antibacterial properties, have the potential to reduce microbial infections in the treatment of malignancies.

Conjugation of antimicrobial peptides to enhance therapeutic efficacy

The growing prevalence of antimicrobial resistance (AMR) has brought with it a continual increase in the numbers of deaths from multidrug-resistant (MDR) infections. Since the current arsenal of antibiotics has become increasingly ineffective, there exists an urgent need for discovery and development of novel antimicrobials. Antimicrobial peptides (AMPs) are considered to be a promising class of molecules due to their broad-spectrum activities and low resistance rates compared with other types of antibiotics. Since AMPs also often play major roles in elevating the host immune response, the molecules may also be called "host defense peptides." Despite the great promise of AMPs, the majority remain unsuitable for clinical use due to issues of structural instability, degradation by proteases, and/or toxicity to host cells. Moreover, AMP activities in vivo can be influenced by many factors, such as interaction with blood and serum biomolecules, physiological salt concentrations or different pH values. To overcome these limitations, structural modifications can be made to the AMP. Among several modifications, physical and chemical conjugation of AMP to other biomolecules is widely considered an effective strategy. In this review, we discuss structural modification strategies related to conjugation of AMPs and their possible effects on mode of action. The conjugation of fatty acids, glycans, antibiotics, photosensitizers, polymers, nucleic acids, nanoparticles, and immobilization to biomaterials are highlighted.

Various Biomimetics, Including Peptides as Antifungals

Biomimetics, which are similar to natural compounds that play an important role in the metabolism, manifestation of functional activity and reproduction of various fungi, have a pronounced attraction in the current search for new effective antifungals. Actual trends in the development of this area of research indicate that unnatural amino acids can be used as such biomimetics, including those containing halogen atoms; compounds similar to nitrogenous bases embedded in the nucleic acids synthesized by fungi; peptides imitating fungal analogs; molecules similar to natural substrates of numerous fungal enzymes and quorum-sensing signaling molecules of fungi and yeast, etc. Most parts of this review are devoted to the analysis of semi-synthetic and synthetic antifungal peptides and their targets of action. This review is aimed at combining and systematizing the current scientific information accumulating in this area of research, developing various antifungals with an assessment of the effectiveness of the created biomimetics and the possibility of combining them with other antimicrobial substances to reduce cell resistance and improve antifungal effects.

Fluoroquinolone-Based Organic Salts (GUMBOS) with Antibacterial Potential

Antimicrobial resistance is a silent pandemic considered a public health concern worldwide. Strategic therapies are needed to replace antibacterials that are now ineffective. One approach entails the use of well-known antibacterials along with adjuvants that possess non-antibiotic properties but can extend the lifespan and enhance the effectiveness of the treatment, while also improving the suppression of resistance. In this regard, a group of uniform materials based on organic salts (GUMBOS) presents an alternative to this problem allowing the combination of antibacterials with adjuvants. Fluoroquinolones are a family of antibacterials used to treat respiratory and urinary tract infections with broad-spectrum activity. Ciprofloxacin and moxifloxacin-based GUMBOS were synthesized via anion exchange reactions with lithium and sodium salts. Structural characterization, thermal stability and octanol/water partition ratios were evaluated. The antibacterial profiles of most GUMBOS were comparable to their cationic counterparts when tested against Gram-positive S. aureus and Gram-negative E. coli, except for deoxycholate anion, which demonstrated the least effective antibacterial activity. Additionally, some GUMBOS were less cytotoxic to L929 fibroblast cells and non-hemolytic to red blood cells. Therefore, these agents exhibit promise as an alternative approach to combining drugs for treating infections caused by resistant bacteria.

Photocatalytic degradation of four emerging antibiotic contaminants and toxicity assessment in wastewater: A comprehensive study

Excessive usage and unrestricted discharge of antibiotics in the environment lead to their accumulation in the ecosystem due to their highly stable and non-biodegradation nature. Photodegradation of four most consumed antibiotics such as amoxicillin, azithromycin, cefixime, and ciprofloxacin were studied using Cu2O-TiO2 nanotubes. Cytotoxicity evaluation of the native and transformed products was conducted on the RAW 264.7 cell lines. Photocatalyst loading (0.1-2.0 g/L), pH (5, 7 and 9), initial antibiotic load (50-1000 μg/mL) and cuprous oxide percentage (5, 10 and 20) were optimized for efficient photodegradation of antibiotics. Quenching experiments to evaluate the mechanism of photodegradation with hydroxyl and superoxide radicals were found the most reactive species of the selected antibiotics. Complete degradation of selected antibiotics was achieved in 90 min with 1.5 g/L of 10% Cu2O-TiO2 nanotubes with initial antibiotic concentration (100 μg/mL) at neutral pH of water matrix. The photocatalyst showed high chemical stability and reusability up to five consecutive cycles. Zeta potential studies confirms the high stability and activity of 10% C-TAC (Cuprous oxide doped Titanium dioxide nanotubes for Applied Catalysis) in the tested pH conditions. Photoluminescence and Electrochemical Impedance Spectroscopy data speculates that 10% C-TAC photocatalyst have efficient photoexcitation in the visible light for photodegradation of antibiotics samples. Inhibitory concentration (IC50) interpretation from the toxicity analysis of native antibiotics concluded that ciprofloxacin was the most toxic antibiotic among the selected antibiotics. Cytotoxicity percentage of transformed products showed r: -0.985, p: 0.01 (negative correlation) with the degradation percentage revealing the efficient degradation of selected antibiotics with no toxic by-products.

N-Acylated Ciprofloxacin Derivatives: Synthesis and In Vitro Biological Evaluation as Antibacterial and Anticancer Agents

A novel series of N-acylated ciprofloxacin (CP) conjugates 1-21 were synthesized and screened as potential antimicrobial agents. Conjugates 1 and 2 were 1.25-10-fold more potent than CP toward all Staphylococci (minimal inhibitory concentration 0.05-0.4 μg/mL). Most of the chloro- (3-7), bromo- (8-11), and CF₃-alkanoyl (14-16) derivatives expressed higher or comparable activity to CP against selected Gram-positive strains. A few CP analogues (5, 10, and 11) were also more effective toward the chosen clinical Gram-negative rods. Conjugates 5, 10, and 11 considerably influenced the phases of the bacterial growth cycle over 18 h. Additionally, compounds 2, 4-7, 9-12, and 21 exerted stronger tuberculostatic action against three Mycobacterium tuberculosis isolates than the first-line antitubercular drugs. Amides 1, 2, 5, 6, 10, and 11 targeted gyrase and topoisomerase IV at 2.7-10.0 μg/mL, which suggests a mechanism of antibacterial action related to CP. These findings were confirmed by molecular docking studies. In addition, compounds 3 and 15 showed high antiproliferative activities against prostate PC3 cells (IC₅₀ 2.02-4.8 μM), up to 6.5-2.75 stronger than cisplatin. They almost completely reduced the growth and proliferation rates in these cells, without a cytotoxic action against normal HaCaT cell lines. Furthermore, derivatives 3 and 21 induced apoptosis/necrosis in PC3 cells, probably by increasing the intracellular ROS amount, as well as they diminished the IL-6 level in tumor cells.

Current scenario of quinolone hybrids with potential antibacterial activity against ESKAPE pathogens

The ESKAPE (Escherichia coli/E. coli, Staphylococcus aureus/S. aureus, Klebsiella pneumonia/K. pneumoniae, Acinetobacter Baumannii/A. baumannii, Pseudomonas aeroginosa/P. aeroginosa and Enterobacter spp.) pathogens, which could escape or evade common therapies through diverse antimicrobial resistance mechanisms and biofilm formation, are deemed as highly virulent bacteria responsible for life-threatening diseases, calling for novel chemotherapeutics. Quinolones including 2-quinolones and 4-quinolones have occupied a propitious place in drug design and development due to their excellent pharmacological profiles. Quinolones especially fluoroquinolones could inhibit the synthesis of nucleic acid of ESKAPE pathogens, leading to the rupture of bacterial chromosome. However, the resistance of ESKAPE pathogens to quinolones develops rapidly and spreads widely. Accordingly, it has become increasingly urgent to enhance the potency of quinolones against both drug-susceptible and drug-resistant ESKAPE pathogens. Quinolone hybrids can bind with different drug targets simultaneously and have been considered as useful prototypes to circumvent drug resistance. The purpose of this review is to summarize the current scenario (2018-present) of quinolone hybrids with potential antibacterial activity against ESKAPE pathogens, together with the structure-activity relationships and mechanisms of action to facilitate further rational design of more effective candidates.

Targeting DNA Topoisomerase II in Antifungal Chemotherapy

Topoisomerase inhibitors have been in use clinically for the treatment of several diseases for decades. Although those enzymes are significant molecular targets in antibacterial and anticancer chemotherapy very little is known about the possibilities to target fungal topoisomerase II (topo II). Raising concern for the fungal infections, lack of effective drugs and a phenomenon of multidrug resistance underlie a strong need to expand the range of therapeutic options. In this review paper, we discussed the usefulness of fungal topo II as a molecular target for new drug discovery. On the basis of previously published data, we described structural and biochemical differences between fungal and human enzymes as well as a molecular basis of differential sensitivity to known anticancer drugs targeting the latter. This review focuses especially on highlighting the differences that may underlie the selectivity of action of new inhibitors. Distinct sites within fungal topo II in comparison with human counterparts are observed and should be further studied to understand the significance of those sites and their possible usage in design of new drugs.

Cell-Penetrating Peptides (CPPs) as Therapeutic and Diagnostic Agents for Cancer

Cell-Penetrating Peptides (CPPs) are short peptides consisting of <30 amino acids. Their ability to translocate through the cell membrane while carrying large cargo biomolecules has been the topic of pre-clinical and clinical trials. The ability to deliver cargo complexes through membranes yields potential for therapeutics and diagnostics for diseases such as cancer. Upon cellular entry, some CPPs have the ability to target specific organelles. CPP-based intracellular targeting strategies hold tremendous potential as they can improve efficacy and reduce toxicities and side effects. Further, recent clinical trials show a significant potential for future CPP-based cancer treatment. In this review, we summarize recent advances in CPPs based on systematic searches in PubMed, Embase, Web of Science, and Scopus databases until 30 September 2022. We highlight targeted delivery and explore the potential uses for CPPs as diagnostics, drug delivery, and intrinsic anti-cancer agents.

Biomass derived self-assembled DNA-dot hydrogels for enhanced bacterial annihilation

Nanotization of biomass for interesting biomedical applications is still in the nascent stage with no visible market available products. While products derived from biomass DNA and protein have unquestionable biocompatibility, induction of desired properties needs careful manipulation of the biomolecules. Herein, for the first time, we report the transformation of onion derived biomass DNA into DNA-dots through its partial hydrothermal pyrolysis to induce improved mechanical and photophysical properties. The DNA-dots were further used as crosslinkers to create a hydrogel through hybridization-mediated self-assembly with untransformed genomic DNA. The DNA dot-DNA hydrogel sustainably delivers the ciprofloxacin antibiotic as well as produces on-demand reactive oxygen species (ROS) with visible light irradiation. This prompted us to explore the hydrogel as a topical formulation for combination antibiotic Antibacterial-Photodynamic Therapy (APDT) applications. Remarkable annihilation of E. coli and S. aureus, and most importantly two drug-resistant strains of E. coli, shows the success of our sustainable approach.

Cell penetrating peptide: A potent delivery system in vaccine development

One of the main obstacles to most medication administrations (such as the vaccine constructs) is the cellular membrane's inadequate permeability, which reduces their efficiency. Cell-penetrating peptides (CPPs) or protein transduction domains (PTDs) are well-known as potent biological nanocarriers to overcome this natural barrier, and to deliver membrane-impermeable substances into cells. The physicochemical properties of CPPs, the attached cargo, concentration, and cell type substantially influence the internalization mechanism. Although the exact mechanism of cellular uptake and the following processing of CPPs are still uncertain; but however, they can facilitate intracellular transfer through both endocytic and non-endocytic pathways. Improved endosomal escape efficiency, selective cell targeting, and improved uptake, processing, and presentation of antigen by antigen-presenting cells (APCs) have been reported by CPPs. Different in vitro and in vivo investigations using CPP conjugates show their potential as therapeutic agents in various medical areas such as infectious and non-infectious disorders. Effective treatments for a variety of diseases may be provided by vaccines that can cooperatively stimulate T cell-mediated immunity (T helper cell activity or cytotoxic T cell function), and immunologic memory. Delivery of antigen epitopes to APCs, and generation of a potent immune response is essential for an efficacious vaccine that can be facilitated by CPPs. The current review describes the delivery of numerous vaccine components by various CPPs and their immunostimulatory properties.

Peptides as Pharmacological Carriers to the Brain: Promises, Shortcomings and Challenges

Central nervous system (CNS) diseases are among the most difficult to treat, mainly because the vast majority of the drugs fail to cross the blood-brain barrier (BBB) or to reach the brain at concentrations adequate to exert a pharmacological activity. The obstacle posed by the BBB has led to the in-depth study of strategies allowing the brain delivery of CNS-active drugs. Among the most promising strategies is the use of peptides addressed to the BBB. Peptides are versatile molecules that can be used to decorate nanoparticles or can be conjugated to drugs, with either a stable link or as pro-drugs. They have been used to deliver to the brain both small molecules and proteins, with applications in diverse therapeutic areas such as brain cancers, neurodegenerative diseases and imaging. Peptides can be generally classified as receptor-targeted, recognizing membrane proteins expressed by the BBB microvessels (e.g., Angiopep2, CDX, and iRGD), "cell-penetrating peptides" (CPPs; e.g. TAT_47-57, SynB1/3, and Penetratin), undergoing transcytosis through unspecific mechanisms, or those exploiting a mixed approach. The advantages of peptides have been extensively pointed out, but so far few studies have focused on the potential negative aspects. Indeed, despite having a generally good safety profile, some peptide conjugates may display toxicological characteristics distinct from those of the peptide itself, causing for instance antigenicity, cardiovascular alterations or hemolysis. Other shortcomings are the often brief lifetime in vivo, caused by the presence of peptidases, the vulnerability to endosomal/lysosomal degradation, and the frequently still insufficient attainable increase of brain drug levels, which remain below the therapeutically useful concentrations. The aim of this review is to analyze not only the successful and promising aspects of the use of peptides in brain targeting but also the problems posed by this strategy for drug delivery.

The Effect of Conjugation of Ciprofloxacin and Moxifloxacin with Fatty Acids on Their Antibacterial and Anticancer Activity

Novel conjugates (CP) of moxifloxacin (MXF) with fatty acids (1m–16m) were synthesized with good yields utilizing amides chemistry. They exhibit a more pronounced cytotoxic potential than the parent drug. They were the most effective for prostate cancer cells with an IC₅₀ below 5 µM for respective conjugates with sorbic (2m), oleic (4m), 6-heptenoic (10m), linoleic (11m), caprylic (15m), and stearic (16m) acids. All derivatives were evaluated against a panel of standard and clinical bacterial strains, as well as towards mycobacteria. The highest activity towards standard isolates was observed for the acetic acid derivative 14m, followed by conjugates of unsaturated crotonic (1m) and sorbic (2m) acids. The activity of conjugates tested against an expanded panel of clinical coagulase-negative staphylococci showed that the compound (14m) was recognized as a leading structure with an MIC of 0.5 μg/mL denoted for all quinolone-susceptible isolates. In the group of CP derivatives, sorbic (2) and geranic (3) acid amides exhibited the highest bactericidal potential against clinical strains. The M. tuberculosis Spec. 210 strain was the most sensitive to sorbic (2m) conjugate and to conjugates with medium- and long-chain polyunsaturated acids. To establish the mechanism of antibacterial action, selected CP and MXF conjugates were examined in both topoisomerase IV decatenation assay and the DNA gyrase supercoiling assay, followed by suitable molecular docking studies.

New Peptide Based Fluconazole Conjugates with Expanded Molecular Targets

Infections of Candida spp. etiology are frequently treated with azole drugs. Among azoles, the most widely used in the clinical scenario remains fluconazole (FLC). Promising results in treatment of dangerous, systemic Candida infections demonstrate the advantages of combined therapies carried out with combinations of at least two different antifungal agents. Here, we report five conjugates composed of covalently linked FLC and cell penetrating or antimicrobial peptide: TP10-7-NH₂, TP10-NH₂, LFcinB(2-11)-NH₂, LFcinB[Nle^1,11]-NH₂, and HLopt2-NH₂, with aspects of design, chemical synthesis and their biological activities. Two of these compounds, namely FLCpOH-TP10-NH₂ and FLCpOH-TP10-7-NH₂, exhibit high activity against reference strains and fluconazole-resistant clinical isolates of C. albicans, including strains overproducing drug transporters. Moreover, both of them demonstrate higher fungicidal effects compared to fluconazole. Analysis performed with fluorescence and scanning electron microscopy as well as flow cytometry indicated the cell membrane as a molecular target of synthesized conjugates. An important advantage of FLCpOH-TP10-NH₂ and FLCpOH-TP10-7-NH₂ is their low cytotoxicity. The IC₉₀ value for the human cells after 72 h treatment was comparable to the MIC₅₀ value after 24 h treatment for most strains of C. albicans. In reported conjugates, FLC was linked to the peptide by its hydroxyl group. It is worth noting that conjugation of FLC by the nitrogen atom of the triazole ring led to practically inactive compounds. Two compounds produced by us and reported herein appear to be potential candidates for novel antifungal agents.

Potential of cell-penetrating peptides (CPPs) in delivery of antiviral therapeutics and vaccines

Viral infections are a great threat to human health. Currently, there are no effective vaccines and antiviral drugs against the majority of viral diseases, suggesting the need to develop novel and effective antiviral agents. Since the intracellular delivery of antiviral agents, particularly the impermeable molecules, such as peptides, proteins, and nucleic acids, are essential to exert their therapeutic effects, using a delivery system is highly required. Among various delivery systems, cell-penetrating peptides (CPPs), a group of short peptides with the unique ability of crossing cell membrane, offer great potential for the intracellular delivery of various biologically active cargoes. The results of numerous in vitro and in vivo studies with CPP conjugates demonstrate their promise as therapeutic agents in various medical fields including antiviral therapy. The CPP-mediated delivery of various antiviral agents including peptides, proteins, nucleic acids, and nanocarriers have been associated with therapeutic efficacy both in vitro and in vivo. This review describes various aspects of viruses including their biology, pathogenesis, and therapy and briefly discusses the concept of CPP and its potential in drug delivery. Particularly, it will highlight a variety of CPP applications in the management of viral infections.

Can Immobilized Artificial Membrane Chromatography Support the Characterization of Antimicrobial Peptide Origin Derivatives?

The emergence and spread of multiple drug-resistant bacteria strains caused the development of new antibiotics to be one of the most important challenges of medicinal chemistry. Despite many efforts, the commercial availability of peptide-based antimicrobials is still limited. The presented study aims to explain that immobilized artificial membrane chromatography can support the characterization of antimicrobial peptides. Consequently, the chromatographic experiments of three groups of related peptide substances: (i) short cationic lipopeptides, (ii) citropin analogs, and (iii) conjugates of ciprofloxacin and levofloxacin, with a cell-penetrating peptide were discussed. In light of the discussion of the mechanisms of action of these compounds, the obtained results were interpreted.

The antibacterial activity of fluoroquinolone derivatives: An update (2018-2021)

Bacterial infection is amongst the most common diseases in community and hospital settings. Fluoroquinolones, exerting the antibacterial activity through binding to type II bacterial topoisomerase enzymes, DNA gyrase and topoisomerase IV, are mainstays of chemotherapy. At present, fluoroquinolones are the most valuable antibacterial agents used popularly. However, the emergence of more virulent and resistant pathogens by the development of either mutated DNA-binding proteins or efflux pump mechanism for fluoroquinolones results in an urgent demand to develop new fluoroquinolones to withstand the drug resistance and to obtain a broader spectrum of activity. This review aims to outline the recent advances of fluoroquinolone derivatives with antibacterial potential and to summarize the structure-activity relationship (SAR) so as to provide an insight for rational design of more active candidates, covering articles published between January 2018 and June 2021.

Cell-Penetrating Peptides and Transportan

In the most recent 25–30 years, multiple novel mechanisms and applications of cell-penetrating peptides (CPP) have been demonstrated, leading to novel drug delivery systems. In this review, I present a brief introduction to the CPP area with selected recent achievements. This is followed by a nostalgic journey into the research in my own laboratories, which lead to multiple CPPs, starting from transportan and paving a way to CPP-based therapeutic developments in the delivery of bio-functional materials, such as peptides, proteins, vaccines, oligonucleotides and small molecules, etc.

Model Amphipathic Peptide Coupled with Tacrine to Improve Its Antiproliferative Activity

Drug repurposing and drug combination are two strategies that have been widely used to overcome the traditional development of new anticancer drugs. Several FDA-approved drugs for other indications have been tested and have demonstrated beneficial anticancer effects. In this connection, our research group recently reported that Tacrine, used to treat Alzheimer's Disease, inhibits the growth of breast cancer MCF-7 cells both alone and in combination with a reference drug. In this view, we have now coupled Tacrine with the model amphipathic cell-penetrating peptide (CPP) MAP, to ascertain whether coupling of the CPP might enhance the drug's antiproliferative properties. To this end, we synthesized MAP through solid-phase peptide synthesis, coupled it with Tacrine, and made a comparative evaluation of the parent drug, peptide, and the conjugate regarding their permeability across the blood-brain barrier (BBB), ability to inhibit acetylcholinesterase (AChE) in vitro, and antiproliferative activity on cancer cells. Both MAP and its Tacrine conjugate were highly toxic to MCF-7 and SH-SY5Y cells. In turn, BBB-permeability studies were inconclusive, and conjugation to the CPP led to a considerable loss of Tacrine function as an AChE inhibitor. Nonetheless, this work reinforces the potential of repurposing Tacrine for cancer and enhances the antiproliferative activity of this drug through its conjugation to a CPP.

Insights into the Membranolytic Activity of Antimalarial Drug-Cell Penetrating Peptide Conjugates

Conjugation of TP10, a cell-penetrating peptide with intrinsic antimalarial activity, to the well-known antimalarial drugs chloroquine and primaquine has been previously shown to enhance the peptide's action against, respectively, blood- and liver-stage malaria parasites. Yet, this was achieved at the cost of a significant increase in haemolytic activity, as fluorescence microscopy and flow cytometry studies showed the conjugates to be more haemolytic for non-infected than for Plasmodium-infected red blood cells. To gain further insight into how these conjugates distinctively bind, and likely disrupt, membranes of both Plasmodium-infected and non-infected erythrocytes, we used dynamic light scattering and surface plasmon resonance to study the interactions of two representative conjugates and their parent compounds with lipid model membranes. Results obtained are herein reported and confirm that a strong membrane-disruptive character underlies the haemolytic properties of these conjugates, thus hampering their ability to exert selective antimalarial action.