Conjugation of isoniazid to a zinc phthalocyanine via hydrazone linkage for pH-dependent liposomal controlled release

Engineering dynamic covalent bond-based nanosystems for delivery of antimicrobials against bacterial infections

Nanodrug delivery systems (NDDS) continue to be explored as novel strategies enhance therapy outcomes and combat microbial resistance. The need for the formulation of smart drug delivery systems for targeting infection sites calls for the engineering of responsive chemical designs such as dynamic covalent bonds (DCBs). Stimuli response due to DCBs incorporated into nanosystems are emerging as an alternative way to target infection sites, thus enhancing the delivery of antibacterial agents. This leads to the eradication of bacterial infections and the reduction of antimicrobial resistance. Incorporating DCBs on the backbone of the nanoparticles endows the systems with several properties, including self-healing, controlled disassembly, and stimuli responsiveness, which are beneficial in the delivery and release of the antimicrobial at the infection site. This review provides a comprehensive and current overview of conventional DCBs-based nanosystems, stimuli-responsive DCBs-based nanosystems, and targeted DCBs-based nanosystems that have been reported in the literature for antibacterial delivery. The review emphasizes the DCBs used in their design, the nanomaterials constructed, the drug release-triggering stimuli, and the antibacterial efficacy of the reported DCBs-based nanosystems. Additionally, the review underlines future strategies that can be used to improve the potential of DCBs-based nanosystems to treat bacterial infections and overcome antibacterial resistance.

Construction Strategy of Functionalized Liposomes and Multidimensional Application

Liposomes are widely used in the biological field due to their good biocompatibility and surface modification properties. With the development of biochemistry and material science, many liposome structures and their surface functional components have been modified and optimized one by one, pushing the liposome platform from traditional to functionalized and intelligent, which will better satisfy and expand the needs of scientific research. However, a main limiting factor effecting the efficiency of liposomes is the complicated environmental conditions in the living body. Currently, in order to overcome the above problem, functionalized liposomes have become a very promising strategy. In this paper, binding strategies of liposomes with four main functional elements, namely nucleic acids, antibodies, peptides, and stimuli-responsive motif have been summarized for the first time. In addition, based on the construction characteristics of functionalized liposomes, such as drug-carrying, targeting, long-circulating, and stimulus-responsive properties, a comprehensive overview of their features and respective research progress are presented. Finally, the paper critically presents the limitations of these functionalized liposomes in the current applications and also prospectively suggests the future development directions, aiming to accelerate realization of their industrialization.

Nanocarriers in Tuberculosis Treatment: Challenges and Delivery Strategies

The World Health Organization identifies tuberculosis (TB), caused by Mycobacterium tuberculosis, as a leading infectious killer. Although conventional treatments for TB exist, they come with challenges such as a heavy pill regimen, prolonged treatment duration, and a strict schedule, leading to multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains. The rise of MDR strains endangers future TB control. Despite these concerns, the hunt for an efficient treatment continues. One breakthrough has been the use of nanotechnology in medicines, presenting a novel approach for TB treatment. Nanocarriers, such as lipid nanoparticles, nanosuspensions, liposomes, and polymeric micelles, facilitate targeted delivery of anti-TB drugs. The benefits of nanocarriers include reduced drug doses, fewer side effects, improved drug solubility, better bioavailability, and improved patient compliance, speeding up recovery. Additionally, nanocarriers can be made even more targeted by linking them with ligands such as mannose or hyaluronic acid. This review explores these innovative TB treatments, including studies on nanocarriers containing anti-TB drugs and related patents.

Lipid-Based Nanocarriers for Neurological Disorders: A Review of the State-of-the-Art and Therapeutic Success to Date

Neurodegenerative disorders including Alzheimer's, Parkinson's, and dementia are chronic and advanced diseases that are associated with loss of neurons and other related pathologies. Furthermore, these disorders involve structural and functional defections of the blood-brain barrier (BBB). Consequently, advances in medicines and therapeutics have led to a better appreciation of various pathways associated with the development of neurodegenerative disorders, thus focusing on drug discovery and research for targeted drug therapy to the central nervous system (CNS). Although the BBB functions as a shield to prevent toxins in the blood from reaching the brain, drug delivery to the CNS is hindered by its presence. Owing to this, various formulation approaches, including the use of lipid-based nanocarriers, have been proposed to address shortcomings related to BBB permeation in CNS-targeted therapy, thus showing the potential of these carriers for translation into clinical use. Nevertheless, to date, none of these nanocarriers has been granted market authorization following the successful completion of all stages of clinical trials. While the aforementioned benefits of using lipid-based carriers underscores the need to fast-track their translational development into clinical practice, technological advances need to be initiated to achieve appropriate capacity for scale-up and the production of affordable dosage forms.

Application of Lipid-Based Nanocarriers for Antitubercular Drug Delivery: A Review

The antimicrobial drugs currently used for the management of tuberculosis (TB) exhibit poor bioavailability that necessitates prolonged treatment regimens and high dosing frequency to achieve optimal therapeutic outcomes. In addition, these agents cause severe adverse effects, as well as having detrimental interactions with other drugs used in the treatment of comorbid conditions such as HIV/AIDS. The challenges associated with the current TB regimens contribute to low levels of patient adherence and, consequently, the development of multidrug-resistant TB strains. This has led to the urgent need to develop newer drug delivery systems to improve the treatment of TB. Targeted drug delivery systems provide higher drug concentrations at the infection site, thus leading to reduced incidences of adverse effects. Lipid-based nanocarriers have proven to be effective in improving the solubility and bioavailability of antimicrobials whilst decreasing the incidence of adverse effects through targeted delivery. The potential application of lipid-based carriers such as liposomes, niosomes, solid lipid nanoparticles, nanostructured lipid carriers, nano and microemulsions, and self-emulsifying drug delivery systems for the treatment of TB is reviewed herein. The composition of the investigated lipid-based carriers, their characteristics, and their influence on bioavailability, toxicity, and sustained drug delivery are also discussed. Overall, lipid-based systems have shown great promise in anti-TB drug delivery applications. The summary of the reviewed data encourages future efforts to boost the translational development of lipid-based nanocarriers to improve TB therapy.

Development and characterization of catechin-in-cyclodextrin-in-phospholipid liposome to eradicate MRSA-mediated surgical site infection: Investigation of their anti-infective efficacy through in vitro and in vivo studies

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the prime pathogens responsible for surgical site infection (SSI). Treatment of SSI remains challenging because of resistant nature of MRSA, which is a major threat in recent years. Our previous work revealed the antibacterial potential of catechin isolated from cashewnut shell against MRSA. However, the application of catechin to treat MRSA-mediated SSI is hampered because of its poor solubility and low trans-dermal delivery. Hence, the present study focused on developing catechin-in-cyclodextrin-in-phospholipid liposome (CCPL) and evaluating its physicochemical characteristics and anti-infective efficacy through in vitro and in vivo models. Encapsulation of catechin with β-cyclodextrin and soybean lecithin was confirmed through UV-Vis spectroscopy, FTIR, and XRD techniques, while TEM imaging revealed the size of CCPL (206 nm). The CCPL displayed a higher level of water solubility (25.13%) and in vitro permeability (42.14%) compared to pure catechin. A higher level of encapsulation efficiency (98.9%) and antibacterial activity (19.8 mm of ZOI and 31.25 μg/mL of MIC) were noted in CCPL compared to the catechin/cyclodextrin complex. CCPL recorded significant and dose-dependent healing of the incision, significant reduction of bacterial count, improved epithelization, and effective prevention of inflammation in skin samples of SSI-induced Balb/c mice. Data of the present work suggest that the CCPL could be considered as a novel and potential candidate to mitigate MRSA-mediated SSI after clinical trials.

Dual pH-Responsive Macrophage-Targeted Isoniazid Glycoparticles for Intracellular Tuberculosis Therapy

Tuberculosis (TB) is a global epidemic that kills over a million people every year, particularly in low-resource communities. Mycobacterium tuberculosis, the most common bacterium that causes TB, is difficult to treat, particularly in its latent phase, in part due to its ability to survive and replicate within the host macrophage. New therapeutic approaches resulting in better tolerated and shorter antibiotic courses that target intracellular bacteria are critical to effective treatment. The development of a novel, pH-responsive, mannosylated nanoparticle, covalently linked with isoniazid, a first-line TB antibiotic, is presented. This nanoparticle drug delivery agent has increased macrophage uptake and, upon exposure to the acidic phagolysosome, releases isoniazid through hydrolysis of a hydrazone bond, and disintegrates into a linear polymer. Full antibiotic activity is shown to be retained, with mannosylated isoniazid particles being the only treatment exhibiting complete bacterial eradication of intracellular bacteria, compared to an equivalent PEGylated system and free isoniazid. Such a system, able to effectively kill intracellular mycobacteria, holds promise for improved outcomes in TB infection.

Nano-based anti-tubercular drug delivery: an emerging paradigm for improved therapeutic intervention

Tuberculosis (TB) classified as one of the most fatal contagious diseases is of prime concern globally. Mycobacterium tuberculosis is the causative agent that ingresses within the host cells. The approved conventional regimen, though the only viable option available, is unfavorably impacting the quality of life of the affected individual. Despite newer antibiotics gaining light, there is an unending demand for more therapeutic alternatives. Therefore, substantial continuous endeavors are been undertaken to come up with novel strategies to curb the disease, the stepping stone being nanotechnology. This approach is instrumental in overcoming the anomalies associated with conventional therapy owing to their intriguing attributes and leads to optimization of the therapeutic effect to a certain extent. This review focusses on the different types of nanocarrier systems that are being currently explored by the researchers for the delivery of anti-tubercular drugs, the outcomes achieved by them, and their prospects.

Synthesis and Characterization of pH-Sensitive Inulin Conjugate of Isoniazid for Monocyte-Targeted Delivery

The use of particles for monocyte-mediated delivery could be a more efficient strategy and approach to achieve intracellular targeting and delivery of antitubercular drugs to host macrophages. In this study, the potential of inulin microparticles to serve as a drug vehicle in the treatment of chronic tuberculosis using a monocytes-mediated drug targeting approach was evaluated. Isoniazid (INH) was conjugated to inulin via hydrazone linkage in order to obtain a pH-sensitive inulin-INH conjugate. The conjugate was then characterized using proton nuclear magnetic resonance (¹HNMR), Fourier transform infrared spectroscopy (FTIR) as well as in vitro, cellular uptake and intracellular Mycobacterium tuberculosis (Mtb) antibacterial efficacy. The acid-labile hydrazone linkage conferred pH sensitivity to the inulin-INH conjugate with ~95, 77 and 65% of the drug released after 5 h at pH 4.5, 5.2, and 6.0 respectively. Cellular uptake studies confirm that RAW 264.7 monocytic cells efficiently internalized the inulin conjugates into endocytic compartments through endocytosis. The intracellular efficacy studies demonstrate that the inulin conjugates possess a dose-dependent targeting effect against Mtb-infected monocytes. This was through efficient internalization and cleavage of the hydrazone bond by the acidic environment of the lysosome, which subsequently released the isoniazid intracellularly to the Mtb reservoir. These results clearly suggest that inulin conjugates can serve as a pH-sensitive intracellular drug delivery system for TB treatment.

Encapsulation of Isoniazid-conjugated Phthalocyanine-In-Cyclodextrin-In-Liposomes Using Heating Method

Liposomes are reputed colloidal vehicles that hold the promise for targeted delivery of anti-tubercular drugs (ATBDs) to alveolar macrophages that host Mycobacterium tuberculosis. However, the costly status of liposome technology, particularly due to the use of special manufacture equipment and expensive lipid materials, may preclude wider developments of therapeutic liposomes. In this study, we report efficient encapsulation of a complex system, consisting of isoniazid-hydrazone-phthalocyanine conjugate (Pc-INH) in gamma-cyclodextrin (γ-CD), in liposomes using crude soybean lecithin by means of a simple organic solvent-free method, heating method (HM). Inclusion complexation was performed in solution and solid-state, and evaluated using UV-Vis, magnetic circular dichroism, ¹H NMR, diffusion ordered spectroscopy and FT-IR. The HM-liposomes afforded good encapsulation efficiency (71%) for such a large Pc-INH/γ-CD complex (PCD) system. The stability and properties of the PCD-HM-liposomes look encouraging; with particle size 240 nm and Zeta potential −57 mV that remained unchanged upon storage at 4 °C for 5 weeks. The release study performed in different pH media revealed controlled release profiles that went up to 100% at pH 4.4, from about 40% at pH 7.4. This makes PCD-liposomes a promising system for site-specific ATBD delivery, and a good example of simple liposomal encapsulation of large hydrophobic compounds.