Bifunctional backbone modified squaramide dipeptides as amyloid beta (Aβ) aggregation inhibitors

Alzheimer's disease (AD) is a devastating neurodegenerative condition with complex pathophysiology. Aggregated amyloid beta (Aβ) peptide plaques and higher concentrations of bio-metals such as copper (Cu), zinc (Zn), and iron (Fe) are the most significant hallmarks of AD observed in the brains of AD patients. Therefore simultaneous inhibition of Aβ peptide aggregation and reduction of metal stress may serve as an effective therapeutic approach for treating Alzheimer's disease. A series of bifunctional dipeptides bearing squaramide backbone were synthesized and investigated for their ability to chelate metal ions and prevent Aβ peptide aggregation. Dipeptides with Valine (V) and Threonine (T) substitutions at the C-terminus exhibited preferential chelation with Cu(II), Zn(II), and Fe(III) metal ions in the presence of other metal ions. They were also found to inhibit the aggregation of Aβ peptide in-vitro. A further molecular dynamics (MD) simulation study demonstrated that these two dipeptides interact with the Aβ peptide in the hydrophobic core (KLVFF) region. Circular dichroism (CD) study revealed slight conformational change in the Aβ peptide upon the interactions with dipeptides. Apart from metal chelation and inhibition of Aβ peptide aggregation, the selected dipeptides were found to possess anti-oxidant properties. Therefore, the squaramide backbone-modified dipeptides may serve as an active bifunctional scaffold towards the development of new chemical entities for the treatment of Alzheimer's disease.

Lysine-Specific Demethylase 1 (LSD1) Inhibitors: Peptides as an Emerging Class of Therapeutics

Aberrant expression of the epigenetic regulator lysine-specific demethylase 1 (LSD1) has been associated with the incidence of many diseases, particularly cancer, and it has evolved as a promising epigenetic target over the years for treatment. The advent of LSD1 inhibitor-based clinical utility began with tranylcypromine, and it is now considered an inevitable scaffold in the search for other irreversible novel LSD1 inhibitors (IMG-7289 or bomedemstat, ORY1001 or iadademstat, ORY-2001 or vafidemstat, GSK2879552, and INCB059872). Moreover, numerous reversible inhibitors for LSD1 have been reported in the literature, including clinical candidates CC-90011 (pulrodemstat) and SP-2577 (seclidemstat). There is parallel mining for peptide-based LSD1 inhibitors, which exploits the opportunities in the LSD1 substrate binding pocket. This Review highlights the research progress on reversible and irreversible peptide/peptide-derived LSD1 inhibitors. For the first time, we comprehensively organized the peptide-based LSD1 inhibitors from the design strategy. Peptide inhibitors of LSD1 are classified as H3 peptide and SNAIL1 peptide derivatives, along with miscellaneous peptides that include naturally occurring LSD1 inhibitors.

Reactive oxygen species-responsive thymine-conjugated chitosan: Synthesis and evaluation as cryogel

Chitosan (CS) is a biodegradable, biocompatible cationic polysaccharide based natural polymer with antibacterial and anti-inflammatory properties. Hydrogels made from CS have been found their applications in wound healing, tissue regeneration and drug delivery. Although, mucoadhesive properties resulted from the polycationic nature of CS, in hydrogel form amines are engaged in interactions with water leading to decrease in mucoadhesive properties. In case of injury, presence of elevated level of reactive oxygen species (ROS) has inspired many drug delivery platform to conjugate ROS responsive linkers for on demand drug delivery. In this report we have conjugated a reactive oxygen species (ROS) responsive thioketal (TK) linker and nucleobase thymine (Thy) with CS. Cryogel from this doubly functionalized polymer CS-Thy-TK was prepared through crosslinking with sodium alginate. Inosine was loaded on the scaffold and studied for its release under oxidative condition. We anticipated that the presence of thymine shall retain the mucoadhesive nature of the CS-Thy-TK polymer in hydrogel form and when placed at the site of injury, due to the presence of excessive ROS at inflammatory condition, loaded drug shall release due to degradation of the linker. Porous cryogel scaffold was prepared via chemical crosslinking of amine functional group of chitosan with carboxylic acid containing polysaccharide sodium alginate. The cryogel was evaluated for porosity (FE-SEM), rheology, swelling, degradation, mucoadhesive properties and biocompatibility. Resulted scaffold was found to be porous with average pore size of 107 ± 23 μm, biocompatible, hemocompatible and possesses improved mucoadhesive property (mucin binding efficiency of 19.54 %) which was found to be 4 times better as compared to chitosan (4.53 %). The cumulative drug release found to be better in the presence of H₂O₂ (~90 %) when compared to that of PBS alone (~60-70 %)_. Therefore, the modified CS-Thy-TK polymer may hold potential as interesting scaffold in case of conditions associated with elevated ROS level such as injury and tumor.

Synthesis and Investigation of Backbone Modified Squaramide Dipeptide Self-Assembly

Dipeptides are minimalistic peptide building blocks that form well ordered structures through molecular self-assembly. The driving forces involved are cooperative noncovalent interactions such as π-π stacking, hydrogen bonding, and ionic as well as hydrophobic interactions. One of the most intriguing self-assembled motifs that has been extensively explored as a low molecular weight hydrogel for drug delivery, tissue engineering, imaging and techtonics, etc. is Phe-Phe (FF). The backbone of the dipeptide is very crucial for extending secondary structures in self-assembly, and any subtle change in the backbone drastically affect the molecular recognitions. The squaramide (SQ) motif has the unique advantage of hydrogen bonding which can promote the self-assembly process. In this work we have integrated the SQ unit into the dipeptide FF backbone to achieve molecular self-assembly. The resulting carbamate protected backbone modified dipeptide (BocFSAF-OH, 10) has exhibited molecular self-assembly with a fibrilar network. It formed a stable hydrogel (with CAC of 0.024 ± 0.0098 wt %) via the solvent switch method and was found to possess excellent enzymatic stability. The dipeptide and the resulting hydrogel were found to be cytocompatible. When integrated with a polysaccharide based biopolymer, e.g. sodium alginate, the resulting matrix exhibited strong hydrogel character. Therefore, the dipeptide hydrogel of 10 may find its applications in a variety of fields including drug delivery and tissue engineering.

Peptide-Chitosan Engineered Scaffolds for Biomedical Applications

Peptides are signaling epitopes that control many vital biological events. Increased specificity, synthetic feasibility with concomitant lack of toxicity, and immunogenicity make this emerging class of biomolecules suitable for different applications including therapeutics, diagnostics, and biomedical engineering. Further, chitosan, a naturally occurring linear polymer composed of d-glucosamine and N-acetyl-d-glucosamine units, possesses anti-microbial, muco-adhesive, and hemostatic properties along with excellent biocompatibility. As a result, chitosan finds application in drug/gene delivery, tissue engineering, and bioimaging. Despite these applications, chitosan demonstrates limited cell adhesion and lacks biosignaling. Therefore, peptide-chitosan hybrids have emerged as a new class of biomaterial with improved biosignaling properties and cell adhesion properties. As a result, recent studies encompass increased application of peptide-chitosan hybrids as composites or conjugates in drug delivery, cell therapy, and tissue engineering and as anti-microbial material. This review discusses the recent investigations involving chitosan-peptide materials and uncovers various aspects of these interesting hybrid materials for biomedical applications.

Bioactive role of plant stress hormone methyl jasmonate against lipopolysaccharide induced arthritis

The current investigation was carried out to screen antiarthritic potential of Methyl Jasmonate (MJ) against lipopolysaccharide (LPS) induced arthritis. Cartilage damage was induced in experimental animals by intraplantar administration of LPS (1 mg/kg) and antiarthritic effect of MJ was screened in two doses of MJ-1 (20 mg/kg), MJ-2 (40 mg/kg) by intraperitoneally administration. Indomethacin (30 mg/kg p.o.) was used as standard drug. The severity of arthritis was evaluated by assessing arthritis score, secondary lesions, motility test, stair climbing ability, and dorsal flexion pain score method. The estimation of blood cytokine tumor necrosis factor- aplha (TNF-α),interleukine (IL-2 and IL-6) and thymus/spleen index was carried out to access the severity of inflammation. Estimation of hepaticenzymatic antioxidant activity superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione peroxidase (GPx)and radiological examination was carried out on 28^th day. Results indicated that MJ showed significant reduction in severity of arthritis by decreasing arthritis score, secondary lesions where as significant increase in motility, climbing ability and flexion pain score was observed. Significant decreased in blood cytokine viz. TNF-α, IL-2, IL-6 andthymus/spleen index was observed in MJ treated animals in dose dependent manner. MJ treated animals showed significant increased and restoration of hepatic antioxidant enzymatic activityof SOD, CAT, GSH, GPx where asradiological examination indicates protective effect on joint structure as compared to LPS treated rats. These current studies conclude that MJ has protective role in arthritis.

Sono-chemical synthesis of ZnO nano-particles and their application in hydrogen sulphide gas sensing

Herein we describe synthesis of ZnO nanoparticles by using alkaline solution of ZnX2 (X = NO3, Cl) under ultrasound energy of 20 KHz. The reaction can be completed in about 1-2 hours. As prepared powders were analyzed by XRD measurement to find that the product is hexagonal phase pure ZnO. UV-Visible measurement of aq. solution showed absorption band at -365 nm and photoluminescence (PL) indicated multiple bands in visible region due to deep traps owing to high temperature sintering. The hydrophilicity can be imparted by use of a suitable polyelectrolyte. Freshly prepared samples showed good dispersion in aqueous and alcoholic medium. The thick films derived from the ZnO nano-particles showed excellent sensing for hydrogen sulphide gas.