Synthetic gel against transmission of HIV-1 and HSV-2

In a recent study published in advanced science In the scientific journal, researchers evaluated the effectiveness of synthetic mucin gel in inhibiting transmission of human immunodeficiency virus-1 (HIV-1) and herpes simplex virus-2 (HSV-2).

Studies have shown that SARS-CoV-2 infection can be effectively prevented by mucin in a glycan-dependent manner. In addition, myosin-rich synthetic mucus biomaterials 5B (MUC5B) are more successful in containing influenza A infection than MUC5AC. In general, mucins and mucin-produced substances have been shown to contribute significantly to the prevention of viral infection. Mucus contains mucin and viral inhibitors, which can attach to viruses and prevent them from infecting epithelial cells and spreading.

Synthesis of BSM Derivatives

In this study, researchers used different types of cells, including primary immune cells, to determine whether bovine submandibular gels (BSM) had “mucus-like” functions in preventing HIV-1 and HSV-2.

The team effectively incorporated aldehydes or hydrazides into the BSM molecules. When added to a solution, the aldehydes and hydrazides from BSM can create dynamic covalent hydrazone bonds, culminating in the creation of BSM gels. To produce the BSM derivatives, the coupling chemistry of dimethylamino-morpholino-carbinium hexafluorophosphate (COMU) with N,N-diisopropylethylamine (DIPEA) was used. The impeded base was a proton scavenger rather than competing with the amine as a nucleophilic in the presence of DIPEA due to the nucleophilic substitution between amines and activated acids.

The researchers initially added 3-amino-1,2-propanediol to the active carboxyl groups of BSM to create BSM cis-diol derivatives, which were then subjected to cyclic oxidation to create BSM aldehyde derivatives. In contrast to neighboring diolates on glycosaminoglycans that have a transient geometry, the flexible neighboring diols on the 3-amino-1,2-propanediol residue enabled selective and efficient oxidation, while preserving the original structure.

As amide I peak at 1647 cm^-1 Converted to 1637 cm^-1 (not BSM adjusted) at 1534 cm^-1 Converted to 1542 cm^-1 (Non-modified BSM) Compared with BSM cis-diol derivatives, the attenuated total reflection–Fourier transform infrared (ATR-FTIR) spectra of BSM-aldehyde derivatives were consistent with that of BSM cis-diol derivatives. Periodic acid tests were used to validate the reagent-based Schiff synthesis of BSM-aldehyde derivatives.

Using the cross-linking chemistry of carbodihydrazide (CDH)-hydrazone, BSM gels were produced. Compared with BSM aldehyde and BSM hydrazide derivatives, BSM gels revealed two additional peaks at 798 cm.^-1 and 1260 cm^-1. In addition, for BSM gels, two peaks are specific to hydrazide at 3,226 cm^-1 and 3317 cm^-1 disappeared. The data indicated consumption of hydrazide with hydrazone bond formation. Once enough pressure was applied, the bonds ruptured before they could regenerate. With the help of this chemistry, hydrogels with stress-relieving and self-healing properties have been developed.

BSM Gels Formed With Hydrazone Bonds

Using a commercial shear rheometer, the team investigated the viscoelastic properties of BSM gels such as gel behavior in a linear response system, liquefaction of gels and self-healing properties after exposure to large strains. Time-dependent scanning analyzes showed that BSM-based fixed gels were synthesized. Moreover, shortly after mixing, the modulus of elasticity (G′) reached a plateau-like state about 60 s after the material response predominance. Frequency scans subsequently verified that the gels were effectively and covalently crosslinked because no apparent frequency-dependent flexibility was observed in the tested frequency range.

Furthermore, by observing the robust stress-attenuating behavior in combination with the efficient and rapid self-healing behavior, the team demonstrated the dynamic nature of gels formed from covalent hydrazone bonds. This self-healing mechanism allowed the system to restore 85% to 13% of its previous rigidity as well as to qualitatively restore the gel state.

Dynamic or non-covalent covalent bonding can produce self-healing gels. Delayed dynamic equilibrium gels are more stable due to the use of dynamic covalent bonds. However, the rapid self-healing behavior of the gel revealed a rapid dynamic equilibrium in the dynamic covalent bonds of the CDH-hydrazone-producing BSM gel.

Protective efficacy of BSM gels against HIV-1 and HSV-2 infection

The team evaluated whether synthetic BSM gel could mimic the protective role against viral infection. This was determined by comparing in the laboratory Protective efficacy of BSM gels, BSM solutions and hydroxyethyl cellulose (HEC). Due to the shear-thinning properties and modulus of elasticity comparable with BSM synthetic gels, 2% HEC gels were used.

Compared to BSM solutions alone, BSM gels have improved prevention effectiveness In the current study against HIV-1 CCR5 infection of the TZM.bl cell line. Human peripheral blood-derived mononuclear cells (hPBMCs) obtained from healthy donors showed that BSM gels had significantly higher protective efficacy than BSM solutions.

Overall, the study results showed that the gels suppressed HIV-1 and HSV-2 infection in immune and epithelial cells by about 70% and 80%, respectively. Altogether, the team has created a gel-based lubricant with great potential for application in the prevention of people exposed to HIV-1 and/or HSV-2.