Chemoenzymatic Synthesis of D-Glucitol-Based Non-Ionic Amphiphilic Architectures as Nanocarriers

Abstract

Newer non-ionic amphiphiles have been synthesized using biocompatible materials and by following a greener approach i.e., D-glucitol has been used as a template, and hydrophobic and hydrophilic segments were incorporated on it by using click chemistry. The hydrophilic segments in turn were prepared from glycerol using an immobilized Candida antarctica lipase (Novozym-435)-mediated chemoenzymatic approach. Surface tension measurements and dynamic light scattering studies reflect the self-assembling behavior of the synthesized amphiphilic architectures in the aqueous medium. The results from UV-Vis and fluorescence spectroscopy establish the encapsulation of guests in the hydrophobic core of self-assembled amphiphilic architectures. The results of 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay indicate that the amphiphiles are well tolerated by the used A549 cell lines at all tested concentrations.

Keywords: Candida antarctica lipase; D-Glucitol; click chemistry; cyto-compatible; nanocarrier; non-ionic amphiphiles.

Scheme 1

Synthesis of glucitol-3,4-acetonide-1,6-diazide and hydrophobic backbone. (i) acetone, H₂SO₄, 18 h, 30 °C; (ii) 70% CH₃COOH, 35 min, 35 °C; (iii) p-toluenesulfonyl chloride, pyridine, 4 h, −5–0 °C; (iv) NaN₃, Dimethylformamide (DMF), 70 °C, 12 h; (v) C₆H₅C≡CH, CuSO₄∙5H₂O, sodium ascorbate, THF:H₂O (3:1); (vi) 9, [Cu(PPh₃)₃]Br, N,N-diisopropylethylamine (DIPEA), Dichloromethane (DCM), 30 °C, 24 h; (vii) K₂CO_3, propargyl bromide, acetone, 50 °C, 12 h; (viii) NaH, propargyl bromide, THF, 25 °C, 12 h.

Figure 1

Proposed schematic representation of self-assembly formed by amphiphilic architectures in aqueous solution.

Scheme 2

Synthesis of glyceryl azide. (i) Novozym-435, vinyl acetate, THF, 37 °C; (ii) mesyl chloride, triethylamine, DCM, 0–25 °C, 2h; (iii) NaN₃, DMF, reflux, 12 h; (iv) K₂CO₃, EtOH, 12 h.

Scheme 3

Synthesis of triglyceryl azide. (i) 2,2-dimethoxypropane, pTSA, 12 h; (ii) mesyl chloride, triethylamine, DCM, 0–25 °C, 2h; (iii) NaN3, DMF, reflux, 12 h; (iv) Dowex-50 resin, MeOH, 50 °C, 12 h.

Scheme 4

Synthesis of methoxy polyethyleneglycol (PEG) azide. (i) mesyl chloride, triethylamine, THF, 0–25 °C, 5h; (ii) NaN₃, DMF, 30 °C, 48 h.

Scheme 5

Synthesis of amphiphilies. (i) [Cu(PPh₃)₃]Br, DIPEA, DCM/DCM:DMF (1:1), 30 °C, 72 h.

Figure 2

Plot of critical aggregation concentration (CAC) determination of amphiphile 24 using surface tension measurement.

Scheme 6

General structure of amphiphile.

Figure 3

Cryo-TEM image of amphiphile 25 showing micellar assembly (indicated by arrows) and surface contamination (indicated by white circles) at different magnification.

Scheme 7

Structure of Nile Red and Dexamethasone.

Figure 4

Emission spectra of Nile red encapsulated in the amphiphiles 21–25 in aqueous media and absorption spectra of Nile red encapsulated in the amphiphile solutions 21–25 in methanol.

Figure 5

Guest loading capacity (mmol/mol) and guest loading efficiency (mg/g) of amphiphiles 21–25 for Nile red and dexamethasone.

Figure 6

Cytotoxicity profile of amphiphiles 21–25 determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay in A549 cells 24 h post treatment. Each bar represents the mean value of three independent experiments (n = 3) measured in triplicate with SEM.