Sustained intrathecal delivery of amphotericin B using an injectable and biodegradable thermogel

Figures & data

Figure 1. Characterization of PLGA–PEG–PLGA triblock copolymer. (A) The structure of PLGA-PEG-PLGA triblock copolymer. (B) The ¹H NMR spectrum of PLGA–PEG–PLGA triblock copolymer in CDCl3. (C) GPC spectra of PLGA–PEG–PLGA triblock copolymer.

Table 1. Characterization of PLGA–PEG–PLGA triblock copolymer.

Sample	Mn^a	PEG Mn^b	LA/GA (mol/mol)^a	Mn^c	(Mw/Mn)^c
PLGA-PEG-PLGA	1790-1500-1790	1500	2.2	5720	1.28

^aMn of PLGA blocks was calculated via ¹H NMR. ^bMn of PEG block was provided by Aldrich. ^cMeasured by GPC.

Figure 2. Characterization of sol-gel transition. (A) Phase diagram of PLGA–PEG–PLGA triblock copolymer aqueous solution (25 wt%). (B) The storage modulus G′ and loss modulus G″ of copolymer aqueous solution (25 wt%) as a function of temperature. (C) The storage modulus G′ and loss modulus G″ of copolymer aqueous solution (25 wt%) as a function of temperature with different AMB loading. (D) The change of blank gel (above) and AMB in the gel (below) with the temperature rise from room temperature to 37 °C.

Figure 3. Cumulative release profiles of AMB in gel with specific concentrations in PBS at 37 °C. The concentration of the polymer was kept at 25 wt% (n = 3).

Table 2. First-order kinetic assessment of the in vitro release data.

AMB concentration (mg/mL)	K	M∞	R^2
2	0.0567	102.7	0.9985
4	0.0652	85.9	0.9877
8	0.0679	72.4	0.9944

Table 3. Tarlov’s score within 7 days after intrathecal administration in rats.

Day	Blank gel (n = 8)	NS (n = 8)	AMB solution (n = 18)	AMB in gel (n = 18)	p^a
Before dosing	16 ± 0	16 ± 0	16 ± 0	16 ± 0	<.05
Day 1	16 ± 0	16 ± 0	6.11 ± 6.01	14.06 ± 3.04	<.05
Day 2	16 ± 0	16 ± 0	5.50 ± 6.11	15.61 ± 0.78	<.05
Day 3	16 ± 0	16 ± 0	5.56 ± 6.31	16 ± 0	<.05
Day 4	16 ± 0	16 ± 0	4.67 ± 6.47	16 ± 0	<.05
Day 5	16 ± 0	16 ± 0	4.89 ± 6.66	15.11 ± 3.77	<.05
Day 6	16 ± 0	16 ± 0	4.61 ± 6.94	15.11 ± 3.77	<.05
Day 7	16 ± 0	16 ± 0	4.28 ± 7.11	15.11 ± 3.77	<.05

^ap values were the result of Mann-Whitney U test in AMB solution group and AMB in gel group.

Figure 4. Toxicology study in rats. (A) The survival rate of intrathecal injection of AMB in gel and AMB solution in rats. (p < .05; n = 18) (B) H & E staining of the spinal cord on the 7th day after intrathecal injection of AMB in gel, AMB solution, blank gel, and Normal Saline.

Figure 5. Therapeutic effect in rats. (a) The count of CSF on the 14th day after modeling. (b) The count of cerebrospinal fluid culture on the 21st day after modeling. (B) Latex agglutination test of CSF on the 14th and 21st days after modeling. **p < .05; (n = 6).