5. Miscellaneous excipients. Bulking agents are substances that can
prevent the effective components of the formulation from
escaping along with the water vapor and promote fixation of
the effective components in the material. Typical bulking compounds are mannitol, lactose, and gelatin. The addition of
bulking agents (easy to crystallize) into the formulation of
freeze-drying products has additional functions such as:
(1) providing adequate mechanical support for the final
Table 3
Typical surfactants used for freeze-drying of proteins [8]
Name
Tween 80
Triton X-100
Sucrose fatty acid monoester
3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS)
Hydroxypropyl-β-cyclodextrin (HP-β-CD)
Sodium dodecanesulphonate (SDS)
Brij35 Brij30
Lubrol-px
Pluronic F127
Table 4
Amino acids as protective agents for proteins [7, 8]
Name
Formula
MW (g/mol)
Tg (
C)
Proline
(CH 2 ) 3 NHCHCOOH
115.13
Glycine
CH 2 NH 2 COOH
75.07
À37
Glutamic acid
(CH 2 ) 2 NH 2 CH(COOH) 2
147.13
À17
Histidine
NHCHNCHCCH 2 CH(NH 2 )COOH
155.16
À32
Arginine
HNC(NH 2 )NH(CH 2 ) 3 CH(NH 2 )COOH
174.20
4-Hydroxyproline
NHCH 2 CH(OH)CH 2 CHCOOH
131.13
L-Serine
HOCH 2 CH(NH 2 )COOH
105.09
β-Alanine
CH 2 (NH 2 )CH 2 COOH
89.09
À65
Lysine hydrochloride
H 2 N(CH 2 ) 4 CH(NH 2 )COOH.HCl
182.65
Lysine
H 2 N(CH 2 ) 4 CH(NH 2 )COOH
146.19
Sarcosine
CH 3 NHCH 2 COOH
89.09
γ-Aminobutyric acid
H 2 NCH 2 CH 2 CH 2 COOH
103.12
688
Baolin Liu and Xinli Zhou