Formulation of sustained release aqueous Zn-hirudin suspensions

Zn2+-triggered self-assembly of Gonadorelin [6-D-Phe] to produce nanostructures and fibrils

A synthetic derivative, GnRH [6-D-Phe], stable against enzymatic degradation, self-assembles and forms nanostructures and fibrils upon a pH shift in the presence of different concentrations of Zn²⁺in vitro. Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR–FTIR) revealed the existence of higher order assembly of Zn²⁺: GnRH [6-D-Phe]. Nuclear Magnetic Resonance spectroscopy (NMR) indicated a weak interaction between Zn²⁺ and GnRH [6-D-Phe]. Atomic Force Microscopy (AFM) showed the existence of GnRH [6-D-Phe] oligomers and fibrils. Molecular Dynamic (MD) simulation of the 10:1 Zn²⁺: GnRH [6-D-Phe] explored the interaction and dimerization processes. In contrast to already existing short peptide fibrils, GnRH [6-D-Phe] nanostructures and fibrils form in a Tris-buffered pH environment in a controlled manner through a temperature reduction and a pH shift. The lyophilized Zn²⁺: GnRH [6-D-Phe] assembly was tested as a platform for the sustained delivery of GnRH [6-D-Phe] and incorporated into two different oil vehicle matrices. The in vitro release was slow and continuous over 14 days and not influenced by the oil matrix.

Metal ions guided self-assembly of therapeutic proteins for controllable release: from random to ordered aggregation

PURPOSE

To make a comparative study on sustained delivery performance of rhIFN with random amorphous and spherical crystal-like ordered self-assemblies.

METHODS

The rhIFN self-assemblies were identified in batch crystallization mode. Physico-chemical characteristics were compared, including morphology, XRD, FTIR, CD, biological potency, the dissolution behaviors in vitro and plasma pharmacokinetics in vivo. Moreover, molecular simulation was performed to better understand their binding site and mode.

RESULTS

Here, we suggest that random amorphous and spherical ordered self-assemblies allow for long action without new molecular entities generation or carriers employed. By manipulating supersaturation, the ordered aggregates were self-organized at high concentration of Zn(II) (>100 mM) in pH 5.5-6.0, which was the first time that spherical semi-crystals of rhIFN can act as a depot source for the sustained delivery of biologically active proteins. The secondary structure and biological potency of rhIFN were unchanged after aggregation. Compared with that of the native rhIFN, both self-assemblies exhibited slower absorption and extended elimination profiles after s.c. administration, which were characterized as 4.75 ± 0.82 h and 10.58 ± 1.86 h of terminal half-life for random amorphous and spherical ordered self-assemblies, respectively.

CONCLUSIONS

The work described here demonstrates the possibility of self-assemblies of biomacromolecules for controllable release application of therapeutic proteins.

Zinc-leuprolide complex: preparation, physicochemical characterization and release behaviour from in situ forming implant

Leuprolide acetate (LA) has been accepted as treatment for prostatic cancer and is currently also being evaluated in phase II clinical trials for the treatment of Alzheimer's disease. In this study, the zinc complex of leuprolide was prepared and its structure determined by Fourier-transform infrared (FTIR), differential scanning calorimetry (DSC), UV, X-ray diffraction (XRD), atomic absorption spectroscopy, elemental analysis, and compared with these parameters for leuorolide acetate. Also, the in vitro release profile of leuprolide and its complex form in situ forming implant (ISFI) in comparison to a commercial formulation (Eligard) was investigated. These studies indicate that the zinc complex can be effectively synthesized and influenced on tri-phasic pattern after burst release of LA from the ISFI and shifts this trend to a continuous release profile. Non-linear regression test confirmed this transformation as a zero-order release profile as well.