In Vitro Degradation Behavior of Microspheres Based on Cross-Linked Dextran

Abstract

The aim of this study was to investigate the in vitro degradation of hydroxyl ethyl methacrylated dextran (dex-HEMA) microspheres. Dextran microspheres were incubated in phosphate buffer pH 7.4 at 37°C, and the dry mass, mechanical strength, and chemical composition of the microspheres were monitored in time. The amount and nature of the formed degradation products were established for microspheres with different cross-link densities by FT-IR (Fourier transformed infrared spectroscopy), NMR, mass spectrometry, SEC analysis, and XPS (X-ray photoelectron microscopy). The dex-HEMA microspheres DS 12 (degree of HEMA substitution; the number of HEMA groups per 100 glucose units) incubated at pH 7.4 and 37°C showed a continuous mass loss, leaving after 6 months a residue of about 10% (w/w) of water-insoluble products. NMR, mass spectrometry, and SEC showed that the water-soluble degradation products consisted of dextran, low molecular weight pHEMA (M n ≈ 15 kg/mol), and small amounts of unreacted HEMA and HEMA-DMAP (intermediate reaction product of the Baylis-Hillman reaction of HEMA with DMAP (4-dimethyl aminopyridine)). Microscopy revealed that the waterinsoluble residue consisted of particles with shape and size similar to that of nondegraded microspheres. However, these particles had lost their mechanical strength as evidenced from micromanipulation experiments. FT-IR and XPS (X-ray photoelectron microscopy) revealed that these particles consisted of pHEMA, of which a small fraction was soluble in methanol (M n ranging between 27 and 82 kg/mol). The insoluble material likely consisted of lightly cross-linked pHEMA. In conclusion, in vitro degradation of dex-HEMA microspheres results in the formation of water-soluble degradation products (mainly dextran), leaving a small water-insoluble residue mainly consisting of pHEMA.

Self‐Exploding Beads Releasing Microcarriers

“…DMAEMA oligomers are generated as degradation products, [28,30,31] which increase the inner (osmotic) pressure in the LbL coated gel beads. Figure 3 shows the behavior of the LbL coated gel beads containing (A) nondissolved and (B) dissolved CaCO 3 cores upon adding NaOH.…”

Heterogeneous and homogeneous structure dextran–poly(methacrylic acid) interpenetrating network hydrogels: synthesis and an application study

“…Sometimes the erosion of hydrogels chemically or enzymatically may be useful and they have been designed accordingly. These hydrogels undergo weight loss continuously before reaching their equilibrium swelling , . To investigate the chemical resistance of INHs prepared in this study in acidic, basic and water media, swelling studies were carried out at ambient temperature.…”

Structural Evolution and Copper‐Ion Release Behavior of Cu‐pHEMA Hybrids Synthesized In Situ

“…1) is characterized by stretching-band peaks at 1723 cm À1 [n (C¼O)] and 1158 cm À1 [n (CÀO)], and a bending-mode peak at 1020 cm À1 [d (CÀOH)]. [13,14] The FTIR-ATR spectrum of the Cu(II)-pHEMA hybrid reveals a characteristic peak over the range of $1630-1650 cm À1 and becomes more pronounced in intensity when increasing both the copper and water concentrations upon polymerization. This indicates that the water molecules coordinated with the copper ions forming a coordinated complex with hydrogen bonds, CuÀ(OH), showing a HOH vibration mode at 1647 cm À1 .…”