Controlled Delivery Achieved with Bi‐Layer Matrix Devices Produced by Co‐Injection Moulding

Abstract

The aim of this study was to design new soy protein-based bi-layered co-injection moulded matrix systems aimed to achieve controlled drug delivery. The devices consisted of a drug-free outer layer (skin) and a drug-containing core. The systems overcame the inherent disadvantage of non-linear release associated with diffusion-controlled single-layer matrix devices by providing additional releasing area with time to compensate for the decreasing release rate. As expected, the bi-layer devices presented a significant decrease in drug release rate when compared with a correspondent single layer matrix system. The skin thickness and the degree of crosslinking of the core appeared to be very important tools to tailor the release patterns. Furthermore, due to the amphoteric nature of the soy protein, the developed devices evidenced a pH-dependent behaviour. The mechanisms of drug release were also elucidated at two different pH values: i) pH 5.0, near the isoelectric point of soy (low matrix solubility); and ii) pH 7.4, physiological pH (high matrix solubility). Consequently, changing the release medium from pH 5.0 to pH 7.4 after two hours, led to an abrupt increase in drug release and the devices presented a typical controlled drug delivery profile: slow release/fast release. These evidences may provide for the development of individual systems with different release onsets that in combination may exhibit drug releases at predetermined times in a pre-programmed way. Another possibility is the production of three-layer devices presenting bimodal release profiles (fast release/slow release/fast release) by similar technologies. Scanning electron micrograph of a developed bi-layer device.

Materials in particulate form for tissue engineering. 1. Basic concepts

“…Regarding the release profile, strategies to control or render it more adequate for a particular application, by means of modifying parameters such as the surface (by coating, chemical modification) or creating dual-release systems (layers of materials that can incorporate different molecules) (Kim and Valentini, 1997;Vaz et al, 2004), can greatly improve the properties of several materials, and should be actively pursued. 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 …”

Alimentary ‘green’ proteins as electrospun scaffolds for skin regenerative engineering

“…The suitability of soy protein for biomedical applications has been well demonstrated (Vaz et al ., , , , ; Silva et al ., , ; Curt et al ., ; Luo et al ., ). For example, Vaz et al .…”

“…In this study we focused on electrospinning two plant‐derived natural polymers. Soy protein was selected for its potential in tissue‐engineering applications (Vaz et al ., , , , ; Silva et al ., , ; Curt et al ., ; Luo et al ., ). Soy protein isolate (SPI), commercially purified to a purity of > 90%, consists of two main fractions of protein, namely a 7 S fraction, which is pure glycinin, and an 11 S fraction, comprising mostly β ‐conglycinin as well as small quantities of γ ‐conglycinin, lipoxygenases, α ‐amylases and haemagglutinins (Nielsen, ).…”

Soybean protein films. Characterization and potential as novel delivery devices of Duddingtonia flagrans chlamydospores

“…Aldehydes such as glutaraldehyde (Caillard et al, 2008), glyoxal (Vaz et al, 2004), and 134 formaldehyde (Chen et al, 2008) film for CRD should be homogeneous, mechanically strong such it do not fracture 150 during processing or storing but sufficiently ductile to be shaped into the desired dosage 151 form, c.a. a cylinder able to potentially be administrated to the animal via an 152 esophagogastric probe to the rumen where spores would be released.…”