Hydrogel Materials

Abstract

In Chap. 2, we discussed the fundamental behavior behind the release of drug molecules from matrix species in response to degradation (i.e., chemical or enzymatic), erosion (i.e., surface or bulk), and swelling (i.e., crosslinks). In the case of swellable systems, we limited our focus only to the adjustment of swelling characteristics based on changing the crosslink density, polymer molecular weight between crosslinks, and hydrophilicity. These underlying features provide information regarding the pharmacokinetics of the system; however, they provide little indication of the physical requirements for actual therapeutic applications. For example, what if a swellable system reached a point within the human body where the matrix could not sustain its own structural integrity? What would be the consequences of the system breaking apart? Could we see premature drug release [1], an inflammatory response [2], or perhaps worse, the occlusion of an artery [3]? When we use swellable systems in physiological environments, care must be taken to understand the properties, both chemical and physical, to which it will be exposed throughout its life cycle within the body.In this chapter, we will discuss aqueous swellable systems classified as hydrogels [4], and their applications as implantable [5] and injectable [6] systems. Hydrogels are a species of crosslinked, hydrophilic, polymer molecules that absorb large amounts of water (≤99 %) to form a three-dimensional network. There is a broad application base for hydrogel materials, ranging from tissue engineering scaffolds [7] to breast implants [8] to contact lenses [9] (discussed in Chap. 2, Sect. 2.3). For the purposes of our current discussion, we will focus on implantable biosensors for diabetes treatment [10] and injectable hydrogels for cartilage repair [11]. We begin

Biodegradable polymeric injectable implants for long‐term delivery of contraceptive drugs

“…An n- value of 0.5, according to the Korsmeyer-Peppas equation, also suggested Fickian diffusion for both 12.5% and 24% drug loadings 3438 . Fickian diffusion occurs due to the random molecular motion of drugs where there is a net movement from a region of high concentration to a region of lower concentration 39 . This, along with a decrease in drug release rate over time, evident from the plots of cumulative LNG release (Figure 7), can be attributed to the depletion of drug in the matrix over time, where the distance for diffusion (diffusion path length) becomes increasingly greater as the boundary between the drug matrix and the drug-depleted matrix recedes with time 40 .…”

Doxorubicin-fucoidan-gold nanoparticles composite for dual-chemo-photothermal treatment on eye tumors

“…Thus, TUNEL assay will further be conducted to detect apoptosis after the combined treatment. Since solid tumors have wider and looser blood vessels (i.e., leaky vasculature; 200 nm ∼ 1.2 µm in size depending on tumor type) than normal tissue does (<10 nm in size) [ 59 , 60 ], the current nanoparticles (116.7 ± 40.6 nm) may readily be transferred to and accumulated into the tumor due to enhanced permeability and retention (EPR) effect [ 61 ]. Intraperitoneal or intravenous injection of Dox-Fu@AuNPs will thereby be performed to identify the feasible detection of the tumor margin with PAI.…”

Exogenous Contrast Agents in Photoacoustic Imaging: An In Vivo Review for Tumor Imaging

“…They are increasingly combined with organics nanoparticles and biodegradable polymers to build a new generation of contrast agents that enhance specific parameters. In addition, their size, shape, mechanical flexibility and surface chemistry can be modified to optimize their efficacy in clinical applications [ 47 , 48 , 49 ]. Due to their in vivo high biocompatibility, fluorescent nature, and modification flexibility, Xiao et al [ 50 ] synthesized and characterized melanin carbonaceous dots (MCDs) for dual PAI and fluorescence imaging of breast cancer tumors in mice.…”