Attachment of alginate microcapsules onto plasma‐treated PDMS sheet for retrieval after transplantation

Abstract

Although transplantation of microencapsulated islets has been proposed as a therapy for the treatment of diabetes mellitus, limited retrievability of the cells has impeded its medical usage. To achieve retrieval of microencapsulated islets, capsules were attached to polydimethylsiloxane (PDMS) with a biocompatible adhesive. Because the hydrophobic nature of the PDMS surface prevents attachment, surface modification is essential. Alginate microcapsules were attached to modified PDMS sheets, and the mechanical stability of the resulting constructs was determined. Acrylic acid (AA) and acrylamide (AM) mixtures were grafted on the surfaces of PDMS sheets using a two-step oxygen plasma treatment (TSPT). TSPT-PDMS was characterized according to water contact angle and zeta-potential measurements. The contact angle was altered by changing the ratio of AM to AA to generate hydrophilic surface. Evaluation of the surface charge at pH 2, 7, and 12 confirmed the presence of polar groups on the modified surface. Microcapsules were attached to TSPT-PDMS using Histoacryl® and shown to be in a monolayered and half-exposed state. The shear stress resistance of alginate capsules attached to the PDMS sheet indicates the possibility of transplantation of encapsulated cells without scattering in vivo. This method is applicable to retrieve microencapsulated porcine islets when required.

Treatment of diabetes with encapsulated pig islets: an update on current developments

“…Their primary drawback is that it is difficult to remove them completely, especially if there is pericapsular fibrotic overgrowth (PFO) after implantation. Nevertheless, a novel method, attachment of microcapsules to a plasma-treated polydimethylsiloxane (PDMS) sheet, appears to be applicable for retrieving microencapsulated pig islets when required (Shin et al, 2013).…”

Application of Fragrance Microcapsules onto Cotton Fabric after Treatment with Oxygen and Nitrogen Plasma

“…A major problem associated with the application of microcapsules on textiles is the loss of textile functionality after a few wash cycles, even if binders are used in the application. Factors that influence the increase in wash resistance are the use of acrylic binders, proper curing conditions, and plasma pretreatment [11][12][13][14][15][16][17][18][19]. The advantage of plasma pretreatment is that it is a dry process that enables an introduction of functional groups on fibers and polymers in an environmentally friendly manner.…”

“…All these requirements can be accomplished by using a low-pressure plasma that would properly activate the surface, but it would also make it possible to treat materials that may be strongly affected or even destroyed by high temperatures [26][27][28][29][30][31][32][33][34]. Previously published research on improving the adsorption or adhesion of microcapsules using plasma has mainly focused on atmospheric dielectric barrier discharge (DBD) air plasma on cotton/polyester, wool and natural cork [13,15,18], atmospheric air corona plasma on bamboo [16], and low-pressure oxygen plasma on polydimethylsiloxane [17]. The improved adsorption of crosslinkers and phase change materials on plasma-treated materials was attributed to the increased wettability and surface energy, either due to the higher plasma dosage (in W•min/m 2 ) or the power of the plasma reactor (in W).…”

Progress and challenges in macroencapsulation approaches for type 1 diabetes (T1D) treatment: Cells, biomaterials, and devices

“…In particular, Calafiore’s Minimal Volume Capsules which are small alginate micro-capsules with 300–400 µm in diameter were implanted intraperitoneally in patients under echography guidance and local anesthesia and showed clinical relevance with reduced exogenous insulin requirements (Basta et al, 2011b; Calafiore et al, 2006a, c). The large surface area to volume ratio is advantageous for mass transport in microcapsules; however, limitations of this technology include the need for a large transplantation site that accommodates the necessary number of capsules, a favorable microvascular bed that provides immediate nutrient access, difficulty in microcapsule removal if required, and insufficient long-term survival rates for functional islets to adequately address the daily insulin requirement (Khanna et al, 2010; Levesque et al, 1992; Moya et al, 2010; Shin et al, 2013). Though notable applications of microcapsules have been attempted in large animals (Elliott et al, 2005; Wang et al, 1997) and human subjects (Basta et al, 2011a; Calafiore et al, 2006b; Elliott et al, 2007; Limited, 2012; Soon-Shiong, 1999; Tuch et al, 2009), the challenges such as cell sources, implant location, mass transfer, and vascularization remain unsolved.…”