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Nanomaterials in Chemotherapy
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
P. K. Hashim, Anjaneyulu Dirisala
As early as 1906, As early as 1906, Nobel laureate Nobel laureate Paul Ehrlich proposed the design of a “magic bullet” to alter the drug distribution by conjugating toxic drugs to site-specific targeting antibodies, which can selectively target the cancer cells to improve therapeutic efficacy with minimal toxicity to healthy cells [7]. In 1955, the first polymer–drug conjugate was reported by von Horst Jatzkewitz [8]. In 1964, a silicone rubber (Silastic) prosthesis was demonstrated as an implantable carrier for prolonged drug therapy [9]. In the same year, liposome structure was also reported [10] followed by an exploration of its potential for drug delivery [11], which became one of the breakthroughs in the field of DDS. Since then, a myriad of nanoscale DDSs composed of various kinds of lipids encapsulated with different therapeutic agents as well as diagnostic agents together with methods for ligand functionalization have been developed [12]. In 1973, Gregory has demonstrated that the liposome could be used for anticancer drug loading [13]. In 1976, Kopf et al. reported the first polymeric micelle nanocarrier for the delivery of low molecular weight drugs [14] and in the same year, Langer et al. demonstrated the first sustained release polymer system for delivery of macromolecular drugs [15]. In 1995, Doxil® (PEGylated liposomal DOX) was approved by the FDA, the first nano-DDS for ovarian cancer, AIDS-related Kaposi’s sarcoma, and multiple myeloma [16]. A brief historical timeline of major advancements in the field of cancer nanomedicine is shown in Figure 8.1.
Methods for Casting Airways
Published in Joan Gil, Models of Lung Disease, 2020
Many different kinds of silicone rubber are available and, as with the polyester resins, it may be necessary to experiment to find one to suit a particular application. Their use for airway casting was introduced by Frank and Yoder (1966). They give very accurate reproductions, are strong, stretchable, flexible, and return to their original shape. They undergo very little volume change on setting, may be pruned by cutting, and are immiscible with water. They have the disadvantage of being rather viscous, and require either a high pressure or, preferably, a long time for injection to be completed.
A Novel Approach for Finishing Various Implants
Published in S Santhosh Kumar, Somashekhar S. Hiremath, Role of Surface Modification on Bacterial Adhesion of Bio-Implant Materials, 2020
S Santhosh Kumar, Somashekhar S. Hiremath
A viscoelastic polymer commonly used in the development of abrasive media acts as a carrier medium and carries abrasive particles. It has viscous and elastic properties that help in distributing the axial and radial force on the abrasive particles with the help of applied extrusion pressure. Some of the commonly used polymer carriers are polyborosiloxane, silicone rubber, silly putty, natural rubber, styrene butadiene rubber, butyl rubber, etc. In the present investigation, silicone rubber is selected as a viscoelastic polymer media (carrier media) because of its unique properties like wide temperature range (–101°C to 316°C), less cost compared to other synthetic rubbers (Aggarwal, 1987), good thermal conductivity, abrasion resistance, chemical stability (Shit and Shah, 2013), high tear strength and elongation, good processability and not sticky to surfaces, which are the basic requirements for abrasive media. Also, it is one of the most widely used in manufacturing components of aerospace, aviation, medical, semiconductor, and automotive industries. The literature shows that silicone rubber is the best suitable abrasive media, and it has compatibility with a wide range of abrasive particles and is also mechanically stable. The selected type of silicone rubber is Bluesil HCR 1940 LA2, and its physical properties are listed in Table 4.8.
Haemodialysis catheters – a review of design and function
Published in Expert Review of Medical Devices, 2022
HD catheters are generally manufactured from semi-rigid polymer materials such as polyurethane or polyvinyl, or from soft flexible polymers like silicone-plastic or medical-grade silicone. Firm catheters are easier to insert percutaneously, are resistant to kinking, and may be of smaller gauge because of the ability to manufacture the device with thinner walls and hence a relatively large inner lumen. The drawback of such stiffness, however, is greater mechanical trauma. Inflexible polymers of prototypical catheters were superseded by pliable silicone rubber and silicone plastic because they are less traumatizing and less thrombogenic [3], and therefore better-suited for long-term use. Currently, most catheter products are again composed of polyurethane; modern polyurethane substances, such as polyurethane carbonate, are thermosensitive, meaning they soften with increased temperature after insertion, and are more biocompatible [11].
Catechol-modified chitosan hydrogel containing PLGA microspheres loaded with triclosan and chlorhexidine: a sustained-release antibacterial system for urinary catheters
Published in Pharmaceutical Development and Technology, 2022
Chengxiong Lin, Zhengyu Huang, Tingting Wu, Weikang Xu, Ruifang Zhao, Xinting Zhou, Zhibiao Xu
As the base material, the silicone rubber was cleaned for 15 min with steady shaking in a 1:1 mixture of ammonia (33% v/v) and hydrogen peroxide (30% v/v), then rinsed with RO and dried with nitrogen gas (Milo et al. 2016). The silicone rubber was then submerged in dopamine hydrochloride solution (2 mg/ml) and shaken for 3 h. All samples were sonicated for 15 min in DO and dried with nitrogen gas again. Chi-C was dissolved in PBS buffer at a concentration of 2 mg/ml, and then drug-carrying microspheres were added at a 40:1 mass ratio to the Chi-C solution. For a dopamine-soaked silicone rubber sample (100 mm × 10 mm), 2.05 g Chi-C/microsphere composite hydrogel was initially coated on the surface of silicon rubber and dried with nitrogen gas. After preparation, they were immersed in Chi-C solution (2 mg/ml) again for 10 min, then washed with RO and dried with nitrogen gas. This procedure was repeated three times. Due to the difference of drugs, the samples were divided into four groups, namely group 1: 2.05 g Chi-C; group 2: 2.00 g Chi-C + 0.05 g TCS microspheres; group 3: 2.00 g Chi-C + 0.05 g CHX microspheres; group 4: 2.00 g Chi-C + 0.025 g TCS microspheres + 0.025 g CHX microspheres.
Pharmaceutical implants: classification, limitations and therapeutic applications
Published in Pharmaceutical Development and Technology, 2020
Zahra Mohtashami, Zahra Esmaili, Molood Alsadat Vakilinezhad, Ehsan Seyedjafari, Hamid Akbari Javar
Folkman and Long proposed the possibility of using a sealed segment of silicone rubber as a carrier for prolonged drug therapy after they were able to anesthetize rabbits by passing gas into the Silastic® arterio-venous shunt (Folkman et al. 1966; Hoffman 2008; Meng and Hoang 2012). In 1969, a report was released by Dzuik and Cook for ready penetration of steroidal hormone through silicon, and in the mid-1970s, Folkman and his former postdoc, Bob Langer, published an influential paper revealing that protein could be gradually released in its active form from non-degradable, hydrophobic polymer matrices (Dash and Cudworth 1998). These were the first steps of the long road of implantable drug delivery systems. The exponential growth in implant usage not only as delivery systems but also as biomedical devices in the cardiovascular disease like a heart valve or pacemaker or coronary stent, ocular and orthopedic, and aesthetics like breast reconstructions, shows their daily increasing values (Arsiwala et al. 2014; Ye et al. 2014).