Review-SIMC 2016; 2016:e00012 ft

Science Insights Materials & Chemistry, 11 January 2016
2016: e00012
Doi: 10.15354/simc.16.re012
Biomaterials
 
Review (Narrative)
Biomedical Materials and Medicine Development
Andrew F. Murphy, PhD1,*
 
Author Affiliations
1: Division of Biology and Chemistry (DBC), The BASE, Chapel Hill, NC 27157, USA.
* Correspondence to: Dr. Andrew F. Murphy, PhD, Email: afmurphy@basehq.org.
 
Sci Insigt Met Chem. 2016;2016:e00012. doi:10.15354/simc.16.re012
 
SUMMARY

Biomedical materials or biomaterials are defined as “non-viable materials used in different medicinal devices, proposed to act together with biological systems”. Usually, biomedical materials are infrequently used as isolated materials, however, they are more regularly incorporated into implants or devices. The biological reaction to the ultimate fabricated biomedical device will finally direct its achievement or failure. Ideal biomaterial retain both the biological properties that are required to interact with cellular surroundings, as well as the chemical and physical properties needed for a preferred application, for example, biological stability and strength in the pattern of joint replacements. The development of these materials initiates with the investigation at the molecular level.■

KEYWORDS   Materials; Chemistry; Medical Science; Health

 
Biomedical materials or biomaterials are defined as “non-viable materials used in different medicinal devices, proposed to act together with biological systems” (Ratner et al., 2004). Usually, biomedical materials are infrequently used as isolated materials, however, they are more regularly incorporated into implants or devices. The biological reaction to the ultimate fabricated biomedical device will finally direct its achievement or failure (Hench, 1998). This field is rapidly growing over the past half century because via developments in materials production techniques collectively with a demanding use of engineering methods to the design of biomaterials specifically for medicinal developments. More than any other discipline of materials science, biomaterials is an interdisciplinary field, and research in this field is projected by researchers of various backgrounds for example, biologists and chemists, materials and chemical engineers, etc. Advancement in this discipline critically relies on the transference of knowledge and communication among disciplines, as well as the reliable, widespread accessibility of these materials to assist the research. Few of the furthermost promising disciplines in medicinal research, including restorative/regenerative medicine and drug delivery, are facilitated by the progress of key biomedical materials (Ratner et al., 2004). Ideal biomaterial retain both the biological properties that are required to interact with cellular surroundings, as well as the chemical and physical properties needed for a preferred application, for example, biological stability and strength in the pattern of joint replacements. The development of these materials initiates with the investigation at the molecular level (Ratner et al., 2004).
 

Cis-9-Octadecene-1-thiol

This molecule is structured to make disordered self assembled monolayers which may have a substantial impact on the fluidity of maintained lipid membranes. A cis double-bond presents a twist in the hydrophobic alkyl-chains, upsetting the packing performance as compared with saturated alkyl-thiol molecules and leading towards disordered monolayers which mimic fluid biological lipid-membranes (Rawicz et al., 2000, Silvius, 1982). These monolayers can be used as backings for unseating of model lipid-membranes on the monolayer reformed substrates (Jans et al., 2009). The terminal thiol group of the cis- 9-Octadecene-1-thiol permits for any assembly on gold surfaces (Bain et al., 1989) or functionalization through a wide-ranging variability of biological entities, such as by means of the thiol-ene chemistry or reactions with sensitive double-bonds of maleimide (Kosif et al., 2010) and acryloyl compounds (Dondoni, 2008).
 

Poly(N-isopropylacrylamide)

Tissue engineering has developed an important therapeutic entity in the management of diseased or damaged tissues and organs, for example, urinary bladders and blood vessels (Vacanti, 2001). However, key challenges that are still needed to be overcome, in exacting the building of tissues with higher cell densities and the inhibition of post transplantation inflammation. A favorable tissue-engineering method depends on the practice of cell-culture surfaces grafted with poly(N-isopropylacrylamide) (Yamada et al., 1990). The very basic clue is that cell adhesion or detachment on PNIPAM modified-substrates can be accomplished by a modest temperature switch. Cultured cells can be collected from the smart PNIPAM surfaces in the shape of a tissue like cellular monolayer/cell sheet, basically by reducing the cell-culture temperature from 37-20 °C once confluence has been succeeded. This cell-manipulation technology empowers the transplantation of cell-sheets to host tissues devoid of the usage of biodegradable polymer scaffoldings, overwhelming a key limitation of conventional tissue-engineering. Special importance is employed in the fabrication and design of modified surfaces used to acquire multi functional cell-sheets.
PNIPAM is solvable in organic solvents, for example, acetone, chloroform, methanol and many other alcohols. Similarly, it is soluble in H2O, as long as the solution is reserved sensibly cold. Heating an aqueous PNIPAM solution earlier 32 °C, the cloud point (CP) or lower critical solution temperature (LCST) suddenly transforms the clear solution into a milky-suspension. The incident is reversible: as shortly as the milky-suspension is cooled beneath 32 °C it recuperates its clarity (Schild, 1992). Heskins and Guillet (1968) published the first phase-diagram of the H2O/PNIPAM system, which they fabricated by evaluating the phase transition temperature as a function of PNIPAM concentration (Heskins and Guillet, 1968). Almost at the same time period, it became well-known that cross-linked PNIPAM networks (e.g. gels) also display interested properties in water, for example, they are extremely swollen in the cold water, but shrink as they are heated over 32 °C. As in case of PNIPAM solutions, the performance of the gels is adjustable, for example, swelling back to their original volume as they are cooled underneath 32 °C. Hundreds of swelling or shrinking cycles can be executed through a gel, with no signal of material exhaustion. This unfamiliar occurrence was observed by Allan S. Hoffmann, who was amongst the first to practice the temperature prompted phase transition of the PNIPAM byproducts as a prompt to regulate phenomena related to biomedical uses, for example, the liberation of a drug or dye (Ding et al., 1996). This ground-breaking work placed the basis of the discipline of reactive systems, that lasts to attract the fancy of researchers (Stuart et al., 2010). The heat induced phase-transition showed by the aqueous PNIPAM solutions is not distinctive, as several other water soluble polymers have cloud-points. Nevertheless, PNIPAM leftovers the forerunner for biomedical uses due to the sharpness of transition, a transition-temperature that is adjacent to the body temperature, the strength of the polymer himself, and the accessibility of evidence on the polymer and its phase-transition. At the molecular-level, the macroscopic phase transition relates to the lack of moisture of the PNIPAM chains and consequent collapse of the discarded hydrophobic chains into compacted globules that cumulative into bigger mesoglobules (Okada and Tanaka, 2005). Though, the phase-transition is not only reliant on the temperature induced molecular reorganization. Numerous other reasons can disturb the CP of PNIPAM, even though the effects are not all the times predictable.
 

PEG Based Hydrogels

Many biomedical material scaffoldings established for tissue-engineering presentations are comparatively identical and deficit the organization and complexity of the Invivo cellular micro-environment. However, these consistent scaffoldings have permitted significant development in accepting the cellular responses to their micro-environment, interpreting the dynamic affiliation among biomaterial properties and their impact on biological purpose may perhaps necessitate further spatially and temporally difficult scaffolds. Hence, several patterning techniques have been established to permit control overhead the performance of biomechanical and biochemical clues in both space and time. To discover the cellular responses to forceful modifications in 3D-matrix properties, scaffolding alterations must be executed in a method well-suited with the conservation of cell-viability. As a result, several of the patterning methods useful to glass and silicon substrates cannot be enthusiastically transitioned to these applications. Although these techniques will be debated in the perspective of poly ethylene glycol (PEG) based hydrogels, they can officially be useful to any optically translucent, photo-active substrate. Hydrogels are a class of biomedical material scaffoldings, which have been extensively used in multifaceted device construction, drug liberation and tissue-engineering. PEG based hydrogels, specifically, have recognized exceptionally useful for tissue-engineering applications. PEG is Food and Drug Administration (FDA) ratified for a range of applications and shows extraordinary bio-compatibility and minute or no immunogenicity. Further, PEG based hydrogels exhibit tunable mechanical properties in the series suitable to soft-tissue redevelopment. Notably for patterning applications, PEG based hydrogels are basically resistant to cell adhesion and protein adsorption, therefore providing biological “blank slates” upon which anticipated bio functionality can be fabricated (Gombotz et al., 1991). To produce PEG hydrogels, separate PEG chains that have been functionalized with two or more cross-linkable groups, for example acrylates, are liquefied in aqueous solution, diversified with suitable photoinitiator such as 2,2 dimethoxy-2-phenyl acetophenone, and visible to ultraviolet or visible light (West and Hubbell, 1995). The acrylate groups cross link through free-radical polymerization to formulate an unsolvable hydrogel system. These polymerization procedures need between 1 to 10 minutes of radiance, dependent on the photoinitiator and the intensity of light source, and can be directed under mild circumstances that permit preservation of cell viability. Though the polymerization procedure is fast, its well-organized quenching by oxygen and other free-radicals is supposed to preserve the spatial-localization of the light induced polymerization that is crucial to high-fidelity pattern development.
 

Stent

A stent is a mesh like tube that helps the blood vessels from the inside to retain them open afterwards interventional treatment with a balloon and a catheter (Hench and Polak, 2002). Occasionally a stent reasons restenosis; in this situation cells mount up inside the inserted stent as a consequence of inflammation owing to an immune reaction. There are generally two solutions for restenosis. First is application of medicines to the stent to reduce the buildup of cells. The second is the exclusion by autonomous withdrawal of a stent after its required period of usage.
 
Bioabsorbable Stents
In common, there are two types of bioabsorbale materials. The first one is prepared of polymer, poly-L-lactic acid (PLLA) and the second is made of metal. The PLLA stent by the Kyoto Medical Planning Co. Ltd., entitled an IGAKI-TAMAI stent, will be degraded into water and carbon dioxide, and be absorbed next 2 to 3 years afterwards implantation (Nishio et al., 2012). Benefits of polymer stents above metal stents are the applicability to the patients with metal-allergies and the informal mixing of medicines into these stents. The corporation Sentan Iryo Kaihatsu manufactured a stent made of a magnesium-calcium alloy, prepared from essential metals required for the human body. It will progressively dissolve in the body due to corrosion. The retaining period in the body can be controlled by the ratio of calcium in the alloy. Metal stents are outstanding in plasticity, strength and recoil avoidance. Professor Egashira working with Sentan Iryo Kaihatsu to build drug eluting stents (DES) that will entirely wane from the vessels after a definite critical period.
 
Drug Eluting Stents (DES)
Professor Kensuke Egashira of Faculty of Medical Sciences of Kyushu University prepared a stent that delivers nucleic medicine to avoid restenosis. This is called a drug eluting stent (DES). He practices the 7ND gene, which contains the manifestation of MCP, a key factor of swelling. Nanoparticles of this are diversified with poly vinyl alcohol (PVA). The elements are covered with decomposable poly lactic acid (PLA) in order to avoid too rapid a release of the content. The covering also controls the charge of the particle-surface that makes endocytosis of the elements by targeted cells easier. The Professor Egashira's investigation team evaluated the expression of 7ND genes and found no in-stent restenosis. NF-FB Decoy (which imprisons the transcription factor, NF-B, accountable for inflammation) was also verified as an applicant for DES. The outcomes looked respectable (Nakano et al., 2009).
 

ARTICLE INFORMATION
 
Author Affiliations: Division of Biology and Chemistry (DBC) (Murphy), The BASE, Chapel Hill, NC 27157, USA.
Author Contributions: Dr Andrew F. Murphy had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Murphy.
Acquisition, analysis, or interpretation of data: Murphy.
Drafting of the manuscript: Murphy.
Critical revision of the manuscript for important intellectual content: Murphy.
Statistical analysis: N/A.
Obtained funding: N/A.
Administrative, technical, or material support: Murphy.
Study supervision: Murphy.
Conflict of Interest Disclosures: Andrew F. Murphy declared no competing interests of this manuscript submitted for publication.
Funding/Support: N/A.
Role of the Funder/Sponsor: N/A.
How to Cite This Paper: Murphy AF. Biomedical materials and medicine development. Sci Insigt Mat Chem. 2016;2016:e00012.
Digital Object Identifier (DOI): http://dx.doi.org/10.15354/simc.16.re012.
Article Submission Information: Received, November 06, 2015; Revised: December 09, 2015; Accepted: December 12, 2015.
 

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