Electrospinning is a simple and versatile method for fibers preparation, which employs electrostatic forces that strength a polymer jet to generate continuous fibers with diameters ranging from micrometers down to several nanometers. Electrospinning is an interesting technique for spinning PLLA. The process offers an excellent opportunity for designing the surface morphology and porosity of the fibers to provide the most appropriate interface for biomedical application. In most of these applications, the properties of polymers are modified using fillers and fibers to suit the high strength/specific properties requirements. Polymer composites offer advantages over other conventional materials when specific properties are compared.
[1] The study found that biodegradable drug delivery membranes that were fabricated from Poly(α-L-alanine) (PLLA) and chlorhexidine (CHX)-gluconate via electrospinning could steadily and continuously inhibit the growth of bacteria. Bacterial growth curves were used to evaluate on a real-time basis the relationship between drug delivery speeds of the membranes and growth rates of bacteria in different phases. The results of this experiment show that CHX drug delivery membranes fabricated via electrospinning are a typical rate-preprogrammed drug delivery system, which can effectively inhibit the growth of bacteria. In this experiment where bacteria growth curves are used to evaluate the inhibiting capability of CHX releasing membranes, it is found that (1) biodegradable CHX delivery membranes can be fabricated via electrospinning, CHX can effectively inhibit the growth of bacteria, and the concentration level of CHX released by the delivery membranes can have a say over the
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inhibiting duration; (2) previous studies have focused on the delivery efficiency of Polymer/CHX or simply on the drug delivery efficiency. Only a few of them have evaluated the inhibiting capability of Polymer/CHX matrix (Inhibition Zone), but evaluations of bacteria inhibiting capability based on Inhibition Zone are only qualitative, not quantitative. Therefore, this experiment proposes to evaluate on a real-time basis the impacts of drug delivery speeds of the membranes on the growth rates of bacteria in different phases; (3) as growth curves of a single bacterium can only conclude whether the membranes possess characteristics of drug delivery systems, bacteria that are of the same strain (competent cells and plasmid inserted competent cells) but grow at different speeds are used to evaluate whether such drug delivery membranes are a rate-preprogrammed drug delivery system.
[2] This study proposes a novel idea, i.e. to produce bio-degradable GTR or GBR membranes with calcium carbonate and its polymorphism, aragonite, through electrospinning. Biomineralization is the formation process of minerals within organisms. With huge organic molecules, organisms can limit the crystallization of inorganic minerals within to nanometers. Some organisms transform minerals into calcite, some transform minerals into aragonite, while some have dual formations. Calcium carbonate enjoys fair bio-compatibility, while its polymorphism has a different lattice structure which means different mechanical properties. This experiment shows that the addition of calcium carbonate and its polymorphism which have different lattice structure, to PLLA can produce GBR membranes or
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GTR membranes with different mechanical properties. We can tell that PLLA with 5% calcite enjoys a higher 0.2% offset yield strength than pure PLLA by approximately 17％, and PLLA with 5% aragonite enjoys a higher 0.2% offset yield strength than pure PLLA by approximately 35 ％ . Furthermore, the 0.2% offset yield strength of PLLA with 5% aragonite is higher than that of PLLA with 5% calcite by 18％. There is no doubt that, be GTR membranes or GBR membranes, excellent biocompatibility, controllable biodegradability, cytocompatibility, suitable microstructure (pore size and porosity), and mechanical properties are required as long as medical applications are involved. The polymer PLLA experimented in this study is biocompatible and biodegradable, and calcite as well as aragonite added is calcium carbonate. Calcium carbonate has been recognized as bone filling material and its good osteoconductivity has been approved in recent studies. In this study, electrospinning is utilized to produce membranes as previous studies have pointed out that such method can create suitable microstructure (pore size and porosity) with the potential to promote osteoblastic cell function and bone regeneration. As a result, the biggest challenge with GTR membranes or GBR membranes is how to adjust(change) the mechanical properties of the membranes in accordance with locations and functions of such membranes. This study proposes a novel idea, i.e. to produce bio-degradable GTR or GBR membranes with calcium carbonate (calcite) and its polymorphism, aragonite, through electrospinning. Calcium carbonate enjoys fair bio-compatibility, while its polymorphism has a different lattice structure which means different
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mechanical properties. Therefore, calcite or aragonite can be opted based on different application purposes. Moreover, calcite and aragonite can be mixed to various percentage to generate bio-degradable membranes that can meet needs/objectives of different applications.
[3] Many polymers used in consumer products are degraded by UV light, and need addition of UV absorbers to inhibit attack, especially if the products are exposed to sunlight. UV absorption and anti-oxidation agents are now the most prominent and effective ultraviolet resistance for plastics materials.
This article provides a comprehensive review of the ultraviolet resistance ability, bio-degradation and structural differences of UV absorption and anti-oxidation agents. The PLLA has a good ability in anti-ultraviolet. We use the elements (UV absorption and anti-oxidation agents) composite with PLLA by electrospinning in our study. We observed the PLLA/ UV absorption (Benzophenone-12) fiber membranes higher than PLLA membrane 14.9% in UVA ratio and PLLA/ anti-oxidation agents (Chemfos-168) fiber membranes higher than PLLA membrane 17.9% in UVA ratio. As mentioned in previous literature, the I875/I1452 Raman intensity ratio signals results of bio-degradation and structural differences.
In this experiment, although both are bio-degradable membranes, the the PLLA/ UV absorption (Benzophenone-12) fiber membranes higher than PLLA membrane 61.6% in I875/I1452 Raman intensity ratio and PLLA/
anti-oxidation agents (Chemfos-168) fiber membranes higher than PLLA membrane 3.7% in I875/I1452 Raman intensity ratio. So PLLA Add UV absorption (Benzophenone-12) fiber membranes can achieve good UV
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resistance and fast bio-degradation.
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