Some Significant Trends in The Antimicrobial Treatment of Silk

The article provides some useful insights on recent trends in the antimicrobial
treatment of silk. The antimicrobial activity of silk fabric pretreated with Moreinga
oilfera and dyed with natural coloring matter extracted from madder using microwave
heating methods, has been investigated. On the one hand the dyeability was enhanced
and on the other the antimicrobial activity against certain types fungi and bacteria
have revealed high inhibition percent than untreated samples. The microwave method
of heating adopted proves to be more economical and ecofriendly in comparison with
conventional techniques. An attempt has been made to produce an antibacterial and
absorbable fixation screw by adding gentamicin to silk based materials. The objective has
been to avoid removal of internal fixation devices after an orthopaedic surgery caused
by implant associated infections and non absorbing materials that contributed to second
surgical procedure. Alum mordanted and unmordanted silk fabrics have been dyed with
green walnut shell. Improved antimicrobial effect has been observed on selected strains
of bacteria.


Introduction
Natural dyes have attracted attention during recent years [1,2].
Textile materials and clothing are known to be prone to microbial attack since they offer the fundamental necessities for microbial growth [3]. Natural fibres comprising of cellulose and protein, provide moisture, oxygen, nutrients and temperature for bacterial growth and multiplication. This often results in objectionable odour dermal infection, product deterioration allergic responses and often related diseases [4]. Owing to aging population and improving medical care, the use of internal fixation devices, particularly metallic materials is widespread and expected to increase in the future. But in order to remove internal fixation devices, second surgical procedures are normally resorted. A study reveals that about 5% of all orthopaedic procedures in US and nearly 81% of implants inserted for fracture fixation are removed after fracture healing which greatly increases the pain and financial burden for patients [5][6][7]. The demerits associated with rigid plate and screw fixation, including, infection, exposure, retained implants and pain can result in another surgery [8][9][10][11][12]. Antimicrobial finishes prevent the growth of microorganisms on fabrics used in wide variety of apparel, home furnishing, commercial and industrial products. Fabrics will have a longer life when treated with some type of antimicrobial finishes that reduce or prevent damage from microorganisms [13].

Natural Dyed Pre-Treated Silk Having Antimicrobial Properties
The consumers are aware of hygienic lifestyle and there is a necessity of textile product with antimicrobial properties. Many antimicrobial agents like quaternary ammonium compounds and recently nano silver are available for textile finishing [14,15].
The use of natural products such as chitosan and natural dyes for antimicrobial finishing of textiles has been widely reported [16,17]. For achievement of the maximum gain, an ideal antimicrobial treatment of textile should fulfil many criteria [18]. of bacterial and fungal species but at the same time exhibit low toxicity to consumers, e.g., not cause toxicity, allergy or irritation to the user. Chitosan comes into focus and is advocated as an ideal antimicrobial agent [19]. Morienga Olifera contributes products of excellent nutritional quality mainly due to the wide variety of it, to its exceptional medicinal properties and to its use in human feeding. It is also used as flocculent in water treatment.
Also, it is useful in the production of biodiesel, ethanol, oil and gums; as well as in the control of vectors and infections caused by microorganisms and as biopesticide. Root, flowers, bark, stem, leaves and seeds of Morienga Olifera possess antimicrobial properties.
In Egypt the sowing and establishment of Morienga Olifera has increased remarkably, according to the scientific strategy followed    The increasing of concentration of Moreinga olefera shows more tendencies to deposit on the surface of the fabrics, resulting in hydroxyl groups more easily accessible to microorganisms. Silk fabrics treated with Moreinga olefera and dyed with the madder natural dye display high growth reduction of microbes. The pretreated silk fabrics and dyed with madder natural dye display high growth reduction of microbes compared to untreated [20].
The research proves the feasibility of high quality pretreatment with natural dye extracted from madder, thus creating new opportunities for the environment and and the fabric industry to catch up the current consumer trends.

Antibacterial and Absorbable Silk Based Fixation Material in Orthopaedics
During the past few decades, the development and use of resorbable fixation devices of differing polymer compositions including Poly-L-Lactic acid, polyglycolic acid, and polylactic co glycolic acid, a number of potential merits have been shown to reduce the need for hardware removal and the risk of growth restriction and transcranial migration [21,22]. However, identified complications of resorbable fixation devices include infections, self limited local inflammatory reactions, palpability, and device removal [23][24][25][26][27][28]. It has been reported that the incidence of infections ranges from 0.2 to 2%, the incidence of inflammation reactions ranges from 0.7 to 14%, and the incidences of all causes of plate or screw removal range from 0.3 to 4%. A bioabsorbable ciprofloxacin containing bone screw has been explored to prevent biomaterial related infection but its lower strength and the abovementioned disadvantages have restricted the widespread clinical application of these resorbable implants [29].
Low load prearticular fractures such as craniao facial fractures, calcaneal fractures, and metacarpal fractures remain the best indications for their use [30][31][32]. It has been recently reported that silk based screws may become an option for resorbable fixation devices that overcome the limitations of conventional resorbable materials due to their impressive mechanical features, biocompatibility, ability to promote bone remodelling and environmental stability [33]. In addition, the potential utility of easy implantation, autoclave sterilization and FDA approved uses benefit their application as a medical device [34]. But, similar to other biomaterials, silk based screws may carry an elevated risk of implant-associated infections because of the formation of bacterial biofilms [34][35][36][37]. The research considered indicates that silk fibrion partly promotes the growth of S.Aureus bacteria, which may be the major disadvantage of the use of these screws as a fixation device.
The paramount importance of infection prevention should be emphasized because implant associated infections are difficult to cure due to bacterial biofilms, and in many cases, removal is the only remedy [38]. Several biomaterial surface modifications have been proposed to impart silk fibroin with antibacterial properties, such as combination with chitosan, chemical attachment of antimicrobial peptides and loading with silver nano particles [39][40][41][42]. However, in clinical applications, internal fixation materials must be autoclaved for sterilization, and high temperatures may affect the antibacterial properties of antimicrobial peptides [43].
Silk based fixation materials will remain in the body for a long time, even for more than a year, but the safety of the long term and continuous release of silver nano particles in the body is not clear [44]. Furthermore, internal fixation materials require a specific material form, and mechanical strength, so these materials may be unsuitable for silk based fixation materials.
The preparation of antibacterial silk based screws has been explored, from the incorporation of an antibacterial agent, gentamicin to provide high and durable antimicrobial activity. In the research considered herein, the properties of the silk based screws containing gentamicin, such as the mechanical features, swelling properties, biocompatibility, and degradation, were tested in vitro.  The objective of the present study was to produce an antibacterial and absorbable fixation material with potential to solve this difficult clinical problem by simply combining gentamicin and silk. In the past several decades, many studies have focused on antibacterial silk-based materials to prevent infections. The following three aspects led us to select gentamicin. Foremost, we observed that gentamicin sulfate can dissolve in silk solution uniformly as a result of its good solubility in water. Second, most clinical isolates of S. aureus and gram-negative rods that are thought to be mainly responsible for implant-associated infections in orthopedic surgery are sensitive to gentamicin [42]. In addition, gentamicin is one of the few thermostable antibiotics. In this study, gentamicin sulfate was successfully incorporated within  In addition, the results of the CCK-8 assay and flow cytometry analysis indicate that there were no detrimental effects on cell proliferation or apoptosis from the PSS or GSS1. Thus, GSS exhibited good biocompatibility, similar to that of PSS, whose excellent biocompatibility was reported in previous studies. Therefore, incorporating gentamicin sulfate does not change the biocompatibility of silk protein. The degradation of PSS was consistent with a second-order polynomic trendline, which agrees with previous studies. Interestingly, the degradation rate of GSS1 was apparently faster than that of PSS and was consistent with a third-order polynomic trendline. One explanation for this difference may be associated with the voids that increased the surface area exposed to the enzyme. We may assume that these voids are due to the dissolution of gentamicin particles, resulting in a porous structure because the sizes of the voids were similar to those of the gentamicin particles.
If this is the case, the degradation rate of GSS may be tunable by changing the number and size of the gentamicin particles. However, these approximations cannot directly represent degradation in vivo due to the complex environment in the body, such as the presence of various enzymes and cell types. In the future, research on in vivo degradation will need to be explored. We believe that GSS can be an optimal fixation material whose initial strength can provide excellent fixation with a mass loss profile that is suitable for the bone-healing process. The rapid swelling of the silk screws results in a reduction in mechanical strength, which may cause the implantation process to fail. In addition, the increase in the diameter of the screws during the operation will make it difficult for the surgeon to implant the screws. Therefore, the decreased water-absorbing capacity of GSS1 in is beneficial to the implantation of the screw by the surgeon. For at least 30 min, the diameter of GSS1 did not increase significantly when it came into contact with water in the body, which is a sufficient time for the surgeon to implant the screw.
However, the limitation of these GSS is the size of the screws.
When the sizes of the molds were increased to increase the diameter of the blanks and the screws, there were bubbles in the silk blanks that would affect the functioning and mechanical stability of the screws. Future research should be conducted to verify the features of GSS in vivo, such as their antibacterial ability, regulation of degradation and biocompatibility, and to investigate their detailed mechanism. Pure silk based screws promoted the growth of S.Aureus in vitro. To prevent implant associated infections after fixation surgery, gentamicin was successfully incorporated into silk based screws [45]. Gentamicin loaded silk based screws not only retained the impressive mechanical features and biocompatibility of pure silk based screws but also exhibited high and durable antimicrobial activity against S.Aureus and E.Coli in vitro. The degradation rate of gentamicin based screws increased, which was related to the dissolution of gentamicin particles, leaving a porous structure.
In addition, the decreased water absorption of gentamicin based screws will give the surgeon more time to implant this screw.
Findings reveal that the antibacterial silk based fixation material can overcome the limitations of metal and traditionally resorbable devices, with great potential for use in orthopaedic implants to reduce the incidence of second surgical procedures for a given clinical application.

Conclusion
Silk fabric pretreated with Morienga Olifera exhibit higher inhibition percent than untreated samples with regard to antimicrobial activity against selected bacteria and fungi, besides other benefits such as better dyeability. The antimicrobial activity with some kinds of Bacteria and Fungi were tested, and the results indicated that the samples pretreated exhibit higher inhibition percent than the untreated samples. An antibacterial and absorbable fixation screw by adding gentamicin to silk-based materials has been developed. The antibacterial activity was assessed against Staphylococcusaureus (S. aureus) and Escherichia coli (E. coli) in vitro by plate cultivation and scanning electron microscopy (SEM). The properties, such as the mechanical features, swelling properties, biocompatibility and degradation, of gentamicin-loaded silk-based screws (GSS) in vitro, have also been studied. The GSS showed significant bactericidal effects against S. aureus and E.
coli. The antibacterial activity remained high even after 4 weeks of immersion in protease solution. In addition, the GSS maintained the remarkable mechanical properties and excellent biocompatibility of pure silk-based screws (PSS). Interestingly, after gentamicin incorporation, the degradation rate and water-absorbing capacity increased and decreased, respectively. These GSS provide both impressive material properties and antibacterial activity and have great potential for use in orthopedic implants to reduce the incidence of second surgeries.