The same but different: setal arrays of anoles and geckos indicate alternative approaches to achieving similar adhesive effectiveness

The functional morphology of squamate fibrillar adhesive systems has been extensively investigated and has indirectly and directly influenced the design of synthetic counterparts. Not surprisingly, the structure and geometry of exemplar fibrils (setae) have been the subject of the bulk of the attention in such research, although variation in setal morphology along the length of subdigital adhesive pads has been implicated in the effective functioning of these systems. Adhesive setal field configuration has been described for several geckos, but that of the convergent Anolis lizards, comprised of morphologically simpler fibrils, remains largely unexplored. Here we examine setal morphology along the proximodistal axis of the digits of Anolis equestris and compare our findings to those for a model gecko, Gekko gecko. Consistent with previous work, we found that the setae of A. equestris are generally thinner, shorter, and present at higher densities than those of G. gecko and terminate in a single spatulate tip. Contrastingly, the setae of G. gecko are hierarchically branched in structure and carry hundreds of spatulate tips. Although the splitting of contacts into multiple smaller tips is predicted to increase the adhesive performance of a fiber compared to an unbranched one, we posited that the adhesive performance of G. gecko and A. equestris would be relatively similar when the configuration of the setal fields of each was accounted for. We found that, as in geckos, setal morphology of A. equestris follows a predictable pattern along the proximodistal axis of the pad, although there are several critical differences in the configuration of the setal fields of these two groups. Most notably, the pattern of variation in setal length of A. equestris is effectively opposite to that exhibited by G. gecko. This difference in clinal variation mirrors the difference in the direction in which the setal fields of anoles and geckos are peeled from the substrate, consistent with the hypothesis that biomechanical factors are the chief determinants of these patterns of variation. Future empirical work, however, is needed to validate this. Our findings introduce Anolis lizards as an additional source of inspiration for bio-inspired design and set the stage for comparative studies investigating the functional morphology of these convergent adhesive apparatuses. Such investigations will lead to an enhanced understanding of the interactions between form, function, and environment of fibril-based biological adhesive systems.

Colloblasts act as a biomechanical sensor for suitable prey in Pleurobrachia

Ctenophores are a group of largely-planktonic, gelatinous carnivores whose most common method of prey capture is nearly a phylum-defining trait. Tentaculate ctenophores release an unknown proteinaceous adhesive from specialized colloblast cells lining their tentacles following prey contact with the tentacles. There exist no extant studies of the mechanical properties of colloblast adhesive. We use live microscopy techniques to visualize adhesion events between Pleurobrachia pileus colloblasts and probes of different surface chemistries in response to probing with varying contact areas. We further define two mechanisms of adhesion termination upon probe retraction. Adapting a technique for measuring surface tension, we examine the adhesive strength of tentacles in the ctenophore Pleurobrachia bachei under varying pH and bonding time conditions, and demonstrate the destructive exhaustion of colloblast adhesive release. We find that colloblast-mediated adhesion is rapid, and that the bonding process is robust against shifts in ambient pH. However, we find that the Pleurobrachia colloblast adhesive system is among the weakest biological adhesive systems yet described. We place this surprising observation into a broader ecophysiological context by modeling prey capture for prey of a range of sizes. We find that limited use of colloblast adhesive with high surface area contact is suitable both for capturing appropriately sized prey and rejecting, by detachment, prey above a certain size threshold. This allows Pleuro-brachia, lacking a mechanism to directly “see” potential prey they are interacting with, to invest in capturing only prey of an appropriate size, decreasing the risk of injury.Summary statementCtenophore colloblast adhesive is found to be strong, but few colloblasts are simultaneously active, producing a weakly-adhering system. A physical model demonstrates how such a system may filter unsuitable prey.

Evaluation of leakage resistance improvement in transconjunctival sutureless vitrectomy sclerotomies closed with adhesives. an experimental study

Background The purpose of this paper is to study the utility of adhesives (artificial-cyanoacrylate and biological-fibrin glue) for improving transconjunctival sutureless vitrectomy (TSV) sclerotomy closure competency. Methods Experimental and observer-masked study in which after performing TSV in cadaveric pig eyes, different adhesives were tested on sclerotomy entrances in order to determine if they improved closure competency in face of progressive intraocular pressure increase. In 76 eyes cyanoacrylate-treated sclerotomies were compared with sclerotomies in which no additional manoeuvre to aid closing was performed; in 76 eyes fibrin glue with no manoeuvre; and in the last 76 eyes, cyanoacrylate-treated sclerotomies were compared with fibrin glue-treated sclerotomies. Results A total of 228 eyes had a 23-gauge TSV performed. Both cyanoacrylate and fibrin glue treated sclerotomies achieved higher mean opening pressures when compared with nontreated sclerotomies in the same eye (p < 0.002). When cyanoacrylate was compared with biological adhesive in the same eye, no statistically significant differences were obtained (p = 0.216). Discussions This experimental study provides support for the possible role of adhesives in improving TSV sclerotomy closure competency in clinical practice.

Isolation, characterization of Bacillus sp. producing heavy metal absorption γ-PGA

Poly-gamma-glutamic acid (γPGA), which is a biodegradable, non-immunogenic and unusual anionic amino-acid polymer consist of D- and L-glutamic acid units, was exploited for a wide array of useful applications. Bacillus are well known cellular system important for fermentation to synthesize γPGA, which is used as thickener, drugs carrier, cryoprotectant, humectant, biological adhesive, flocculants, or heavy metal absorbent. This study focused on the isolation of Bacillus spp. that is possible to produce γ-PGA from different soil samples from different places in Vietnam. Study the effect of precursors, temperature, carbon sources, times and pH on γ-PGA production. From 31 soil samples and 4 straws samples, strain 20.2 which produced the highest γ-PGA yields (riches 15.2 mg/ml), was identified as Bacillus sp. 20.2 by molecular biology method. The suitable conditions for growing of Bacillus sp. 20.2 strain to produce γ-PGA are at 37°C, pH 7 after 72 hours. Citric acid instead of glucose in a GSP medium is better for producing γ-PGA by strain Bacillus sp. 20.2. Poly-gamma-glutamic acid (γ-PGA) là một polymer amino-acid gồm D và L-glutamic acid, có khả năng phân hủy sinh học, không gây miễn dịch, đã được ứng dụng rộng rãi trong công nghiệp, y học. Bacillus subtilis được biết đến là hệ thống tế bào ý nghĩa quan trọng trong quá trình lên men để tổng hợp γ-PGA. γ-PGA hòa tan trong nước, phân hủy sinh học và không độc đối với con người và môi trường. γ-PGA ổn định với nhiều protease vì các protease thường không nhận acid γ-glutamic (Obst et al., 2004). γ-PGA có cấu trúc đồng phân đơn giản, không gây miễn dịch. Do đó, γ-PGA đã được quan tâm ứng dụng trong các lĩnh vực như y học, công nghiệp thực phẩm, mỹ phẩm và đặc biệt là xử lý nước nhiễm kim loại nặng. Trong nghiên cứu này chúng tôi tập trung phân lập, tuyển chọn các chủng Bacillus có khả năng sinh tổng hợp PGA cao. Sau đó định danh và đánh giá khả năng sinh tổng hợp PGA từ chủng đã phân lập được. Kết quả cho thấy từ 34 mẫu rơm và đất, chúng tôi đã phân lập được chủng với mã số 20.2 có khả năng sinh PGA cao nhất đạt 15.2 mg/ml. Chủng này đã được định danh bằng phân tích trình tự gene 16S rRNA và thuộc loài Bacillus sp. Môi trường thích hợp sinh tổng hợp PGA là GSP ở điều kiện 37oC pH7 sau 72 giờ nuôi cấy.