Analysis of the major epitope of the alpha2 chain of bovine type I collagen in children with bovine gelatin allergy

Process optimization and character evaluation of Bletilla striata polysaccharide (BSP) and chitosan (CS) composite hemostatic sponge (BSP-CS)

Bletilla striata polysaccharide (BSP) and chitosan (CS) were chemically cross-linked using oxalyl chloride to prepare a composite hemostatic sponge (BSP-CS), and the process parameters were optimized using the Box-Behnken design (BBD) with response surface methodology. To optimize the performance of the hemostatic sponge, we adjusted the ratio of independent variables, the amount of oxalyl chloride added, and the freeze-dried volume. A series of evaluations were conducted on the hemostatic applicability of BSP-CS. The characterization results revealed that BSP-CS had a stable bacteriostatic effect on Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa within 72 h, and the bacteriostatic rate was above 30%. The CCK-8 cytotoxicity test demonstrated that BSP-CS had a certain effect on promoting cell proliferation of L929 cells. In the mouse tail-cutting experiment, the hemostasis time of BSP-CS was 463.0±38.16 s, shortened by 91.3 s on average compared with 554.3±34.67 s of the gauze group. The blood loss of the BSP-CS group was 28.47±3.74 mg, which was 34.7% lower than that of the control gauze group (43.6±3.83 mg). In the in vitro coagulation experiment, the in vitro coagulation index of the BSP-CS group was 97.29%±1.8%, which was reduced to 8.6% of the control group. The CT value of the BSP-CS group was 240±15 s, which was 155 s lower than that of the gauze group (355±31.22 s). All characterization results indicate that BSP-CS is an excellent hemostatic material.

Desired properties of polymeric hydrogel vitreous substitute

Vitreous replacement is a commonly employed method for treating a range of ocular diseases, including posterior vitreous detachment, complex retinal detachment, diabetic retinopathy, macular hole, and ocular trauma. Various clinical substitutes for vitreous include air, expandable gas, silicone oil, heavy silicone oil, and balanced salt solution. However, these substitutes have drawbacks such as short retention time, cytotoxicity, high intraocular pressure, and the formation of cataracts, rendering them unsuitable for long-term treatment. Polymeric hydrogels possess the potential to serve as ideal vitreous substitutes due to their structure-mimicking to natural vitreous and adjustable mechanical properties. Replacement with hydrogels as the tamponade can help maintain the shape of the eyeball, apply pressure to the detached retina, and ensure the metabolic transport of substances without impairing vision. This literature review examines the required properties of artificial vitreous, including the optical properties, rheological properties, expansive force action, and physiological and biochemical functions of chemically and physically crosslinked hydrogels. The strategies for enhancing the biocompatibility and injectability of hydrogels are also summarized and discussed. From a clinical ophthalmology perspective, this paper presents the latest developments in vitreous replacement, providing clinicians with a comprehensive understanding of hydrogel clinical applications, which offers guidance for future design directions and methodologies for hydrogel development.

Effect of collagen denaturation degree on mechanical properties and biological activity of nanofibrous scaffolds

Further progress in regenerative medicine and bioengineering highly depends on the development of 3D polymeric scaffolds with active biological properties. The most attention is paid to natural extracellular matrix components, primarily collagen. Herein, nonwoven nanofiber materials with various degrees of collagen denaturation and fiber diameters 250-500 nm were produced by electrospinning, stabilized by genipin, and characterized in detail. Collagen denaturation has been confirmed using DSC and FTIR analysis. The comparative study of collagen and gelatin nonwoven materials (NWM) revealed only minor differences in their biocompatibility with skin fibroblasts and keratinocytes in vitro. In long-term subcutaneous implantation study, the inflammation was less evident on collagen than on gelatin NWM. Remarkably, the pronounced calcification was revealed in the collagen NWM only. The results obtained can be useful in terms of improving the electrospinning technology of collagen from aqueous solutions, as well as emphasize the importance of long-term study to ensure proper implementation of the material, taking into account the ability of collagen to provoke calcification.

Biological Application of Novel Biodegradable Cellulose Composite as a Hemostatic Material

Degradable hemostatic materials have unique advantages in reducing the amount of bleeding, shortening the surgical operation time, and improving patient prognosis. However, none of the current hemostatic materials are ideal and have disadvantages. Therefore, a novel biodegradable cellulose-based composite hemostatic material was prepared by crosslinking sodium carboxymethyl cellulose (CCNa) and hydroxyethyl cellulose (HEC), following an improved vacuum freeze-drying method. The resulting cellulose composite material was neutral in pH and spongy with a density of 0.042 g/cm³, a porosity of 77.68%, and an average pore size of 13.45 μm. The composite's compressive and tensile strengths were 0.1 MPa and 15.2 MPa, respectively. Under in vitro conditions, the composites were degraded gradually through petite molecule stripping and dissolution, reaching 96.8% after 14 days and 100% degradation rate at 21 days. When implanted into rats, the degradation rate of the composite was slightly faster, reaching 99.7% in 14 days and 100% in 21 days. Histology showed a stable inflammatory response and no evidence of cell degeneration, necrosis, or abnormal hyperplasia in the tissues around the embedded material, indicating good biocompatibility. In the hemorrhagic liver model, the time to hemostasis and the total blood loss in the cellulose composite group was significantly lower than in the medical gauze group and the blank control group (P < 0.05). These data indicate that the novel cellulose composite is a promising implantable hemostatic material in clinical settings.

Effects of Algan hemostatic agent foam in rat femoral artery injury model: A randomized animal trial

Background/Aim: Nowadays, many deaths are related to vessel injury-induced blood loss. Failure to control bleeding also increases the risk of death. This study aimed to investigate the hemostatic effects of the Algan Hemostatic Agent (AHA) foam application in a rat model in which severe femoral artery bleeding was induced. Methods: Fourteen rats were randomly assigned to two groups: (1) control (physiological saline) (n = 7) and (2) AHA foam (n = 7). The left femoral artery of the rats was incised and when the bleeding started, and the area was pressed with another sponge for 10 s in all rats. Afterwards, physiological saline solution impregnated gauze or AHA foam was placed over same area. A chronometer was started and area was checked after 2 min. If no bleeding occurred during the first 2 min of application, it was recorded as “successful”. If bleeding occurred, the same procedure was repeated up to three times. If hemostasis could not be achieved even after the third application, it was considered a failure, and “failed” was recorded. All animals were sacrificed under high anesthesia for least 10 min after the experiment. Results: Application of AHA resulted in complete (100%) control of bleeding in all rats within the first 2 min. In control group, hemostasis was achieved in 1 out of 7 (14.3%) rats by the third application. Failure was recorded for the remaining six rats. The hemostatic success rate of the AHA foam was significantly higher than the rates of control group (P = 0.005). Conclusion: AHA foam is a very effective hemostatic agent and can be applied easily on vascular trauma models. Further studies are needed to elucidate hemostatic features of AHA.

Enhancing islet transplantation using a biocompatible collagen-PDMS bioscaffold enriched with dexamethasone-microplates

Islet transplantation is a promising approach to enable type 1 diabetic patients to attain glycemic control independent of insulin injections. However, up to 60% of islets are lost immediately following transplantation. To improve this outcome, islets can be transplanted within bioscaffolds, however, synthetic bioscaffolds induce an intense inflammatory reaction which can have detrimental effects on islet function and survival. In the present study, we first improved the biocompatibility of polydimethylsiloxane (PDMS) bioscaffolds by coating them with collagen. To reduce the inflammatory response to PDMS bioscaffolds, we then enriched the bioscaffolds with dexamethasone-loaded microplates (DEX-µScaffolds). These DEX-microplates have the ability to release DEX in a sustained manner over 7 weeks within a therapeutic range that does not affect the glucose responsiveness of the islets but which minimizes inflammation in the surrounding microenvironment. The bioscaffold showed excellent mechanical properties that enabled it to resist pore collapse thereby helping to facilitate islet seeding and its handling for implantation, and subsequent engraftment, within the epididymal fat pad (EFP). Following the transplantation of islets into the EFP of diabetic mice using DEX-µScaffolds there was a return in basal blood glucose to normal values by day 4, with normoglycemia maintained for 30 days. Furthermore, these animals demonstrated a normal dynamic response to glucose challenges with histological evidence showing reduced pro-inflammatory cytokines and fibrotic tissue surrounding DEX-µScaffolds at the transplantation site. In contrast, diabetic animals transplanted with either islets alone or islets in bioscaffolds without DEX microplates were not able to regain glycemic control during basal conditions with overall poor islet function. Taken together, our data show that coating PDMS bioscaffolds with collagen, and enriching them with DEX-microplates, significantly prolongs and enhances islet function and survival.

Production of protein-based polymers in Pichia pastoris

Materials science and genetic engineering have joined forces over the last three decades in the development of so-called protein-based polymers. These are proteins, typically with repetitive amino acid sequences, that have such physical properties that they can be used as functional materials. Well-known natural examples are collagen, silk, and elastin, but also artificial sequences have been devised. These proteins can be produced in a suitable host via recombinant DNA technology, and it is this inherent control over monomer sequence and molecular size that renders this class of polymers of particular interest to the fields of nanomaterials and biomedical research. Traditionally, Escherichia coli has been the main workhorse for the production of these polymers, but the methylotrophic yeast Pichia pastoris is finding increased use in view of the often high yields and potential bioprocessing benefits. We here provide an overview of protein-based polymers produced in P. pastoris. We summarize their physicochemical properties, briefly note possible applications, and detail their biosynthesis. Some challenges that may be faced when using P. pastoris for polymer production are identified: (i) low yields and poor process control in shake flask cultures; i.e., the need for bioreactors, (ii) proteolytic degradation, and (iii) self-assembly in vivo. Strategies to overcome these challenges are discussed, which we anticipate will be of interest also to readers involved in protein expression in P. pastoris in general.

Preventing iatrogenic gelatin anaphylaxis

OBJECTIVE

To assess the iatrogenic risks of gelatin allergy and identify resources for patient management.

DATA SOURCES

A literature review was performed using PubMed and public databases provided by the National Library of Medicine.

STUDY SELECTIONS

Reports of iatrogenic gelatin allergy associated with vaccines, hemostatic agents, intravenous colloids, medicinal capsules, and intraoperative surgical supplies.

RESULTS

Gelatin ingredients may not be identified by electronic medical record safeguards, and an exhaustive listing of potential iatrogenic exposures is elusive. The National Library of Medicine AccessGUDID (https://accessgudid.nlm.nih.gov/) can be a useful resource in evaluating medical devices for gelatin content. Unexpected sources of iatrogenic gelatin exposure include hemostatic agents, vascular grafts, intravascular cannulas, bone replacement implants, and emergency resuscitation fluids.

CONCLUSION

Vigilance is important within medical systems to avoid inadvertent gelatin exposure when caring for patients with gelatin allergy. Additional safeguards are needed to remove latent health care system errors that fail to prevent gelatin administration in this at-risk population.

A novel human-like collagen hemostatic sponge with uniform morphology, good biodegradability and biocompatibility

Biodegradable sponges, as a promising hemostatic biomaterial, has been clinically required over the past decades. Current hemostatic sponges are generally prepared by crosslinking and freeze-drying, but the quality control or biocompatibility is often unsatisfactory due to the freezing-caused morphological non-uniformity and the toxicity of raw materials or cross-linkers. The crosslinking often greatly retards the degradation of the sponges and thus affects the healing of the wound. In this work, we prepared a novel hemostatic sponge using human-like collagen and glutamine transaminase (non-toxic cross-linker) and optimized its morphology via “two-step” freezing instead of conventional “one-step” freezing. The resulting sponge showed a good biocompatibility in cytotoxicity and implantation tests and had a significant hemostatic effect in ear artery and liver injury models. Moreover, the sponge could be degraded high efficiently by several common enzymes in organisms (e.g. I collagenase, trypsase, and lysozyme), which means that the sponge can be easily digested by metabolism and can facilitate seamless healing. Finally, both the front and back of the sponge prepared via two-step freezing was more uniform in morphology than that prepared via one-step freezing. More importantly, two-step freezing can be used as a universal approach for preparation of diverse uniform biomaterials.

Potential food allergens in medications

Excipients are substances in pharmaceuticals other than the active ingredients. Some excipients are foods or substances derived from foods, raising the possibility that these substances would pose a hazard to patients with food allergy. This review describes which food-derived substances are used as pharmaceutical excipients in which medications and reviews published data regarding the safety of the administration of these medications to recipients with food allergy. Such reactions are rare, usually because the amount of food protein is not present in a large enough quantity to elicit a reaction. When a food protein appears as an unintentional contaminant, the amount, if any, that is present might be variable and might elicit reactions only from some lots of medication or only in some patients. In most circumstances these medications should not be routinely withheld from patients who have particular food allergies because most will tolerate the medications uneventfully. However, if a particular patient has had an apparent allergic reaction to the medication, potential allergy to the food component should be investigated.

Cutaneous wound healing after treatment with plant-derived human recombinant collagen flowable gel

Chronic wounds, particularly diabetic ulcers, represent a main public health concern with significant costs. Ulcers often harbor an additional obstacle in the form of tunneled or undermined wounds, requiring treatments that can reach the entire wound tunnel, because bioengineered grafts are typically available only in a sheet form. While collagen is considered a suitable biodegradable scaffold material, it is usually extracted from animal and human cadaveric sources, and accompanied by potential allergic and infectious risks. The purpose of this study was to test the performance of a flowable gel made of human recombinant type I collagen (rhCollagen) produced in transgenic tobacco plants, indicated for the treatment of acute, chronic, and tunneled wounds. The performance of the rhCollagen flowable gel was tested in an acute full-thickness cutaneous wound-healing rat model and compared to saline treatment and two commercial flowable gel control products made of bovine collagen and cadaver human skin collagen. When compared to the three control groups, the rhCollagen-based gel accelerated wound closure and triggered a significant jumpstart to the healing process, accompanied by enhanced re-epithelialization. In a cutaneous full-thickness wound pig model, the rhCollagen-based flowable gel induced accelerated wound healing compared to a commercial product made of bovine tendon collagen. By day 21 post-treatment, 95% wound closure was observed with the rhCollagen product compared to 68% closure in wounds treated with the reference product. Moreover, rhCollagen treatment induced an early angiogenic response and induced a significantly lower inflammatory response than in the control group. In summary, rhCollagen flowable gel proved to be efficacious in animal wound models and is expected to be capable of reducing the healing time of human wounds.

Plant-derived human collagen scaffolds for skin tissue engineering

Tissue engineering scaffolds are commonly formed using proteins extracted from animal tissues, such as bovine hide. Risks associated with the use of these materials include hypersensitivity and pathogenic contamination. Human-derived proteins lower the risk of hypersensitivity, but possess the risk of disease transmission. Methods engineering recombinant human proteins using plant material provide an alternate source of these materials without the risk of disease transmission or concerns regarding variability. To investigate the utility of plant-derived human collagen (PDHC) in the development of engineered skin (ES), PDHC and bovine hide collagen were formed into tissue engineering scaffolds using electrospinning or freeze-drying. Both raw materials were easily formed into two common scaffold types, electrospun nonwoven scaffolds and lyophilized sponges, with similar architectures. The processing time, however, was significantly lower with PDHC. PDHC scaffolds supported primary human cell attachment and proliferation at an equivalent or higher level than the bovine material. Interleukin-1 beta production was significantly lower when activated THP-1 macrophages where exposed to PDHC electrospun scaffolds compared to bovine collagen. Both materials promoted proper maturation and differentiation of ES. These data suggest that PDHC may provide a novel source of raw material for tissue engineering with low risk of allergic response or disease transmission.

Collagen: finding a solution for the source

Extracellular matrix (ECM)-based scaffolds, through their inherent bioactivity and molecular recognition signals, provide the ideal substrate for tissue engineering and regenerative applications. Collagen, the most abundant ECM protein, has proven itself to be a very versatile material with applications in many fields, including the leather and food industries, cosmetics, drug delivery, and tissue engineering. However, doubts persist about the optimal source of collagen for tissue engineering applications, given possible immunogenicity and disease transmission associated with animal sources and reduced bioactivity and availability of recombinant technologies. In this special edition, an attempt is made to elucidate the advantages of plant-derived human recombinant collagen and its applications in tissue engineering, particularly skin and wound healing. While results are promising, the widespread use of animal-derived collagen means that recombinant technologies may find applications in niche areas.

Direct assessments of the antioxidant effects of the novel collagen peptide on reactive oxygen species using electron spin resonance spectroscopy

In the present study, we evaluated the antioxidant effects of a pepsin-treated novel collagen peptide (P-NCP) on reactive oxygen species (ROS) such as hydroxyl radical (HO(•)), superoxide anion radical (O(2)(•-)), and singlet oxygen ((1)O(2)), and the effects on cell viability after ultraviolet ray (UV) irradiation of human fibroblasts. We confirmed, using electron spin resonance, that P-NCP directly inhibited HO(•) and (1)O(2). Furthermore, addition of P-NCP to fibroblasts inhibited cell death induced by UVA (400-315 nm) irradiation in a dose-dependent manner. In addition, the antioxidant effect on (1)O(2) was observed in the peptide fractions rich in Gly, Pro, Hyp, Glu, Ala, and Arg. We found that Gly, Hyp, Glu, and Ala directly scavenged (1)O(2). These results indicated that a peptide sequence including Gly, Hyp, Glu, and Ala could play a key role in the antioxidant effects of P-NCP on (1)O(2). It was suggested that P-NCP can inhibit photo-aging related to ROS owing to its antioxidant effects.

A reliable enzyme linked immunosorbent assay for the determination of bovine and porcine gelatin in processed foods

Since gelatin-containing foods pose a risk for eliciting allergic reactions in sensitized individuals, a novel sandwich enzyme linked-immunosorbent assay (ELISA) for the detection and quantification of bovine and porcine gelatin in processed foods was developed. Rabbits and goats were immunized with bovine gelatin, and three antisera (pAb1 and pAb2 from rabbits, and pAb3 from goats) were obtained. We established a sandwich ELISA method based on a combination of these antibodies. In this study, two sandwich ELISA methods, rabbit pAb2-pAb1 and goat pAb3-pAb3, were evaluated for sensitivity, specificity, cross-reactivity, and applicability. Both ELISA methods were highly specific for bovine and porcine gelatin but had little reactivity with fish gelatin. The detection and quantification limits for porcine gelatin were found to be 0.78 ng/mL and 1.56 ng/mL, respectively. The established sandwich ELISA methods produced no false-positives, except for heated meat products or false negatives when various commercial foods were analyzed for their gelatin content. The rabbit pAb2-pAb1 ELISA cross-reacted with boiled squid, while the goat pAb3-pAb3 ELISA did not. Thus, the proposed goat pAb3-pAb3 ELISA method is a reliable tool for the detection of gelatin contaminants present in processed foods.

Recombinant microbial systems for the production of human collagen and gelatin

The use of genetically engineered microorganisms is a cost-effective, scalable technology for the production of recombinant human collagen (rhC) and recombinant gelatin (rG). This review will discuss the use of yeast (Pichia pastoris, Saccharomyces cerevisiae, Hansenula polymorpha) and of bacteria (Escherichia coli, Bacillus brevis) genetically engineered for the production of rhC and rG. P. pastoris is the preferred production system for rhC and rG. Recombinant strains of P. pastoris accumulate properly hydroxylated triple helical rhC intracellularly at levels up to 1.5 g/l. Coexpression of recombinant collagen with recombinant prolyl hydroxylase results in the synthesis of hydroxylated collagen with thermal stability similar to native collagens. The purified hydroxylated rhC forms fibrils that are structurally similar to fibrils assembled from native collagen. These qualities make rhC attractive for use in many medical applications. P. pastoris can also be engineered to secrete high levels (3 to 14 g/l ) of collagen fragments with defined length, composition, and physiochemical properties that serve as substitutes for animal-derived gelatins. The replacement of animal-derived collagen and gelatin with rhC and rG will result in products with improved safety, traceability, reproducibility, and quality. In addition, the rhC and rG can be engineered to improve the performance of products containing these biomaterials.

Expression and characterization of a low molecular weight recombinant human gelatin: development of a substitute for animal-derived gelatin with superior features

Gelatin is used as a stabilizer in several vaccines. Allergic reactions to gelatins have been reported, including anaphylaxis. These gelatins are derived from animal tissues and thus represent a potential source of contaminants that cause transmissible spongiform encephalopathies. We have developed a low molecular weight human sequence gelatin that can substitute for the animal sourced materials. A cDNA fragment encoding 101 amino acids of the human proalpha1 (I) chain was amplified, cloned into plasmid pPICZalpha, integrated into Pichia pastoris strain X-33, and isolates expressing high levels of recombinant gelatin FG-5001 were identified. Purified FG-5001 was able to stabilize a live attenuated viral vaccine as effectively as porcine gelatin. This prototype recombinant gelatin was homogeneous with respect to molecular weight but consisted of several charge isoforms. These isoforms were separated by cation exchange chromatography and found to result from a combination of truncation of the C-terminal arginine and post-translational phosphorylation. Site-directed mutagenesis was used to identify the primary site of phosphorylation as serine residue 546; serine 543 was phosphorylated at a low level. A new construct was designed encoding an engineered gelatin, FG-5009, with point mutations that eliminated the charge heterogeneity. FG-5009 was not recognized by antigelatin IgE antibodies from children with confirmed gelatin allergies, establishing the low allergenic potential of this gelatin. The homogeneity of FG-5009, the ability to produce large quantities in a reproducible manner, and its low allergenic potential make this a superior substitute for the animal gelatin hydrolysates currently used to stabilize many pharmaceuticals.