Bioactive hydrogel scaffolds reinforced with alkaline-phosphatase containing halloysite nanotubes for bone repair applications.

Alkaline phosphatase (ALP), biomineralization promoting enzyme, was immobilized in halloysite (HAL) nanotubes and used as a bioactive component of the chitosan (CH) and chitosan-collagen (C-CH) hydrogel scaffolds for bone regeneration. The influence of HAL-ALP and collagen on the properties of the obtained materials was studied. 30 wt% of HAL-ALP increased significantly the swelling ratio of chitosan-based scaffolds. The presence of both: collagen and HAL-ALP had positive effect on the scaffolds' porosity, which was considerably higher for C-CH. The presence of HAL has improved the mechanical properties of both types of scaffolds, while the addition of 20% of collagen to the chitosan hydrogels have considerably decreased their storage modulus. Biomineralization tests showed that although mineral was formed in both CH and C-CH scaffolds with HAL-ALP, the process was more effective for collagen-containing hydrogels. Biological studies, performed using MG-63 osteoblast-like cell line showed that C-CH scaffolds, especially those after biomineralization, were a better material for cell adhesion and growth. Both types of scaffolds degraded slowly in physiological pH. C-CH scaffolds containing 30% of HAL-ALP have the highest potential as bioactive material for bone regeneration.

Acyclovir in the Treatment of Herpes Viruses - A Review.

BACKGROUND: Herpes Simplex (HSV) viruses are widely spread, highly contagious human pathogens. The statistics indicate that 50-90% of adults worldwide are seropositive for these viruses, mainly HSV-1 and HSV-2. The primary infection results in the appearance of watery blisters (cold sores) on the skin, lips, tongue, buccal mucosa or genitals. The ocular infection is the major cause of corneal blindness in the Western World. Once the HSV virus enters human body, it cannot be completely eradicated because HSV viruses are able to change into their latent form which can survive the treatment. The viron resides in trigeminal ganglia of the host, who becomes vulnerable to the reoccurrence of the disease during the whole lifespan. The neurotropic and neuro-invasive properties of HSV are responsible for neurodegenerative illnesses, such as Alzheimer's disease. Acyclovir and its analogues, being the inhibitors of the viral DNA replication, are the only approved medicines for HSV infection therapies. OBJECTIVE: The current paper presents the up-to-date overview of the important pharmacological features of acyclovir, its analogues and their delivery systems including the mechanism of action, routes of administration, absorption and metabolism, as well as side effects of the therapy. CONCLUSION: Acyclovir remains the gold standard in the treatment of herpes virus infections, mainly due to the emerging of the new delivery systems improving considerably its bioavailability. The analogues of acyclovir, especially their esters, characterized by significantly higher bioavailability and safety, may gradually replace acyclovir in selected applications.

Halloysite-alkaline phosphatase system-A potential bioactive component of scaffold for bone tissue engineering.

Alkaline phosphatase (ALP) was sucessfully incorporated into the halloysite (HAL) nanotubes, as confirmed by FTIR-ATR and XRD analyses. The loading efficiency (LE) of ALP was found to be 13.5%, while its encapsulation efficiency (EE) was estimated to be around 27%, as determined using the Bradford test. The influence of the immobilization in HAL on the enzyme activity was measured using standard ALP activity assay. Immobilized ALP effectively induced the bomineralization process, as showed by SEM, EDS, and XRD studies. As a result, calcium phosphate was produced in the form of hydroxyapatite cauliflower-like structures, with a slight content of calcium hydroxide. Interestingly, the encapsulation of ALP guest molecules in the HAL nanotubes considerably increased its thermal stability, most probably due to the heat sink effect. The activity of HAL-bound ALP was also found to be pH-independent in the wide range of pH values (3-10) due to the amphoteric nature of the aluminum oxide lining the HAL nanotube internal surface. Due to an increased resistance to the unfavorable conditions, which are often encountered during scaffold preparation or sterilization, ALP-HAL nanocomposite material may constitute an attractive bioactive component of the scaffolds for bone regeneration.