Microspheres cellulose

Excipients like dibutyl phthalate were used as plasticizers for controlled-release microspheres of theophylline and sulfamethazine prepared by spray-drying. Likewise, citric acid was used as plasticizer for spray-dried sodium carboxymethyl cellulose and hydroxypropylmethyl cellulose microspheres containing theophylline.Excipients were found to affect the release rate of theophylline with citric acid and triethylene citrate giving the slowest and fastest rate, respectively, as compared with polyethylene glycol and glycerin excipients. 

Arica, B. Arica, M.Y. Kas, H.S. Hincal, A.A. Hasirci, V. In-vitro studies of enteric coated diclofenac sodium car-boxymethyl cellulose microspheres. J. Microencapsul. 1996, H (6), 689-699. 

The microspheres mentioned above are all spherical and no change of the diameter and aggregation of the microspheres takes place during the reaction of surface modification. The surface charge of every microsphere can be determined by electrophoresis. For instance, the zeta potentials of our cellulose triacetate, Cell-OH, crosslinked Cell-OH, Cell-CM, Cell-SE, Cell-NHa, Cell-DEAE, Cell-DEAE(Me), and benzyl cellulose microspheres were —19.9, —2.1, —2.7, —17.1, —20.9, +4.6, +14.2, +15.1, and —65.2 mV, respectively. This result indicates that anionic and cationic microspheres with the same average diameter but different surface charges can be prepared by this method. 

The surface hydrophobicity of microspheres is one of the main factors regulating phagocytosis of microspheres by M. Microspheres having different hydrophobicities can be prepared by conversion of the hydrophilic surface of cellulose microspheres into a hydrophobic one by allowing alkyl amines of different carbon numbers or aromatic and cycloaliphatic amines to link to the cellulose microspheres using the CNBr activation method [30], which is widely used in Sepharose gel preparation for... 

Coupling reactions of various proteins to the cellulose microspheres can be conducted by the CNBr activation method [29]. The proteins employed are bovine serum albumin (BSA), bovine immunoglobulin G(IgG), gelatin, tuftsin, and human serum fibronection (FN). 

Hg. 11. Effect of the surface charge on phagocytosis of modified cellulosic microspheres (1) Cell-OH. (2) crc s-linked Cell-OH, (3) CeU-CM. (4) CeU-SE, (5) Cell-NH, (6) CeU-DEAE, (7) Cell-DEAE (Me), (8) lhilo triacetate, and (9) benzyl cellulose micro-spheres... 

Fig. 14. Effect of the zeta potential on phagocytosis of modified cellulosic microspheres by M< >. (See Fig. 12. concerning the number in the Fig.)...

Table 2 summarizes the results of M<[) phagocytosis of cellulose microspheres whose surfaces were grafted with various protein molecules, together with the microspheres not grafted or modified by coulping with a -hexyl (Q) chain, as well as polystyrene microspheres. In addition, the effect of fetal calf serum (FCS) added to M<[) cultures... 

Table 2. Phagocytosis of Protein-Grafted Cellulose Microspheres by Macrophages...

As is well known, protein adsorption generally takes place onto the foreign surfaces, especially when they are moderately hydrophobic. It is likely that protein des-sorption also depends on the hjdrophobicity of the surface to which the protein has been adsorbed. Presumably, the more strongly the protein is adsorbed, the less readUy it may be desorbed. In this connection, the surface of Cg upW cellulose microspheres is hydrophobic and is strongly adsorbed by proteins and also highly resistant... 

It is also used in hot-melt extruded films for topical use. When it is produced with chlorpheniramine maleate, the matrix is stabilized, allowing film processing at lower temperatures. Mucoadhesive hydroxypropyl cellulose microspheres have been prepared for powder inhalation preparations. A specification for hydroxypropyl cellulose is included in the Food Ghemicals Godex (EGG). 

Zinotti C, Kedzierewicz F, Hoffman M, Maincent P. Preparation and characterization of ethyl cellulose microspheres containing 5-fluorouracil. J Microencapsul 1994 11 555-563. 

Ghorab MM, Zia H, Luzzi LA. Preparation of controlled release anticancer agents I 5-fluorouracil—ethyl cellulose microspheres. / Microencapsul 1990 7(4) 447-454. 

Chen SJ, Chen RR, Chen PF, Lin WJ. In vitro modified release of acyclovir from ethyl cellulose microspheres. Journal of Microencapsulation. September-October 2001 18(5) 559-565. PubMed PMID 11508761. 

Thakare M, Israel B, Garner ST, Ahmed H, Garner P, Elder D et al. Formnlation parameters and release mechanism of theophylline loaded ethyl cellulose microspheres Effect of different dnal snrfac-tant ratios. Pharmaceutical Development and Technology. September-Octoher 2013 18(5) 1213-1219. PubMed PMID 21991996. 

G, K. Jani, M. C. Gohel. Effects of selected formulation parameters on the enuap-ment of diclofenac sodium in ethyl cellulose microspheres. J. Controlled Release. 43 245-250. 1997. 

Bayoni M.A., Influence of polymers weight ratio and pH of polymers solution on the characteristics of chitosan car-boxymethyl cellulose microspheres containig theophyline. Boll. Chem. Farm., 142, 2003, 336-342. 

Liu H, et al. Hydroxyapatite/polyurethane scaffold incorporated with drug-loaded ethyl cellulose microspheres for bone regeneration. J Biomed Mater Res B Appl Biomater 2010 95(1) 36 6. 

Details are given of the development of ethyl cellulose microspheres for prolonged drug delivery with reduced burst effect. Ethyl cellulose microspheres loaded with ibuprofen were prepared with and without PS. Characterisation was undertaken using drug loading measurements, FTIR, DSC and SEM. In vitro release studies were performed to determine the influence of PS on ibuprofen release. 15 refs. 

Journal of Microencapsulation 18, No.5, Sept./Oct. 2001, p.559-65 IN VITRO MODIFIED RELEASE OF ACYCLOVIR FROM ETHYL CELLULOSE MICROSPHERES... 

Ti02-loaded 25-pm carbon microspheres were prepared from Ti02-loaded cellulose microspheres, formed by one-step phase separation using cellulose xantate and sodium polyacrylate aqueous solutions with dispersed TiOj powder (P25) [264]. The titania particles were located preferentially on the external microsphere surface, whose content was either 41.5 or 15.6 mass%. Decomposition of acetaldehyde under UV irradiation was found to be enhanced in comparison with as-received P25 powder. 

Shi P, Zuo Y, Zou Q, Shen J, Zhang L, Li Y, Morsi YS. Improved properties of incorporated chitosan film with ethyl cellulose microspheres for controlled release. Int Pharm. 375 (1-2) 67-74, 2009. 

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